The contribution of natural and anthropogenic causes to soil acidification rates under different fertilization practices and site conditions in southern China.

Excessive application of mineral fertilizers has accelerated soil acidification in China, affecting crop production when the pH drops below a critical value. However, the contributions of natural soil acidification, induced by leaching of bicarbonate, and anthropogenic causes of soil acidification, induced by nitrogen (N) transformations and removal of base cations over acid anions, are not well quantified. In this study, we quantified soil acidification rates, in equivalents (eq) of acidity, by assessing the inputs and outputs of all major cations and anions, including calcium, magnesium, potassium, sodium, ammonium, nitrate, bicarbonate, sulphate, phosphate and chloride, for 13 long-term experimental sites in southern China. The acidification rates strongly varied among fertilizer treatments and with the addition of animal manure. Bicarbonate leaching was the dominant acid production process in calcareous soils (23 keq ha-1 yr-1) and in non-calcareous paddy soils (9.6 keq ha-1 yr-1), accounting for 80 % and 68 % of the total acid production rate, respectively. The calcareous soils were strongly buffered, and acidification led no or a limited decline in pH. In contrast, N transformations were the most important driver for soil acidification at one site with upland crops on a non-calcareous soil, accounting for 72 % of total acid production rate of 8.4 keq ha-1 yr-1. In this soil, the soil pH considerably decreased being accompanied by a substantial decline in exchangeable base cation. Reducing the N surplus decreased the acidification rate with 10 to 54 eq per kg N surplus with the lowest value occurring in paddy soils and the highest in the upland soil. The use of manure, containing base cations, partly mitigated the acidifying impact of N fertilizer inputs and crop removal, but enhanced phosphorus (P) accumulation. Combining mineral fertilizer, manure and lime in integrative management strategies can mitigate soil acidification and minimize N and P losses.

Soil microeukaryotic communities and phosphorus-cycling microorganisms respond to chloropicrin fumigation and azoxystrobin application.

Fumigants and fungicides are effective at controlling soil-borne pathogens but might also adversely affect soil beneficial microbes, such as soil phosphorus (P) solubilizing microbes, further altering nutrient cycling processes. Therefore, this study investigated the effects of the fumigant chloropicrin (CP) and the fungicide azoxystrobin (AZO) on soil microeukaryotes and P-cycling related soil bacteria through a greenhouse experiment. Soil microeukaryotic communities and bacterial communities containing two phosphomonoesterase encoding genes (phoC and phoD) were analysed using high-throughput sequencing methods. Results showed that, when applied at the field recommended application dosage, the fungicide AZO had no significant influence on the community structure of soil microeukaryotes and phoD-containing bacteria. However, in CP-fumigated soils, the soil microeukaryotic community composition changed from fungi-dominated to protist-dominated. CP fumigation significantly decreased the total phoC/phoD gene copy number but increased the relative abundance of some phoC/phoD-containing bacteria (such as Sinorhizobium and Streptomyces), which are significantly positively correlated to available P compositions in soil. The structural equation model (SEM) confirmed that CP fumigation could affect soil available P content directly by altering phoC-/phoD-containing bacteria, or indirectly by affecting phoC/phoD gene abundance and acid/alkaline phosphatases activity in soil. The inconsistent changes in phoC/phoD-containing bacteria, phoC/phoD gene number, and the phosphomonoesterase activities indicated that enzyme secretion may not be the only way for P solubilizing soil microorganisms to regulate P availability after soil fumigation. The outcome of this study can provide theoretical support for the design of soil beneficial microorganism recovery strategies and the regulation of phosphate fertilizer after soil fumigation.

Greenhouse gas emissions, carbon stocks and wheat productivity following biochar, compost and vermicompost amendments: comparison of non-saline and salt-affected soils.

Understanding the impact of greenhouse gas (GHG) emissions and carbon stock is crucial for effective climate change assessment and agroecosystem management. However, little is known about the effects of organic amendments on GHG emissions and dynamic changes in carbon stocks in salt-affected soils. We conducted a pot experiment with four treatments including control (only fertilizers addition), biochar, vermicompost, and compost on non-saline and salt-affected soils, with the application on a carbon equivalent basis under wheat crop production. Our results revealed that the addition of vermicompost significantly increased soil organic carbon content by 18% in non-saline soil and 52% in salt-affected soil compared to the control leading to improvements in crop productivity i.e., plant dry biomass production by 57% in non-saline soil with vermicompost, while 56% with the same treatment in salt-affected soil. The grain yield was also noted 44 and 50% more with vermicompost treatment in non-saline and salt-affected soil, respectively. Chlorophyll contents were observed maximum with vermicompost in non-saline (24%), and salt-affected soils (22%) with same treatments. Photosynthetic rate (47% and 53%), stomatal conductance (60% and 12%), and relative water contents (38% and 27%) were also noted maximum with the same treatment in non-saline and salt-affected soils, respectively. However, the highest carbon dioxide emissions were observed in vermicompost- and compost-treated soils, leading to an increase in emissions of 46% in non-saline soil and 74% in salt-affected soil compared to the control. The compost treatment resulted in the highest nitrous oxide emissions, with an increase of 57% in non-saline soil and 62% in salt-affected soil compared to the control. In saline and non-saline soils treated with vermicompost, the global warming potential was recorded as 267% and 81% more than the control, respectively. All treatments, except biochar in non-saline soil, showed increased net GHG emissions due to organic amendment application. However, biochar reduced net emissions by 12% in non-saline soil. The application of organic amendments increased soil organic carbon content and crop yield in both non-saline and salt-affected soils. In conclusion, biochar is most effective among all tested organic amendments at increasing soil organic carbon content in both non-saline and salt-affected soils, which could have potential benefits for soil health and crop production.

Major drivers of soil acidification over 30 years differ in paddy and upland soils in China.

Elevated nitrogen (N) fertilization has largely increased crop production in China, but also increased acidification risks, thereby threatening crop yields. However, natural soil acidification due to bicarbonate (HCO3) leaching and base cation (BC) removal by crop harvest also affect soil acidity whereas the input of HCO3 and BC via fertilizers and manure counteract soil acidification. Insights in rates and drivers of soil acidification in different land use types is too limited to support crop- and site-specific mitigation strategies. In this study, we assessed the historical changes in cropland acidification rates and their drivers for the period 1985-2019 at 151 sites in a typical Chinese county with the combined nutrient and soil acidification model VSD+. VSD+ could well reproduce long-term changes in pH and in the BC concentrations of calcium, magnesium and potassium between 1985 and 2019 in non-calcareous soils. In paddy soils, the acidity production rate decreased from 1985 onwards, mainly driven by a pH-induced reduction in HCO3 leaching and N transformations. In upland soils, however, acidity production was mainly driven by N transformations and hardly changed over time. Crop BC removal by harvesting played a minor role in both paddy and upland soils, but its relative importance increased in paddy soils. The acidity input was partly neutralized by HCO3 input from fertilizers and manure, which decreased over time due to a change from ammonia bicarbonate to urea. Soil buffering by both BC and aluminium release decreased in paddy soils due to a reduction in net acidity production, while it stayed relatively constant in upland soils. We conclude that acidification management in paddy soils requires a focus on avoiding high HCO3 leaching whereas the management in upland soils should focus on balancing N with recycling organic manure and crop residues.

New vegetable field converted from rice paddy increases net economic benefits at the expense of enhanced carbon and nitrogen footprints.

China accounts for around 50 % of the global vegetable harvested area which is expected to increase continuously. Large cropland areas, including rice paddy, have been converted into vegetable cultivation to feed an increasingly affluent population and increase farmers' incomes. However, little information is available on the balance between economic benefits and environmental impacts upon rice paddy conversion into vegetable fields, especially during the initial conversion period. Herein, the life cycle assessment approach was applied to compare the differences in agricultural input costs, yield incomes, net economic benefits (NEB), carbon (C) and nitrogen (N) footprints and net ecosystem economic benefits (NEEB) between the double rice paddy (Rice) and newly vegetable field (Veg) converted from Rice based on a four-year field experiment. Results showed that yield incomes from Veg increased by 96-135 %, outweighing the increased agricultural input costs due to higher inputs of labor and pesticide, thus significantly increasing NEB by 80-137 %, as compared to Rice. Rice conversion into Veg largely increased C footprints by 2.3-10 folds and N footprints by 1.1-2.6 folds, consequently increasing the environmental damage costs (EDC) by 2.2 folds on average. The magnitudes of increases in C and N footprints and EDC due to conversion strongly declined over time. The NEEB, the trade-offs between NEB and EDC, decreased by 18 % in the first year, while increasing by 63 % in the second year and further to 135 % in the fourth year upon conversion. These results suggested that rice paddy conversion into vegetable cultivation could increase the NEB at the expense of enhanced EDC, particular during the initial conversion years. Overall, these findings highlight the importance of introducing interventions to mitigate C and N footprints from newly converted vegetable field, so as to maximize NEEB and realize the green and sustainable vegetable production.

Spatial variation in actual and required nitrogen use efficiency and the potential to close the gap by management practices.

To boost crop production, China uses almost a third of the world's nitrogen (N) fertilizer. However, N losses due to enhanced application of N fertilizers has led to surface water and groundwater pollution. A reduction in N losses without reducing crop yields is possible by increasing nitrogen use efficiency (NUE), which is important for the effective management of local crop production and water quality. This study used two representative agricultural counties in China (Quzhou and Qiyang) to assess if it is possible to achieve N loss thresholds in surface and groundwater by optimizing N management measures while maintaining actual crop production. We used a spatially explicit N balance model to assess the spatial variation in actual N inputs to soil and N losses to water, and in critical N losses and associated agricultural N inputs. We also used this model to calculate the spatial variation in actual NUEs and the required NUE to align actual crop production with N thresholds. We then assessed the feasibility of achieving the necessary NUE changes through optimizing agricultural N management strategies. It was found that actual N input exceeded critical N input in 95 and 83 % of the agricultural area in Quzhou and Qiyang, respectively. To meet actual crop production without exceeding N loss thresholds, the NUE needs to increase with 11 to 15 % whereas the total N input needs to be reduced by 37 %. NUE gaps can be closed by reducing N rates, enhancing organic manure recycling, and using efficiency-enhancing fertilizers, with optimal combinations being dependent on site conditions.

Soil organic carbon priming co-regulated by labile carbon input level and long-term fertilization history.

Labile carbon (C) input and fertilization have important consequences for soil organic matter (SOM) decomposition via the priming effect (PE), thereby impacting soil fertility and C sequestration. However, it remains largely uncertain on how the labile C input levels interact with long-term fertilization history to control PE intensity. To clarify this question, soil samples were collected from a 38-year fertilization field experiment (including five treatments: chemical nitrogen fertilizer, N; chemical fertilizer, NPK; manure, M1; 200 % manure, M2; NPK plus M2, NPKM2), with strongly altered soil physiochemical properties (i.e., soil aggregation, organic C and nutrient availability). These soil samples were incubated with three input levels of 13C-glucose (without glucose, control; low, 0.4 % SOC; high, 2.0 % SOC) to clarify the underlying mechanisms of PE. Results showed that the PE significantly increased with glucose input levels, with values increasing from negative or weak (-2.21 to 3.55 mg C g-1 SOC) at low input level to strongly positive (5.62 to 8.57 mg C g-1 SOC) at high input level across fertilization treatments. The increased PE intensity occurred along with decreased dissolved total nitrogen (DTN) contents and increased ratios of dissolved organic C to DTN, implying that the decline in N availability largely increased PE via enhanced microbial N mining from SOM. Compared to N and NPK treatments, the PE was significantly lower in the manure-amendment treatments, especially for low input level, due to more stable SOM by aggregate protection and higher N and phosphorus availability. These results suggested that manure application could alleviate SOM priming via increased soil C stability and nutrient availability. Collectively, our findings emphasize the importance of long-term fertilization-driven changes in labile C inputs, SOM stability, and nutrient availability in regulating PE and soil C dynamics. This knowledge advances our understanding of the long-term fertilization management for soil C sequestration.

Do not ignore the effects of phosphorus and potassium addition on microbial carbon use efficiency.

P or PK addition significantly affected microbial CUE. No significant linear correlation between respiration rates and microbial CUE under N addition when NP and NPK addition were excluded.

Response of soil phosphatase activity and soil phosphorus fractions to the application of chloropicrin and azoxystrobin in ginger cultivation.

BACKGROUND: Soil fumigation can change soil nutrient cycling processes by affecting soil beneficial microorganisms, which is a key issue for soil fertility. However, the effect of combined application of fumigant and fungicide on soil phosphorus (P) availability remains largely unclear. We investigated the effects of the fumigant chloropicrin (CP) and the fungicide azoxystrobin (AZO) on soil phosphatase activity and soil P fractions in ginger production using a 28-week pot experiment with six treatments: control (CK), a single application of AZO (AZO1), double applications of AZO (AZO2), CP-fumigated soil without AZO (CP), CP combined with AZO1 (CP + AZO1) and CP combined with AZO2 (CP + AZO2). RESULTS: AZO application alone significantly increased the soil labile P fractions (Resin-P + NaHCO3 -Pi + NaOH-Pi) at 9 weeks after planting (WAP) but decreased the soil phosphatase activity at 28 WAP. CP fumigation significantly reduced the soil phosphatase activity but increased the proportions of soil labile P fractions (Resin-P + NaHCO3 -Pi + NaHCO3 -Po) to total P (TP) by 9.0-15.5% throughout the experiment. The combined application of CP and AZO had a synergistic effect on soil phosphatase activity and soil P fractions compared with a single application. CONCLUSION: Although AZO application and CP fumigation can increase soil available P in the short term, they might negatively affect soil fertility in the long run by inhibiting soil phosphatase activity. Soil microbial activities, especially microorganisms related to P cycling, may be responsible for the variations in soil P availability, but further research is needed. © 2023 Society of Chemical Industry.

Achieving high yield and nitrogen agronomic efficiency by coupling wheat varieties with soil fertility.

Wheat breeding has progressively increased yield potential through decades of selection, markedly increased the capacity for food production. Nitrogen (N) fertilizer is essential for wheat production and N agronomic efficiency (NAE) is commonly index used for evaluate the effects of N fertilizer on crop yield, calculated as the difference of wheat yield between N fertilizer treatment and non-N fertilizer treatment divided by the total N application rate. However, the impact of variety on NAE and its interaction with soil fertility remain unknown. Here, to clarify whether and how wheat variety contributes to NAE, and to determine if soil conditions should be considered in variety selection, we conduct a large-scale analysis of data from 12,925 field trials spanning ten years and including 229 wheat varieties, 5 N fertilizer treatments, and a range of soil fertility across China's major wheat production zones. The national average NAE was 9.57 kg kg-1, but significantly differed across regions. At both the national and regional scales, variety significantly affected NAE, and different varieties showed high variability in their performance among low, moderate, and high fertility soils. Here, superior varieties with both high yield and high NAE were identified at each soil fertility fields. The comprehensive effect of selecting regionally superior varieties, optimizing N management, and improving soil fertility could potentially decrease the yield gap by 67 %. Therefore, variety selection based on soil conditions could facilitate improved food security while reducing fertilizer inputs to alleviate environmental impacts.

Mechanism of Potassium Release from Feldspar by Mechanical Activation in Presence of Additives at Ordinary Temperatures.

To improve the potassium availability of feldspar at ordinary temperatures, the mechanical grinding and addition of sodium hydroxide/salts were employed to study the effects of mechanical activation and strong alkali addition on particle characteristics, water-soluble potassium, and the available potassium of feldspar. A laser particle size analyzer was utilized for the direct determination of particle size distribution (PSD) using ground samples. The Brunauer-Emmett-Teller (BET) method was employed for specific surface areas. X-ray diffraction (XRD) was employed for structural characterization, scanning electron microscopy (SEM) for morphology exploration, and energy dispersive spectroscopy (EDS) to determine the chemical composition of potassium feldspar powder. The results revealed that the mechanical activation of potassium feldspar could reduce the particle size and produce agglomerated nanoparticles in the later period. The addition of NaOH and sodium salt did not cause agglomeration, and NaOH dissolved the nanoparticles. The water-soluble potassium content of feldspar in each treatment increased during mechanical grinding, from 21.64 mg kg-1 to 1495.81 mg·kg-1, by adding NaOH 5% weight of potassium feldspar powder and to 3044.08 mg·kg-1 by adding NaOH 10% weight with effects different from those of mechanical shaking. By comparison, only 162.93 mg·kg-1 water-soluble potassium was obtained by adding NaOH 5% weight. The dissolved potassium in the former case was significantly higher than in the latter, and the addition of NaOH and sodium salts significantly enhanced the water-soluble potassium contents due to ion exchange. Furthermore, the addition of sodium hydroxide improved the water-soluble potassium due to its mechanochemical action on potassium feldspar. The mechanical energy changed the crystal structure of potassium feldspar, explaining the increase in available potassium. The addition of sodium salts did not promote change in the feldspar's structure, thereby did not raise the available potassium content. The reason for this was related to the mechanochemical action on sodium hydroxide and feldspar, which could promote the dissolution of fine particles, thereby incrementing the available potassium.

Zinc portioning and allocation patterns among various tissues confers variations in Zn use efficiency and bioavailability in lentil genotypes.

Zinc (Zn) is essential for plants and animals as it plays significant roles in several physiological and biological processes. Its deficiency in soil results in low Zn content food and is one of the major reasons for Zn malnutrition in humans. Biofortification of crops with zinc (Zn) is a viable approach to combat malnutrition, especially in developing countries. A hydroponic study was executed to study response and Zn partitioning in various lentil genotypes. Eight preselected lentil genotypes (Line-11504, Mansehra-89, Masoor-2006, Masoor-85, Line-10502, Markaz-09, Masoor-2004, and Shiraz-96) were grown in solution culture with two Zn levels (control and adequate Zn). Plants were sown in polythene lined iron trays with a two inch layer of prewashed riverbed sand. After 10 days of germination, seedlings were transplanted to a 25L capacity container with nutrient solution for 15 days, and afterward, these plants were divided into two groups, receiving either 2.0 mM Zn or no Zn levels. Three plants of each genotype were harvested at the vegetative growth stage (60 DAT) and the remaining three at physiological maturity (117 DAT). Plants were partitioned into roots, shoots, and grains at harvest. Significant variations in root and shoot dry matter production, grain output, partitioning of Zn in plant parts (root, shoot, and grain), grain phytate reduction, and Zn bioavailability were observed among genotypes. Lentil root accumulated more Zn (54 mg kg-1) with respect to shoot Zn (51 mg kg-1) under Zn supply. The Zn efficient genotypes (Line-11504 and Mansehra-89) produced more root and shoot dry weights at both harvests. There was a positive correlation between the relative growth rate of root and grain phytate concentration (r = 0.55) and [phytate]:[Zn] ratio (r = 0.67). Zn-efficient genotype Mansehra-89 had a maximum root shoot ratio (0.57) and higher grain Zn (60 mg kg-1) with a respectively reduced grain phytate (17 µg g-1) and thus, had more Zn bioavailability (3.01 mg d-1). The genotypic ability for Zn uptake and accumulation within different plant tissues may be incorporated into future crop breeding to improve the nutrition of undernourished consumers.

Interactive salinity and water stress severely reduced the growth, stress tolerance, and physiological responses of guava (Psidium Guajava L.).

Salinity and water stress are serious environmental issues that reduced crop production worldwide. The current research was initiated (2012) in the wirehouse of the Institute of Soil and Environmental Sciences, University of Agriculture, Faisalabad, Pakistan to investigate the growth, stress tolerance, and physiological responses of guava to salinity and water shortage. Guava was grown for one year in pots containing soil with Eight treatments (control, 10 dS m-1, 20 dS m-1, 40 dS m-1, control + water stress (WS), 10 dS m-1 + WS, 20 dS m-1 + WS, 40 dS m-1 + WS) in a completely randomized design. The results indicated that plant growth, stress tolerance, and physiological parameters declined at higher salinity and water stress and could not survive at 40 dS m-1. The 20 dS m-1 + WS caused a > 70% decline in dry weights of shoot and root regarding control. Similarly, the highest decrease in stress tolerance was noticed in 20 dS m-1 + WS followed by the 20 dS m-1 treatment than control. Our findings validated that guava can be cultivated on soils having salinity ≤ 10 dS m-1 but it could not be cultivated on soils having salinity ≥ 20 dS m-1 with limited water supply.

Responses of crop productivity and reactive nitrogen losses to the application of animal manure to China's main crops: A meta-analysis.

The effective utilization of manure in cropland systems is essential to sustain yields and reduce reactive nitrogen (Nr) losses. However, there are still uncertainties regarding the substitution of mineral nitrogen (N) fertilizer with manure in terms of its effects on crop yield and Nr losses. We conducted a comprehensive meta-analysis of wheat, maize, and rice applications in China and discovered that substituting mineral N fertilizer with manure increased wheat and maize yields by 4.9 and 5.5 %, respectively, but decreased rice yield by 1.7 %. The increase of yield is larger at low N application and low mineral N substitution rates ((SR) ≤30 %) for silt soils, warm regions, and acidic soils. High SR (>70 %) decreased rice yield as well as the N use efficiency of wheat and maize. Substitution of mineral N fertilizer with manure resulted in lower NH3 volatilization for wheat (48.7 %), lower N2O and NH3 emissions, and N runoff for maize (12.8, 49.6, and 66.7 %, respectively), and lower total Nr losses for rice (11.3-26.5 %). The loss of Nr was significantly and negatively correlated with soil organic carbon content. The rate of N application, soil properties, and climate were critical factors influencing N2O and NH3 emissions and N leaching, whereas climate or soil properties were the dominant factors influencing response in N runoff. We concluded that in silt soils, warm regions, and neutral soils, a ≤ 50 % substitution of mineral N fertilizer with manure can sustain crop yields while mitigating Nr losses.

Association Between Serum Asprosin and Diabetic Nephropathy in Patients with Type 2 Diabetes Mellitus in the Community: A Cross-Sectional Study.

Objective: To explore the association between serum asprosin and diabetic nephropathy (DN) in patients with type 2 diabetes mellitus (T2DM) in the community. Methods: In this cross-sectional study, we retrospectively collected the clinical data of T2DM patients from a community health service center in southeastern Shanxi Province between November 2019 and July 2021. Logistic regression analysis was used to calculate the odds ratio (OR) and the 95% confidence interval (95% CI) of asprosin levels on the risk of DN. Results: Among 498 T2DM patients included in this study, 221 had microalbuminuria, 105 had massive albuminuria, and 172 did not have any signs of nephropathy. Serum asprosin level was positively correlated with diastolic blood pressure, body mass index, triglycerides, aspartate aminotransferase, alanine aminotransferase, creatinine, ACR and albumin-to-creatinine ratio (all P < 0.05) and negatively correlated with low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, fasting plasma glucose, HbA1c and estimated glomerular filtration rate (all P < 0.05). After adjusting for covariates, increased asprosin was associated with diabetic nephropathy (all OR = 2.560, 95% CI: 1.1592-4.116; P < 0.001). Conclusion: The risk of DN significantly increases with serum asprosin levels, especially among female patients.

Vulnerability and driving factors of soil inorganic carbon stocks in Chinese croplands.

The long-term stability of soil inorganic carbon (SIC) and its minimum contribution towards global C cycle has been challenged, as recent studies have showed rapid decreases in SIC stocks in intensive agricultural systems. However, the extent of SIC losses and its driving factors remains unclear. Here, we compared changes in SIC density (SICD) in Chinese croplands between the 1980s and 2010s. The SIC contents in 1980s were obtained from second national soil survey (n = 949) and published studies (n = 47). The SIC contents in 2010s were based on resampling of soil profiles from the same locations during 2019 and 2020 (n = 30), as well as data from published studies and national soil survey (n = 903). We found that Chinese croplands have lost 27-38% of SICD from the 0-40 cm soil layer and that the soil pH has decreased by 0.53 units over the past 30 years. These SIC losses increased with the ratio of precipitation (P) to potential evapotranspiration (PET) and most notably with nitrogen (N) fertilization. The SICD decreased greatly in humid and semiarid regions, and these losses were enhanced by high N fertilization rates; however, the SICD increased in very arid regions. This analysis demonstrates that the water balance and N fertilization are major drivers leading to dramatic losses of SICD in croplands and, consequently, to decreases in soil fertility and functions.

Effects of chloropicrin fumigation and azoxystrobin application on ginger growth and phosphorus uptake.

Soil chloropicrin (CP) fumigation helps to increase crop yields by eliminating soil-borne diseases which inhibit plant growth. However, little is known about the effect of the CP fumigation combined with fungicide application on plant growth and nutrient uptake. In this study, we conducted a mesocosm experiment with six treatments: CK (untreated soil), AZO1 (a single application of azoxystrobin (AZO)), AZO2 (double applications of AZO), CP (CP fumigation with no AZO), CP+AZO1 (CP combined with AZO1) and CP+AZO2 (CP combined with AZO2) to investigate the effects of CP fumigation and AZO application on ginger growth and phosphorus (P) uptake. Results showed that a single application of AZO had no significant effect on ginger height, biomass and P uptake whether treated with or without CP fumigation, whereas double applications of AZO combined with CP fumigation significantly improved ginger height and the total amount of P in root (P < 0.05). Meanwhile, AZO residues were similar in all treatments with the same number of applications, with less than 50% remaining in the soil after 7 days applied, indicating that CP fumigation treatment did not influence AZO degradation in ginger cultivation. In addition, although the differences in P use efficiency observed across the different treatments were not significant, they nevertheless suggest that the P budget and soil microbial activity may contribute to those differences. Therefore, further studies should be done to link P cycling with microbial communities, and how these related to fumigation and fungicide application.

Calculation of spatially explicit amounts and intervals of agricultural lime applications at county-level in China.

Liming is a long-established and widely used agricultural practice to ameliorate soil acidity and improve crop production. Sustainable liming strategies for regional applications require information on both lime requirements and liming intervals given land use and soil dependent acidification rates. We developed a method to optimize lime requirements and liming intervals at regional level. Lime requirements were based on soil pH buffering capacity and liming intervals were estimated by ongoing soil acidity production, derived from major cations and anions balances in cropland systems. About 66% of croplands in Qiyang required liming to raise soil pH to 6.5, with a total lime requirement of 2.4 × 105 t CaCO3, with an average rate of 2.4 t ha-1 for paddy soils and 2.6 t ha-1 for upland soils. The remaining 34% were mainly calcareous soils. Nutrient management practices and crop rotations, affecting N transformation and crop removal, were the main drivers controlling the spatial variation in total acid production in non-calcareous soils, on average contributing 73% and 25%, respectively. Under current soil acidification rates, 33% of Qiyang's croplands would need liming within 30 years after raising the soil pH to 6.5. Averaged liming interval was 20 years, and 6.8 t ha-1 would be required to maintain soil pH ranges between 5.5 and 6.5. Areas with high soil acidification risk were mostly located in the southeast of Qiyang.

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Understanding the decomposition dynamics and driving factors of manure in the soil subjected to different reclaimed years could provide theoretical basis to rational utilization of manure and soil fertility improvement in coal mining area. Cattle manure and pig manure were mixed with soils subjected to different reclaimed years (one year, R1; 10 years, R10; and 30 years, R30) at the ratio of manure carbon to soil mass of 4 to 100, so as to examine manure decomposition characteristics using the nylon mesh bag (15 cm deep of soil buried) in the Shanxi coal mine reclamation area, with no manure addition as control (CK). Soil samples were collected at day 12, 23, 55, 218, 281, and 365 to measure the contents of soil manure residual, soil microbial biomass carbon (MBC), and dissolved organic carbon (DOC). The contributions of soil properties, manure properties, and hydrothermal condition to manure decomposition were quantified. The results showed that the decomposition rates of pig manure were significantly higher than cattle manure. The humification coefficient of pig manure (average 46.3%) was lower than that of cattle manure (average 71.7%). The humification coefficient of pig manure was significantly lower in the 30-year reclaimed soil (44.5%) compared to the 1-year and 10-year reclaimed soil (average 47.2%). There was no significant difference in the humification coefficient of cattle manure among the three reclaimed soils. The proportion and decomposition rate constant of labile carbon pool of pig manure and cattle manure were significantly different, with values of 52% and 26%, and 0.00085 and 0.00074 ℃-1, respectively. The positive effect of pig manure on MBC and DOC in reclaimed soil was significantly higher than that of cattle manure over 0-218 days, but no difference over 281-365 days. The magnitude of the enhancement of MBC and DOC in those three reclaimed soils after manure amendments showed a similar trend of R1 >R10 ≈ R30. Results of variance partitioning analysis showed that manure decomposition was mainly controlled by manure properties (17.9%) when considering soil properties, manure properties, and hydrothermal condition. In conclusion, the decomposition of pig manure but not cattle manure was regulated by reclamation year. Cattle manure, with higher humification coefficient than pig manure, was recommended for reclaimed mining area to improve soil fertility.

Spatial changes and driving variables of topsoil organic carbon stocks in Chinese croplands under different fertilization strategies.

The effect of different fertilization strategies on changes in soil organic carbon (SOC) largely depends on the current status of a given agricultural region. We analysed the results of 90 long-term field trials (20-37 years) in Chinese croplands to determine the effects of fertilization strategies [i.e., no fertilizer (CK), chemical fertilizer (NPK), manure only (M) and manure plus chemical fertilizers (NPKM)] on soil organic carbon stock (SOCs) at 0-20 cm depth in the North (NC), Northeast (NEC), Northwest (NWC) and South (SC) China. Compared with initial values, SOCs increased by 24-68% and 24-74% under NPKM and M applications, respectively, over the experimental periods. Furthermore, final SOCs under NPKM in NEC and NWC were significantly higher than those under other treatments, but there was no significant difference between NPKM and M in SC and no significant differences among fertilizer treatments in NC. Average SOC stock change rates (SOCr) were positive under all treatments for all regions except for CK and NPK in NEC, which were negative. There were regional differences in treatment effects: all treatments showed significantly different rates in NC and NWC, whereas there were no significant differences between the M and NPKM in NEC and SC. Random forest (RF) modeling showed that among the selected variables initial SOCs was the most important in accounting for differences in SOCr, followed by soil bulk density, mean annual temperature and precipitation for all treatments. Soil total nitrogen content was also an important explanatory variable for SOCr for CK and NPK, and soil pH for M. This study has highlighted the main driving variables of SOC change which can be of use in optimizing fertilization strategies, by taking account of the baseline SOCs status and environmental factors for different regions, to minimize soil carbon emissions while maximizing carbon sequestration in soils.