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Field cultivation practices have changing the carbon and nitrogen cycles in farmland ecosystem, soil organic carbon (SOC) and total nitrogen (TN) were the important pa- rameters in maintaining soil quality and increasing agricultural productivity, however, N application's effects on the SOC and TN storage capacity under intensive wheat- maize cropping system remain unclear. Therefore, we investigated the characteristics and relationships of SOC and TN for wheat-maize cropping system under nitrogen treatments. In doing so, continuous applications of four nitrogen application rates were examined: 0, 180, 240 and 300 kg ha-1 (N0, N180, N240 and N300, respectively). Wheat yields under N180 and N240 were significantly higher than that under N300, while the maize yields under N180, N240 and N300 were significantly higher than that under N0 by 79.79, 85.23 and 86.85%, respectively; the TN content and storage were significantly higher under N240 than that under other N levels in 40-60 cm soil layer after wheat growing season; the SOC content and storage under N180 and N240 were significant higher than that under N300 in 20-40 cm after maize growing season. The correlations between SOC and TN contents (or storage) were stronger after wheat planting than maize planting. These findings provide a basis for further studies on the effect of long-term N application on SOC and TN storage, crop quality and nitrogen use efficiency under wheat-maize cropping systems. [ABSTRACT FROM AUTHOR]

Knowledge about the changes in soil organic carbon (SOC) stocks and grain yields under different field management practices is necessary for achieving agricultural sustainability. An 8‐yr experiment for testing different tillage and straw management practices was conducted in a wheat (Triticum aestivum L.)–maize (Zea mays L.) rotation system in the southern Loess Plateau of China. Three tillage methods (control with no‐tillage and straw removal [CK], no‐tillage with straw stubbles 30–40 cm in height [NT], and rotary tillage with straw incorporation [RT]) were applied before maize planting, and two straw treatments (straw return [SR] and no straw return [SR0]) were applied after maize harvest. Over the 8 yr, SOC stocks exhibited similar dynamic changing trends in all treatments but were higher under NT, RT, and SR than under CK‐SR0. Compared with the initial soil, SOC stock increased the most (34.1%) in NT‐SR. Compared with the CK‐SR0, the NT‐SR, RT‐SR, CK‐SR, NT‐SR0, and RT‐SR0 increased wheat grain yields by 47.2, 36.8, 24.9, 25.1, and 20.0%, respectively. Similar trends were found for maize grain yields. The NT, RT, and SR increased crop yield stability with the highest sustainable yield index in NT‐SR for both wheat (.67) and maize (.70). Overall, the combination of no‐tillage with wheat straw stubbles 30–40 cm in height and maize straw return was the best strategy for improving SOC stocks, grain yields, and agricultural sustainability for grain production in dry, sub‐humid areas of northwestern China. Core Ideas: No‐tillage (NT) and rotary tillage (RT) increased SOC stocks compared with control.NT, RT, and straw return (SR) increased crop yield stability.NT‐SR is an optimal strategy for improving agricultural sustainability. [ABSTRACT FROM AUTHOR]

Straw return is an effective measure to promote sustainable agriculture by significantly improving soil fertility. At present, few studies have been conducted on the most effective carbon enhancing management measures for various crops. Therefore, we conducted a meta-analysis using data collected from 184 literature sources, comprising 3297 data sets to analyze the carbon increase effects of straw returning in three main crops (rice, maize, and wheat) in China and to explore the influence mechanism of natural factors, soil properties, straw return measures, and cropping systems on the carbon enhancement effect. The study showed that straw return significantly increased soil organic carbon and the rate of increase was higher for wheat at 15.88% (14.74%–17.03%) than for rice at 12.7% (11.5%–13.91%) and maize at 12.42% (11.42%–13.42%), with varying degrees of improvement in other soil physicochemical properties. Natural factors have the greatest impact on the carbon increasing effect of rice fields, reaching 28.8%, especially at temperature between 10 °C and 15 °C, less than 800 mm precipitation, low latitude, and short frost-free period. Maize and wheat are most affected by soil properties, reaching 41% and 34.5% respectively. Furthermore, field management practices also play a pivotal role, organic carbon increasing obviously was observed when the C/N ratio of exogenous nutrients is bigger than 20 with the low initial organic matter. Shallow tillage and less than 7.5 t hm−2 straw returning with 3–10 years to the field are ideal for rice and maize. Crop rotation, especially in drylands, increased soil organic carbon more significantly than continuous. The results of our analysis can provide valuable insights into the effect of straw return on carbon increase. In the future, the soil carbon can be improved by adopting rational cropping patterns and straw return measures with taking into account climate and soil characteristics for different crops. [Display omitted] • The effects of straw return on soil organic carbon in three major crops were studied using meta-analysis. • SOC levels significantly increased for rice, maize, and wheat after straw return. • The impact of natural factors, soil properties, straw return measures, and cropping systems varied for different crops. • The increase in SOC for rice was largely influenced by natural factors, while for maize and wheat by soil properties. [ABSTRACT FROM AUTHOR]

The effect of conservation tillage on soil organic carbon (SOC) sequestration and crop production is controversial in semi‐arid areas. In addition, fertilisation is another essential factor affecting soil carbon pool and crop yields. We sought to explore the changes of SOC pool and crop productivity after optimising fertilisation and tillage. An 11‐year field experiment on the Loess Plateau in China was conducted to evaluate the effects of (i) fertilisation (balanced fertilisation, low fertilisation, conventional fertilisation) and (ii) tillage (no‐tillage, subsoiling, ploughing) on input‐C, SOC stocks, labile C fractions, C pool management index (CMI) and wheat yield. SOC stock accumulation at 0–35 cm depth under balanced fertilisation increased by 59% compared to conventional fertilisation due to the larger amount and stabilisation efficiency of input‐C. Simultaneously, balanced fertilisation increased labile C contents and CMI at 0–10 cm depth. For tillage, no‐tillage and subsoiling improved input‐C and its stabilisation efficiency, and increased SOC stocks compared to ploughing. Balanced fertilisation combined with no‐tillage or subsoiling produced greater SOC stocks at 0–35 cm depth compared to other treatments. No‐tillage increased labile C contents and CMI at 0–10 cm depth, while subsoiling increased labile C contents and CMI at 0–10 and 35–50 cm depths. Wheat yield and sustainable yield index (SYI) were positively correlated with SOC, and the effect of SOC contributed to SYI largely through indirect effects of dissolved organic C and particulate organic C. Wheat yield and SYI were increased by optimising fertilisation and tillage, and the greatest yield was under balanced fertilisation combined with the subsoiling treatment. Our findings suggested that balanced fertilisation combined with subsoiling was an effective practice for increasing SOC sequestration, soil quality, wheat yields and had great potential application on the Loess Plateau in China. Highlights: C sequestration under conservation tillage and fertilisation are controversial in semi‐arid areas.Balanced fertilisation promoted SOC sequestration in no‐tillage and subsoiling treatments.Subsoiling improved soil quality at 0–10 and 35–50 cm depths due to the greater SOC and labile C.Subsoiling was superior to no‐tillage and ploughing in maintaining crop productivity. [ABSTRACT FROM AUTHOR]

In agro‐ecosystems, fertilization practices must accomplish high and stable crop productivity, with maximum soil organic carbon (SOC) sequestration to address climate change and food security challenges. However, the impacts of these practices on SOC and crop yields are variable over the long‐term duration, and an improved understanding of the factors influencing SOC sequestration and sustainable productivity is still needed to provide evidence‐based management decisions. Therefore, we conducted a meta‐analysis to evaluate the impact of long‐term (≥10 years) application of different fertilizer management practices adapted across China on crop productivity, yield sustainability, and SOC sequestration. Results indicated that unbalanced mineral fertilizer (UMF), balanced mineral fertilizer (BMF), organic fertilizers (OF), combined unbalanced mineral and OF, and combined balanced mineral and organic fertilizers (BMOF) significantly enhanced the grain yield, and SOC sequestration compared with control (p <.05). For UMF, the increases in SOC and grain yields were least among fertilization practices. Comparing OF, BMF mostly produced more grain yields, but with a slight increase in C sequestration. Highest SOC sequestration rate of 0.43 Mg C ha−1 yr−1 was recorded in BMOF, among all the treatments. The data obtained indicated that SOC sequestration is highly time‐dependent. Irrespective of fertilization mode, SOC gradually increased and attained the peak of sequestration rate in the initial two decades rather than at later stages of fertilizer addition. The linear fitted model indicated that an increase in SOC sequestration benefits sustainable productivity. The available data indicate that crop yields can be improved by 143 kg ha−1 for rice (Oryza sativa), 255 kg ha−1 for maize (Zea mays), and 202 kg ha−1 for wheat (Triticum aestivum) with every 1 Mg ha−1 increase in SOC stock by fertilization in the root zone. In crux, BMOF can maintain and improve soil quality while producing high and stable crop yields. [ABSTRACT FROM AUTHOR]

BACKGROUND: An irrigation regime is an important factor in regulating soil CO2 emissions from wheat fields. Deficit irrigation can be applied easily in the fields and has been implemented in northwest China. Previous studies have mainly focused on the effects of deficit irrigation on crop yield and quality. Studies on its environmental impacts are sparse. RESULTS: Soil CO2 fluxes from deficit‐irrigated fields were lower than those from full irrigation (CK) during most of the growing season. Cumulative soil CO2 emissions from deficit‐irrigated fields were reduced by 10.2–25.5%, compared with the CK. Peaks of soil CO2 fluxes were observed 3–7 days after irrigation in the water‐filled pore space (WFPS) range of 65.7–80.4%. Under different irrigation regimes, significant positive correlations were observed between soil CO2 fluxes and WFPS (P < 0.01), but no significant correlations were found between soil CO2 fluxes and soil temperature. Compared to CK, yields for the T1, T2, and T4 were significantly reduced (P < 0.05) but the yield for T3 was only reduced by 2.3% (P > 0.05); T3 significantly reduced soil CO2 emissions by 10.2% (P < 0.05) and reduced the irrigation water amount by 5.7%. CONCLUSION: Deficit irrigation effectively reduced CO2 emissions from winter wheat field soils. T3 may be a water‐saving, CO2 emission‐reducing and high‐yield irrigation regime for winter wheat fields in northwest China. The research laid a preliminary theoretical foundation for formulating winter wheat irrigation systems that are water saving, emission reducing, and that produce high yields. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Straw return is a promising method for managing soil organic carbon (SOC) in agricultural soils and thus may promote sustainable land use. However, the optimal straw-return strategy for economically sustainable grain production in intensive winter wheat (Triticum aestivum L.)-summer maize (Zea mays L.) cropping systems remains uncertain. A 4-yr field experiment was conducted in the central North China Plain to determine the effects of straw return on SOC stock and lability, soil enzyme activity, and grain yield, and to further evaluate the sustainability of crop production in intensive wheat-maize double-cropping systems. Four treatments were tested: no straw return (NR), return of wheat straw (WR), return of maize straw (MR), and return of both wheat and maize straw (WR+MR). Compared with the initial value, SOC stocks significantly increased by 2.8, 5.4, and 13.1% in WR, MR, and WR+MR, respectively, and significantly decreased by 2.9% in NR. Stocks of KMnO4-oxidizable C and microbial biomass C; activities of soil invertase, protease, and dehydrogenase; and the C management index were significantly higher with than without straw return and followed the order NR < WR < MR < WR+MR. Yields of wheat and maize were highest in WR+MR, but economic sustainability was higher in WR and MR relative to NR and WR+MR. Our results indicate that return of either wheat or maize straw is sufficient to maintain SOC levels and may be the optimal strategy for economically sustainable grain production in the central North China plain. [ABSTRACT FROM AUTHOR]

Abstract: The Loess Plateau in northwest China is one of the most eroded landscapes in the world, and it is urgent that alternative practices be evaluated to control soil erosion. Our objective was to determine how three different tillage practices for monoculture of winter wheat (Triticum aestivum L.) affected soil organic carbon (SOC) and N content after 11 years. Conventional tillage with residue removal (CT), shallow tillage with residue cover (ST), and no-tillage with residue cover (NT) were investigated. Carbon and N in various aggregate-size classes and various labile organic C fractions in the 0–15- and 15–30-cm soil layers were evaluated. The ST and NT treatments had 14.2 and 13.7% higher SOC stocks and 14.1 and 3.7% higher total N (Nt) stocks than CT in the upper 15cm, respectively. Labile C fractions: particulate organic C (POC), permanganate oxidizable C (KMnO4-C), hot-water extractable C (HWC), microbial biomass C (MBC) and dissolved organic C (DOC) were all significantly higher in NT and ST than in CT in the upper 15cm. KMnO4-C, POC and HWC were the most sensitive fractions to tillage changes. The portion of 0.25–2mm aggregates, mean weight diameter (MWD) and geometric mean diameter (GMD) of aggregates from ST and NT treatments were larger than from CT at both 0–15- and 15–30-cm soil depths. The ST and NT treatments had significantly higher SOC and Nt in the 0.25–2mm fraction at both depths and significantly higher Nt content in the upper 15cm. Positive significant correlations were observed between SOC, labile organic C fractions, MWD, GMD, and macroaggregate (0.25–2mm) C within the upper 15cm. We conclude that both variants of conservation tillage (NT and ST) increase SOC stock in the rainfed farming areas of northern China and are therefore more sustainable practices than those currently being used. [Copyright &y& Elsevier]

Abstract: In areas where two crops are grown per year or three crops every 2 years, the status of residual soil nutrients after the harvest of the first crop is critical to the crop to be grown immediately after, while the postharvest soil nutrient status can be influenced by irrigation applied to the test crop. This study determined the effect of various soil water treatments applied to the test crop on the status of postharvest residual soil nutrient pools in an arid environment. Spring wheat (Triticum aestivum L.) was grown as test crop under conditions of full- (as control), high-, moderate-, and low-water conditions during jointing, booting-heading, and grain filling stages, in 2003 and 2004. Compared to the control, grain yield and water use efficiency (WUE) were significantly increased by subjecting the wheat crop to moderate-water conditions during various growth stages, and low-water conditions at jointing stage in both years. Soil C at harvest decreased linearly with increased grain yield of the test crop. Moderate- to high-water conditions during jointing stage resulted in 12–24% greater soil C in the top 40cm depth in 2003, with a marginal difference in 2004. Water treatments impacted the status of residual soil nutrients in 2003; soil total N and available soil P in the top 40cm depth were significantly higher in low- to moderate-water treatments compared to the control, while in 2004 significantly higher total N and P, available N, P and K were found only in the top 20cm depth. Increased yield of wheat test crop with moderate-water resulted in increased postharvest residual soil nutrients, whereas the ratios of C/N, C/P, and C/K were largely influenced by years and were less related to water treatments. We conclude that the determination of postharvest soil C and nutrient elements may provide useful information in monitoring potential changes of soil nutrient status over time in the intensified cropping systems, and that the recommendation of fertilization for the crop to be grown immediately following the first crop can be established by simply analyzing the productivity of the first crop without intensive measurements of soil nutrients. [Copyright &y& Elsevier]

Abstract: A spatially referenced biophysical model, the water and nitrogen management model (WNMM), was developed and shown to simulate dynamic soil water movement and soil–crop carbon (C) and nitrogen (N) cycling under a given agricultural management, for the purpose of identifying optimal strategies for managing water and fertiliser N under intensive cropping systems (mainly wheat–maize) in the North China Plain and other regions in the world. A uniform data structure, ARC GRID ASCII format, was used both in GIS and WNMM for achieving a close Model-GIS coupling. A significant part of WNMM adopts and modifies concepts and components from widely used models, with a focus on soil N transformations. WNMM simulates the key processes of water dynamics in the surface and subsurface of soils: including evapotranspiration, canopy interception, water movement and groundwater fluctuations; heat transfer and solute transport; crop growth; C and N cycling in the soil–crop system; and agricultural management practices (crop rotation, irrigation, fertiliser application, harvest and tillage). The model runs on a daily time step at any desired scale and is driven by lumped variables (meteorological and crop biological data) in text data format, and spatial variables (soil and agricultural management) in ARC GRID ASCII format. In particular, WNMM simulates all key N transformations in agricultural fields, including mineralisation of fresh crop residue N and soil organic N, formation of soil organic N, immobilisation in biomass, nitrification, ammonia (NH3) volatilisation, denitrification and nitrous oxide (N2O) emissions. WNMM has been successfully applied in Fengqiu County, Henan Province and Luancheng County, Hebei Province, China at site and regional scales. The key WNMM components were intensively calibrated and verified against comprehensive field measurements of soil water content, evapotranspiration, crop leaf area index and yield, NH3 volatilisation, denitrification and N2O emissions as well as nitrate (NO3 −)–N concentrations in the soil solution. A sensitivity analysis showed that WNMM was sensitive to changes in meteorological variables, soil hydraulic properties, land use and agricultural management. At the site scale, WNMM simulated well soil water content, crop growth and yield, NH3 volatilisation and soil NO3 −–N concentration. There was uncertainty in simulating soil denitrification and N2O emissions, when the predicted peaks of denitrification and N2O emissions at very wet conditions could not be confirmed because of limitations in the acetylene-inhibition method for measuring denitrification. At county scale, WNMM simulation of crop yield in Fengqiu County explained 22% of the variation in observed crop yields, and 31% of crop yield variation in Luancheng County where soil variation was less. These results are considered acceptable because factors such as soil salinity and other nutrient deficiencies, which have not been considered in this version of WNMM, may play a role. The source code for the WNMM is available on request. [Copyright &y& Elsevier]

The practice of crop rotation can significantly impact carbon sequestration potential. In exploring whether crop rotation has the potential to improve soil carbon sequestration in China's Loess Plateau, soil organic carbon (SOC), soil water content (SWC), soil bulk density (SBD), and soil pH were compared across the 0–1.0 m soil profile, under four crop rotation patterns: lentil–wheat–maize, wheat–potato–lentil, wheat–maize–potato, and wheat–flax–pea. The lentil–wheat–maize and wheat–maize–potato rotations have been practiced over the past 20 years, while the wheat–potato–lentil and wheat–flax–pea rotations were established in 1978 (~40 year rotations). The results showed that under the 20-year lentil–wheat–maize rotation, SOC was not significantly different to that of the wheat–maize–potato rotation, at 6.81 g kg−1 and 6.91 g kg−1, respectively. However, under the lentil–wheat–maize rotation, SWC (9.81%) and SBD (1.19 Mg m−3) were significantly higher, but soil pH (8.42) was significantly lower than the same metrics under wheat–maize–potato rotation (8.43% and 1.16 Mg m−3, and 8.50, respectively). For the 40-year rotations, SWC (9.19%) and soil pH (8.41) under the wheat–potato–lentil were not significantly different to that of the wheat–flax–pea (8.87%, and 8.40, respectively). SOC (6.06 g kg−1) was significantly lower, but SBD (1.18 Mg m−3) was significantly higher under the wheat–potato–lentil than the wheat–flax–pea (7.29 g kg−1, and 1.15 Mg m−3, respectively) rotations. Soil carbon sequestration for the lentil–wheat–maize and wheat–potato–lentil rotations was co-influenced by SWC, SBD, and soil pH, while for wheat–maize–potato and wheat–flax–pea rotations, it was co-influenced by SWC and soil pH. The economic value of the four studied crops is, in order: potato > maize > wheat > flax. The results of the present study suggest that the lentil–wheat–maize and maize–flax–pea rotations are the most suitable patterns to optimize simultaneous economic and ecological development of the study area. [ABSTRACT FROM AUTHOR]