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Appropriate fertilization is an important component for ensuring high crop yields and avoiding the disadvantages of non-point source pollution. We used the North China Plain as the study area and seven long-term experiments to investigate how different nitrogen application rates and fertilization modes (no fertilizer CK, fertilizer NPK, organic fertilizer M, organic-inorganic combined application NPKM) would affect crop yield and the efficient use of nitrogen. We found that there was a parabolic trend between crop yield and fertilization amount. The highest crop yield appeared in the combined application of organic and inorganic fertilizers and different fertilization modes affected crop yield. We found no significant difference between NPKM and NPK treatments for wheat yield, with both higher than with M and CK treatments. For maize crops, there was no significant difference in crop yield between NPKM, NPK and M although they had significantly higher yields than with CK treatment. The nitrogen utilization rate decreased with higher nitrogen application and fertilization modes had certain effects on nitrogen utilization rates. We found no significant difference in nitrogen use efficiency between NPKM and NPK treatment for wheat, but they were higher than with M treatment. There was no significant difference in nitrogen use efficiency between NPKM, NPK and M for maize. This comprehensive analysis of the effects of nitrogen application rate and fertilizer replacement ratio on wheat yield showed that, in the North China Plain, there was great potential to replace chemical fertilizers with organic fertilizers. This replacement would not significantly decrease crop yields, and possibly led to higher yields than with purified fertilizer. However, in order to avoid a significant decrease in crop yields, total N input should be determined when replacing chemical fertilizer with organic fertilizer.

The humification coefficient of input organic material(h)and decomposition rate(k)of soil organic carbon(SOC)are two key parameters that control the SOC turnover processes. Many previous studies have investigated how elements such as water and temperature can affect these processes, but how the SOC content can affect its own turnover processes is seldom concerned. We developed computer models to test the effect of the SOC content on the SOC turnover processes and its underlying mechanisms. The results showed that however h and k changed the SOC content, it also changed asymptotically with time, and eventually reached equilibrium; When assuming that these two parameters were constant with the SOC content, the SOC content would linearly increase without being limited by the C input level; The SOC content would increase asymptotically with the C input level when assuming that h decreased with the SOC content and k increased simultaneously; An asymptotic relationship between the SOC content and C input level would occur. The changes in h and k with the SOC content were termed as negative feedback to SOC turnover. Further study on the mechanisms underlying the negative feedback supported the asymptotic relationship between the SOC content and C input level. We suggest that the negative feedback of SOC turnover is reasonable, and it is necessary and possible to consider this effect in model development.

Conservation tillage has numerous ecological benefits. For example, it is conducive to the sustainable development of agricultural ecosystems. This paper compared and analyzed various studies on the effects of conventional and protective tillage measures on soil aggregates, soil organic carbon, soil microorganisms, and soil nematodes at home and abroad. The effects of conservation tillage on soil aggregates and biological characteristics were largely manifested as follows:Conservation tillage reduced the damage of large soil aggregates, reduced aggregate turnover rates, and improved the stability of soil structures. Conservation tillage increased the total surface soil contents of organic carbon and active organic carbon. Conservation tillage could increase the microbial biomass in cultivated layers, with a particularly significant impact on fungal biomass. Conservation tillage increased the microbial biomass and microbial diversity in aggregates to varying degrees, but did not change the microbial population distribution patterns in aggregates. Conservation tillage increased soil nematode abundance. It also increased the maturity and structure indexes of nematode communities in undisturbed soil and soil aggregates of all sizes, but does not change the total number of nematodes, nutritional groups, functional groups, or ecological distribution patterns of indexes in agglomerates. Based on the current research status at home and abroad, this article looks forward to the future research focus of conservation tillage with the goal of providing theoretical support for selecting conservation tillage measures in accordance with local conditions and promoting the sustainable development of agriculture in China.

The aim of this study was to quantify the effects of different mulch planting patterns on soil enzyme activity and organic carbon mineralization in a tea plantation. The cover crop diversity experiment was conducted in the Tanjiawan tea garden, Yunyang District, Shiyan City, Hubei Province. Four cover crop planting modes were set up, namely no crop cover(A0), two cover crops(A1), four cover crops (A2), and eight cover crops(A3). The enzyme activity, organic carbon mineralization rate, and cumulative mineralization of the 0~20 cm and 20~40 cm soil layers in the tea plantation were measured, and the data was fitted to the first order kinetic equation to obtain the mineralization potential(Cp)and mineralization constant(k)of organic carbon. The results showed that, the soil enzyme activity in the mulch plot was generally higher than that in the control plot, and the enzyme activity in the 0~20 cm soil layer was higher than that in the 20~40 cm layer. Different mulch types had significant effects on soil catalase and urease activity(PPCp/k value was as follows:A1 > A2 > A3 > A0. In the 20~40 cm soil layer, the Cp/k value was as follows:A1 > A2 > A0 > A3. This suggests that the organic carbon mineralization of A1 was the strongest in both soil layers. Moreover, the microbial biomass carbon and soluble organic carbon of A1 were higher than those of the other treatments, thereby providing sufficient nutrients for crop growth and development. A1 had the highest pH value, which was conducive to soil acidification.

This study was performed in a tea garden in Xupingsi Village, Tanjiawan Town, Yunyang District, Shiyan City, Hubei Province, to evaluate the effects of different mulching crop patterns on soil microbial community functions in 0~15 and 15~30 cm soil layers of the tea garden. Four treatments were selected:Natural grasses(CK), ryegrass+white clover(EZ), ryegrass+white clover+bluegrass+red clover(SZ), and ryegrass+white clover+bluegrass+red clover+purple fescue+hairy raccoon+cosmos+zinnia(BZ). The results showed that the activities of urease, invertase, catalase, and phosphatase in the 0~15 cm soil layer treated with SZ were higher than those in the other treatments; The activities of urease, catalase, and phosphatase in the 15~30 cm soil layer treated with SZ were higher than those in the other treatments, whereas the activity of invertase was lower than that in the other mulching treatments. The mulching crops increased the average well color development(AWCD)of microbial communities in the 0~15 cm soil layer; AWCD was the highest in the SZ treatment, indicating the highest utilization efficiency of the carbon source. The mulching crops improved the soil microbial richness index, evenness index, and dominance index in the 0~15 cm soil layer, but had few effects on these parameters in the 15~30 cm soil layer. The results indicate that the mulching crops can improve soil enzyme activity and microbial community functional diversity, and SZ treatment had the best effect on the 0~15 cm soil layer. The findings of this study would be able to provide a theoretical basis for analyzing the effects of different mulching crop patterns on soil functional diversity of microbial communities in tea plantations in the future.

The effect of different arrangements of grasses, flowering plants(Asteraceae), and legume crops on the number and diversity dynamics of arthropod communities was determined in a tea orchard in Xupingsi Village, Tanjiawan Town, Yunyang District, Shiyan City, Hubei Province. For this, 4 treatments were established:Natural grasses(CK), ryegrass+white clover(EZ), ryegrass+white clover+bluegrass+ red clover(SZ), and ryegrass+white clover+bluegrass+red clover+purple fescue+hairy raccoon+cosmos+zinnia(BZ). The community composition and dynamics of richness index, divesity index, and evenness index of arthropods were determined. The results showed that the arthropod community composition in the tea orchard with different cover crops was similar to that in the tea orchard with CK, with the largest number of Diptera and the least number of Araneae insects. Compared with that in the CK, the number of Lepidoptera increased significantly under the different cover crop treatments(PP>0.05). Homoptera insects increased significantly by 92.47%(PP>0.05). The dynamics of diversity, evenness, and richness indices of arthropod communities in the tea orchard with different cover crops were basically the same; The richness index was the highest on August 26 and was higher in the tea orchard with different cover crops than in that with natural grasses on September 30. The arthropod community diversity index for EZ treatment, the diversity, richness, and evenness indices for SZ treatment, and the diversity and evenness indices for BZ treatment were significantly higher than those of the CK in the tea orchard.

In May 2017, the Innovative Integration and Demonstration of Green and Efficient Agricultural Technology in Danjiangkou Water Conservation Area, belonging to the Cooperative Innovation Project of Agricultural Science and Technology Innovation Program of Chinese Academy of Agricultural Sciences, was officially launched. The aim of the cooperative project was to tackle problems in green and efficient agricultural production, planting and breeding coupling, ecological cycling, non-point source pollution control, and multi-functional rural ecosystem construction. In accordance with the ideas of single technology standardization, composite technology integration, and systematic technology systematization, the cooperative project innovatively integrated 10 key technologies that refer to the utilization of biodiversity, adjustment of agricultural planting structure, green and efficient production of main agricultural products in the whole industrial chain, new pattern of planting and breeding cycle, highly effective ecological facility agriculture, and rural domestic pollutant control in Danjiangkou. We have summarized and provided a comprehensive technical solution for green and efficient agriculture in a water conservation area, which can be copied and extended experience and used as a demonstration model for similar areas. The achievements of this project will provide effective scientific and technological support for water quality and safety in the South-to-North Water Diversion, promote green development of agriculture, increase farmer income, and alleviate poverty in water conservation areas.

To collect basic data for the comprehensive analysis and evaluation of the soil ecological effects of restoring farmland to grassland, we evaluated the various characteristics of soil nematode communities in restoring cultivated land to artificial grassland in the Danjiangkou water ecological conservation function area. In this study, three alfalfa(Medicago sativa)meadows with the same soil type and three years' fallow usage were selected as representative plots for the restoration of farmland to grassland. A maize(Zea Mays)field with adjacent unreturned cropland was used for comparison to analyze the changing characteristics of nematodes in the returned cropland soil in September 2017. The results showed that the water content was significantly increased by 15.86% and pH was significantly decreased by 5.06% in the 0~10 cm soil layer; The pH was significantly reduced by 4.57%, and effective phosphorus content was significantly reduced by 26.83% in the 10~20 cm soil layer. A total of 18 307 soil nematodes and 49 genera were identified in the alfalfa grassland, and a total of 10 706 soil nematodes and 45 genera were identified in the corn field. The soil nematode c-p group was transferred from the short-generation to the long-generation and soil environment was less disturbed. The diversity and stability increased and structural index(SI)and enrichment index(EI)showed that returning farmland to grass improved soil health and reduced the degree of soil disturbance. The number of soil nematodes was significantly correlated with soil pH, water content, total nitrogen, and nitrate nitrogen content; The relative abundance of bacterivores nematodes and fungal nematodes was significantly correlated with soil available phosphorus content; The relative abundance of plant parasitic nematodes, and catch/omnivorous nematodes was significantly correlated with organic carbon and ammonium nitrogen content and significantly correlated with total nitrogen content. The soil pH value, total N, and available P contents can be changed by restoring farmland to grassland, which can alter the community structure and diversity of soil nematodes and improve soil health.

In order to provide a theoretical basis for ecological management model in an orchard, we investigated the characteristics of soil microbial community composition under cover crop treatments in a kiwifruit orchard in the water source conservation area of Danjiangkou. We used the phospholipid fatty acid(PLFA)method to analyze the effects of different treatments(T1:Cover crop left on soil after cutting; T2:Cover crop and removed after cutting; CK:Clean tillage)on soil microbial community structure. The results showed that the total PLFAs, microbial biomass carbon, and nitrogen of cover crop treatments(T1 and T2)were significantly higher than that of CK(P

To clarify the ecological adaptability of the invasive plant Flaveria bidentis to heavy metal-contaminated habitats, we simulated habitats with different concentrations of cadmium(Cd)by pot experiments, and the plasticity of responses of growth, and physiological and ecological characteristics as well as heavy metal enrichment characteristics in response to the environmental stress were studied. Additionally, the tolerance mechanisms of plant were further explored. The results showed that high concentration heavy metal treatment(8 mg·kg-1)significantly inhibited the growth and biomass of Flaveria bidentis, both of which showed a decreasing trend with the increase of Cd concentration; The content of malondialdehyde(MDA)and the fluorescence intensity of DCF increased gradually with the increase of Cd concentration, which indicated the active oxygen content increased. Under low(2 mg·kg-1)and medium(4 mg·kg-1)concentrations of cadmium, the Flaveria bidentis reduced its active oxygen content by increasing superoxide dismutase(SOD), peroxidase(POD)and catalase (CAT)activities. However, the activities of antioxidant enzymes decreased under the high concentration(8 mg·kg-1)treatment; The content of Cd in the tissues of Flaveria bidentis showed the rule of root > leaf > stem. With the increase of Cd concentration, the content of heavy metals in the tissues increased gradually, and the Cd concentration and transfer coefficient in the roots and aboveground parts increased first and then decreased. Under heavy metal stress, the phenotypic plasticity index(PPI)of root biomass, leaf biomass and heavy metal enrichment of Flaveria bidentis was higher(>0.5),which indicated that Flaveria bidentis may accumulate nutrients mainly through root and leaf biomass processes, and regulate the enrichment and transfer of heavy metals in the body to adapt to heavy metal polluted habitats.

Farmland management measures can have a significant impact on the carbon cycle of farmland ecosystems, which can affect soil fertility, agricultural production, and food security, and more broadly, climate change and environmental health. In this paper, the effects of different farmland management measures(fertilization methods, planting systems, and farming models)on soil organic carbon, greenhouse gas emissions, and soil microorganisms were reviewed. The increase in soil organic carbon was fastest when organic and inorganic fertilizer were applied. Moreover, there was a threshold effect between the amount of fertilizer applied and the soil carbon inventory. The application of organic fertilizer increased the CO2 emissions flux in the soil, and the application of phosphorus and potassium fertilizers reduced the globe warming potential of farmland soil more than nitrogen fertilizer. Increasing the application ratio of organic fertilizer to phosphate fertilizer was beneficial, leading to an increase in microbial richness in the soil and accumulation of microbial biomass carbon. Planting structure and planting density both affected the carbon storage of farmland soil, and planting structure had a significant impact on greenhouse gas emissions in farmland ecosystems. Compared with traditional monoculture planting, crop rotation and intercropping could effectively reduce the greenhouse gas emissions of farmland. At the same time, crop rotation was more conducive to increasing soil microbial diversity than continuous cropping. Conservation tillage improved the efficiency of farmland soil carbon, reduced greenhouse gas emissions, and had a positive impact on microbial activity, diversity, community structure, and carbon source utilization. Finally, we summarized the application of international mainstream carbon models to farmland ecosystems, and present future development prospects.

As one of the epigenetic modifications, DNA methylation has become ubiquitous in plant genome DNA. It not only plays an important role in rapid adaptation to new environments but also participates in the process of plant growth and organ differentiation. In this study, we constructed an optimized MSAP system to analyze the methylation variation characteristics of different organs at different developmental stages of the same organs of Flaveria bidentis. The results showed that the organ-specific MSAP system amplified 536 bands by using 13 pairs of primers, in which the primer EhHM7 made the greatest contribution to epigenetic diversity, and the percentage of polymorphism was 92.45%. The developmental stage-specific MSAP system amplified 407 bands by using 14 pairs of primers, in which EcHM1 had the greatest contribution to epigenetic diversity, and the percentage of polymorphism was 80.56%. The results of varying themethylation type showed that there were significant differences in methylation levels among the different organs (roots, stems, and leaves)at different developmental stages of the same organs (old leaves and young leaves), among the three methylation variants of hemi-methylation, full methylation, and overall methylation, the methylation rate of the stem tissue was the highest, reaching 30.28%, 19.37% and 49.66%, respectively.The full-methylated and overall methylated rate of the old leaf tissue were significantly higher than those of the young leaf tissue, reaching 33.29% and 52.77%, respectively.The principal component analysis showed that the individual distribution of leaves of Flaveria bidentis were more intensive than that of roots and stem organs, and the young leaves were denser than the old leaves, which indicated that there were larger differences between individual roots and stems. This individual difference was greater than that of the leaves of Flaveria bidentis, and the individual difference of old leaves were greater than that of young leaves, which could not be ignored during sample collection. Therefore, during the studies on the invasiveness of Flaveria bidentis by using epigenetic methods, it is necessary to formulate a scientific sampling plan and consider plant organ and growth stage specificity as important factors.

In a rhizobox experiment with phosphorus(P) fertilizer application and P-deficiency, planting wild-type rice(Nipp), P-efficient mutant rice(PHO2), P-efficient transgenic rice(OsPT4) were chosen to evaluate effects of phosphorus efficient transgenic rice on inorganic phosphorus in the rhizosphere and non-rhizosphere soil. The obtained results were summarized as follows:(1)Significant higer dry weight and P accumulation were observed in OsPT4 and PHO2 than in Nipp, but lower total P and inorganic phosphorus observed in OsPT4 and PHO2 than in Nipp;(2)The concentrations of inorganic phosphorus fractions in the rhizosphere and non-rhizosphere soil were sorted as follows:O-P > Fe-P > Al-P > Ca-P, and the order of inorganic phosphorus fractions adapted to three rice materials;(3)When added phosphorus fertilizer, the concents of rhizospheric Al-P, Fe-P and non-rhizospheric Ca-P in three rice materials had no significant difference. The concents of rhizospheric soil O-P and Ca-P in OsPT4 and PHO2 were significantly inferior to Nipp, and their concents of non-rhizospheric soil Al-P, Fe-P and O-P were significantly lower than Nipp. When added no phosphorus fertilizer, the concents of rhizospheric Al-P, O-P, Ca-P and non-rhizosphere Al-P, Ca-P in three rice materials had no significant difference, and the concents of rhizosphere Fe-P and non-rhizosphere soil Fe-P, O-P in OsPT4 and PHO2 were significantly lower than Nipp, but rhizosphere Ca-P was significantly higher than Nipp.

In order to seek and estimate the fertilizer application from main crops in China, this paper analyzed the current use of fertilizer, as well as the use of fertilizer in different crops for more than 30 years. We found that the crop fertilizer usage was growing from 12.694 million tons in 1980 to 59.959 million tons in 2014, with the overall raise of 4.7 times, and an annual growth rate of 4.67%. Fertilizer usage from cereal crop contributed the most to the total use, with the fertilizer application from 27.124 1 million tons in 1980 to 34.153 5 million tons in 2014, but the ratio of its fertilizer usage to the total fertilizer consume from crops in China decreased from 60.02% in 1998 to 49.75% in 2014. The fertilizer application from vegetable and fruit crops grew most rapidly, with an raise of 2.1 times from vegetables crops, increasing from 6.045 1 million tons in 1998 to 12.913 6 million tons in 2014, and its ratio to the total fertilizer application in crops from 13.38% in 1998 to 18.81% in 2014. The fertilizer application from fruit increased from 5.315 5 million tons in 1998 to 12.234 2 million tons in 2014, increasing by 2.4 times compared with that in 1998, and its ratio to the total fertilizer application from crops increased from 11.76% in 1998 to 17.82% in 2014. In addition, according to our study, great regional differences in the gross amount of fertilizer usage were found, with a decreasing trend from east to west, with the highest usage in East China and Central China. In accordance with the per unit use of fertilizer, it decreased from east to west, the same from south to north, with the highest fertilizer application in South China and East China.

Flaveria bidentis is a worst weed newly invaded in China, studying on its stoichiometry can help us understand its strategy to invade and adapt in different environments. In a green house, we studied the effect of soil N, P addition on F. bidentis plant growth, N, P stoichiometry characteristics and leaf chlorophyll content. The results showed that the effect of different N or P level on leaf N:P was significantly different with equivalent N:P ratio used. Leaf N:P was reduced significantly with N, P addition increasing, but above ground biomass was decreased also, this effect was mainly attributed to the amount of N used. When leaf N:P was larger than 21.24, plant growth rate became lower, which was in line with the growth rate hypothesis. Soil N and leaf N content had a positive correlation with leaf chlorophyll content of F. bidentis. Both F. bidentis leaf N (P) content and aboveground biomass were increasing firstly and falling later with soil N (P) content increasing. N and P were regarded as growth restrictive elements, when leaf N:P was below 20.86 and above 21.24, respectively.

In order to evaluate the potential effects of rest grazing on organic carbon storage on the Stipa baicalensis steppe in Inner Mongolia, compared the S. baicalensis steppes after rest grazing for 3 years, 6 years, and 9 years, using potassium dichromate heating method, this study analyzed the organic carbon storage of plant and soil in the steppes among different periods of rest grazing. The results indicated that as the rest grazing years prolonged, the biomass included above-ground parts, litters and underground plant parts(roots) of the plant communities all increased, meanwhile the carbon content of the biomass increased with the rest grazing years prolonged. For the zero rest grazing (RG0) steppe and the steppes after a rest grazing of 3 years (RG3a), 6 years (RG6a), 9 years (RG9a), the carbon storage in above-ground parts of plant communities were 42.60 g C/m 2 , 66.33 g C/m 2 , 83.46 g C/m 2 , 100.29 g C/m 2 respectively; the carbon storage of litters were 7.85 g C/m 2 , 9.12 g C/m 2 , 9.18 g C/m 2 , 11.54 g C/m 2 separately; the carbon storage of underground plant parts (0–100 cm) were 281.40 g C/m 2 , 576.38 g C/m 2 , 745.33 g C/m 2 , 1279.61 g C/m 2 respectively; and the carbon storage in 0–100 cm soil were 22991.14 g C/m 2 , 24687.75 g C/m 2 , 26564.86 g C/m 2 ,33041.55 g C/m 2 . The results suggested that as the rest grazing years prolonged, the organic carbon storage in plant communities and soil increased. The carbon storage of underground plant parts and soil organic carbon mainly concentrated in 0–40 cm soil. After rest grazing for 3 years, 6 years, and 9 years, the increased soil organic carbon were as the 81.14%, 85.84%, and 89.46% of the total increased carbon; From the perspective of carbon sequestration cost, the total cost of RG3a, RG6a and RG9a were 2903.40 RMB/hm 2 , 5806.80 RMB/hm 2 , and 8710.20 RMB/hm 2 . The cost reduced with the extension of rest grazing years, 0.17 RMB/kg C, 0.16 RMB/kg C, 0.09 RMB/kg C for RG3a, RG6a and RG9a respectively. From the growth characteristics of grassland plants, the spring was one of the two avoid grazing periods, timely rest grazing could effectively restore and update grassland vegetation, and was beneficial to the sustainable use of grassland. From the available data, the organic carbon storage of RG9a was the highest, while the cost of carbon sequestration was the lowest. Therefore, spring rest grazing should be encouraged to continue for it was proved to be a very efficient grassland use measures.

In this paper, eight nitrogen treatments were applied at 0 g·m -2(N0), 1.5 g·m -2(N15), 3.0 g·m -2(N30), 5.0 g·m -2(N50), 10.0 g·m -2(N100), 15.0 g·m -2(N150), 20.0 g·m -2(N200), 30.0 g·m -2(N300) as NH 4 NO 3 and adding water to simulate summer rainfall of 100 mm, the interactive experiment was set to explore the effects of nitrogen and water addition in Stipa baicalensis steppe on soil nutrients, enzyme activities and soil microbial biomass. The results showed that the nitrogen and water addition changed soil physico-chemical factors obviously, the content of soil total organic carbon, total nitrogen, nitrate nitrogen and ammonium nitrogen increased along with the increasing of application rate of nitrogen, on the contrary, the soil pH value had decreasing trend. Appropriate application of nitrogen could enhance the activity of urease and catalase but decreased the activity of polyphenol oxidase. Nitrogen and water addition had significant effect on soil microbial biomass C and N. Higher level of N fertilizer significantly reduced microbial biomass C, and the microbial biomass N was on the rise with the application rate of nitrogen. The addition of water could slow the inhibition of nitrogen to microorganism and increase the microbial biomass C and N. A closed relationship existed in soil nutrient, activities of soil enzyme and soil microbial biomass C and N. The significantly positive correlation existed between total N, organic C, nitrate N and catalase, significantly negative correlation between nitrate N, ammonium N, total N and polyphenol oxidase. Microbial biomass N was significantly positive correlated with total N, nitrate N, ammonium N, catalase, phosphatase, and was negative correlated with polyphenol oxidase. Microbial biomass C was significantly positive correlated with polyphenol oxidase, and was negative correlated with catalase.

The purification effect on domestic sewage were researched in the new-type of duplex subsurface flow constructed wetlands, of which pollutants were analyzed through the small scale test on the purification effect under different conditions of hydraulic loading, season,aeration pattern. The results showed that water quality of the system was stabilized, which could reach the 1 class A criteria specified in the Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant ( GB 18918-2002).The removal rate of COD，NH3-N could reach up to 87.2%, 68.9% under the conditions of the hydraulic load being 184 mm·d-1.And there were still more than 20% removal efficien-cy of various pollutants on the conditions of low temperature in winter. Orthogonal test showed that the optimum operating conditions was 28.6℃for the temperature, 0.184 m3·m-2·d-1 for hydraulic loading, and 2.4 d for hydraulic retention time. The experimental research showed that pre-aeration was significantly better than the anaerobic treatment on purifying effect.