Organic wastes have a positive impact on soil physical and chemical properties in the agroecosystems. However, its main effects on soil organic carbon (SOC) or total organic carbon, TOC (SOC and ...coal-C) contents as well as their effects on soil physico-chemical properties are still unclear. Two types of organic wastes (maize straw and manure) were utilized in dryland affected by mining activities to quantify their relative effect on soil physico-chemical properties. Regression analysis was used to assess the relationship between the soil physical properties, SOC, and TOC as well as their respective contributions to improving these properties. Treatments included control (CK), straw (S), low manure (LM), medium manure plus straw (S-MM), and high manure plus straw (S-HM). The results showed that SOC, soil bulk density, mean weight diameter (MWD), soil total porosity, soil penetration resistance, saturated hydraulic conductivity, and soil infiltration rate were strongly influenced by the application of organic wastes. A stronger linear relationship between SOC and the MWD, (R2 = 0.93, p < 0.05) compared to that between TOC and MWD indicated the important role of SOC in improving soil aggregation relative to the effect of TOC. According to the principal component analysis (PCA), the application of organic wastes had stronger effects on SOC contents and physical properties than TOC (SOC and coal-C). These findings advance our understanding of the actual effect of organic wastes on soil physical properties and SOC in dryland affected by mining activities and could inform fertilizer management decisions to improve soil properties.
Determining the effects of fertilization regimes on soil aggregates, carbon (C) and nitrogen (N) distribution, and pH is essential for improving soil structure and soil organic carbon (SOC) ...accumulation to help in proper soil fertility management. Based on a 41-year field fertilization experiment conducted on dark brown soil in northeast China, we examined the soil aggregate size distribution and associated C, N, and pH to provide a scientific basis for elucidation of the mechanisms underlying the effects of fertilization treatments on soil structure and fertility. Six different fertilization treatments included no fertilizer (CK), low-dose chemical fertilizer (NP), moderate-dose chemical fertilizer (2NP), high-dose chemical fertilizer (4NP), normal-dose organic fertilizer (M), and normal-dose organic fertilizer plus moderate-dose chemical fertilizer (M+2NP). Our findings showed that compared to CK, M and M+2NP significantly increased the proportion of macroaggregates by 40% and 28%, respectively, whereas 4NP significantly decreased it by 19%. The mean weight diameter (MWD) and geometric mean diameter (GMD) under M and M+2NP were significantly higher than that under CK, at 12–21% and 24–36%, respectively. The fractal dimension (D) value of M+2NP was significantly lower than those of 2NP and 4NP by 4% and 5%, respectively. Soil pH under the M treatment was highest, followed by M+2NP. Soil pH under 2NP and 4NP more significantly decreased, by 0.1 and 0.2 units, than under M treatment. Soil pH values were correlated with the proportion of soil macroaggregates, MWD, and GWD, respectively (p < 0.05). Relative to CK, M and M+2NP increased the contents and stocks of SOC (by 40–49% and 89–93%, respectively) and total N (59–68% and 119–123%, respectively). Furthermore, the contents and stocks of aggregate-associated SOC and total N decreased following the order: NP > 2NP > 4NP. Overall, the long-term application of organic fertilization regimes (M and M+2NP) effectively improved soil aggregation as well as SOC accumulation and decreased soil acidification in dark brown soil in northeast China.
Long-term fertilization alters soil microbiological properties and then affects the soil organic carbon (SOC) pool. However, the interrelations of SOC with biological drivers and their relative ...importance are rarely analyzed quantitatively at aggregate scale. We investigated the contribution of soil microbial biomass, diversity, and enzyme activity to C pool in soil aggregate fractions (>5 mm, 2–5 mm, 1–2 mm, 0.25–1 mm, and <0.25 mm) at topsoil (0–15 cm) from a 27-year long-term fertilization regime. Compared to CK (no fertilization management), NP (inorganic fertilization alone) decreased all of the microbial groups’ biomass, while NPS and NPM (inorganic fertilization plus the incorporation of maize straw or composted cow manure) significantly reduced this negative effect of NP on microbial biomass and increased the microbial contribution to C pool. The results show that microbial variables were significantly correlated with SOC content in >0.25 mm aggregates rather than in <0.25 mm aggregates. Fungal variables (fungal, AM biomass, and F/B ratio) and enzyme activities (BXYL and LAP) in >0.25 mm aggregates explained 21% and 2% of C, respectively. Overall, organic matter addition could contribute to higher C storage by boosting fungal community and enzyme activity rather than by changing microbial community diversity in macro-aggregates.
No‐tillage (NT) has been shown to control soil degradation by impacting soil aggregates (i.e., basic units of soil structure, whose characteristics mediate key soil processes, like carbon ...sequestration). However, there has been no systematic analysis of the impacts of NT on soil aggregation and aggregate‐associated soil organic carbon (SOC) at global level. We conducted a global meta‐analysis of 89 publications to elucidate the changes in soil aggregation and aggregate‐associated SOC under NT. Notably, we quantified the roles of diverse environmental and agronomic factors (e.g., climatic conditions, experimental duration, cropping intensity, soil texture, and initial SOC/pH) in the changes in those variables. Relative to conventional tillage (CT), NT significantly increased the proportions of water‐stable large (LM) and small (SM) macro‐aggregates and the mean weight diameter (MWD) (by 49%, 11%, and 23%, respectively) but decreased the proportions of micro‐aggregates (MIC) and silt plus clay‐size particles (SC) (by 11% and 16%, respectively). NT significantly enhanced SOC concentrations in LM (17%), SM (14%), MIC (10%), and SC (7%) compared to CT. Furthermore, the random forest (RF) model demonstrated that climatic conditions, experimental duration, and soil texture were the predominant factors controlling the changes in aggregation and aggregate‐associated SOC under NT. Overall, our results indicate that NT is an effective strategy to enhance soil aggregation and aggregate‐associated SOC, yet variations in responses are determined by specific environmental/agronomic factors. This study provided a basis for identifying site‐specific NT practice that could help improve soil structure and SOC sequestration, ultimately controlling soil degradation in croplands.
Understanding the global patterns and controls on soil aggregation and associated organic carbon (OC) is essential to improve soil carbon storage and mitigate climate warming. Crop rotation is an ...important feature of sustainable agricultural management and influences multiple soil properties. However, the effects of crop rotation on soil aggregation and associated OC remain poorly understood. We conducted a meta-analysis of 2199 paired observations from 53 studies to quantitatively analyze crop rotation-induced changes in soil aggregation and associated OC and elucidate optimal climatic, edaphic, and agronomic factors. Overall, crop rotation improved the proportions of macroaggregates (> 0.25 mm) by 7–14%, aggregate stability by 7–9%, and OC contents in all sizes of aggregates by 7–8% relative to continuous monoculture. Crop rotation increased soil aggregation and associated OC mainly in regions with mean annual temperature between 8 and 15℃, mean annual precipitation between 600 and 1000 mm, and also in topsoil (0–20 cm) with loamy textures and medium levels of initial soil OC (10–15 g kg−1), total nitrogen (0.75–1.50 g kg−1), and pH (6−8). Greater increases in soil aggregation and associated OC induced by crop rotation were associated with sub-soiling, no-till, straw retention, combined manure-inorganic fertilizers, and a lower nitrogen fertilization input rate with more rotation cycles and longer rotation length. Crop rotation effects were especially strong when the previously cultivated crop was soybean. The variance partitioning analysis revealed that variations in crop rotation-induced changes in soil aggregation and associated OC were mainly explained by climate (26–35%) and soil properties (17–34%). The random forest model indicated that climate (mean annual temperature and precipitation) and initial soil OC were the predominant controls on the effects of crop rotation. Overall, these findings suggest that the use of crop rotation can help sequester carbon by improving soil aggregation and associated OC, and highlight the importance of climate and initial soil OC in site-specific crop rotation systems to the sustainability of agroecosystems.
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•Crop rotation overall improved the proportions of macroaggregates (7–14%) and aggregate stability (7–9%).•Crop rotation generally increased OC content in all aggregate size classes by 7–8%.•Crop rotation-induced effects on soil aggregation and associated OC varied with climatic, edaphic, and agronomic factors.•Climate and initial soil carbon content were the main controlling factors for crop rotation effects.
The priming effect is an essential mediator in the soil carbon (C) cycle. There is a growing concern about the priming effect induced by labile C input. However, the driving factors of the priming ...effect under agroecosystems with different historical tillage management remain unclear. By conducting a laboratory incubation experiment, the priming effect and the fate of 13C-labeled glucose (1.658 atom%) were quantified in two soils (Cambisols and Phaeozems) that underwent the 12-year or 13-year tillage managements: rotary tillage without straw retention (RTN), and no-tillage with straw retention (NTS), and a grassland (GRL). After the 31-day incubation, RTN that had nitrogen (N) limitation emitted 26.7% more total C and 35.0% glucose-derived C than NTS across the two soil types. In Cambisols, the RTN exhibited 21.2% and 47.5% higher priming effect than NTS and GRL, respectively; while in Phaeozems, the RTN had 29.5% and 34.8% lower priming effect than NTS and GRL. Moreover, RTN showed 81.8% lower and 26.7% higher microbial C use efficiency (CUE) than NTS in Cambisols and Phaeozems, respectively. The higher N availability, CUE, and labile C retention which consists of the sum of glucose-derived microbial biomass C, total dissolved organic C, and organo-mineral C were the major contributors to the lower priming effect under long-term tillage management. A positive priming effect was observed across all treatments after glucose addition as a result of stimulating microbial activities, and then the increased microbial activities promoted co-metabolism. At the early stages, the priming effect was driven by “microbial N-mining”, and the driving force was dominated by “microbial stoichiometric decomposition” at later stages. These findings provide a more accurate understanding of soil organic C dynamics. The results can be used to predict the change of soil organic C under long-term tillage management, which are critical for sequestrating the elevated atmospheric C concentrations.
•The positive PE is caused by the microbial co-metabolism after glucose addition.•The microbial mechanisms for PE at different stages are varied.•Legacy effect of the long-term tillage management regulate CUE.•Nutrient availability and CUE determine the magnitude of the PE.
•We compared aggregate stability, SOC stocks and microbial community composition across three management practices in a dryland cropping system.•Reduced tillage with residue incorporation enhanced ...aggregate stability and SOC stocks relative to conventional tillage with residue removal.•SOC stocks correlated strongly with gram negative bacteria (GN), and aggregate stability was positively related to arbuscular mycorrhizal fungi (AMF).•SOC and stability of individual aggregate size classes are more closely related to microbial community composition than microbial biomass.•GN and fungi were the top two microbial predictors of SOC and overall aggregate stability.
Increasing soil carbon (C) stocks and improving soil structure are critical challenges in semi-arid agroecosystems. Conservation tillage has been widely applied to promote aggregate stability, enhance soil organic C (SOC) storage, and conjointly influence microbial community composition. However, the relation among soil microbial groups, aggregate stability and SOC stocks under management practices remains unclear. We conducted a 17-year field experiment in a spring maize cropping system on the Loess Plateau of northwest China, comparing three types of management: conventional tillage with residue removal (CT-RR), reduced tillage with residue incorporation (RT-RI) and no-tillage with residue mulching (NT-RM). We evaluated aggregate stability index (ASI), SOC stocks and microbial community composition at 0–10 and 10–25 cm. The results showed that RT-RI and NT-RM significantly increased ASI by 11% and 16% relative to CT-RR in the 0–10 cm layer; RT-RI significantly increased ASI by 13% relative to CT-RR in the 10–25 cm layer (p < 0.05). The RT-RI increased the SOC concentrations and SOC stocks of macroaggregates (>250 μm), which harbor most of the total SOC stocks in bulk soil. Both RT-RI and NT-RM increased total microbial biomass and biomass of six microbial groups (i.e., gram-negative bacteria (GN), gram-positive bacteria (GP), total bacteria (B), total fungi (F), arbuscular mycorrhizal fungi (AMF) and saprophytic fungi (SF)) at 0–10 cm, and RT-RI increased the above groups at 10–25 cm. Across a range of microbial community indicators, we found strong positive relationships between SOC and GN, ASI and AMF in bulk soil. A random forest analysis indicated that GN and F were the best microbial predictors of SOC concentrations and overall aggregate stability, whereas AMF/SF was the best predictor of SOC concentrations within aggregates and the stability of individual aggregate size classes. These results demonstrated a strong link between aggregate stability, SOC dynamics and microbial community composition, and suggest that conservation tillage increases both soil aggregation and SOC storage, thus providing sustainability and technical feasibility for the development of dryland agroecosystems.
Nitrogen addition can weaken yield reduction under no-tillage, a fundamental component of conservation tillage. However, the potential long-term benefits of nitrogen addition in enhancing the yield ...capacity of no-tillage by improving soil quality remain uncertain. Here we investigated the effects of tillage and nitrogen addition on both yield and soil quality through a comprehensive long-term experiment. We found that increased nitrogen inputs resulted in higher yield under no-tillage, particularly in wet years. Over an 18-year period, the rate of yield enhancement attributed to nitrogen addition varied from 8.2 % to 24.5 %, resulting in the most optimal yield under no-tillage with adequate nitrogen addition. Similarly, soil quality of no-tillage exhibited improvement with nitrogen inputs, especially in terms of organic carbon and the availability of nitrogen and phosphorus, thereby enhancing production potential. This study concluded that adequate nitrogen addition further improved both crop production and the sustainability of no-tillage systems.
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Negative pressure irrigation (NPI), which is a new subsurface irrigation technique, promotes vegetable yield, water productivity (WP), and nitrogen use efficiency (NUE). However, it is not clear how ...NPI improves vegetable growth, especially in terms of water supply characteristics and uniformities of soil water and nitrogen. In this study, a cucumber pot experiment that had 0 kPa (PW1), –5 kPa (PW2), –10 kPa (PW3), –15kPa (PW4), and traditional irrigation (PCK) treatments under nitrogen application (N1) and no application (N0) was conducted to reveal the water supply characteristics of NPI and its effect on vegetable growth. There are two main water supply characteristics: 1) automatically supplying irrigation water based on the consumption of soil water, and 2) keeping soil water content stable during the vegetable growth period. In addition, the relationship between vegetable growth and soil water and NO3–-N distribution uniformities throughout the soil profile was investigated by carrying out two tomato field experiments. The treatments of one tomato experiment were NPI with –5 kPa (F1W) and furrow irrigation (F1CK). We also carried out NPI with –5 kPa (F2W), furrow irrigation (F2CK), and drip irrigation (F2D) in another tomato experiment. The results showed that cumulative water application under N1 was higher than under N0 in the PW1, PW2, and PW3 treatments in the cucumber experiment. Volumetric soil water content under the NPI system was more stable during the vegetative growth period than under traditional irrigation. The NPI system also increased yields under appropriate pressures (–10–0 kPa) compared to the PCK treatment in the cucumber experiment. The NPI in the two tomato experiments reduced fertilizer inputs and irrigation compared to furrow irrigation and drip irrigation. However, the irrigation method had no significant influence on the tomato yield in the two tomato experiments.
•Negative pressure irrigation (NPI) kept soil water content stable.•The NPI supplies irrigation water automatically according to water consumption.•The uniformities of soil water and NO3--N were promoted by NPI.•The NPI with appropriate water supply pressure is a promising irrigation technique.
•These soil physical properties studied in our research were affected by both tillage management and growth stage.•Increasing lower limit of least limiting water range can decrease soil water ...availability.•Combining least limiting water range with soil moisture can provide a better understanding of soil-crop relationship.•Grain yield mainly driven by lower limit of least limiting water range and penetration resistance.
Tillage management is a key factor driving changes in soil physical properties (SPP) and crop yield around the world. However, there is a lack of knowledge about the relationships between SPP and crop yield. The dynamic of SPP during the growth period is also seldom taken into account to understand suitable soil physical environment for crop growth. Moreover, the crop growth process cannot be explained by an individual SPP substantially. The least limiting water range (LLWR), which integrates soil penetration resistance, air porosity, and soil water potential, may provide a better understanding of soil-crop relationship, especially in regions with limited precipitation. Our objective was to explain how dynamic SPP affected grain yield during the growth period. A long-term field experiment was established in 2003, with continuous spring maize, on sandy loam soil. Seasonal changes of SPP (i.e. bulk density, penetration resistance, porosity, mean weight diameter, LLWR, and plant available water) were determined under reduced tillage with residue incorporated (RT-RI), conventional tillage with residue removal (CT), and no-tillage with residue mulch (NT-RM). The results showed that these SPP were affected by both tillage management and growth stage. Bulk density, porosity, S index, and mean weight diameter were not effective indicators to explain the changes of grain yield under the three tillage managements. The range of LLWR was narrower than plant available water (PAW) during the growth period and more sensitive to assess soil water availability under RT-RI, CT, and NT-RM. NT-RM significantly increased the lower limit of LLWR, which made it more difficult for root water uptake. Hence, RT-RI presented higher corn yield compared to NT-RM, even if the water content remained lower. Redundancy analysis further indicated that maize yield was mainly driven by lower limit of LLWR and penetration resistance. Overall, LLWR was an aggregative indicator including not only soil penetration resistance but also air porosity and soil water potential, which can better explain the change of grain yield under the long-term tillage management in semi-arid region.
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