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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]

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]