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For a long time, intercropping and rotation of leguminous with non-leguminous crops is widely used to reduce the application of nitrogen fertilizer and increase yield in agroecosystems. At present, most researchers considered that this management measure is helpful for reducing fertilizer consumption and increasing its efficiency, as it can improve nutrient supply of legumestonon-legumes, the spatial nutrient utilization efficiency by enhancing soil spatial heterogeneity, and improve soil structure and disease resistance. However, current theories cannot fully explain the positive effect of crop rotation and inter-cropping systems involving legumes. A large amount of hydrogen (H 2 ) can be produced as an obligatory by-product of nitrogenase responsible for nitrogen (N 2 ) fixation in the root nodules of leguminous plants. Despite of substantial amounts of H 2 enriched in the rhizosphere of legumes, only a minor proportion of H 2 is found to leak to soil surface. Increasing evidence showed that most H 2 released in soil is immediately depleted in the surrounding of N 2 -fixing nodules by H 2 -oxidizing bacteria (HOB) thriving in soil. HOB can use H 2 as an electron donor to assimilate and fix CO 2 through redox reactions to synthesize cellular substances and consequently promote plant growth. To date, however, little is known about the biological mechanism and ecological process behind the "hydrogen fertilizer effect". Therefore, we review the H 2 -induced plant growth-promoting effects and its microbiological mechanisms. Our aims were to explore a new way for enhancing agroecosystem production, and to provide scientific basis for future utilization of H 2 in agricultural production practices.

Soil organic carbon (SOC) is essential for maintaining soil fertility and promoting sustainable agricultu-ral development. We investigated the impact of long-term tillage practices on soil organic carbon storage (SOCS) and its components in dryland farming areas of the black soil region, based on a 39-year tillage practice experiment. We compared the effects of different tillage practices (conventional rotary and ridge tillage, CT; no-tillage, NT; subsoiling tillage, ST; moldboard plowing, MP) on SOCS, active organic carbon components, and microbial necromass carbon (MNC) content in the 0-40 cm soil layer. The results showed that, compared to CT, NT significantly increased the contents of SOCS, SOC, dissolved organic carbon (DOC), microbial biomass carbon (MBC), easily oxidizable organic carbon (EOC), and MNC in the 0-20 cm soil layer. Both ST and MP significantly improved the contents of SOCS, SOC, and EOC in 0-20 and 20-40 cm soil layers compared to CT and increased MBC content in the 20-40 cm soil layer. Additionally, MP treatment significantly improved the contents of DOC, particulate organic carbon, and MNC in the 20-40 cm soil layer compared to other treatments. ST and MP significantly reduced the contribution rate of MNC to SOC in both soil layers compared to CT and NT treatments. Results of structural equation modeling showed that enhancing the mean weight diameter of soil aggregates, field capacity, and total phosphorus content, along with increasing the activities of β-glucosidase, amylase, and lignin peroxidase, could promote MNC accumulation. MP treatment facilitated the uniform distribution of SOC, active organic carbon, and MNC in the 0-40 cm soil layer, which was more conducive to the fixation of SOC in farmland in the black soil region.

The mechanism for water-saving and high-yield of wide-range precision sowing technology remains unclear. We investigated the impact of wide-range precision sowing on the physiological characteristics of root system, water consumption, and grain yield of wheat 'Jimai 22' during the growing seasons of 2017-2019. We set up two planting modes: wide precision sowing and conventional strip sowing, and three row spacings of 20 cm, 25 cm, and 30 cm under water-saving cultivation with supplemental irrigation to examine the effects of planting modes on root biomass and senescence characteristics of wheat, water utilization characteristics, interplant evaporation, grain yield, and water utilization efficiency. The results showed that the 25 cm treatment (K25) led to an increase in root weight density, root soluble protein content, and root activity by 7.2%-23.9%, 8.7%-25.1%, 10.7%-29.9%, and 7.3%-27.6%, 8.0%-38.5%, 15.2%-32.7%, respectively, compared to the other treatments. At the same row spacing, the wide-range precision sowing treatment showed a significantly higher soil water storage consumption and proportion to total water consumption compared to the conventional strip-tillage treatment. Additionally, irrigation and interplant evaporation were lower in the wide-range precision sowing treatment. The K25 treatment exhibited significantly higher water consumption and modal coefficient of water consumption from flowering to ripening than other treatments. Furthermore, it had significantly higher seed yield, water utilization efficiency, and irrigation utilization efficiency than the other treatments. We found that a 25 cm spacing in the lower rows and density of 180-270 plants·m -2 was the water-saving and high-yielding planting pattern of wide-range precision sowing wheat in Huang-Huai-Hai region.

Soil organic matter serves as a crucial indicator for soil quality. Albic soil, characterized by a barrier layer, exhibits limitations in organic matter content, which can adversely affect crop growth and development. To elucidate the impact of deep mixing of various organic materials on the redistribution of organic matter in the surface soil of albic soil could provide theoretical and technical insights for establishing suitable plough layers for albic soil in Northeast China. We conducted a two-year positioning experiment in Shuangyashan, Heilongjiang Province with five treatments, conventional shallow tillage (0-15 cm, CK), inversion tillage (0-35 cm) without or with straw return (T 35 and T 35 +S), inversion tillage with cattle manure (T 35 +M) and cattle manure plus maize straw (T 35 +S+M). The results showed that soil fertilization via deep mixing of organic materials to a depth of 35 cm significantly increased maize yield in albic soil, with the T 35 +S+M treatment demonstrating the most pronounced effect, yielding an average production of 2934.76 kg·hm -2 . Compared to CK, the T 35 treatment resulted in a significant 8.4% decrease in organic matter content in the tillage layer, a significant 7.6% increase in organic matter in the sub-tillage layer, and a relative richness degree of soil organic matter in the sub-tillage layer increased by 17.5%. Deep mixed return of organic materials following deep ploughing markedly increased organic matter content of the plough layer, with organic matter conversion ranging from 16.3% to 31.0%. In comparison to the T 35 treatment, there was no significant increase in soil organic matter content in the T 35 +S tillage layer and sub-tillage layer. Conversely, soil organic matter content increased by 4.6% and 6.9% in the T 35 +M and T 35 +S+M treatments, with corresponding increase of 11.2% and 15.4% in sub-tillage layer, respectively. Additionally, the soil organic matter richness index in sub-tillage layer increased by 2.5% and 5.1%, respectively. There was a significant positive correlation between organic matter content in the entire plough layer and maize yield, with a contribution rate of 17.5%. Therefore, the utilization of organic fertilizer or a combination of organic fertilizer and straw deep mixing can quickly fertilize albic soil by increasing soil organic matter content in both the whole tillage layer (0-35 cm) and the sub-tillage layer (15-35 cm).

Clarifying current situation of farmers' fertilization and yield in citrus producing areas and the effects of different fertilization measures can provide a scientific basis for improving the yield and quality of citrus in China. We retrieved 92 literatures on citrus fertilization from the CNKI and Web of Science to examine the impacts of nitrogen (N), phosphorus (P or P 2 O 5 ), and potassium (K or K 2 O) fertilizer dosage and partial productivity under farmers' conventional fertilization and experts' optimized fertilization, as well as the effects of optimized fertilization measures on citrus yield and quality by using meta-analysis approach. The average conventional application rates of N, P 2 O 5 , and K 2 O were 507.3, 262.2, and 369.3 kg·hm -2 in citrus production in China. Compared with conventional fertilization, optimized fertilization resulted in a reduction of N and P 2 O 5 by 14.7% and 8.3%, an increase in K 2 O application by 6.6%, which promoted partial productivity of N, P 2 O 5 , and K 2 O fertilizers by 7.8%, 18.4%, and 14.7%, correspondingly. The optimized fertilization resulted in 11.9% and 2.8% increase in fruit yield and single fruit weight, while improved vitamin C content (Vc, 3.1%), total soluble solids (TSS, 5.9%) and total sugar content (TSC, 8.6%). Additionally, it also led to a reduction in titratable acid (TA, -3.4%) and total acid content (TAC, -3.6%), and consequently elevated the TSS/TA (14.0%) and TSC/TAC (9.5%). Among different optimized fertilization methods, the effect of optimized NPK + medium and/or micro element fertilizer on citrus yield and fruit quality was the best, especially NPK decrement ≤25% between optimized NPK measures. The effect of conventional NPK + organic fertilizer was higher than conventional NPK + medium and/or micro element fertilizer. However, different citrus varieties, including mandarins, pomelos, and oranges, showed different responses to optimized fertilization. Optimized fertilization management could synergistically improve citrus yield, fertilizer use efficiency, and fruit quality. Therefore, the strategy of integrated nutrient management1 with reducing NPK fertilizer, balancing medium and/or micro nutrient fertilizer and improving soil fertility by organic fertilizer should be adopted according to local conditions in citrus producing areas of China.

To provide a theoretical basis and technical support for the high-yield and high-efficiency production of wheat, we examined the effects of different tillage patterns on wheat grain yield of Jimai 22 and the physiological mechanisms in an experiment with three treatments: 14 years in rotary tillage (R), minimal and no tillage (S), and minimal and no tillage with a 2-year subsoiling interval (SS). We assessed the light interception by wheat plant canopy, the distribution of photosynthate transport, and grain yield for the three cultivation modes. The results showed that leaf area index was significantly higher for SS treatment than the other treatments at 14-28 days after anthesis. The interception rate and amount of photosynthetically active radiation in the upper and middle layers of wheat canopy were significantly higher for SS treatment than R and S treatments at 21 days after anthesis. The contribution rate of grain assimilation and the distribution proportion of 13 C assimilated in grain, and the maximum and average filling rates, were the highest under SS treatment. The 1000-kernel weight for SS treatment increased by 8.7% and 9.6%, and the grain yield increased by 14.2% and 19.4% compared with R and S treatments, respectively. SS treatment significantly improved light energy utilization by wheat canopy, promoted the accumulation and transport of dry matter, increased the grain-filling rate, increased grain weight, which together contributed to the highest grain yield. Therefore, SS was the optimal tillage pattern under the conditions of this experiment.

Crop health directly affects yields and food security. At present, agrochemicals such as fertilizers and pesticides are mainly used in agricultural production to promote crop health. However, long-term excessive utilization of agrochemicals will damage the ecological environment of farmlands and increase the safety risk of agricultural products. It is urgent to explore efficient and environment-friendly agricultural products. Rhizosphere microbiome are considered as the second genome of plants, which are closely related to crop health. Understanding the key functional microbes, microbe-microbe interactions, and plant-microbe interactions are fundamental for exploring the potential of beneficial microbes in promoting crop health. However, due to the heterogeneity and complexity of the natural environment, stimulating the function of indigenous microorganisms remains uncertain. Synthetic microbial community (SynCom) is an artificial combination of two or more different strain isolates of microorganisms, with different taxonomic, genetic, or functional characteristic. Because of the advantages of maintaining species diversity and community stability, SynCom has been widely applied in the fields of human health, environmental governance and industrial production, and may also have great potential in promoting crop health. We summarized the concept and research status of SynCom, expounded the principles and methods of constructing SynCom, and analyzed the research on the promotion of crop health by exploring the mechanism of plant-microbe interactions, promoting plant growth and development, and improving stress resistance. Finally, we envisaged the future prospects to guide the using SynCom to improve crop health.

To understand the effects of different stover mulching amounts in no-tillage on soil carbon and nitrogen contents and enzyme activities, finding a stover mulching amount which can meet the requirement of soil carbon and nitrogen accumulation while maximizing economic benefits, we conducted a long-term conservation tillage field experiment since 2007 in Mollisols area of Northeast China. We analyzed soil carbon and nitrogen contents, enzyme activities and economic benefits under conventional tillage (Control, CT), no-tillage without stover mulching (NT 0 ), no-tillage with 33% stover mulching (NT 33 ), no-tillage with 67% stover mulching (NT 67 ), and no-tillage with 100% stover mulching (NT 100 ) before planting in May 2020. The results showed that compared with CT, NT 0 did not affect soil organic carbon (SOC) and total nitrogen (TN) contents, but increased soil organic carbon recalcitrance and decreased the availability of dissolved organic nitrogen (DON) and ammonium nitrogen. Compared with NT 0 , no-tillage with stover mulching significantly increased SOC contents in 0-10 cm layer and increased with the amounts of stover. In addition, NT 67 and NT 100 significantly increased SOC stocks, facilitating the accumulation of soil organic matter. The effects of different stover mulching amounts on soil nitrogen content in 0-10 cm layer were different. Specifically, NT 33 increased DON content and DON/TN, NT 67 increased DON content, while NT 100 increased TN content. Compared with CT, NT 0 decreased peroxidase (POD) activity in 0-10 cm layer. Compared with NT 0 , NT 33 increased β-glucosidase (βG), cellobiase (CB), 1,4-β-N-acetylglucosaminidase (NAG), polyphenol oxidase (PPO) and POD activities, while NT 67 only increased CB, NAG and POD activities in 0-10 cm soil layer, both alleviated microbial nutrient limitation. NT 100 increased PPO activity in 10-20 cm layer. NT 33 increased carbon conversion efficiency of stover compared with NT 100 , and had the highest economic benefit. In all, no-tillage with 33% stover mulching was the optimal strategy, which could promote nutrient circulation, boost stover utilization efficiency, improve the quality of Mollisols, and maximize guaranteed income.

The proportion and area of ratoon rice planting in China have been substantially increased, due to continuous improvement of rice breeding methods and consecutive innovation of cultivation technology, which has developed into one of rice planting modes with significant production efficiency. Combining the experience in research and practice, from the perspective of crop physiology and ecology, we reviewed the current situation and prospects of high-yielding formation and physiological mechanisms of ratoon rice. We focused on four key aspects: screening and breeding of ratoon rice cultivars and the classification; suitable stubble height for mechanically harvested ratoon rice, as well as water and fertilizer management; dry matter production and allocation in ratoon rice and the relationship with yield formation; regenerative activity and vigor of ratoon rice roots and their relationship with rhizosphere micro-ecological characteristics. As for the extending of mechanized low-cut stubbles ratoon rice technique, we should properly regulate the rhizosphere system, coordinate rhizosphere nutrient supply, germination of axillary buds, and tillering regeneration, to achieve the target of "four-high-one-low", that is high regeneration coefficient, high number of regeneration panicle, high harvest index, high yield, high quality, low-carbon and safe, aiming to improve the sustainability of ratoon rice industry.

The composition and stability of soil aggregates are important indicators for measuring soil quality, which would be affected by land use changes. Taking wetlands with different returning years (2 and 15 years) in the Yellow River Delta as the research object, paddy fields and natural wetlands as control, we analyzed the changes in soil physicochemical properties and soil aggregate composition. The results showed that soil water content, total organic carbon, dissolved organic carbon and total phosphorus of the returning soil (0-40 cm) showed an overall increasing trend with returning period, while soil pH and bulk density was in adverse. There was no significant change in clay content, electrical conductivity, and total nitrogen content. The contents of macro-aggregates and micro-aggregates showed overall increasing and decreasing trend with returning period, respectively. The stability of aggregates in the topsoil (0-10 cm) increased with returning years. Geometric mean diameter and mean weight diameter increased by 8.9% and 40.4% in the 15 th year of returning, respectively, while the mass proportion of >2.5 mm fraction decreased by 10.5%. There was no effect of returning on aggregates in subsoil (10-40 cm). Our results indicated that returning paddy field to wetland in the Yellow River Delta would play a positive role in improving soil structure and aggregate stability.

Under the context of global climate change and growing population, irrigation and fertilization have become important ways to ensure food production, with consequences on water cycling, energy flow, and materials cycling in terrestrial ecosystems. In the land surface model (LSM), coupling irrigation and fertilization schemes are of great importance for clearly understanding the land-atmosphere interactions to ensure food security. We reviewed the expression methods of three key parameters, namely, the applied method, usage, and time in the parameterization process of irrigation and fertilization (nitrogen fertilizer) in LSM. We found that the ways to irrigate and ferti-lize in LSM are different from the ways used in actual practice due to the limitation of the high resolution of spatio-temporal data, which makes it difficult to understand the actual influences of irrigation and fertilization on grain yield, environment, and local climate. Finally, we proposed future works: 1) taking the differences of crop water demand into account and making the different irrigation thresholds for different crops to properly evaluate the total and intensity of water consumption of different crops; 2) using the field records and the regional grid data of fertilization and irrigation developed in recent years to develop parameterized schemes that are more in line with actual agricultural operations, which can accurately reveal their economic, ecological, and climatic effects; 3) developing fertilization diagnosis scheme considering crop type, phenological stage, and soil basic fertility as the supplementary scheme in LSM, to improve the applicability and simulation accuracy of LSM in the areas without nitrogen fertilizer data.

We conducted a field experiment in the dry farming area in south Ningxia from 2018 to 2021, to explore the influence of tillage methods combined with mulching on soil bulk density, aggregate content, soil water storage and potato yield under different precipitation years. There were four tillage methods (15 cm depth ploughing, and 30 cm, 40 cm and 50 cm depth subsoiling) and three mulching measures (mulching with oat straw, plastic film and no mulching), with the ploughing depth of 15 cm without mulching as control. The results showed the combination of tillage and mulching effectively reduced soil bulk density in 0-60 cm layer after three years of farming compared with that prior to the experiment. Under the same tillage mode, the best effect was achieved in mulching with oat straw under different precipitation years. To be specific, the best effect in 20 cm and 40 cm soil layers was achieved in mulching with oat straw for 30 cm depth subsoiling, in 60 cm soil layer for 15 cm ploughing in wet year, and for 40 cm depth subsoiling in 20 cm, 40 cm and 60 cm soil layers in normal and dry years. In 0-20 cm soil layer, the content of >0.25 mm soil aggregate was the highest for 40 cm depth subsoiling with oat straw mul-ching in all the three years. In 20-40 cm soil layer, the content was the highest for 15 cm depth ploughing with oat straw mulching in wet year, and for 40 cm depth subsoiling with oat straw mulching in normal and dry years. In 40-60 cm soil layer, content was the highest for 15 cm depth ploughing with plastic film mulching, 30 cm depth subsoiling with plastic film mulching, and 30 cm depth subsoiling with oat straw mulching in wet, normal and dry years, which was increased by 18.8%, 27.0%, and 35.8%, respectively, compared with the control. In the key growth stage (from squaring to tuber expansion) of potatoes, soil water storage in 0-100 cm layer was optimal for 30 cm depth subsoiling with oat straw mulching in wet year and for 40 cm depth subsoiling with oat straw mulching in normal and dry years, with an increase of 19.4%, 19.5%, and 23.7%, respectively. Potato yield was the highest for 30 cm depth subsoiling with oat straw mulching in wet year and for 40 cm depth subsoiling in normal and dry years, with an increase of 84.6%, 81.7%, and 106.3%, respectively. The correlation analysis showed that improved soil physical properties played a significant role in increasing potato yield, with the most significant role of soil bulk density and soil water storage at the squaring stage. Potato yield was high at a tillage depth of 34.67-36.03 cm. We concluded that the combination of tillage method and mulching could effectively improve soil physical pro-perties and increase soil water storage in the growth stage of potatoes, thereby significantly increa-sing potato yield. Potato yield in dry farming area could be enhanced through 30 cm depth subsoiling with oat straw mulching in wet years, and 40 cm depth subsoiling with oat straw mulching in normal and dry years.

Improving soil fertility is one of the key approaches for ecological restoration of the wind-sand area in northwest Liaoning Province. Taking wind-sand area in northwest Liaoning Province as test object, we conducted a fertilization experiment with treatments of inorganic fertilizer (nitrogen, phosphorus and potassium fertilizers), organic fertilizer, combined application of organic and inorganic fertilizers, and organic fertilizer combined with a biologically organic matrix (γ-polyglutamic acid), and no fertilizer as control. We measured soil organic matter content and extractable cations concentrations, vegetation coverage, and biomass under different fertilization treatments and determine the suitable fertilization mode. The results showed that compared to the control, inorganic fertilizer rapidly increased vegetation coverage and biomass, but high levels of inorganic fertilizer (150 kg N·hm -2 ) led to soil acidification and Ca 2+ leaching. Organic fertilizer increased soil organic matter content, exchangeable K + , Ca 2+ , and Mg 2+ contents, as well as coverage and biomass vegetation, especially combined with γ-polyglutamic acid. Overall, the combination of low levels of inorganic fertilizer (50 kg N·hm -2 ) and moderate levels of organic fertilizer (30000 kg·hm -2 ) was the best fertilization practice for the rapid and stable restoration of grassland in wind-sand area. Moreover, the extra addition of γ-polyglutamic acid (60 kg·hm -2 )could effectively improve soil fertility.

We analyzed the particle size distribution of soil aggregates in 0-20 and 20-40 cm soil layers of rice-wheat rotation field based on a field plot test with two treatments, conventional straw returning (CK) and straw returning with the addition of straw decomposition promoting microbial inoculants (IT). We evaluated the water stability indices of soil aggregates (the number of soil water stable large aggregates R 0.25 , the average weight diameter MWD, and the geometric average diameter GMD), and measured the contents of soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) in the soil aggregates of ＜0.053, 0.053-0.25, 0.25-1, ＞1 mm. The results showed that: 1) The number of aggregates ＜0.053, 0.053-0.25, ＞0.25 mm in the 0-20 and 20-40 cm soil layers under IT decreased by 10.0% and 6.8%, increased by 3.0% and 5.7%, and 17.9% and 26.1% compared with CK, respectively. IT effectively increased R 0.25 , MWD, and GMD by 26.4%, 20.0%, 18.2% and 18.2%, 10.5%, 10.0% in 0-20 and 20-40 cm soil, respectively. 2) Compared to CK, the TP content of 0.25-1 mm aggregates in 0-20 and 20-40 cm soil under IT was significantly increased by 40.3% and 37.5%, respectively, without difference in TN and SOC contents. There was no significant difference in nutrient contents of the other aggregates between the treatments. The contents of SOC and TN in large aggregates (>0.25 mm) were higher than those in silty aggregates (<0.053 mm). Compared to CK, the cumulative contribution rates of SOC, TN and TP of <0.053 mm aggregates under IT were decreased in two soil layers. There was no significant difference in the nutrient cumulative contribution rates of 0.053-0.25 mm aggregates between treatments. The cumulative contribution rates of SOC, TN, and TP of large aggregates (>0.25 mm) under IT were 32.1%, 19.6%, 52.8% and 22.8%, 11.8%, 42.9% higher than those under CK in 0-20 and 20-40 cm soils, respectively. 3) The number of <0.053 mm aggregates was significantly negatively correlated with SOC and TP contents, while that of 0.053-0.25 mm aggregates was negatively correlated with nutrient content. The number of large aggregates (>0.25 mm) were significantly positively correlated with SOC, TN, and TP contents. In conclusion, straw returning with microbial-inoculant addition could promote the formation of soil macroaggregates (>0.25 mm), and improve the water stability of soil aggregates, increasing nutrient contents in soil macroaggregates, with the nutrients transferring from silty aggregates to macroaggregates.

To elucidate the agronomic and environmental effects of single basal application of controlled-release blended fertilizer in summer maize, and optimize management measures of nitrogen fertilizer for grain production in North China Plain, we conducted a field experiment in Dezhou Modern Agricultural Science and Technology Park in Shandong Province. There were four treatments: CK (no N fertilizer), FFP (farmer's fertilizing practice, 240 kg N·hm -2 ), OPT (optimized nitrogen application, 210 kg N·hm -2 ), and CRBF (controlled-release blended fertilizer with single basal application, 210 kg N·hm -2 ). We compared maize yield and reactive nitrogen loss, and quantitatively evaluated the carbon and nitrogen footprints by using life cycle assessment method. The results showed that nitrogen application significantly increased summer maize yield. Compared with FFP, OPT and CRBF increased summer corn yield by 0.7% and 2.9%, respectively, decreased the total amount of ammonia volatilization, N 2 O emission, and nitrate leaching by 13.0% and 72.7%, 13.3% and 37.5%, 20.5% and 23.5% respectively. Compared with CK, nitrogen application significantly increased the global warming potential (GWP) of summer maize production. Compared with FFP, GWP and greenhouse gas emission intensity of OPT decreased by 3.8% and 4.2%, while the reduction of CRBF were 8.7% and 12.0%, respectively. Compared with CK, nitrogen application significantly increased the carbon and nitrogen footprint of summer maize production. The production and transportation of nitrogen fertilizer and soil greenhouse gas emission were the main contributing factors of the carbon footprint, with contribution rates of 54%-60% and 24%-31%, respectively. Nitrate leaching was the main contributing factor of nitrogen footprint, with contribution rate of 57%-94%. Compared with FFP, the carbon and nitrogen footprints of OPT and CRBF were reduced by 11.0% and 16.5%, 19.6% and 28.4%, respectively. Considering the yield, reactive nitrogen loss and carbon and nitrogen footprint, we recommended the single basal application of controlled-release blended fertilizer as an effective nitrogen fertilizer management measure to promote grain clean production in the North China Plain.

The middle and lower reaches of the Yangtze River is one of main grain production areas in China, which is of great significance to food security. Understanding the carbon footprint of major grain crop production is helpful to develop high-yield and low-carbon agriculture. Based on the data of yield, sown area and farmland production input of main grain crops (rice, wheat and maize) in six provinces (Jiangsu, Anhui, Jiangxi, Hubei, Hunan, and Zhejiang) in the middle and lower reaches of the Yangtze River from 2011 to 2020, we estimated carbon footprint in the production of the three grain crops. The results showed that from 2011 to 2020, yield per unit area, planting area, and total yield of rice, wheat and maize were the highest in Jiangsu Province. In terms of area-scaled carbon footprint, rice in the middle and lower reaches of the Yangtze River had the highest area-scaled carbon footprint, with an average of 2.0 t CE·hm -2 , followed by wheat and maize. The area-scaled carbon footprint of the three staple crops was increasing. In terms of yield-scaled carbon footprint, rice was the highest, with an average of 0.8 kg CE·kg -1 , followed by wheat and maize. In terms of carbon input structure, irrigation electricity, chemical fertilizers and pesticides accounted for a relatively high proportion. Irrigation electricity accounted for 35.0%, 36.3%, and 33.2% of the total carbon input of rice, wheat and maize, respectively. Chemical fertilizers accounted for 28.8%, 32.5%, and 32.5%, respectively, while pesticides accounted for 24.2%, 13.3% and 11.5%, respectively. In terms of carbon efficiency, maize had the highest (3.9 kg·kg -1 CE), followed by rice and wheat. With the green development of agriculture, carbon emission in the production of major grain crops in the middle and lower reaches of the Yangtze River could be reduced by improving irrigation efficiency, fertilizer utilization efficiency, pesticide utilization efficiency and mechanized operation efficiency, as well as diversification of straw returning, cultivation of new varieties and policy leverage.

The application of biochar can improve soil fertility and benefit sustainable agricultural development and carbon neutrality simultaneously. To better understand the effects of biochar addition on nitrogen transformation and N 2 O emission in a coastal saline-alkali soil and its potential mechanisms, we conducted a 60-day laboratory incubation experiment with six treatments, i.e ., ammonium sulfate (N 150 mg·kg -1 ), ammonium sulfate + 0.4% (weight/weight) biochar, ammonium sulfate + 0.6% biochar, ammonium sulfate + 0.8% biochar, ammonium sulfate + 1.6% biochar, and ammonium sulfate + 0.2% biochar and 0.2% organic fertilizer (based on equivalent N basis). The results showed that soil nitrogen transformation was mainly affected by biochar addition at the early stage of incubation. Biochar addition significantly increased the contents of nitrate and ammonium. Biochar addition significantly increased soil net nitrification rate, but the magnitude of such increases decreased with increasing biochar addition level. Similar temporal change patterns of N 2 O emissions were observed in all treatments, and the N 2 O emissions mainly occurred in the first 30 days of incubation. Compared with the CK, biochar addition significantly reduced the cumulative N 2 O emission, and the decrement increased with increasing biochar addition levels. In conclusion, the effects of biochar and nitrogen fertilizer addition on soil nitrogen transformation and N 2 O emission varied with the application rate. Biochar addition with a rate of 0.8% (W/W) increased soil inorganic nitrogen content and decreased soil N 2 O emission. It could provide theoretical basis and reference for the formulation of reasonable plans for the improvement and utilization of biochar in coastal saline-alkali soil.

Plant functional traits have an essential role in community formation and ecosystem function. Unlike natu-ral ecosystems, agroecosystems are affected by natural conditions and human management. Plant ( i.e ., crop)functional traits in the agroecosystems are thus shaped by natural and human selection. We reviewed the development of functional trait research, focusing on crop functional traits, research methods of agroecosystems based on traits, and the application of functional traits in agriculture. We then elaborated on the effect of domestication on crop trait trade-offs, the relationship between community functional structure and agroecosystem services, and the application of functional traits in weed management, cover cropping, and intercropping systems. Future research directions of crop functional traits include enriching the types of agroecosystems and crop species in studies, buil-ding up a crop functional trait database, and focusing on agroecosystem multifunctionality.

Clarifying the effect of different maize straw returning methods on soil temperature is crucial for optimizing the management of farmland straw and the efficient utilization of heat resources in the black soil region of Northeast China. To investigate the impacts of straw returning methods on soil temperature, we conducted a field experiment with four treatments during 2018 and 2020, including plough tillage with straw returning (PTSR), rotary tillage with straw returning (RTSR), no-tillage with straw returning (NTSR), and a control treatment of conventional ridge tillage without straw returning (CT). We measured soil temperature and water content at the 5 cm, 15 cm and 30 cm soil layer, and the straw coverage rate during the 3-year maize growth period. We further analyzed the differences of soil temperature in different soil layer under different treatments, accumulated soil temperature and growing degree-days (GDD) above 10 ℃, daily dynamics of soil temperature, the production efficiency of air accumulated temperature among different treatments, and explored factors causing the difference of soil temperature and the production efficiency of air accumulated temperature. Our results showed that different treatments mainly affected soil temperature from the sowing to emergence stage (S-VE) of maize. The daily average soil temperature showed a trend of CT>PTSR>RTSR>NTSR. The differences of soil temperature under different treatments showed a decreasing trend as growth process advanced and soil depth increased. Compared with the CT treatment, soil temperature at 5 cm depth was decreased by 0.86, 1.84 and 3.50 ℃ for PTSR, RTSR, and NTSR treatments, respectively. NTSR significantly reduced the accumulated temperature of ≥10 ℃ in different soil layers and GDD. The accumulated temperature ≥ 10 ℃ at the 5, 15, and 30 cm soil layers decreased by 216.2, 222.7, and 165.1 ℃·d, and the GDD decreased by 201.9, 138.7 and 123.9 ℃·d, respectively. In addition, production efficiency of air accumulated temperature decreased by 9.7% to 15.6% for NTSR. Conclusively, PTSR and RTSR had significant impacts on topsoil temperature during the maize growing period from sowing to emergence, but did not affect the accumulated soil temperature and the production efficiency of air accumulated temperature. However, NTSR significantly reduced topsoil temperature and production efficiency of air accumulated temperature.

To clarify the photosynthetic mechanism contributing to the enhancement of intercropping advantages through co-ridge intercropping of maize and peanut, we conducted a field randomized block experiment under two phosphorus levels of 0(P 0 ) and 180 kg P 2 O 5 ·hm -2 (P 180 ) with flat intercropping of maize and peanut (FIC) as the control. We analyzed the effects of co-ridge intercropping of maize and peanut (RIC) and groove-ridge intercropping of maize and peanut (GIC) on crop leaf area index (LAI), SPAD values, CO 2 carboxylation ability, photosystems coordination ( Φ PSⅠ/PSⅡ ), and intercropping advantage of yield. The results showed that RIC significantly increased SPAD value at the silking stage of intercropping maize, and significantly improved the apparent quantum yield of photosynthesis (AQY), maximum electron transfer rate ( J max ), maximum rate of Rubisco carboxylation ( V c,max ), net photosynthetic rate at the CO 2 saturation ( A max ) and Φ PSⅠ/PSⅡ of intercropping maize compared with those of FIC and GIC at silking stage and milking stage, but reduced the ratio of variable fluorescence F k to amplitude F j - F o ( W k ) and the ratio of variable fluorescence F j to amplitude F p - F o ( V j ) of the functional leaf photosystem Ⅱ (PSⅡ) at the milking stage of maize. There were no significant differences in these parameters between FIC and GIC. Compared with FIC, both RIC and GIC increased LAI of intercropping peanut at late growth stage and SPAD value at pod setting stage, significantly improved V c,max , A max , and Φ PSⅠ/PSⅡ , and reduced W k and V j values of intercropping peanut functional leaves at pod expanding stage. The difference in these parameters between RIC and GIC were not significant. The land equivalent ratio and intercropping advantages of RIC were higher than those of FIC and GIC. Phosphorus application could further promote V c,max , J max , A max and Φ PSⅠ/PSⅡ of intercropping maize and peanut, and significantly improve yield advantages of intercropping. The findings indicated that co-ridge intercropping could enhance CO 2 carboxylation and fixation by improving photosynthetic electron transport and pho-tosystems coordination, improve the photosynthetic rate of functional leaves of maize and peanut, thus increase crop yield and intercropping advantages.

We investigated root and soil nutrient characteristics in the monoculture and continuous alfalfa/oat intercropping in the high-yield years by using soil filling and frame planting method in the field, and analyzed the relationship between root systems and soil nutrients. The results showed that intercropping reduced root weight and total root length proportion of oat in the 0-10 cm soil layer compared with the monoculture. However, intercropping significantly increased root weight and root surface area of oat in the 20-30 cm soil layer, root length and root density of alfalfa in the 10-20 cm soil layer, and the contents of available phosphorus and organic matter of the alfalfa/oat intercropping system in the 0-40 cm soil layer. As the planting years increased, total root length, root weight, root surface area, and proportion of root weight and root length of alfalfa in the 0-20 cm soil layer gradually increased in the intercropping system, and the root weight, total root length, root surface area, and root average diameter of oat increased, especially the root weight and root surface area of oat in the 20-30 cm soil layer. Moreover, the content of available nutrients in all soil layers decreased subsequently. In the alfalfa/oat intercropping system, continuous intercropping could significantly increase total root length of alfalfa in the 10-20 cm soil layer, improve root weight and root surface area of oat in the 20-40 cm soil layer (especially in the 20-30 cm soil layer). With the increases of planting years, intercropping intensified the absorption and competition of available nutrients by the roots of alfalfa and oat in the 0-40 cm soil layer, thereby reduced the accumulation of available nutrients in the soil.

Urease inhibitors and nitrification inhibitors can enhance nitrogen (N) fertilizer utilization efficiency and reducing N losses through regulating urea-N transformation. Common urease or nitrification inhibitors, however, are predominantly chemically synthesized and high-cost. Furthermore, their inhibitory effects are mediated by soil pro-perties, climatic conditions, and crop systems. In this study, we conducted a field experiment using natural synergists humic acid/zeolite, along with chemical nitrification inhibitor dicyandiamide (DCD) and their combination to elucidate the impacts of natural synergists combined with chemical inhibitors on annual yield, nitrogen utilization efficiency, soil nitrate-N accumulation, and nitrogen balance within the wheat/maize rotation system. The treatments included no nitrogen fertilizer application (CK), single application of urea (N), urea +DCD (ND), urea + humic acid (NH), urea + zeolite (NP), urea + urease inhibitor N-butylthiophosphoric triamide + DCD (NUD), urea + humic acid + DCD (NHD), and urea + zeolite + DCD (NPD). The results showed that, compared to the treatments NH and NP, the integration of humic acid or zeolite with DCD (NHD and NPD) significantly increased maize yield (11268 and 11397 kg·hm -2 ) and total annual yield (20494 and 20582 kg·hm -2 ), which were comparable to those of combined chemical urease and nitrification inhibitors (NUD). The NHD and NPD treatments had higher nitrogen utilization efficiency and lower soil nitrate-N accumulation in 80-100 cm soil layer across all seasons relative to the N treatment, which had no significant difference compared to the NUD treatment. Furthermore, a decline in soil nitrogen surplus by 10.7% and 13.9% was observed when comparing the NHD and NPD treatments with the NH and NP treatments, respectively. These findings suggested that combined humic acid or zeolite and chemical nitrification inhibitors could effectively enhance crop yield and N utilization efficiency and meet the requirements of the green and environmental preservation of modern agriculture.

Aiming at solving the problems of soil environment deterioration and the decline of both yield and quality caused by excessive application of chemical fertilizer, we investigated the effects of rotted corn straw on the soil environment of root zone, yield and quality of cucumber with 'Jinyou 35' cucumber as the experimental material. There were three treatments, namely, combined application of rotted corn straw and chemical fertilizer (T 1 , the total nitrogen fertilizer application were 450 kg N·hm -2 , of which 9000 kg·hm -2 rotted corn straw was used as the subsoil fertilizer, and the rest was supplemented with chemical fertilizer), pure chemical fertilizer (T 2 , the total nitrogen fertilizer application was the same as T 1 ) and no fertilization (control). The results showed that the content of soil organic matter in root zone soil in T 1 treatment was much higher, but no difference between T 2 treatment and the control, after two continuous plantings in one year. The concentrations of soil alkaline nitrogen, available phosphorus, available potassium of T 1 and T 2 in cucumber root zone were higher than that in the control. T 1 treatment had lower bulk density, but markedly higher porosity and respiratory rate than T 2 treatment and the control in root zone soil. The electric conductivity of T 1 treatment was higher than that of the control, but significantly lower than T 2 treatment. There was no significant difference in pH among the three treatments. The quantity of bacteria and actinomycetes in cucumber rhizosphere soil were the highest in T 1 , and the lowest in the control. However, the highest quantity of fungi was found in T 2 . The enzyme activities of rhizosphere soil in T 1 treatment were markedly higher than those of the control, whereas those of T 2 treatment were significantly lower or had no significant difference relative to the control. The cucumber root dry weight and root activity of T 1 were significantly higher than that of the control. The yield of T 1 treatment increased by 10.1%, and fruit quality improved obviously. The root activity of T 2 treatment was also significantly higher than that in the control. There was no significant difference in root dry weight and yield between T 2 treatment and the control. Furthermore, T 2 treatment revealed a decrease in fruit quality relative to T 1 treatment. These results suggested that the combined application of rotted corn straw and chemical fertilizer could improve soil environment, promote root growth, enhance root activity and improve yield and quality of cucumber in solar-greenhouse, which could be popularized and applied in protected cucumber production.

Understanding the effects of different tillage practices on functional microbial abundance and composition in nitrogen (N), phosphorus (P) and sulfur (S) cycles are essential for the sustainable utilization of black soils. Based on an 8-year field experiment located in Changchun, Jilin Province, we analyzed the abundance and composition of N, P and S cycling microorganisms and their driving factors in different depths of black soil under no til-lage (NT) and conventional tillage (CT). Results showed that compared with CT, NT significantly increased soil water content (WC) and microbial biomass carbon (MBC) at soil depth of 0-20 cm. Compared with CT, NT significantly increased the abundances of functional and encoding genes related to N, P and S cycling, including the nosZ gene encoding N 2 O reductase, the ureC gene performing organic nitrogen ammoniation, the nifH gene encoding nitrogenase ferritin, the functional genes phnK and phoD driving organic phosphorus mineralization, the encoding pyrroloquinoline quinone synthase ppqC gene and the encoding exopolyphosphate esterase ppX gene, and the soxY and yedZ genes driving sulfur oxidation. The results of variation partitioning analysis and redundancy analysis showed that soil basic properties were the main factors affecting the microbial composition of N, P and S cycle functions (the total interpretation rate was 28.1%), and that MBC and WC were the most important drivers of the functional potential of soil microorganisms in N, P and S cycling. Overall, long-term no tillage could increase the abundance of functional genes of soil microorganisms by affecting soil environment. From the perspective of molecular biology, our results elucidated that no tillage could be used as an effective soil management measure to improve soil health and maintain green agricultural development.

Conservation tillage is an important management practice to guarantee soil fertility in degraded Mollisols. It is still unclear, however, whether the improvement and stability of crop yield under conservation tillage can be sustainable with increasing soil fertility and reducing fertilizer-N application. Based on a long-term tillage experiment initiated in Lishu Conservation Tillage Research and Development Station by Chinese Academy of Sciences, we conducted a 15 N tracing field micro-plot experiment to investigate the effects of reducing nitrogen application on maize yield and fertilizer-N transformation under long-term conservation tillage agroecosystem. There were four treatments, including conventional ridge tillage (RT), no-tillage with 0% (NT0), 100% (NTS) maize straw mul-ching, and 20% reduced fertilizer-N plus 100% maize stover mulching (RNTS). The results showed that after a complete cultivation round, the average percentages of fertilizer N recovery in soil residues, crop usage, and gaseous loss were 34%, 50%, and 16%, respectively. Compared with conventional ridge tillage, no-tillage with maize straw mulching (NTS and RNTS) significantly increased the use efficiency of fertilizer N in current season by 10% to 14%. From the perspective of N sourcing analysis, the average percentage of fertilizer N absorbed by crop parts (including seeds, straws, roots, and cobs) to the total N uptake reached nearly 40%, indicating that soil N pool was the main source of N for crop uptakes. In comparison with conventional ridge tillage, conservation tillage significantly increased total N storage in 0-40 cm by reducing soil disturbance and increasing organic inputs, and thus ensured the expansion and efficiency increment of soil N pool in degraded Mollisols. Compared with conventional ridge tillage, NTS and RNTS treatments significantly increased the maize yield from 2016 to 2018. In all, by improving fertilizer nitrogen utilization efficiency and maintaining the continuous supply of soil nitrogen, long-term management of no-tillage with maize straw mulching could achieve a stable and increasing maize yield in three consecutive growing seasons and simultaneously reduce environmental risks derived by fertilizer-N losses, even under the condition of 20% reduction of fertilizer-N application, and thus actualize the sustainable development of agriculture in Mollisols of Northeast China.

To investigate the effects of no-tillage and different amounts of stover mulch on soil microbial community composition and their residues, we set up a field experiment of different amounts of stover mulch under no-tillage on the long-term maize conservation tillage station located in the Mollisols area of Northeast China (built in 2007), including without stover mulch (NT0), 1/3 stover mulch (NT1/3), 2/3 stover mulch (NT2/3) and full stover mulch (NT3/3), and the conservation tillage (plowing without stover mulch, CT) as control. We analyzed phospholipid fatty acid, amino sugar biomarker and soil physicochemical properties at different soil layers (0-5 cm, 5-10 cm, 10-20 cm). The results showed that compared to CT, no-tillage without stover mulch (NT0) did not affect soil organic carbon (SOC), total nitrogen (TN), dissolved organic carbon and nitrogen (DOC, DON), water content, microbial community and their residue. The main effects of no-tillage and stover mulch were found in the topsoil. Specifically, the NT1/3, NT2/3 and NT3/3 significantly increased SOC content by 27.2%, 34.1% and 35.6%, respectively, phospholipid fatty acid content was significantly increased under NT2/3 and NT3/3 by 39.2% and 65.0%, respectively, and NT3/3 significantly increased the content of microbial residue-amino sugar by 47.2% in the depth of 0-5 cm compared with CT. The variations in soil properties and microbial community induced by no-tillage and different amounts stover mulch decreased with soil depth, with almost no difference in the 5-20 cm soil layer. SOC, TN, DOC, DON, and water content were the main factors influencing the composition of the microbial community and the accumulation of microbial residue. Microbial biomass was positively correlated with microbial residue, particularly fungal residue. In conclusion, all stover mulch treatments promoted SOC accumulation to different degrees. When there is sufficient stover, it is advisable to opt for no-tillage with full stover mulch, as it is most conducive to the increases of soil microbial biomass, microbial residue and SOC. In case when the amount of stover is inadequate, however, no-tillage with 2/3 stover mulch can still improve soil microbial biomass and SOC content. This study would provide practical guidance for stover management in conservation tillage and sustainable agricultural development in the Mollisols area of Northeast China.

We examined the effects of fertile soil layer construction technology on soil fertility and maize yield with a 3-year field experiment in Albic soil in Fujin, Heilongjiang Province. There were five treatments, including conventional tillage (T15, without organic matter return) and fertile soil layer construction methods [deep tillage (0-35 cm) with straw return, T35+S; deep tillage with organic manure, T35+M; deep tillage with straw and organic manure return, T35+S+M; deep tillage with straw, organic manure return and chemical fertilizer, T35+S+M+F]. The results showed that: 1) compared with the T15 treatment, maize yield was significantly increased by 15.4%-50.9% under fertile layer construction treatments. 2) There was no significant difference of soil pH among all treatments in the first two years, but fertile soil layer construction treatments significantly increased soil pH of topsoil (0-15 cm soil layer) in the third year. The pH of subsoil (15-35 cm soil layer) significantly increased under T35+S+M+F, T35+S+M, and T35+M treatments, while no significant difference was observed for T35+S treatment, compared with T15 treatment. 3) The fertile soil layer construction treatments could improve the nutrient contents of the topsoil and subsoil layer, especially in the subsoil layer, with the contents of organic matter, total nitrogen, available phosphorus, alkali-hydrolyzed nitrogen and available potassium being increased by 3.2%-46.6%, 9.1%-51.8%, 17.5%-130.1%, 4.4%-62.8%, 22.2%-68.7% under the subsoil layer, respectively. The fertility richness indices were increased in the subsoil layer, and nutrient contents of the subsoil layer were close to those of topsoil layer, indicating that 0-35 cm fertile soil layer had been constructed. 4) Soil organic matter contents in the 0-35 cm layer were increased by 8.8%-23.2% and 13.2%-30.1% in the second and third years of fertile soil layer construction, respectively. Soil organic carbon storage was also gradually increased under fertile soil layer construction treatments. 5) The carbon conversion rate of organic matter was 9.3%-20.9% under T35+S treatment, and 10.6%-24.6% under T35+M, T35+S+M, and T35+S+M+F treatments. The carbon sequestration rate was 815.7-3066.4 kg·hm -2 ·a -1 in fertile soil layer construction treatments. The carbon sequestration rate of T35+S treatment increased with experimental periods, and soil carbon content under T35+M, T35+S+M and T35+S+M+F treatments reached saturation point in the experimental second year. Construction of fertile soil layers could improve the fertility of topsoil and subsoil and maize yield. In term of economic benefits, combination application of maize straw, organic material and chemical fertilizer within 0-35 cm soil, cooperating with conservation tillage, is recommended for the Albic soil fertility improvement.

In recent years, the degradation of cropland soils in Northeast China, such as "thinned, barren, and hardened", has become increasingly serious, with consequences on sustainable development of agriculture. Based on the data from Soil Types of China (1980s) and Soil Series of China (2010s), we examined the change patterns of soil nutrient conditions across different regions and soil types in Northeast China over the past 30 years through the statistical analysis of large samples. The results showed that: 1) from the 1980s to the 2010s, soil nutrient indicators in Northeast China changed to different degrees. Soil pH decreased by 0.03. Soil organic matter (SOM) content decreasd most prominently, by 8.99 g·kg -1 or 23.6%. Soil total N (TN), total P (TP) and total K (TK) contents showed increasing trends, with increases of 17.1%, 46.8%, and 4.9%, respectively. 2) Changes in soil nutrient indicators differed across different provinces and cities. Soil acidification in Liaoning was the most obvious, with pH decreasing by 0.32. SOM content in Liaoning decreased most significantly, by 31.0%. Soil TN, TP, and TK contents in Liaoning increased most significantly by 73.8%, 248.1% and 44.0%, respectively. 3) The changes of soil nutrients varied greatly among soil types, with brown soil and kastanozems showing the greatest decrease in pH. The SOM content of all soil types showed a decreasing trend, with 35.4%, 33.8% and 26.0% reduction in brown soil, dark brown forest soil and chernozem respectively. The greatest increase in TN, TP and TK contents were observed in brown soil by 89.1%, 232.8%, and 48.5%, respectively. In summary, declining organic matter content and soil acidification were the core problems of soil degradation in Northeast China from the 1980s to the 2010s. Reasonable tillage methods and targeted conservation strategies are critically needed to ensure the sustai-nable development of agriculture in Northeast China.

Understanding the effects of different fertilization treatments on microbial functional diversity in loess tableland wheat soil in south Shanxi Province can provide the theoretical basis from the perspective of microbial functional diversity for chemical fertilizer reduction, wheat yield increase, and soil fertility improvement in dryland soil. We conducted a long-term field experiment with seven fertilization treatments in winter wheat cultivation area of loess tableland in south Shanxi Province, including straw charcoal fertilizer (SF), bacterial fertilizer (BF), organic fertilizer (OF), humic acid fertilizer (HF), monitoring fertilizer (MF), farmer fertilizer (FF) and no fertilizer (CK). We employed Biolog-ECO microplate technique to investigate the differences of carbon source utilization capacity and functional diversity of soil microorganisms. The results showed that all the fertilization treatments could improve the metabolic activity and functional diversity of soil microbial community. Carbon source utilization was the most efficient in SF, with the overall soil microbial utilization ability of the 31 carbon sources and the utilization ability of different guilds of carbon sources being improved. Functional diversity, richness, and dominance based on microbial carbon sources utilization were significantly higher in SF treatment than that under other five treatments, and the evenness was higher than BF. Results of principal component analysis (PCA) and biclustering heatmap analysis showed that different fertilization treatments had significant effects on the metabolic function of microbial community. SF treatment could promote the functional diversity of soil microbial community, especially for the utilization of carbohydrates, carboxylic acids and amino acids. In conclusion, straw charcoal fertilizer had positive effects on soil microbial activity in wheat soil of loess tableland in south Shanxi Province.

We comprehensively quantified the influence of cover crops on soil carbon and nitrogen storage in Chinese orchards by a meta-analysis based on the literature published during 1990 to 2020. The factors influencing soil carbon and nitrogen storage were also analyzed. The results showed that compared with clean tillage, soil carbon and nitrogen storage under the cultivation of cover crops considerably increased by 31.1% and 22.8%, respectively. Intercropping legumes enhanced soil organic carbon storage by 4.0% and total nitrogen storage by 3.0% compared with non-legumes. The effect of mulching duration was most prominent at 5-10 years, with 58.5% and 32.8% increases in soil carbon and nitrogen storage, respectively. The largest increase in soil carbon and nitrogen storage (32.3% and 34.1%, respectively) occurred in areas with low initial organic carbon (<10 g·kg -1 ) and total nitrogen (<1.0 g·kg -1 ). In addition, suitable mean annual temperature (10-13 ℃) and precipitation (400-800 mm) markedly contributed to soil carbon and nitrogen storage in the middle and lower reaches of the Yellow River. The findings indicated that multiple factors influence the synergistic changes in soil carbon and nitrogen storage in orchards, while intercropping with cover crops is an effective strategy for enhancing soil carbon and nitrogen sequestration.

The effects of nitrogen fertilizer and biochar on topsoil quality in the drylands of northwest China were studied in field trials for two years. A split plot design with two factors was adopted, with five nitrogen rates (0, 75, 150, 225 and 300 kg N·hm -2 ) as main plots, and two rates of biochar (0 and 7.5 t·hm -2 ) as submain plots. We collected soil samples at 0-15 cm depth after two years of winter wheat-summer maize rotation and measured physical, chemical, and biological properties. The minimum data set (MDS) was established by using principal component analysis and correlation analysis to analyze the responses of soil quality to nitrogen fertilizer and biochar addition. The results showed that the combined application of nitrogen fertilizer and biochar could improve soil physical properties, increase macroaggregate content, reduce soil bulk density, and increase soil porosity. Both fertilizer application and biochar application had a significant effect on soil microbial biomass carbon and nitrogen. The application of biochar could improve soil urease activity and the contents of soil nutrients and organic carbon. Six out of 16 indicators (urease, microbial biomass carbon, total phosphorous, total nitrogen, pH, and available potassium) relating to soil quality were used to construct MDS, and soil quality index (SQI) was calculated. The variation range of SQI was 0.14-0.87, with that of 225 and 300 kg N·hm -2 nitrogen application combined with biochar application being significantly higher than other treatments. Soil quality could be significantly improved by application of nitrogen fertilizer and biochar. Interactive effect was observed, which was particularly stronger under high nitrogen application rate.

To determine the optimal planting density under wide-width sowing condition, we investigated the effects of different planting densities on photosynthetic characteristics of flag leaves, senescence characteristics of flag lea-ves and roots, grain yield, and water use efficiency under four planting density levels, 90×10 4 plants·hm -2 (D 1 ), 180×10 4 plants·hm -2 (D 2 ), 270×10 4 plants·hm -2 (D 3 ) and 360×10 4 plants·hm -2 (D 4 ), in field condition set in Yanzhou, Shandong during the growing season of 2018-2019 and 2019-2020. The results showed that compared with D 1 and D 4 treatments, D 2 treatment significantly improved photosynthetic characteristics of wheat flag leaves during grain filling, increased the activity of superoxide dismutase (SOD) and soluble protein content, reduced the malondialdehyde (MDA) content, and delayed the senescence of flag leaves and roots. Compared with other treatments, D 2 treatment significantly increased root length, root surface area and root volume in 0-40 cm soil layer. Compared with D 1 , D 3 and D 4 treatments, the grain yield of D 2 treatment was increased by 11.8%, 2.5%, 6.4% in 2018-2019 and 22.7%, 5.7%, 17.1% in 2019-2020, respectively. In addition, water use efficiency was increased by 9.2%, 8.8%, 14.2% in 2018-2019 and 21.1%, 6.2%, 21.5% in 2019-2020, respectively. The planting density at 180×10 4 plants·hm -2 improved photosynthetic characteristics of flag leaves and root morphology during filling stage, delayed plant senescence, increased grain number per spike and grain weight. Consequently, the highest grain yield and water use efficiency were obtained under D 2 treatment, which was the optimal treatment under the experimental wide-width sowing condition.

By combining the composting process with soil culture experiment, we conducted an experiment with four treatments, including conventional chemical fertilizer (CK), chemical fertilizer + compost maturity reaching 50% germination index (GI, the same below) organic fertilizer (CO1), chemical fertilizer + compost maturity reaching 80% GI organic fertilizer (CO2), chemical fertilizer + compost maturity reaching 100% GI organic ferti-lizer (CO3). We measured soil microbial biomass nitrogen (MBN), mineral nitrogen (NH 4 + -N, NO 3 - -N), net nitrification rate, microbial biomass carbon (MBC), dissolved organic carbon (DOC), soil urease and soil protease, aiming to reveal the regulatory effect of soil MBN on mineral nitrogen. The results showed that organic fertilizer application significantly increased MBN and NH 4 + -N concentrations by 50.1%-62.4% and 109.9%-147.1%, reduced NO 3 - -N concentration and net nitrification rate by 23.3%-46.8%, and 26.2%-51.5%, and enhanced MBC, DOC, urease and protease activities by 33.8%-69.6%, 7.4%-20.8%, 11.2%-69.0% and 9.4%-25.1%, respectively. The change ranges of CO2 and CO3 were significantly higher than CO1. Redundancy analysis (RDA) and structural equation model (SEM) results showed that the application of organic fertilizer with higher degree of maturity (GI≥80%) positively regulated soil MBC, MBN, NH 4 + -N, and the activities of urease and protease, but had a negative effect on soil net nitrification rate. The combined application of chemical fertilizers and high decomposed organic fertilizers could significantly increase soil MBN and NH 4 + -N contents, as well as soil urease and protease activities, but reduce soil net nitrification rate. To efficiently utilize organic solid wastes, it is recommended to use chemical fertilizer in combination of organic fertilizers with 80% decomposing degree in practical production to reduce the cost in both economy and time.

We conducted a two-factor split-plot experiment to examine the alteration of soil inorganic phosphorus forms and phosphorus availability under straw mulching and phosphorus fertilizer rates. The main factor was straw mulching and non-mulching, while the sub-factor was phosphorus supply rates, including 0, 75, and 120 kg·hm -2 . We analyzed the characteristics of phosphorus adsorption-desorption, the content of inorganic phosphorus components and their relationship with available phosphorus in hilly upland purple soil in Sichuan. Results showed that compared with the non-mulching, the maximum phosphorus adsorption capacity of straw mulching was notably decreased by 7.7% and 7.4% in the two experimental years from 2018 to 2020. The degree of phosphorus saturation and readily desorbable phosphorus of straw mulching were remarkably increased by 35.4% and 21.6% in 2019 and 18.6% and 35.2% in 2020, respectively. The maximum buffer capacity of phosphorus was not different between straw mulching and non-mulching. The maximum phosphorus adsorption capacity and maximum buffer capacity of phosphorus were significantly lower, and the degree of phosphorus saturation was notably higher in the phosphorus application treatment than that under no phosphorus treatment. The readily desorbable phosphorus increased with the increases of phosphorus rates. The contents of dicalcium phosphate (Ca 2 -P), octa-calcium phosphate (Ca 8 -P) and iron phosphorus (Fe-P) in straw mulching treatment were notably higher than those in non-mulching treatment, whereas the content of aluminum phosphorus (Al-P) significantly lower under the straw mulching. Meanwhile, the contents of occluded phosphate (O-P) and apatite (Ca 10 -P) tended to decrease in the straw mulching compared with that under the non-mulching. Phosphorus application increased the content of different inorganic phosphorus components. Compared with the non-mulching, soil available phosphorus content and the phosphorus activation coefficient of straw mulching remarkably increased by 23.2% and 21.3% in 2019, and 9.6% and 8.9% in 2020, respectively. Soil available phosphorus content and phosphorus activation coefficient increased with the increases of phosphorus rate. Results of regression analysis showed that the contribution of inorganic phosphorus components to the availability of available phosphorus in purple soil was Ca 2 -P > Fe-P > Al-P > Ca 8 -P > Ca 10 -P > O-P. Therefore, straw mulching combined with a reasonable phosphorus fertilizer rate could promote the decomposition and transformation of insoluble soil phosphorus to moderately active or easily absorbed phosphorus forms, reduce soil phosphorus adsorption, stimulate soil phosphorus desorption, and improve soil phosphorus availability. Based on the economic benefits, phosphate fertilizer application at the rate of 75 kg·hm -2 combined with straw mulching was recommended in Sichuan hilly dryland, which would be more beneficial in improving soil phosphorus availability.

To clarify the effects of tillage with mulching on potato yield and soil water and heat characteristics, we conducted a field experiment for two consecutive years in arid region of southern Ningxia. The results showed that tillage depths and mulching materials had significant impacts on soil water storage at 0-100 cm layer during the potato sowing period. The interactive effects of tillage depths and mulching materials were not significant. In 2019, the highest soil water storage was obtained in the subsoiling 30 cm with plastic film mulching, while soil water storage under the subsoiling 40 cm with straw mulch was the highest in 2020. Subsoiling 30 cm with plastic film mul-ching and subsoiling 40 cm with straw mulch significantly increased soil water storage by 16.9% and 33.4% compared with the plowing 15 cm with no mulch (CK), respectively. Tillage depths and mulching materials significantly affected soil water storage in the key growth period of potato. Among the tillage systems, the straw mulching plots and plastic film mulching plots had the strongest effect of soil water conservation. Irrespective of the mulching materials, soil water storage was significantly improved in the subsoiling 30-40 cm plots. Mulching materials and the interaction between tillage depths and mulching materials significantly affected soil effective accumulated temperature at 0-25 cm soil layer after sowing to budding. Among the tillage systems, the plastic film mulching plots significantly increased the average soil effective accumulated temperature by 9.3%, whereas the straw mulching plots significantly reduced the temperature by 18.7%, in comparison with no mulching plots. The highest soil effective accumulated temperature during the whole growth period was obtained in the subsoiling 30 cm with plastic film mulching and subsoiling 40 cm with plastic film mulching treatments in 2019 and 2020. The highest potato tuber yield and economic benefit in 2019 were found in the subsoiling 30 cm with straw mulching treatment, respectively, being 84.6% and 107.9% higher than CK. In 2020, the improvement effect of subsoiling 40 cm with straw mulch on potato tuber yield and economic benefit was the strongest, respectively, which were significantly increased by 81.7% and 105.7%, compared with CK. Tillage depths and mulching materials had significant interactive effects on the water and heat use efficiency of crop. The higher water use efficiency was obtained in the subsoiling 30-40 cm with straw mulch treatments, whereas the accumulated temperature use efficiency was increased significantly under different tillage depths with straw mulching treatments compared with CK. Soil water and effective accumulated temperature during the tuber formation stage were the main factors affecting potato total yield, with stronger effect of soil water than that of soil effective accumulated temperature. Therefore, the treatments of subsoiling 30-40 cm with straw mulch could improve soil moisture and heat condition, and realize potato yield and income increase and efficient use of water and heat resources, which have application and popularization value in dryland potato cultivation of southern Ningxia.

Sustainable intensification in agriculture (SI) is a realistic pathway to ensure global food security and deal with famine, poverty, and climate change. We constructed a SI research framework using methods such as literature, induction, and deduction. We reviewed the progress of SI research from four aspects, including the conceptual origin, index system, research scale, and evaluation methods. We discussed the future development path to provide reference for deepening related research of SI and its relation from the multi-disciplinary angle. There are many kinds of research on SI across the world, which give rich connotations to SI based on multiple dimensions of productivity, economy, environment, and society. The evaluation of SI involves productivity, economy, environment, human and society. It has formed a comprehensive evaluation system such as material input, resource productivity, environmental and economic efficiency, and other multiple indicators. Moreover, the evaluation methods of SI mainly include the factor comprehensive evaluation method and index model evaluation method. Studies on SI are not abundant in China, which needs to be enriched. We should break through the constraints of traditional theoretical and methodological frameworks, focus on the transformative scientific issues brought by international development, and explore the research paradigm of SI from the cross-disciplinary perspective.

To clarify the impacts of long-term different fertilization modes on the soil acid hydrolysable organic nitrogen and its components in the double-cropping rice field of southern China, a long-term (36-year) location field experiment was used as a platform to systematically analyze the variations of soil acid hydrolysable organic nitrogen and its components (amino acid nitrogen, amino sugar nitrogen, ammonium nitrogen, unidentified hydrolysable nitrogen) at 0-10 cm and 10-20 cm soil layers under four fertilization treatments, including chemical fertilizer alone (CF), rice straw and chemical fertilizer (RF), 30% organic manure and 70% chemical fertilizer (OM), and control (CK). The relationships of soil acid hydrolysable organic nitrogen content and soil total nitrogen, soil organic carbon content were also analyzed. The results showed that compared with CK, OM and RF treatments significantly increased the contents of total nitrogen, available nitrogen, and organic carbon at both soil layers. The contents of soil acid hydrolysable organic nitrogen at 0-10 cm and 10-20 cm layers of OM, RF and CF treatments were 10.7%-42.6% and 12.2% -51.5% higher than that of CK, respectively. Compared with CF and CK treatments, OM and RF treatments significantly increased the contents of amino acid nitrogen, ammonium nitrogen, unidentified hydrolysable nitrogen and amino sugar nitrogen contents atboth soil layers. The soil acid hydrolysable organic nitrogen and non-hydrolysable nitrogen contents at 0-10 cm and 10-20 cm paddy soils under different fertilization treatments decreased in an order of OM>RF>CF>CK. The contents of soil amino acid nitrogen, ammonium nitrogen, amino sugar nitrogen and non-hydrolysable nitrogen at 0-10 cm soil layer of each fertilization treatment were higher than those at 10-20 cm soil layer. In addition, the contents of soil acid hydrolyzed organic nitrogen were positively correated with the contents of soil total nitrogen and soil organic carbon. In conclusion, RF and OM treatments were beneficial to increase organic nitrogen content at 0-10 and 10-20 cm soil layers of double cropping paddy fields, with postive consequences on nitrogen supply capacity and soil fertility.

The planting effect and the planting potential of 12 cover crops (Leguminous: alfalfa, smooth vetch, hairy vetch, red clover, white clover, common vetch; non-leguminous: sudangrass, green radish, Nitro radish, rape, kale, endive) in the Sanjiang Plain of Northeast China were comprehensively evaluated by soil penetration resistance, pre-winter biomass, root characteristics, and plant nitrogen accumulation. The results showed that all the 12 cover crops grew normally during the experimental sowing period. Compared with the control, all the cover crops successfully reduced soil compactness. The planting of green radish, nitro radish, and sudangrass decreased soil penetration resistance by 47.1%, 43.4% and 33.4%, respectively. The pre-winter total fresh biomass of cover crop populations was between 3.38 and 13.98 kg·m -2 , and the total dry matter mass was between 0.78 and 2.43 kg·m -2 . The biomass of non-leguminous cover crops was significantly higher than that of the leguminous cover crops. The group roots of radish, rape and endive had large volumes. In particular, the nitro radish roots had a vo-lume of 4018.5 cm 3 ·m -2 , and the root system of sudangrass extended over the widest horizontal range. The ash content of leguminous cover crops was significantly lower than that of non-leguminous species, which could provide more organic matter with high decomposability. The total nitrogen accumulation of cover crops varied from 18.72 to 53.09 g·m -2 . Kale and endive accumulated the highest amount of nitrogen and large biomass, which could facilitate nitrogen fixation and accumulation. According to the type of main crops in Sanjiang Plain and canopy structure, planting leguminous (clover, vetch, and alfalfa) and non-leguminous (radish, kale and sudangrass) cover crops to plant inter-row or in a line mixed cropping pattern could regulate soil structure and promote nutrient cycing, with positive effects on the fertility of black soil in the Sanjiang Plain.

Elucidating the interannual variation of soil organic nitrogen fractions and its response to straw returning is of great significance for rational regulation of soil organic nitrogen pool and sustainable soil utilization. We conducted a field microcosm experiment with typic hapludoll soil at the National Field Observation and Research Station of Shenyang Agroecosystems. Three treatments were set, including nitrogen fertilizer addition (200 kg N·hm -2 , the same in other treatments), nitrogen fertilizer addition with 50% straw return, and nitrogen fertilizer addition with 100% straw return. We classified soil organic nitrogen fractions in the 1st, 3rd, 6th, and 9th years of the experiment by using the Bremner acid hydrolysis method. The results showed that the content of amino acid nitrogen increased with the tillage years, with an increase rate of 39.8% compared with 1st year. The content of hydrolyzable unknown nitrogen increased by 10.8% compared with 1st year, which reached the highest in the 3rd year. The content of total soil nitrogen and other organic nitrogen fractions showed limited variation with tillage years. The proportion of hydrolyzable total nitrogen that is relatively easy to mineralize in the total soil nitrogen gradually increased with the tillage years, and that of relatively stable acid insoluble nitrogen to total soil nitrogen gradually decreased, indicating that soil nitrogen availability increased with the tillage years, which would facilitate the soil nitrogen supply capacity. Compared with the treatment without straw returning, adding straw improved soil total nitrogen and each hydrolyzable nitrogen contents, with such positive effect be stronger under the treatment with heavier straw returning. The effect of straw returning on hydrolyzable nitrogen fractions mainly occurred in the 6th and 9th years. The components of soil total nitrogen that have been increased were mainly the amino acid nitrogen and hydrolyzed unknown nitrogen, resulting in increased proportion of hydrolyzable nitrogen. Straw returning could increase soil nitrogen pool and improve soil nitrogen conservation and supply capacity.

We conducted an experiment with five treatments in winter wheat of the dryland of Northwest China, i.e . 30 t·hm -2 cow dung (M) plus different doses of nitrogen fertilizer (0, 75, 150, 225, and 300 kg N·hm -2 ), denoted by M+N 0 , M+N 75 , M+N 150 , M+N 225 , and M+N 300 , respectively. After three years of treatment, wheat yield, grain quality, and soil biological characteristics were measured in two consecutive years (2018 and 2019). The results showed that the combination of manure with nitrogen fertilizer significantly increased wheat yield compared with the manure-only treatment (M+N 0 ). Compared with the manure-only treatment, the combined treatments significantly increased wheat grain protein content, wet gluten, sedimentation value, and extensibility, but not for starch content. Neither wheat yield nor grain quality had significant differences among the M+N 150 , M+N 225 , and M+N 300 treatments, but both were prominently higher than those of M+N 75 . Soil microbial biomass carbon (MBC) and nitrogen (MBN) reached highest in M+N 150 for both years, which were distinctly higher than those of M+N 0 , M+N 225 , and M+N 300 . In 2018, soil β-1, 4-glucosidase, cellobiohydrolase, L-leucine aminopeptidase, β-1,4-N-acetyl glucosaminidase, and alkaline phosphatase activities in M+N 150 treatment were higher than those of other treatments. In 2019, soil enzyme activities (excluding L-leucine aminopeptidase) in M+N 150 were higher than those of M+N 0 and M+N 225 . MBC significantly positively correlated with MBN, and both significantly positively correlated with the activities of cellobiohydrolase, β-1, 4-N-acetyl glucosaminidase, and alkaline phosphatase. MBN significantly positively correlated with total nitrogen content and negatively correlated with NO 3 - . Considering winter wheat yield, grain quality, and soil biological characteristics, M+N 150 was conducive to sustainable production of winter wheat in drylands of Northwest China.

Evaluating ecological sustainability and crop productivity of different crop rotation patterns could provide theoretical support for adjusting and optimizing crop planting structure. We set seven treatments with different rotation crops and periods. We used real-time quantitative PCR to determine the abundance of soil bacterial community and 16S rRNA gene amplicon high-throughput sequencing technology to analyze diversity and taxa composition of soil bacterial community. Both soil available nutrients and succeeding wheat yield were measured. The results showed that, compared with the rotation with summer maize, the rotations with summer peanut or soybean in diffe-rent periods reduced soil organic carbon, mineral nitrogen, and available potassium, but significantly increased soil available phosphorus. The 16S rRNA gene copy numbers of soil bacteria in the treatments of rotations with summer peanut or soybean in different periods were significantly decreased, while community richness and diversity were increased. Different rotation crops significantly changed the structure and taxonomic composition of soil bacterial community. Compared with the rotation with summer maize, the rotations with summer soybean in different periods significantly increased the 1000-grain weight and grain yield of succeeding winter wheat. In conclusion, rotations with summer peanut or soybean in different periods could increase soil available phosphorus content and bacterial diversity, and significantly change soil bacterial community structure. In particular, rotation with summer soybean performed best in promoting yield formation of succeeding winter wheat.

There is close relationship between fertilizer managements and net carbon (C) sink effect, economic benefits in rice paddy ecosystem. Based on a long-term (35-year) field experiment, we analyzed the effects of different fertilization patterns on soil C sequestration rate, C density of topsoil, annual C balance, and economic benefits in the double cropping rice paddy in southern China. There were four fertilization treatments, chemical fertilizer alone (MF), rice straw and chemical fertilizer (RF), 30% organic manure and 70% chemical fertilizer (OM), and without any fertilizer input as a control (CK). The results showed that soil C pool in the double cropping rice paddy field under different fertilization treatments changed from 216.02 to 866.74 kg·hm -2 ·a -1 , and soil C pool under OM treatment were significantly higher than that of MF, RF and CK. The soil C sequestration rates in the double cropping rice paddy field under different fertilization treatments ranged from 51.5 to 650.7 kg·hm -2 ·a -1 , and that of C density of topsoil was from 55.64 to 78.42 t·hm -2 . The order of soil C sequestration rates and C density of topsoil was OM>RF>MF>CK. The change range of C adsorption in the double cropping rice paddy field ecosystem was from 4.42 to 9.32 t C·hm -2 ·a -1 , with an order of OM>RF>MF>CK. Compared with the MF treatment, soil net C sink under OM and RF treatments increased by 27.6% and 13.6%, respectively. The change range of C cost material input ranged from 1.49 to 2.17 t C·hm -2 ·a -1 , and that of annual economic benefits was from 1.30×10 3 to 7.83×10 3 yuan·hm -2 ·a -1 with an order of RF>OM>MF>CK. The net income of economic benefits of OM, RF and MF treatments were significantly higher than that of CK. Generally, soil C sequestration rate, C sink effect and annual economic benefits were increased by the long-term application of organic manure and rice straw returning together with chemical fertilizer, which could increase soil organic carbon storage in the double cropping rice paddy field of southern China.

Using peanut cultivar Huayu 25 and cotton cultivar Liaomian 19 as experimental material, we examined the effects of different intercropping patterns on physiological characteristics of peanut in later growth stage, yield and economic benefit, based on an experiment with five treatments, including intercropping modes of 4 rows peanut and 4 rows cotton (H 4 M 4 ), 6 rows peanut and 4 rows cotton (H 6 M 4 ), 4 rows peanut and 4 rows cotton (H 4 M 2 ), sole peanut (DH) and sole cotton (DM). The results showed that intercropping mode increased the length of main stem and branches of peanut, but decreased green leaves number of main steam, leaf area index, and total dry matter accumulation. Among the intercropping modes, chlorophyll content, chlorophyll fluorescence parameters, root vigor, nitrate reductase activity under H 6 M 4 and H 4 M 2 were significantly higher than that under H 4 M 4 , as well as higher superoxide dismutase, peroxidase, catalase activity and decreased malondialdehyde content. Intercropping significantly reduced peanut and cotton yields, but enhanced the gross economic output value. The yield reduction of H 6 M 4 was the lowest and the economic output was the highest among all the intercropping modes. In addition, the land equivalent ratio of H 6 M 4 was greater than 1, indicating the obvious advantage of intercropping. Our results indicated that appropriate reduction of the ratio of cotton under the peanut-cotton intercropping systems could strengthen root vigor and increased nitrate reductase activity, promote nutrient absorption capacity, reduce senescence, and increase the economic output.

To clarify the desiccation effect of deep soil and water footprint of crop production in two typical dry-farming apple orchards on the Loess Plateau of China, with Luochuan County in semi-humid region and Mizhi County in semi-arid region as two typical apple planting areas, we used the WinEPIC model to quantitatively simulate and analyze the variations of soil moisture from 0 to 15 m and water footprint of apple production during 1980-2020. The results showed that annual yield of mature orchards in Luochuan and Mizhi followed an "S" curve, with the average annual values being 24.64 and 18.42 t·hm -2 , respectively. The average annual evapotranspirations of Luochuan and Mizhi were 623.82 and 458.97 mm, the average annual drought stress days of Luochuan and Mizhi were 20.4 and 52.73 days, and the water overconsumption were 167.94 and 121.15 mm, respectively. The available soil water contents in Luochuan and Mizhi showed a sharp decline from 1 to 25 years old and from 1 to 23 years old, respectively, with average annual soil desiccation rates being 64.6 and 68.03 mm·a -1 , respectively. The dry layer of deep soil for the orchards of Luochuan and Mizhi appeared at the 13th and 7th years, and would be stable after 23 and 22 years, respectively. The formation and stability time of the soil dry layer in the area with high precipita-tion was later than that with low precipitation. Long-term soil moisture deficit would result in irreversible soil dry layer. Water footprint of apple production in Luochuan and Mizhi were low in the early stage and high in the later stage, with the average annual values being 0.187 and 0.194 m 3 ·kg -1 , respectively. Both apple yield and production water footprint were affected by precipitation. To ensure the sustainable and healthy development of apple industry, it was recommended that the optimal planting age of apple trees is about 23 years on the Loess Plateau where water sources is limited, and the maximum should not exceed 25 years.

Exploring the spatio-temporal variation characteristics of carbon source and carbon sink under different disposal methods of crop straw is of great significance for optimizing the utilization policy of crop straw resources in China and realizing the goal of maximizing carbon emission reduction and carbon neutralization. Based on data from National Statistical Yearbook, we examined the changing trends of both the amount and value of carbon emission, carbon emission reduction, carbon sink enhancement under different crop straw disposal methods in 31 provinces of Chinese mainland. The results showed that the mean annual carbon emissions of straw burning in China from 2008 to 2019 were 8.74 million tons of CO 2 e. Since 2014, the mean annual reduction rate of carbon emissions was 17.3%. The mean annual carbon emission reduction of energy utilization was 39.82 million tons of CO 2 e, with solid briquette fuel produced by straw contributing the most with a contribution of about 98%. The amount of carbon sequestration of straw returning to field was increasing annually, with an average annual value of 271 million tons of CO 2 e. There was a carbon ecological surplus in straw disposal in China. The annual growth rate of net carbon emission reduction was 9.8%. The net carbon emission reduction intensity and its value were increasing, reaching 2.62 t·hm -2 and 76.19 yuan·hm -2 in 2019, respectively. A spatial pattern of 'high in the east and low in the west' was observed for the mean annual carbon emissions of straw, energy carbon emission reduction, carbon sink of straw returning to the field, and net carbon emission reduction in China, with main external characteristics of the regional differences and spatial aggregation.

It is of great significance to understand the effects of different rice cultivation methods in southeast China on greenhouse gas emission characteristics and carbon footprint of paddy fields during rice cultivation for rice sustainable production. In this study, the popular conventional rice 'Jiafuzhan' and hybrid rice 'Yongyou 2640' were used as materials to establish four rice cultivation patterns suitable for different ecological types in Fujian Province: 1) double-cropping system, early rice and late rice with Jiafuzhan (D-J); 2) early maturing ratooning system, first season rice and ratooning season rice with Jiafuzhan (R-J); 3) middle-maturing ratooning system, first season rice and ratooning season with Yongyou 2640 (R-Y); and 4) single cropping system with Yongyou 2640 (S-Y), which should be synchronized in heading time with the counterpart (the ratooning season rice). Greenhouse gas emissions from paddy soil were measured by the closed static black box observation method and the gas chromatography method, respectively. The total direct and indirect greenhouse gas emissions (carbon footprints) from different rice farming patterns were evaluated by using the life cycle analysis. The results showed that greenhouse gas emissions in different rice cropping systems were lower in the early growth stage, then decreased after reaching the peak at the booting stage, demonstrating a double peak curve in the whole growth stage, in which the first peak was higher in early season or first season than the second peak in the late season or ratooning season in the cropping patterns. Moreover, the total greenhouse gas emissions were significantly different among cropping systems. The global warming potential (GWP) of different cropping patterns was in order of R-Y>D-J>S-Y>R-J, while the annual greenhouse gas emission intensity (GHGI) was D-J>S-Y>R-Y>R-J. GWP and GHGI of the ratooning system decreased by 26.1% and 14.1%, respectively, compared with those of the double-cropping system. The same pattern was observed in the ratooning rice of Yongyou 2640, which were decreased by 74.3% and 56.7%, respectively, compared with the counterpart, Yongyou 2640 in a single-cropping system synchronized heading. Carbon footprint of rice per unit yield ranged from 0.38-1.08 kg CO 2 -eq.·kg -1 under the different cropping systems, of which the carbon footprint of rice per unit yield was the highest under the double cropping system compared with that under other cropping systems. The reverse was true in the case of carbon footprint of rice per unit yield under the ratooning system with Yongyou 2640. Additionally, the main source of carbon footprint of different rice cropping patterns was CH 4 , contributing 44.2%-71.5%, suggesting that rice ratooning system could significantly reduce global warming potential and carbon emission intensity of rice in comparison with other cropping patterns. Therefore, it is key to select rice varieties with high yield and low carbon emission and to establish the supporting scientific cultivation techniques for effective reduction of CH 4 emission and carbon footprint of paddy fields and promotion of ratooning rice production.

We examined the effects of biochar and urease inhibitors/nitrification inhibitors on nitrification process, ammonia and N 2 O emission in subtropical soil, and determined the best combination of biochar with nitrification and urease inhibitors. This work could provide a theoretical basis for the mitigation of the negative environmental risk caused by reactive nitrogen gas in the application of nitrogen fertilizer. A indoor aerobic culture test was conducted with seven treatments [urea+biochar (NB), urea+nitrification inhibitor (N+NI), urea+urease inhibitor (N+UI), urea+nitrification inhibitor+urease inhibitor (N+NIUI), urea+nitrification inhibitor+biochar (NB+NI), urea+urease inhibitor+biochar (NB+UI), urea+nitrification inhibitor+urease inhibitor+biochar (NB+NIUI)] and urea (N) as the control. The dynamics of soil inorganic nitrogen content, N 2 O emission and the volatility of ammonia volatilization were observed under combined application of biochar with urease inhibitor (NBPT)/nitrification inhibitor (DMPP). The results showed that:1)Compared to the control (5.11 mg N·kg -1 ·d -1 ) during the incubation period, NB treatment significantly increased therate constant of nitrification by 33.9%, and N+NI treatment significantly reduced the nitrification rate constant by 22.9%. NB treatment significantly increased the abundance of ammonia oxidizing bacteria (AOB) by 56.0%. 2) Compared with N treatment, N+NI and NB+NI treatments signi-ficantly enhanced the cumulative emission of NH 3 by 49%. The N+UI treatment reduced the cumulative loss of NH 3 . The inhibition effect of NB+UI treatment was more significant. 3) The emission rate of N 2 O was highest in the first 10 days after fertilization. The N 2 O emission under NB treatment was the earliest, and that of N treatment was the highest (5.87 μg·kg -1 ·h -1 ). The combined application of DMPP and NBPT performed the best in reducing soil N 2 O emission. We estimated global warming potential (GWP) of the direct N 2 O and indirect N 2 O (NH 3 ) emissions. Compared with N treatments, N+NI and NB+NI treatments increased the GWP by 34.8% and 40.9%, respectively. While the NB and NB+UI treatments significantly reduced the GWP by 45.9% and 60.5%, the combination of biochar and urease inhibitor had the best effect on reduction of GWP of soil active nitrogen emissions.

In order to optimize water and fertilizer use in the double-cropping rice in eastern Fujian Province, a field runoff plot experiment was conducted to investigate rice yield, nutrient uptake, and runoff losses of N (nitrogen) and P (phosphorus) in the T 0 (no chemical fertilization with traditional flooding irrigation), T 1 (common chemical fertilizer of 273 kg N·hm -2 , 59 kg P·hm -2 , and 112 kg K·hm -2 combined with traditional flooding irrigation), T 2 (chemical fertilizer of 240 kg N·hm -2 , 52 kg P·hm -2 , and 198 kg K·hm -2 combined with traditional flooding irrigation) and T 3 (chemical fertilizer combined with shallow intermittent irrigation) treatments. Results showed that early rice grain yield in the T 1 , T 2 and T 3 treatments significantly increased by 0.7, 1.0, 1.1 times, late rice grain yield significantly increased by 0.9, 1.1, 1.0 times compared to that in the T 0 treatment, respectively. The T 1 , T 2 and T 3 treatments significantly increased the uptake of N and P in aboveground parts of the plants, especially in grains. The T 1 , T 2 and T 3 treatments significantly increased N uptake by 1.1, 1.2, 1.2 times, increased P uptake by 0.9, 1.4, 1.6 times in early-season grains, and significantly increased N uptake by 0.8, 1.0, 1.0 times, increased P uptake by 0.7, 0.9, 0.9 times in late-season grains, compared to T 0 , respectively. Furthermore, T 3 increased agronomic N use efficiency (AEN) and agronomic P use efficiency (AEP) by 71.1% and 69.2% in early rice plants, increased AEN and AEP by 26.4% and 25.0% in late rice plants, whereas T 3 decreased total dissolved N (DN) by 16.0% in comparison with T 1 . Dissolved inorganic N loss in surface runoff occurred mainly in the form of NO 3 - -N (nitrate N) under different water and fertilizer regimes. However, there were no significant differences in AEN and AEP between T 2 and T 3 treatments. These findings suggested that optimal applications of water and fertilizers (T 3 ) might increase N and P uptake in rice plants, maintain yield, and reduce N loss, especially in the form of NO 3 - -N in surface water from early rice field. In general, this study could provide theoretical support for the optimization of irrigation and fertilization and for the control of N and P non-point source pollution from the double cropping rice paddy fields in eastern Fujian Province.

With continuous increases in the amount and duration of plastic film used, the residual film in farmland soil is accumulated and tended to be fragmented, which affects soil water infiltration. We carried out an experiment of one-dimensional vertical infiltration of soil moisture. We examined the effects of different residual film density and area on soil water cumulative infiltration under 21 experimental treatments with 5 residual film area levels (0.25, 0.5, 1, 2, 8 cm 2 ) and 5 residual film density levels (0, 60, 180, 300, 420 kg·hm -2 ). The results showed that soil water infiltration rate was accelerated and the total infiltration amount was increased by adding a certain amount of residual film into the clay loam soil with bulk density of 1.53 g·cm -3 . The total infiltration amount of different residual film area always appeared mutation or turning point when the single residual film area was 1 cm 2 . When the residual film area and density were larger or smaller than that, the cumulative infiltration amount would be significantly affected, with the treatment of 0.5 cm 2 residual film area and 200 kg·hm -2 residual film density being obvious demarcation. When the residual film area was 0.25 cm 2 , the cumulative infiltration reached the maximum. When the residual film with a single area ≤0.25 cm 2 was uniformly mixed into the soil, the slope of soil water cumulative infiltration curve was significantly different from that of other residual film treatments, forming a "new structure" soil with unique water infiltration characteristics.

A reduction of chemical fertilizers and improving fertilizer utilization rate are important for ensuring a balance between plant growth and minimizing the degradation of the black soil. We conducted a 2-year pot experiment with four treatments during 2019 and 2020, including T 0 : no fertilizer, T 1 : conventional use of chemical fertilizer, T 2 : 15% reduction of the chemical fertilizer combined with 400 kg·hm -2 of humic acid bio-fertilizer (HABF), and T 3 : 30% reduction of the chemical fertilizer combined with 600 kg·hm -2 of HABF, to examine the effect of reduction rates of chemical fertilizers combined with the HABF on soil microbial abundance, enzyme activity and nutrient content in maize cultivation. The results showed that the application of HABF significantly increased the abundance of soil bacteria and fungi, with the number of microbial colonies being positively correlated with the amount of HABF. When measured at the tassel stage of maize growth, T 2 and T 3 treatments significantly increased the activities of urease, sucrase, and catalase in soil by 11.4%-21.6%, 34.9%-46.7%, and 6.5%-13.4%, respectively. The available nitrogen contents in T 2 and T 3 treatments were higher than that in the T 1 treatment by 8.2%-18.1%, which ensured the sufficient nitrogen supply to maize after the tassel stage. Soil available phosphorus and available potassium contents increased by 17.1%-121.0% and 9.6%-57.3%, respectively, compared with T 1 treatment. With the increases of the amount of HABF, the activation effects of soil phosphorus and potassium and dry matter mass per plant increased significantly in T 2 and T 3 treatments compared with T 1 treatment. In conclusion, HABF promoted the proliferation of soil bacteria and fungi, improved activities of catalase, urease, and sucrase, soil nutrient contents, and dry matter mass per plant. The 15% reduction of chemical fertilizer combined with 400 kg·hm -2 of HABF is the most suitable nutrient management strategy for maize production in black soil.