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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. [ABSTRACT FROM AUTHOR]

Basic soil productivity (BSP) is the productive capacity of farmland soils with their own physical and chemical properties during a specific crop season under local field management. Improving BSP as an effective way to increase or maintain crop yield, and researching its changes and potential driving factors under long-term fertilization are crucial for ensuring high and stable crop yields. In this study, the yields of BSP were simulated using the decision support system for agrotechnology transfer (DSSAT) crop model based on three long-term experiments, and its changing characteristics and driving factors were investigated under various fertilization treatments in wheat–maize rotation systems during 1991–2019. Five treatments were included: (1) unfertilized control (CK); (2) balanced mineral fertilization (NPK); (3) NPK plus manure (NPKM); (4) high dose of NPK plus manure (1.5NPKM); and (5) NPK plus crop straw (NPKS). This study found that the BSP of wheat and maize exhibited a fluctuating increase or stable change trend under four fertilization treatments at the Yangling (YL) and Zhengzhou (ZZ) sites, while a fluctuating reduction trend was observed at the Qiyang (QY) site. Compared with CK, NPKM, 1.5NPKM and NPKS significantly (p < 0.05) improved the BSP of wheat and maize at the YL and ZZ sites. The BSP of both maize and wheat under NPKM and 1.5NPKM was significantly (p < 0.05) higher than that under NPK or NPKS, whereas no statistically significant difference was found between NPK and NPKS at the QY site. The contribution rates of basic soil productivity (CBSP) of maize and wheat at the YL (41.5–60.7% and 53.0–64.3%) and ZZ sites (44.4–59.2% and 56.8–66.7%) were overall higher than that at the QY site (25.8–37.6% and 48.3–60.1%). In most cases, the difference in CBSP among different fertilization treatments was consistent with that in BSP. Moreover, a significant positive correlation was recorded between BSP and soil pH (r = 0.73, p < 0.01; r = 0.87, p < 0.01), TN (r = 0.56, p < 0.01; r = 0.62, p < 0.01) and TK content (r = 0.49, p < 0.01; r = 0.58, p < 0.01) in maize and wheat. Soil pH significantly correlated positively with the BSP of maize (R2 = 0.54, p < 0.001) and wheat (R2 = 0.49, p < 0.001) at the QY site, but negative correlation (R2 = 0.20, p < 0.001; R2 = 0.30, p < 0.001) was only found in maize at the YL and ZZ sites. The BSP of maize and wheat showed a significant negative linear correlation with MAP (R2 = 0.49–0.67, p < 0.001) and MAT (R2 = 0.36–0.62, p < 0.001). Random forests (RF) and variance partitioning analysis (VPA) revealed that soil properties and its interaction with the climate showed a higher explanation rate for BSP, indicating that these factors are the key drivers of BSP change. Overall, chemical fertilizers combined with manure can effectively increase BSP, while the effects of fertilizer combined with straw on BSP vary by region. The changes in BSP in wheat–maize cropping were mainly driven by both the soil and its interactions with the climate. [ABSTRACT FROM AUTHOR]

The critical pH was the target pH for soil acidity improvement, which has important guiding significance for agricultural production and sustainable development. A pot experiment was conducted to investigate the effect of soil initial properties affecting the response of wheat growth to pH. 5 soils derived from plate shale, quaternary red earth, river alluvium, tertiary red sandstone, and granite were used in this study. The results showed that the maximum shoot biomasses of wheat were 2.71, 1.17, 2.06, 1.57 and 1.70 g⋅pot-1 for soils derived from plate shale, quaternary red earth, river alluvium, granite, and tertiary red sandstone, respectively. The critical values of pH95%, pH50%, or pH5% were defined as shoot biomass reaching to 95%, 50%, or 5% of maximum values. The pH95%, pH50%, or pH5% were 5.31, 4.42, and 3.53 for soil derived from plate shale, 5.79, 4.79, and 3.80 for quaternary red earth, 5.25, 4.71, and 4.16 for river alluvium, 4.94, 4.61, and 4.29 for tertiary red sandstone granite, and 5.72, 4.66, and 3.59 for granite, respectively. The maximum values of shoot biomass had significant positive correlations with soil initial pH, available P, exchangeable Mg and exchangeable Ca. The pH50% of wheat shoot biomass was negatively correlated with soil initial available P; and the pH50%of wheat height was negatively correlated with soil initial available P and exchangeable Mg. The data indicated that soil initial available P and exchangeable Mg shaped the response of wheat growth to pH and the maximum values of crop biomass were determined by both soil nutrient status and acidity. Therefore, we recommend that co-amelioration of soil fertility and acidity was a practical method to reach a best condition for plant growth. [ABSTRACT FROM AUTHOR]

Background: The contribution of long-term fertilization to soil organic carbon (SOC) storage has been of great concern. To assess the effects of long-term fertilization on SOC storage and stability in top and sub-soil layers, soil samples were collected from a 29-year field experimental station in a typical paddy soil in southern China. The SOC storage of whole soil and SOC fractions was quantified at three soil depths (0–20, 20–40, 40–60 cm) under four treatments: no fertilization (Control), a combination of nitrogen, phosphorus and potassium (NPK), double the rates of NPK (2NPK), NPK plus manure (NPKM). Results: The increase of Cinput-total was significantly higher than that of SOC storage among different treatments (p < 0.05), indicating that soil fixation of exogenous carbon is limited. Besides, the SOC accumulation and sequestration rates patterned as NPKM > 2NPK > NPK, and these rates were higher at 0–20 cm depth as compared to other depth intervals. Furthermore, for the whole profile, the SOC storage of active pool was higher in the Control (39.6 t C ha−1) than in other treatment (36.2 t C ha−1, p < 0.05). Whereas, fertilization increased the SOC storage of passive pool, ranked as NPKM > 2NPK≈NPK > Control (p < 0.05), indicating that fertilization, especially organic combined with inorganic fertilization, improved SOC stability. From the perspective of soil layers, the difference of SOC storage among treatments for passive pool was mainly resulted from the difference at surface soil, and for active pool were the deeper layers. Additionally, manure application increased the difference among soil layers. Conclusion: This study concluded that non-fertilized treatment could improve the SOC storage of active pool especially in deep soil layers, while fertilization especially manure application could improve the SOC storage and stability in surface soil and increased the difference among soil layers. [ABSTRACT FROM AUTHOR]

Purpose : Soil enzymes are the main drivers of microbial catabolic and anabolic processes. However, the response of functional enzymes strategies and microbial metabolic efficiency (MME) to nutrient stoichiometry remains unclear in straw-amended black soil. Methods: Four nutrients gradients of N0, N1, N2, and N3 were set, and N0–N3 mean straw-amended soil with increasing addition of nitrogen (N), phosphorus (P), and sulfur (S). The activities of five enzymes involved in carbon (C), N, and P acquisition were investigated under different nutrient treatments in two soils during an 84-day incubation study. Microbial nutrient availability and C use efficiency (CUE) were assessed based on enzymatic stoichiometry (ES), and their potential relationship to change net soil-C (Net-C) was then established. Results: Compared to soil with straw alone, the Net-C in Gongzhuling and Hailun increased by 1.2–2.3 and 1.3–1.9 times with stoichiometric nutrient management, respectively. ES revealed that microbial metabolism was successively limited by N and P in Gongzhuling soil and was mainly limited by P in Hailun soil. Nutrient supplementation improved the MME, supported by a decrease of − 9.2% (− 3.4 to − 17.8%) in qCO2 and an increase of 10.1% (2.9–23.6%) in CUE. Path analysis suggested that nutrient supplementation influenced Net-C by directly and positively regulating C and P acquisition EEAs and CUE. The Net-C in Gongzhuling was more sensitive to nutrient supplementation, while that in Hailun was more limited by P, indicating that microbial metabolism might be related to soil pH or clay content. Conclusions: Combined addition of straw and N, P, and S improved Net-C by alleviating microbial nutrient limitation and improving CUE, in which process P acquisition enzyme, P availability, and soil properties (pH or clay content) played a key role. [ABSTRACT FROM AUTHOR]

This study investigates 11 agricultural management practices (AMPs) and their effects on seven visual soil quality indicators and soil aggregate stability. The survey carried out across eight pedoclimatic zones in Europe and China was based on visual soil assessments (New Zealand VSA method) performed on soils subject to different soil management practices and nearby similar soils, under similar farming features, without the distinctive soil management practice (control). Fisher's exact test was used to test if the management treatment was independent of the score of each visual soil quality indicator and to test if the management treatment produced a higher frequency of the score 'good'. The results showed a statistically significant (α <.05) higher frequency of the score 'good' for 'soil structure and consistency' and/or 'soil porosity' for six AMPs. For no‐till AMP, the null hypothesis can also be rejected for 'susceptibility to erosion' and 'soil stability' and for 'mulching + permanent soil cover' AMP, for the 'presence of tillage pan' and 'soil colour'. The hypothesis that the management treatment was independent of the score of each indicator was rejected for 'soil structure and consistency' of three AMPs, for 'soil porosity' of three AMPs, for 'soil colour' of one AMP and for the 'presence of tillage pan' of one AMP. This study demonstrates that farming systems sharing a common influential soil management practice at different locations and with different soil types significantly affect the score of some visual soil quality indicators. [ABSTRACT FROM AUTHOR]

The determination of organic nitrogen (N) mineralization is crucial for estimating N availability, quantifying exogenous inputs, and estimating associated environmental impacts. The objective of this study was to explore the effect of long-term various fertilization on soil organic N mineralization potential (NMP), which influences plant N accessibility. Treatments from a 26-year long-term field experiment with no fertilization (CK), chemical fertilizer N at 165 kg N ha−1 and P at 82.5 kg P2O5 ha−1 (NP), NP with K fertilizer at 165, 82.5, 82.5 kg ha−1 N, P2O5 and K2O (NPK), NPK at 165, 82.5, 82.5 kg ha−1 N, P2O5 and K2O with manure at 7857.14 kg ha−1 (NPKM), and NPKM at 165, 82.5, 82.5 kg ha−1 N, P2O5 and K2O with manure at 1.5× application rate (11,785.71 kg ha−1) (1.5NPKM) were examined for potentially mineralizable N by aerobic incubation at 35 °C for 30 weeks. Three pools (Pools I, II, and III) of mineralizable N were recognized. Pool I, the mineralization flush on rewetting in the first 2 weeks; Pool II, gross N mineralization between weeks 2 and 30; and Pool III, the potentially mineralizable N, predicted from the fitted curve, that did not mineralize during the incubation period. Soil microbial biomass carbon (SMBC) and N (SMBN) as well as fixed ammonium (NH4+) contents and relationship with N mineralization rate (k) were also studied. Long-term manure application yielded a significantly higher k (0.32 week−1) than other treatments (0.12–0.22 week−1) but not a significantly higher NMP. Nitrogen mineralization during the wheat and maize-growing seasons was predicted to be 8.7–26.3 (mg N kg−1 soil) and 25.9–42.1 (mg N kg−1 soil), respectively. Both labile mineralizable N pools (Pools I and II) followed the same patterns in the treatments: 1.5NPKM > NPKM > NPK > NP > CK, while the reverse was true for stable N (Pool III). The significant positive correlation between k with SMBC and SMBN (R2 = 0.93, p = 0.008 and R2 = 0.94, p = 0.006) suggested that the higher mineralization rate might be contributed by the higher soil microbial biomass in NPKM. The trends of fixed NH4+ and mineralized N were coupled. Long-term manure application significantly improved the N mineralization rate in soil. Manure application is an effective strategy to enhance soil microbial biomass and soil N availability and has the potential to reduce the dependence upon chemical N fertilization. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Purpose: Soil microbial biomass (SMB), as the source and sink of soil nutrients, and its stoichiometry play a key role in soil organic carbon (SOC) and nitrogen (N) mineralization. The objective of this study was to investigate the responses of SOC and N mineralization to changes in microbial biomass and SOC, N, and phosphorus (P) stoichiometry resulted from long-term fertilization regimes. Materials and methods: Soil was sampled from a rice-wheat rotation system subjected to 37 years of nine fertilization treatments with different nutrient input amounts: control (CK), N alone, N combined with mineral phosphorus (NP), NP plus potassium (NPK), manure alone (M), and M combined with N (MN), NP (MNP), NPK (MNPK), and a higher rate of M with NPK (hMNPK). The sampled soil was incubated for the determination of SOC and N mineralization, C, N, and P stoichiometry of soil and SMB, and associated soil enzymes related to C and N cycling. Results and discussion: Relative to the CK and treatments with mineral fertilizers, treatments with manure (M, MN, MNP, MNPK, and hMNPK) significantly increased SOC and N mineralization by 48–78% and 54–97%, respectively. Microbial metabolic quotient (qCO2) decreased by 32–55% in treatments with manure compared to the N and NP treatments, but showed no effect on the qCO2 when compared to the NPK treatment. The leucine amino peptidase (LAP) enzyme showed significant positive correlation with SOC and N mineralization, and negatively related to the qCO2. Significantly negative correlations were also observed between SOC and N mineralization and soil C:P and N:P ratio, as well as microbial biomass SMBC:SMBP and SMBN:SMBP stoichiometry, respectively. However, the availability of N and P had limited effects on the qCO2 after reaching a certain value (0.69–0.72 mg CO2-C g−1 MBC h−1). Conclusions: Lower soil elemental (C:P and N:P) and microbial biomass stoichiometry (SMBC:SMBP and SMBN:SMBP) and increase of LAP resulted from combined application of manure and mineral fertilizers, accelerated SOC, and N mineralization. Mineral nutrient input with manure amendments could be an optimal strategy to meet the microbial stoichiometric demands and enhance nutrient availability for crops in agricultural ecosystems. [ABSTRACT FROM AUTHOR]

The soil microbial biomass, atmospheric carbon dioxide and abundance of decomposer are influenced by rate and addition pattern of glucose carbon. The present study was conducted to evaluate the effect of single and repeated additions of glucose-C on soil microbial biomass carbon (SMBC) and CO2 response in black soil of China. The incubator study comprising of 116-days was conducted in different fertility levels of black soil of Jilin province of China, to determine the effects of glucose addition patterns viz single addition (2% glucose-C once application) and repeated addition (2% glucose-C in five splits) on soil microbial biomass carbon and CO2 accumulation. Fortygram air dried soil was filled into 250 ml Schott bottle and bottles were arranged in CRD-factorial design with 5 repeats. Factor (A), included glucose addition patterns (single & repeated additions). Factor (B), consisted of soil fertility levels: low, medium and high on the basis of soil organic carbon. Thereafter glucose-C (2%) solution was added drop wise to soil. The addition patterns showed positive response on SMBC, CO2 evolved and CO2 accumulation. Over all mean (low, medium and high fertility soils) of repeated addition depicted 32% and 0.92% higher values of SMBC than control and single additions, respectively. The CO2 emission of repeated addition was 21.3% higher in low fertility soil. The mean CO2 accumulation showed higher values in low fertility soil by single addition than repeated and control in all soils. Single glucose-C addition in combination with different soil fertility levels augmented the microbial biomass and triggered carbon mineralization for shorter period (up to 3 weeks). The repeated addition of glucose in combination with different soil fertility levels also enhanced soil microbial biomass carbon and CO2 in longer incubation period. It is concluded from this study that microbial starvation for organic carbon was very high hence; repeated addition may be suggested to meet C demand of microbes. [ABSTRACT FROM AUTHOR]

Abstract: Long-term fertilization has a significant impact on total soil organic carbon (SOC) stock. However, fertilization impact on physical fractions of SOC is still poorly understood for red soils in southern China. This study assessed the impact of 17years (1990–2007) of long-term fertilization on the changes in different SOC fractions under an intensive maize (Zea mays L)–wheat (Triticum Aestivium L) cropping system in a red soil of southern China through various treatments: the unfertilized control (CK), the recommended applied rates of N (N), NP (NP), NPK (NPK), NPK+manure (NPKM), NPK+straw (NPKS) and manure only (M), and a 150% recommended applied rate of NPK+manure (1.5NPKM). Soil samples from 0 to 20cm soil layer taken in September, 2007, were separated into free particulate organic C (fPOC), intra-microaggregate particulate organic C (iPOC), and mineral associated organic C (MOC) with physical fractionation. In comparison with CK, all the C fractions and maize and wheat yields were significantly increased, except for N and NP treatments. The treatments with manure (M, NPKM, and 1.5NPKM) showed higher C sequestration rates in MOC (323–515kgha−1 yr−1), fPOC (291–408kgha−1 yr−1) and iPOC (162–179kgha−1 yr−1). It was estimated that 8.0 to 35.7% of the gross C input from manure and crop residues over a period of seventeen years contributed to the increase of total SOC stock. Both MOC C sequestration efficiency (CES) and C sequestration distribution (CSD) were the highest among the C fractions for all the treatments. Significantly positive linear correlations were observed between accumulated C sequestrations in all fractions with gross C input and both maize and wheat yields. Our result indicated that MOC was the primary fraction of C sequestration in the red soils. The most efficient fertilization practice for sequestering C in each fraction in the red soils was continuous applications of either manure or manure plus mineral fertilizers. [Copyright &y& Elsevier]

A correction to this paper has been published: https://doi.org/10.1007/s00374-021-01563-3 [ABSTRACT FROM AUTHOR]

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. Image 1 • Physical protection mechanisms were the most dominant in soil profile. • CPOC was the most sensitive fractions. • MNPK and SNPK caused accretion of total SOC content in a soil profile. • The correlations suggested that this soil has not yet reached C saturation. [ABSTRACT FROM AUTHOR]

The original version of this article, unfortunately, contained errors. Corrections in the Table 1 and “Results and discussion” section are presented in this article. [ABSTRACT FROM AUTHOR]

Soil organic carbon (SOC) dynamics in agro-ecosystem is largely influenced by cropping. However, quantifying the contributions of various crops has been lacking. Here we employed a stable isotopic approach to evaluate the contributions of wheat and maize residues to SOC at three long-term experimental sites in north China. Soil samples were collected from 0-20, 20-40, 40-60, 60-80 and 80-100 cm after 13 and 20 years of wheat-maize rotation, and SOC and its stable 13C composition were determined. Our data showed that the δ13C value of SOC varied, on average, from −22.1‰ in the 0-20 cm to −21.5‰ in the 80-100 cm. Carbon input through maize residues ranged from 35% to 68% whereas the contribution of maize residues to SOC (0-40 cm) ranged from 28% to 40%. Our analyses suggested that the retention coefficient was in the range of 8.0-13.6% for maize residues and 16.5-28.5% for wheat residues. The two-fold higher retention coefficient of wheat versus maize residues was due to the differences in the quality of residues and probably also in the temperature during the growing season. Our study highlighted the importance of crop management on carbon sequestration in agricultural lands. [ABSTRACT FROM AUTHOR]

As an effective field management practice for better crop productivity, fertilization showed profound impacts on soil health by altering soil chemical, physical, and biological processes. But, how soil health and related ecosystem multifunctionality (EMF) respond to long-term fertilization remains unclear. In this study, based on a 29-year field experiment, we evaluated soil health and EMF under chemical fertilization versus manure application. Long-term manure application maintained soil pH, significantly increased water-stable aggregate, total and available nutrients, microbial biomass and community (bacteria, fungi, and actinomycetes, etc.), and enzyme activities compared with treatments under chemical fertilizers. Edaphic factors of soil organic carbon (SOC), available phosphorous (AP), fungi, cation exchange capacity, and clay content were identified as key indicators of soil health evaluation by network analysis. The soil health indices (SHIs) of chemical fertilizer treatments were 39–52% lower than that of natural vegetation recovery, with carbon and nutrient cycling, soil biodiversity maintenance, and productivity at low ecosystem function levels. Manure application enhanced soil health by 150–196% compared to unfertilized control by improving SOC, P availability, and sustaining ecosystem functions with carbon and nutrient cycling, soil biodiversity maintenance, buffering and filtering capacity, and productivity at relatively high ecosystem function levels. The individual functions of carbon and nutrient cycling, physical structure stability, and productivity illustrated sensitive responses to the increase in soil health, while inherent soil functions of buffering and filtering capacity and soil biodiversity maintenance were only correlated with high soil health. Manuring improved soil functions and soil health simultaneously, indicating a synergistic relationship. Our findings highlight the significance of manure application to improve soil health and sustain functions in intensive agricultural systems. • SOC, AP, fungi, clay content, and CEC were identified as key indicators. • Natural vegetation recovery improved SHI compared with chemical fertilization. • Manuring improved soil health by sustaining soil multifunction at high levels. • Soil functions had diverse responses to soil health shifts. [ABSTRACT FROM AUTHOR]

• Drainage enhanced N 2 O emission via increased abundances of genes related to N 2 O production. • Labile C addition mitigated the increased N 2 O emission by drainage via increased nosZ abundance. • Nitrogen addition strongly amplified the increased N 2 O emission due to drainage. • N 2 O emission increased with NH 4 + depletion and NO 3 − accumulation following paddy soil drainage. • N 2 O emission was positively correlated with AOA and AOB abundances, and (nirK + nirS)/ nosZ ratio. Conversion from paddy field to upland cultivation, driven by economic benefits, generally increases N 2 O emission. However, the underlying mechanisms regarding the changes in N 2 O emission during the transition period of paddy soil drainage and conversion into upland remain unclear. To address this knowledge gap, a microcosm experiment was conducted to mechanistically elucidate the N 2 O emissions in response to paddy soil drainage and its interaction with carbon (C, glucose) and nitrogen (N, NH 4 Cl) availability. Results showed that N 2 O emissions were significantly lower in the submerged paddy soil (0.51 ± 0.03 mg N kg−1) compared to drained paddy soil (3.63 ± 0.66 mg N kg−1). The increased N 2 O emission was positively associated with soil NH 4 + depletion and NO 3 − accumulation, indicating increased nitrification and NO 3 − supply for denitrification following paddy soil drainage. Substrate C and N availability had little effect on N 2 O emission from submerged paddy soil, but strongly mediated the response of N 2 O emission to paddy soil drainage. High C availability largely mitigated the increased N 2 O emission by drainage, mainly resulting from increased N 2 O-reductase gene (nosZ) abundance. The increased N availability interacting with drainage strongly increased N 2 O emissions by 1.99–16.34 folds, primarily due to increased NO 3 − content and gene abundances of ammonia-oxidizing bacteria (AOB) and nitrite reductase (nirK and nirS). The N 2 O emissions were positively correlated with the abundances of ammonia-oxidizing archaea (AOA), AOB, nirK and nirS genes, and (nirK + nirS)/ nosZ ratio across treatments. Collectively, our findings suggested that the increased N 2 O emission due to paddy soil drainage is regulated by C and N availability, attributed to changes in NO 3 − content and abundances of nitrifying and denitrifying genes. [ABSTRACT FROM AUTHOR]

• Long-term manure application and stover return increased macroaggregate by 10 %. • Manure incorporated soil reduced N retention from chemical fertilizer in all aggregates. • The cPOM, intra-MOM and inter-MOM were the main fractions to retain fertilizer N. • The cPOM in NPKM treatment produced higher biomass than that without manure. • The use efficiency of the retained N in cPOM and inter-MOM were higher than in intra-MOM. Long-term incorporation of manure has shown many benefits to improve soil productivity, but its effects on nitrogen (N) partitioning in soil aggregates and availability to plants is not well understood. The aim of this study was to examine the influence of different long-term field fertilization regimes on N partitioning and availability in soil aggregates. Soils from a field after 25-yr treatments of no fertilization (CK), mineral fertilizer (NPK), NPK with stover return (NPKS), and NPK with manure application (NPKM) were examined for N partitioning after adding 15N-labelled urea and incubating for 42 days. Using a wet sieving procedure, soil was separated into macroaggregates (> 250 μm, coarse particulate organic matter or cPOM), microaggregates (53–250 μm), and silt + clay (< 53 μm, inter mineral-associated OM or inter-MOM). The OM in microaggregates was further separated into fine free POM (ffPOM), physically protected intra-aggregate POM (iPOM), and intra mineral-associated OM (intra-MOM). Total N and 15N concentrations were determined. All fractions except ffPOM (limited mass) were used to cultivate ryegrass (Lolium perenne L.) and 15N uptake was determined. Mass of macroaggregate was 10 % higher from NPKM and NPKS with significantly higher use efficiency than that from NPK while the opposite was true for intra-MOM fraction with no differences in other fractions. The 15N retained in cPOM, intra-MOM, and inter-MOM ranged from 24 to 34%, 28–37 %, and 33–38 %, respectively, and that from ffPOM and iPOM was 1–4% of all retained in aggregates. Ryegrass N uptake was in the range of 14–19 %, 14–24 %, and 3–5% for the cPOM, inter-MOM, and the intra-MOM, respectively. However, the total amount of 15N fertilizer retained in aggregates from the NPKM treatment (14 %) was the lowest due to its higher amount (86 % of 15N) as in soluble phase compared to other treatments (78–83 %). This research concludes that long-term manure application resulted in increased formation of macroaggregates, higher plant-available N in the aggregates, and larger amount of soluble N that contributed to the high yield in the field illustrating the role of manure to improve soil productivity and sustain crop production. [ABSTRACT FROM AUTHOR]

Fig. Relative importance of independent variables for controlling SMBC (a), SMBN (c) changes after manure application as determined using random forests (RF) models and the performance of random forests models for detecting controlling factors of SMBC (b), SMBN (d) change in the croplands in China. • Manure application increased SMBC (40%) and SMBN (55%) related to NPK. • Manure type was the predominant regulator of SMBC responses to manure application. • Local edaphic and climate condition constrain increase in SMBC by manure. Soil microbial biomass carbon (SMBC) and nitrogen (SMBN) are important indices of soil bio-fertility. While intensively managed cropping systems can reduce microbial biomass, application of manure is a potential way to rebuilt microbial biomass and improve soil functions. However, the responses of SMBC and SMBN to manure application relative to mineral fertilizers (NPK) in Chinese cropping systems remains unclear. We conducted a meta-analysis based on 103 peer-reviewed publications with 1448 paired observations to identify the degree to which climate types, soil properties and agricultural managements regulate the responses of microbial biomass to manure amendment relative to NPK. The results indicated that manure application increased SMBC, SMBN, SMBC/soil organic carbon (SOC) and SMBN/soil total nitrogen (TN) by 40%, 55%, 16% and 21%, respectively, across all the observations compared to NPK. SMBC/SMBN under manure amendment (6.58 in average) was lower than that in NPK (7.86 in average). Manure-related factors, e.g. manure types, duration of application, manure-C and N input rates, were the strongest regulators of the response of microbial biomass. Soil properties and climates also contributed to considerable degrees of variation in microbial biomass response based on variance partitioning analysis (VPA). Results of the random forest (RF) models showed that manure type, application rate (manure-C and N input) as well as soil initial properties (SOC, TN and clay contents) were likely the predominant factors controlling the response of microbial biomass to manure application. Our study indicates that manure application can be an effective way to restore the loss of microbial biomass due to intensive application of NPK, yet variations in response are determined by specific manure type, application rate, as well as local conditions of climate and inherent soil properties. [ABSTRACT FROM AUTHOR]