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Straw returning is a vital agronomic practice for soil organic carbon (SOC) sequestration and stabilization by changing the storage and fraction composition. Iron and aluminum (Fe/Al) oxides have a protective effect on SOC through adsorption and co-precipitation, which depends on the fraction composition of SOC itself, especially originated from externally added organic materials. However, the changes and interactions of SOC components and Fe/Al oxides in straw returning soil are not clearly understood. To evaluate the effect of straw returning on SOC composition and Fe/Al oxides, we have conducted an in situ field experiment for 10 yrs., which including five treatments: no rice and wheat straw returning (NRW, as control), total amount wheat straw returning (W), total amount rice straw returning (R), half amount rice and wheat straw returning (HRW), and total amount rice and wheat straw returning (TRW). The results showed that SOC and heavy fraction organic carbon (HFOC) increased under all five treatments, especially for R, HRW, and TRW treatments (P < 0.05). Compared with wheat straw returning, rice straw returning was more conducive to increasing the contents of SOC and its fractions, free Fe/Al oxides, complex aluminum oxides and the carbon utilization efficiency. Collectively, these properties were strongly affected by both the type and amount of straw returning. Soil organic carbon was significantly correlated with HFOC, water-soluble organic carbon, alkali-hydrolyzed nitrogen, available phosphorous, available potassium, and total nitrogen (P < 0.05). Of these, HFOC had the most significant effect on SOC and was vitally important for improving SOC sequestration and stability (P < 0.001). The increase of labile carbon fractions was more conducive to the absorption and utilization of nutrients by crops. Straw returning promoted the interaction between increasing organic matter and complex iron oxide (Fe c). This served to strengthen the protective effect of SOC, which increased the content of Fe c and stability of SOC, resulting in decreased soil pH. Taken together, these results highlight the importance of straw returning in promoting the storage and stability of SOC pool. Critically, rice straw returning can reduce soil pH and Fe c content, therefore could be considered as an ideal model for a rice-wheat rotation system. • Long-term straw returning increased the sequestration and stability of soil organic carbon by increasing heavy fractions. • Soil organic carbon fraction composition and Fe/Al oxides changed simultaneously with straw type and amount. • The effect of labile organic carbon of straw returning on Al oxides was greater than that of Fe oxides. • Rice straw returning has greater potential in improving soil organic carbon and soil properties. [ABSTRACT FROM AUTHOR]

China is a key global region vulnerable to climate change; however, limited studies have focused on the combined impacts of atmospheric CO 2 enrichment and warming on crop production in arable land, especially in rice paddies in China. To address this issue, a 4 year open-air field experiment during 2010–2014 was conducted to simulate the impact of climate change on crop production in a rice paddy in southeast of China. Four treatments including the ambient condition (CK), CO 2 enrichment (500 ppmv, CE), warming of canopy air (2 °C above the ambient, WA), and the combined CO 2 enrichment and warming (CW) were used to investigate the responses of total biomass, crop yield and harvest index. In general, different treatments significantly affected wheat and rice production. Compared to CK, CE significantly increased grain yield of rice by 8%. In contrast, the decreases of 26.2% and 10% in wheat and rice yield were observed under WA. However, there was no significant difference of wheat production between CW and CK, while rice yield and biomass were slightly decreased by a mean of 4.8% and 5.3% over 4 years, indicating the positive effect of CO 2 enrichment was unable to compensate for the negative impact of warming. The interannual variations of the responses were also observed in this study. The variation of wheat yields during 4 years was much higher than that of rice yields; however, significant changes in the stability of rice biomass and harvest index were observed under CE and WA. The results indicated both stabilizing and increasing grain yield under climate change are major challenges for agriculture in developing countries. [ABSTRACT FROM AUTHOR]

Significant efforts have been made to assess the impact of tillage regimes on crop yields and/or greenhouse gas (GHG) emissions across single crop growing season. However, few studies have quantified the impact across a whole rotation cycle in multiple cropping systems. Utilizing on a long-term tillage experiment with the rice–wheat rotation system in East China, we examined the GHG emissions under different tillage practices with or without crop straw incorporation. Results showed that compared to the no-straw control, straw incorporation increased wheat yield by 28.3% ( P < 0.05), irrespective of tillage practices, but had no significant effect on rice yield. Although straw incorporation did not significantly affect CH 4 emissions during the wheat season and N 2 O emissions during the whole rice–wheat cycle, it significantly stimulated CH 4 emissions by 98.8% ( P < 0.01) during the rice season. Also, there were no significant differences in CH 4 and N 2 O emissions between tillage practices during the wheat season. Compared to plowing, rotary tillage increased CH 4 emissions significantly by an average of 38.8% ( P < 0.01) but had no significant impacts on N 2 O emissions during the rice season. Across the rotation cycle, annual yield-scaled global warming potential of CH 4 and N 2 O emissions under no-tillage plus rotary tillage was 26.8% ( P < 0.01) greater than that of rotary tillage plus plowing with or without straw incorporation. Significant interactions between soil tillage and straw management practices were found on annual GHG emissions, but not on crop yields. Together, these results indicate that plowing in the rice season plus rotary tillage in the wheat season may reduce GHG emissions while increasing crop yield in rice–wheat cropping areas. [ABSTRACT FROM AUTHOR]

• 4R strategy for controlling AGNPS pollution was applied in Yangtze River basin. • N and P fertilizer rate reduced by 20 % and 27 % without any yield loss. • More than 40 % of N & P in the drainage was removed by eco-ditches & eco-ponds. • TN in the final field drainage was lower than 2 mg/L during 3 out of 19 times. • TN, NH 4 +-N, TP in the river decreased by 28.9 %, 30.4 %, 21.9 % after eco-restoration. Non-point pollution is becoming one of the main causes of the degradation of rural environment in China. A systematic strategy encompassing source reduction, process retention, nutrient reuse, and water restoration for controlling agricultural non-point source pollution was applied to a 1.5 km2 intensive rice-wheat rotation area at Yaoqiao county, Zhenjiang city, Jiangsu Province, in the downstream reach of the Yangtze River, China, from 2016 to 2018. The results showed that the use of organic and controlled-release fertilizers reduced the total nitrogen (TN) and total phosphorus (TP) input for rice and wheat by 20 % and 27 %, respectively, without any yield loss. The N and P concentration in the ecological ditches declined by 8%–50.4% for TN and 12%–69.7% for TP in comparison with that in the control ditches, and then further declined after the purification of eco-ponds. The removal efficiency was positive related with the N and P centration of inflow. TN concentration in the drainage water finally flow into the Shangshe River was lower than 2 mg/L during three out of 19 times. The river water quality was distinctly improved, wherein the TN, NH 4 +-N, TP, and chemical oxygen demand (COD Cr) concentrations were lower by 28.9 %, 30.4 %, 21.9 %, and 35.5 %, respectively following implementation of ecological water restoration technologies. The water quality improvement was mainly attributed to reduced pollutant load from agricultural fields and the aquatic plant uptake. This study found that the systematic "4R" approach is a promising method for decreasing the N and P loads from agricultural fields and improving the downstream water eutrophication problem, and can be extended to other agricultural intensive regions. [ABSTRACT FROM AUTHOR]