Search

The effect and relative contributions of C and P inputs on soil microbial biomass P (MBP) accumulation were studied in three long-term soil fertility experiments with various soil and climate characteristics at Qiyang, Yangling, and Wulumuqi. The maximum of soil MBP in all three sites was 47.8 mg P kg-1. The MBP accumulated per unit in soil (mg P kg-1 soil) was correlated with a 4.91 mg kg-1 increase in Olsen P. For each unit increase in P surplus (kg P ha-1), manure C (kg C ha-1), and stubble C (kg C ha-1), MBP accumulation increased by 330, 3.7, and 13 units (μg P kg-1 soil), respectively. The soil MBP was positively correlated with crop yield and P uptake, making the soil MBP a useful soil P fertility index. The critical levels of the soil MBP pool were 140 kg ha-1, 57–62 kg ha-1, and 33–35 kg ha-1 in acidic red soil, loessial soil, and grey desert soil, respectively. This is the first report to establish a quantitative index of soil fertility based on the soil MBP pool. Our findings demonstrate that C input is a good driver of soil MBP accumulation. Integration of the soil MBP as an index of soil P fertility into agricultural P management is useful to help manage mineral P fertilizers as part of sustainable agricultural practices.

To evaluate the effect of land use changes on phosphorus pools and its accumulation in the soil profile on loess soils. This study applied a modified Hedley fractionation method to investigate soil P pools in 100-cm soil profile after conversion of wheat-maize (W-M) to greenhouse vegetable (GV) or kiwi orchard (kiwi). Land use changes from W-M to GV significantly increased total P stock by 82% at 0–100-cm soil profile. In particular, conversion from W-M to GV greatly increased easily available P at 0–80 cm by 11–291%, moderately available P at 0–60 cm by 83–253%, and non-available P at 0–40 cm depth by 42–214%, respectively. Conversion from W-M to kiwi also markedly raised total P stock by 15% at 0–100-cm soil profile, in which easily available P and moderately available P at 20 cm depth increased by 161% and 130%, and non-available P at 80–100-cm depth rose by 85.6%. Land use change also caused a shift in the distribution of P pools, i.e., percentages of easily available P rose by 10–13% at 0–80 cm under GV and by 10–15% under kiwi at 0–100 cm over the W-M. Correspondingly, ratios of moderately available P also increased by 7–8% at 20–60-cm depths and by 7–10% at 0–100-cm depths. By contrast, proportions of non-available P decreased. Our results indicate a huge amount of P accumulated into the soil profile, and its solubility also increased, especially under GV, which would have significant environmental consequences. Therefore, rational P management for cash crops should arouse the attentions in all sectors of the society.

Seals, a common part of Chinese painting and calligraphy, play a key role in identification, collection, and other activities of painting and calligraphy. However, most of the seal age-analysis methods are still dependent on the experience and judgement of the experts. Thus, scientific evidence in this field is required. This study aims to explore the changes in the reflectance spectra by heat-aging on seal samples to establish a spectral heat-aging model that can be used to estimate the aging times of seals. An experiment was conducted to detect the reflectance spectral changes of sample seals on Chinese paintings and calligraphy after different heat aging times, and a model incorporating the spectral changes over aging time was built. After heat aging, the visible near-infrared spectra of the seal samples were acquired and analyzed. The results show that the cinnabar pigment contained in the samples exhibited no significant change in spectra. The spectral change bands of the rice paper and the seal-ink did not overlap, and the spectral changes of the seal-ink aging were found to be mainly come from the additive. Its sensitive bands that means those bands with distinct characteristics of reflectance spectra are concentrated in the spectral ranges of 1700−1800 nm and 2250−2400 nm. As the aging time prolonged, the additives of the seals were found to gradually undergo changes, whereas, the composition of the cinnabar pigment tended to be stable. Finally, a spectral heat-aging model was established using multivariable linear regression. The accuracy of this model was tested using 16 samples that were not used during training. The coefficient of determination (R2) value was found to be 0.83, and the correlation between the real and estimated aging times was 0.65. Results demonstrated that the visible near-infrared reflectance spectra changes could be used to estimate the age of seals on Chinese paintings or calligraphy.

National and regional climate-sensitive biomass equations were developed for poplar plantations in China, with mean annual temperature and precipitation significantly affecting predicted biomass. In the context of global climate change, information on forest biomass becomes more and more important, and the impact of climate change on biomass estimation is also receiving increasing attention. Using the dummy variable modeling approach and the error-in-variable simultaneous equations approach, national and regional one- and two-variable individual tree biomass models were developed for poplar plantations in China. The models were based on above- and below-ground biomass data of 450 and 147 destructive sample trees, respectively, collected from poplar plantations in 15 provinces of three regions in China. In addition, combined with climate data of mean annual temperature (T) and mean annual precipitation (P), climate-sensitive individual tree biomass models were established, and the impact of climatic factors on biomass estimation was analyzed. The coefficients of determination of national above- and below-ground biomass models developed in this study were more than 0.90 and 0.82, whereas the mean prediction errors were less than 5% and 10%, respectively. For climate-sensitive biomass models, aboveground biomass was only impacted by T, while belowground biomass was affected by both T and P, and impact of the latter was greater than that of the former. Considering the comprehensive effect of climatic factors to above- and belowground estimation, the total biomass estimates of poplar trees with the same size would reach the maximum in the regions for T = 17 °C and P = 1200 mm, which might provide reference for the scientific management of poplar plantations in China.

The effect of dairy manure amendments to agricultural soil on the yield-scaled nitrous oxide (N2O) emissions remains unclear. We hypothesize that an optimum ratio of dairy manure to synthetic fertilizers leads to large nitrogen use efficiency (NUE) and small yield-scaled N2O emissions. The aims of this study were to (1) quantify the variations in the crop yields and N2O emissions from winter wheat-summer maize cropping systems in Northwest China, (2) determine the responses of the NUE and yield-scaled N2O emission to the ratio of organic materials to synthetic fertilizers, and (3) evaluate the relationship between the NUE and yield-scaled N2O emissions. Field measurements were conducted within long- and short-term fertilization experiments between the years of 2014 and 2016. Treatments included synthetic fertilizers, synthetic fertilizers plus crop residues, and synthetic fertilizers plus dairy manure at both sites. The annual grain yields and N2O emissions varied from 13.3 to 18.0 Mg ha−1 and from 1.3 to 3.6 kg N ha−1, respectively, across the treatments. The yield-scaled N2O emissions related negatively to the NUE, suggesting that agronomic aims of improving NUE are an effective approach to mitigate N2O emissions. The ratio of organic materials to synthetic fertilizers was not a significant limit on the NUE and yield-scaled N2O emissions. We conclude that organic amendments appeared to play a minor influence on the promotion of the NUE and N2O mitigation.

Background Mixed pigment analysis is an important and complex subject in preserving and restoring Chinese paintings since the colors observed by our naked eyes or instruments such as hyperspectral cameras are usually a mixture of several kinds of pigments. The purpose of this study was to explore a more effective method to confirm the type of every pure pigment and their proportion in pigment mixtures on the surface of paintings. Methods Two endmember extraction algorithms were adopted to identify the types of pigments and an improved method of ratio spectra derivative spectrophotometry was used to determine their proportion. Main works (1) Extracting the pure pigment components from mixed spectrum by adopting two blind source separation algorithms: Independent Component Analysis and Non-negative Matrix Factorization; (2) matching the separated pure spectrum with the pigment spectral library built in our laboratory to determine the pigment type; and (3) calculating the proportions of mixed pigments using the Ratio Spectra Derivative Spectrophotometry based on Mode, which is improved based on the original algorithm. Finally, a comparison was made with two abundance inversion algorithms: Least Squares Algorithm and Minimum Volume Simplex Analysis. The correlation coefficient and root mean square error were used to provide evidence for accuracy evaluation. Conclusions (1) Non-negative matrix factorization is more suitable for endmember extraction; and (2) Ratio spectra derivative spectrophotometry based on mode is more suitable for abundance inversion.

It is important to understand soil organic carbon (SOC) sequestration and its relationship with crop productivity. Based on two long-term experiments under irrigated vs rain-fed conditions conducted in the China Loess Plateau, we evaluated SOC sequestration efficiency under diverse fertilization regimes and quantified the relationship between crop yield and SOC. The experiments consisted of a winter wheat-summer maize system under irrigated conditions with nine treatments—nitrogen (N), N and phosphorus (P), N and potassium (K), P and K (PK), combined NPK, crop straw (S) in combination with NPK (SNPK) and dairy manure (M) integrated with NPK (M1NPK and M2NPK)—and a winter wheat-summer fallow system under rain-fed conditions with seven treatments—CK, N, NK, PK, NP, NPK, and MNPK. After 25 years, the SOC storage was generally higher in the irrigated plots than in the rain-fed plots by 6% on average. The carbon sequestration efficiency was higher under the rain-fed (28%) than under the irrigated (19%) condition. The relationship between relative yield and SOC content suggested that the threshold SOC contents for obtaining the highest crop yield were 10.0 and 8.8 g kg−1 for the winter wheat-summer maize and winter wheat-summer fallow cropping systems, respectively. This difference suggests that a higher SOC level is required to support high crop productivity in the irrigated system than in the rain-fed system.

One-pot hydrothermal carbonization approach was employed to synthesize the blue-emission carbon dots derived from chitosan (Cs) and o-phenylenediamine (OPD). The Cs-based carbon dots (Cs–CDs) possessed a certain high quantum yield of 58% and exhibited excellent solubility, stability and fluorescence response in aqueous solutions. The Cs–CDs were designed as a sensor for Cr(VI) and H2O2 determination. The sensing strategy of Cr(VI) was based on the inner filter effect (IFE) and static quenching effect (SQE), showing a good linear correlation ranging from 1 to 130[Formula: see text][Formula: see text]M with a detection limit (LOD) of 0.91[Formula: see text][Formula: see text]M. In addition, the determination for H2O2 was attributed to the elimination of IFE (EIFE) due to the reduction reaction and the detection for H2O2 was in the linear range from 1.0 to 200.0[Formula: see text][Formula: see text]M with LOD of 0.51[Formula: see text][Formula: see text]M. Finally, the proposed designed sensor could be simply applied for detection of Cr(VI) and H2O2 in real samples.

BACKGROUND Plastic film mulch is widely used to improve crop yield and water use efficiency (WUE, yield per unit evapotranspiration) in semi-arid regions. It is commonly applied as partial-film mulch (PM: at least 50% soil cover) or full-film mulch (FM: complete soil cover). The PM has lower economic and environmental cost; hence it would be a superior technology provided it delivers similar gains in yield and WUE in relation to FM. RESULTS To solve contradictory results from individual studies, we compared FM and PM in a meta-analysis of 100 studies with 1881 comparisons (685 for wheat; 1196 for maize). Compared with bare ground, FM and PM both increased yield of wheat (20-26%) and maize (37-52%), and WUE of wheat (16-20%) and maize (38-48%), with statistically undistinguishable differences between PM and FM. The increases in crop yield and WUE were stronger at elevation > 1000 m, with annual precipitation

The preparation of N-doped carbon dots (N-CDs) was facile and efficient by the hydrothermal method, using diethylenetriamine (DETA) and citric acid (CA) as nitrogen source and carbon source, respectively. The fluorescence of N-CDs was effectively quenched by Fe3+. Upon addition of hydroxylamine hydrochloride (HH) to N-CDs/Fe3+ complex dispersion, the fluorescence of N-CDs was significantly recovered. Therefore, we developed an “off-on” fluorescence assay for the detection of HH using N-CDs/Fe3+ as a fluorescence probe. The fluorescence intensity showed linearity with the added HH concentration ranging from 0 to 100 μM with the detection limit of 0.246 μM (S/N = 3). The proposed N-CDs sensing showed high selectivity and sensitivity to detection HH in aqueous solution.

It is of paramount importance to assess phosphorus (P) accumulation and distribution in deep soil profile after land use changes to improve current P management. This study investigated soil P fractions and degrees of P saturation in 300-cm soil profile after conversion of wheat–maize cropping to greenhouse vegetable or kiwi planting in Yangling, Northwest China. Compared with the arable land, vegetable greenhouse or kiwi orchard showed significantly greater soil P accumulation at surface layer, i.e., CaCl2-P increased by 10–20 times, Olsen-P by 3–5 times, Mehlich-3-extracted P by 3–6 times, and organic-P by maximum of 4 times. A degree of P saturation increased from 4 under arable crop to 14% under kiwi orchard and 22% under greenhouse vegetable. Land conversion also markedly increased soil available P (Olsen-P and Mehlich-3-extracted P) distributing in deep soil layers down to 300 cm, especially for greenhouse vegetable, where Olsen-P or Mehlich-3-extracted P contents reached the critical P value for arable crop to achieve maximum yield. Our results indicate a huge amount of P had been further leached down to deep soils under the current management. Hence, there is an urgent need to update the P management strategies under greenhouse vegetable and kiwi orchard, especially for those involving in amendment of organic manure, to prevent the situation from getting worse in future.

Maintaining high crop yield and meanwhile reducing the risk of environmental pollution are of paramount importance for food security and sustainability. The aims of this study were (i) quantify soil NO3− -N buffer capacity under wheat-maize cropping system in Northern China, and (ii) establish agronomic optimum and environmentally safe N rates to guide N recommendation for the region. We compiled data of 76 sets of wheat and 73 sets of maize experiments spanning about 20 years, where N rate experiments conducted and soil NO3− -N content were measured immediately after crop harvest under conventional practice. By applying linear-plateau and plateau-linear models, we computed the soil NO3− -N buffer capacity, agronomic optimum N rate and environmentally safe N rates. Soil NO3− -N buffer capacity ranged from 10 to 221 kg ha−1 for wheat season and from 14 to 212 kg ha−1 for maize season, which were mostly less than 100 kg ha−1 in the region. The agronomic optimum N rates for wheat and maize were 46–221 and 44–250 kg N ha−1 with means of 110 and 127 kg N ha−1, respectively. The environmentally safe N rates were 19–248 kg N ha−1 with mean of 107 kg N ha−1 for wheat, and 36–209 kg N ha−1 with mean of 99 kg N ha−1 for maize. It was found that agronomic optimum N rates from 61% of wheat and 52% of maize were higher than the environmentally safe N rates, implying that current N recommendation had the high potential risk of nitrate leaching. Hence, it is suggested that N recommendation should consider not only the agronomic optimum N but also environmentally safe N rate, especially in areas where are vulnerable to nitrate leaching the latter should be placed at the top priority.

Improved management practices are necessary to increase grain yield and water-use efficiency of rainfed winter wheat in semiarid environments. Yield and its components, evapotranspiration, and accumulation and apparent remobilisation of stem water soluble carbohydrates (WSC) were measured to understand the effects of root pruning and its interactions with seeding rate, water and nitrogen supply. Two factorial studies under straw mulching with continuous wheat were established in the Loess Plateau of China. Study 1 was repeated over four seasons and included six treatments from the combination of three root treatments, i.e. root pruning in winter before dormancy (RPw), root pruning at the re-green stage in spring (RPs) and untreated control (CK), and two seeding rates. Study 2 was repeated over three seasons and included twelve treatments from the combination of two root treatments (RPs and CK), two nitrogen rates and three pre-sowing soil water levels. Yield ranged from 2571 to 7722 kg ha−1, harvest index from 0.28 to 0.56, and water-use efficiency from 5 to 20 kg ha−1 mm−1. Root pruning improved grain yield, harvest index and water-use efficiency by 6–11% across environmental conditions. Grain yield increased more (i) by pruning roots in spring than in winter, (ii) in high plant density than in low plant density crops, and (iii) in low-yielding conditions. It is concluded that spring root pruning is a viable option to improve wheat yield and water use efficiency under straw mulching in semiarid environment.

A high crop yield with the minimum possible cost to the environment is generally desirable. However, the complicated relationships among crop production, nitrogen (N) use efficiency and environmental impacts must be clearly assessed. We conducted a series of on-farm N application rate experiments to establish the linkage between crop yield and N2O emissions in the Guanzhong Plain in Northwest China. We also examined crop yield, partial factor productivity of applied N (PFPN) and reactive N (Nr) losses through a survey of 1 529 and 1 497 smallholder farms that grow wheat and maize, respectively, in the region. The optimum N rates were 175 and 214 kg ha–1 for winter wheat and summer maize, respectively, thereby achieving the yields of 6 799 and 7 518 kg ha–1, correspondingly, with low N2O emissions based on on-farm N rate experiments. Among the smallholder farms, the average N application rates were 215 and 294 kg ha–1 season–1, thus producing 6 490 and 6 220 kg ha–1 of wheat and maize, respectively. The corresponding PFPN values for the two crops were 36.8 and 21.2 kg N kg–1, and the total N2O emissions were 1.50 and 3.88 kg ha–1, respectively. High N balance, large Nr losses and elevated N2O emissions could be explained by the overdoses of N application and low grain yields under the current farming practice. The crop yields, N application rates, PFPN and total N2O for wheat and maize were 18 and 24% higher, 42 and 37% less, 75 and 116% higher, and 42 and 47% less, correspondingly, in the high-yield and high-PFPN group than in the average smallholder farms. In conclusion, closing the PFPN gap between the current average and the value for the high-yield and high-PFPN group would increase crop production and reduce Nr losses or the total N2O emissions for the investigated cropping system in Northwest China.

Nitrogen-doped graphene quantum dots (N-GQDs), with superior biocompatibility, strong resistance to photobleaching and convenient surface grafting, have sparked a surge of related-bio applications. In this study, combined with chromium picolinate (CrPic), N-GQDs synthesized by a facile hydrothermal approach are used to construct an environmentally-friendly sensor for the detection of cholesterol by exploiting the fluorescence enhancement of N-GQDs/CrPic. Herein, CrPic is grafted on N-GQDs via the linker of cysteamine (Cys), and the fluorescence of the N-GQDs is quenched by photoinduced electron transfer (PET), wherein CrPic functions as an electron donating group and the N-GQDs serves as an electron accepting group. Besides, cholesterol is stimulated to form a favourable complex with N-GQDs/CrPic because CrPic also acts as a potential receptor for cholesterol by strong affinity and π–π interaction, and the fluorescence of N-GQDs/CrPic is enhanced indicating that cholesterol could impede electron transfer from CrPic to the N-GQDs. This N-GQDs/CrPic-based sensor has been successfully applied to selectively determine the concentration of cholesterol with a linear range of 0–520 μM and a limit of detection (LOD) of 0.4 μM. Meanwhile, this present sensing strategy in human serum has acceptable practicability, reproducibility and precision.

Application of organic manure combined with synthetic fertilizer can maintain crop yield and improve soil fertility, but the long-term effects of substituting different proportions of synthetic fertilizers with organic manure on N

Additional file 1. Additional figures.

The effect of dairy manure amendments to agricultural soil on the yield-scaled nitrous oxide (N

Straw mulching has been used to improve water use efficiency (WUE, yield per unit evapotranspiration) in the Loess Plateau of China, but the seeding rate may need to be adjusted from conventional practice. We tested the three-way interaction between seeding rate, soil management (conventional tillage and straw mulching) and seasons. Wheat yield ranged from 2851 to 6981 kg ha−1 and WUE from 5.3 to 16.2 kg ha−1 mm−1. Generally, soil water storage was higher and soil temperature was lower under straw mulching than under conventional practice. Evapotranspiration was higher under straw mulching. Yield was significantly affected by the interaction between straw mulching and season. Conventional practice showed significantly higher mean harvest index (HI), yield, and WUE than straw mulching in favorable seasons. However, yield was significantly higher under mulching than under conventional tillage in very dry season. Seeding rate had no effect on yield, but low seeding rate increased HI compared to high seeding rate. It is concluded that low seeding rate would be suitable for straw mulching.

Wise phosphorus (P) management is paramount to ensure food and environmental security and prolong the life of P resources. Long-term experiments under winter wheat–summer maize (with irrigation) and winter wheat–summer fallow (rain-fed) cropping systems were undertaken to investigate P efficiency, soil P availability and P downward movement in the deep profile of a loess soil in China. The four nutrient management regimes in each experiment were: a control without any nutrient input; P and K combined (PK); N, P and K combined (NPK), and organic manure (M) combined with NPK (MNPK). The P efficiency ranged from 20 to 54% under the double cropping system, and from 13 to 33% in the single cropping system over the 25 years studied, and the highest P efficiency was in the NPK treatment in both systems. Application of P significantly increased soil total-P, Olsen-P and CaCl2-P over the years, especially in the MNPK treatment. Two segment regression analyses indicated that Olsen-P was about 14 mg kg−1 or 16 mg kg−1 for optimal crop yield under double cropping or single cropping. In addition, Olsen-P content above 37 mg kg−1 or 57 mg kg−1 led to a significant increase in CaCl2-P content under double cropping or single cropping, which might indicate risk of P leaching. After 24 years of P applications, total P accumulated at various depths depending on treatment under double cropping, but there was no accumulation under single cropping. While Olsen-P leached down to a depth of 300 cm in the MNPK treatments under both cropping systems, and higher concentrations were recorded in the deeper layers in single cropping than in double cropping systems. The Olsen-P leached to a shallower depth in the PK and NPK treatments under single cropping compared to double cropping. We conclude that P supply in excess of the crop’s requirement (e.g. MNPK) or an unbalanced nutrient supply (e.g. PK) resulted in not only low P efficiency and massive accumulation of P in the topsoil but also leaching out of root zone under both irrigated and rain-fed conditions in the loess soil. Thus, P fertilization recommendations need to be adjusted based on changes in soil P over time.

Management of nitrogen (N) fertilizer is critical to avoid the environmental consequences of both over-fertilization and excess reactive N in the system, and chronic under-fertilization and soil mining. Split N application seeks to improve nitrogen use efficiency in both small-holdings and large-scale mechanized farms, but lack of conclusive evidence on its benefits restricts the adoption of this practice. Here we report a global meta-analysis of split N application in wheat using 129 studies with 2661 comparisons. Split N in 3–4 applications improved yield by 7.0 % and grain protein by 5.2 % in relation to single application. The effect of split N on yield was larger for winter wheat than for spring wheat, while split N improved grain protein in both winter and spring wheat. Its effects on both yield and grain protein were larger under conventional tillage, in humid climate especially for winter wheat, in coarse textured soils, on less fertile soils, and at high N rate. Splitting N in 3–4 applications would increase annual production of winter wheat by 12.9 M t grain and 1.3 M t protein globally. By identifying the conditions where split N application is more likely to deliver agronomic benefits, our study would contribute to the targeted adoption of this practice.

The primary aims of this study were to (i) quantify the variations in nitrous oxide (N 2 O) emissions and soil organic carbon (SOC) sequestration rates under winter wheat-summer maize cropping systems in Guanzhong Plain and (ii) evaluate the impact of organic amendments on greenhouse gas mitigation over a long-term period. We measured N 2 O fluxes during the maize season in 2015 under four fertilizer regimes in a long-term fertilization experiment. Soil was treated with only synthetic fertilizers in the maize season and with synthetic fertilizers, synthetic fertilizers plus crop residues and synthetic fertilizers plus low and high levels of dairy manure in the winter wheat season from 1990. The SOC content (0–20 cm) was collected annually at the same site between 1990 and 2015. Synthesis of our measurements and previous observations (between 2000 and 2009) within the investigated agricultural landscape revealed that cumulative N 2 O emissions increased with the SOC content following natural logarithm models during both the maize and winter wheat seasons (r 2 > 0.77, p 2 O emissions and SOC sequestration. The SOC content increased under all fertilizer regimes, and the dynamics were well fitted by the linear and logistic regression models (r 2 > 0.74, p 2 -equivalent ha − 1 ) over the past 25 years. However, this benefit would most likely be offset by high N 2 O emissions at saturated SOC levels before 2020. Our estimates suggest that organic amendments may not be efficient for greenhouse gas mitigation in Guanzhong Plain over a long-term period. We recommend efforts to inhibit N 2 O production via denitrification as being critical to resolving the conflict between SOC sequestration and N 2 O emissions.

The effect and relative contributions of C and P inputs on soil microbial biomass P (MBP) accumulation were studied in three long-term soil fertility experiments with various soil and climate characteristics at Qiyang, Yangling, and Wulumuqi. The maximum of soil MBP in all three sites was 47.8 mg P kg-1. The MBP accumulated per unit in soil (mg P kg-1 soil) was correlated with a 4.91 mg kg-1 increase in Olsen P. For each unit increase in P surplus (kg P ha-1), manure C (kg C ha-1), and stubble C (kg C ha-1), MBP accumulation increased by 330, 3.7, and 13 units (μg P kg-1 soil), respectively. The soil MBP was positively correlated with crop yield and P uptake, making the soil MBP a useful soil P fertility index. The critical levels of the soil MBP pool were 140 kg ha-1, 57–62 kg ha-1, and 33–35 kg ha-1 in acidic red soil, loessial soil, and grey desert soil, respectively. This is the first report to establish a quantitative index of soil fertility based on the soil MBP pool. Our findings demonstrate that C input is a good driver of soil MBP accumulation. Integration of the soil MBP as an index of soil P fertility into agricultural P management is useful to help manage mineral P fertilizers as part of sustainable agricultural practices.

Crop productivity and soil health are limited by organic carbon (OC), however, the variations in the mechanisms of SOC preservation in a complete soil profile subjected to long-term fertilization remains unclear. The objective of the study was to examined the content and profile distribution of the distinctive SOC protection mechanisms on a complete profile (0–100 cm) of Eumorthic Anthrosols in Northwest China after 23 years of chemical and manure fertilization. The soil was fractionated by combined physical-chemical and density floatation techniques. Throughout the profile, significant variations were observed among fractions. In the topsoil (0–20 and 20–40 cm), mineral coupling with the fertilization of manure (MNPK) enhanced total SOC content and recorded for 29% of SOC in the 0–20 and 20–40 cm layers. Moreover, MNPK increased the SOC content of the unprotected cPOC fraction by 60.9% and 61.5% in the 0–20 and 20–40 cm layer, while SOC content was low in the subsoil layers (40–60, 60–80 and 80–100 cm, respectively) compared with the control (C). The highest OC under MNPK in physically protected micro-aggregates (μagg) (6.36 and 6.06 g C kg−1), and occluded particulate organic carbon (iPOC) (1.41 and 1.29 g C kg−1) was found in the topsoil layers. The unprotected cPOC fraction was the greatest C accumulating fraction in the topsoil layers, followed by μagg and H-μSilt fractions in the soil profile, implying that these fractions were the most sensitive to the fertilization treatments. Overall, the unprotected, physically protected, and physico-chemically protected fractions were the dominant fractions for the sequestration of carbon across fertilization treatments and soil layers.

Understanding organic carbon (OC) sequestration in aggregates and OC stability under different fertilization practices is of key importance in improving soil quality and crop productivity and in mitigating the causes of climate change. A long-term field experiment established in 1990 was used to assess the influence of organic and inorganic fertilizers on aggregate-associated OC and its mineralization and on the SOC stock at a soil depth of 0–20 cm under an intensive wheat-maize cropping system on Anthrosol in North China. The study involved three treatments: CK, control without fertilization; NPK, nitrogen (N), phosphorus (P) and potassium (K) fertilizers; MNPK, manure (M) combined with N, P and K fertilizers. Soil samples were collected and analyzed to determine the size distribution of aggregates, which were separated by dry sieving; the concentrations of OC and N in aggregates (> 2, 0.25–2 and

We investigated the effects of different fertilization on weed community composition in long-term cropping experimental plots established 25 years previously in Wuquan, Yangling district, Shaanxi province, north-west China. Our study has focused on the different fertilization systems which would have a significant influence on weed communities in winter wheat field. The field experiments were carried out with seven different fertilization treatments, i.e. no fertilizer or manure input (control, hereafter CK) and various combinations of synthetic nitrogen (N), phosphate (P) and potassium (K) fertilizers, as N, NK, PK, NP and NPK, and dairy manure MNPK. The results revealed the presence of 19 weed species in total, representing 10 families and 19 genera. Higher weed densities and richness indices were observed with treatments receiving no (CK) or unbalanced fertilization (N, NK, PK), whereas lower weed densities and richness indices were found with balanced fertilizer application treatments (NP, NPK and NPK with organic manure). The results also demonstrated that the application of N and P fertilizer had a greater impact on the weed community than the application of K fertilizer.