Effects of rice or wheat residue retention on the quality of milled japonica rice in a rice–wheat rotation system in China

In rice–wheat rotation systems, crop straw is usually retained in the field at land preparation in every, or every other, season. We conducted a 3-year-6-season experiment in the middle–lower Yangtze River Valley to compare the grain qualities of rice under straw retained after single or double seasons per year. Four treatments were designed as: both wheat and rice straw retained(WR), only rice straw retained(R), only wheat straw retained(W), and no straw retained(CK). The varieties were Yangmai 16 wheat and Wuyunjing 23 japonica rice. The results showed contrasting effects of W and R on rice quality. Amylopectin content, peak viscosity, cool viscosity, and breakdown viscosity of rice grain were significantly increased in W compared to the CK, whereas gelatinization temperature,setback viscosity, and protein content significantly decreased. In addition, the effect of WR on rice grain quality was similar to that of W, although soil fertility was enhanced in WR due to straw being retained in two cycles. The differences in protein and starch contents among the treatments might result from soil nitrogen supply. These results indicate that wheat straw retained in the field is more important for high rice quality than rice straw return, and straw from both seasons is recommended for positive effects on soil fertility.

FULL TIME-SPACE GOVERNANCE STRATEGY AND TECHNOLOGY FOR CROPLAND NON-POINT POLLUTION CONTROL IN CHINA

Ensuring food safety while reducing agricultural non-point source pollution is quite challenging,especially in developing and underdeveloped countries.Effective systematic strategies and comprehensive technologies need to be developed for agricultural non-point source pollution control at the watershed scale to improve surface water quality.In this review,a proposal is made for a full time-space governance strategy that prioritizes source management followed by endpoint water pollution control.The 4R chain technology system is specifically reviewed,including source reduction,process retention,nutrient reuse and water restoration.The 4R chain technology system with the full time-space governance strategy was applied at the scale of an administrative village and proved to be a feasible solution for reducing agricultural non-point source pollution in China.In the future,a monitoring system needs to be established to trace N and P transport.Additionally,new smart fertilizer and intelligent equipment need to be developed,and relevant governance standards and supportive policies need to be set to enhance the efficacy of agricultural non-point source pollution control.

Methane emissions from rice fields under continuous straw return in the middle-lower reaches of the Yangtze River

A three-year experiment was conducted in the middle-lower reaches of the Yangtze River in China to study the influence of continuous wheat straw return during the rice season and continuous rice straw return in wheat on methane （CH 4 ） emissions from rice fields in which, the rice-wheat rotation system is the most dominant planting pattern. The field experiment was initiated in October 2009 and has continued since the wheat-growing season of that year. The analyses for the present study were conducted in the second （2011） and third （2012） rice growing seasons. Four treatments, namely, the continuous return of wheat straw and rice straw in every season （WR）, of rice straw but no wheat straw return （R）, of wheat straw but no rice straw return （W） and a control with no straw return （CK）, were laid out in a randomized split-plot design. The total seasonal CH 4 emissions ranged from 107.4 to 491.7 kg/ha （2011） and 160.3 to 909.6 kg/ha （2012）. The increase in CH 4 emissions for treatments WR and W were 289% and 230% in the second year and 185% and 225% in the third year, respectively, in relation to CK. We observed less methane emissions in the treatment R than in CK by 14%-43%, but not statistically significant. Treatment R could increase rice productivity while no more CH 4 emission occurs. The difference in the total CH 4 emissions mainly related to a difference in the methane flux rate during the first 30-35 days after transplant in the rice growing season, which was caused by the amount of dissolved oxygen in paddy water and the amount of reducible soil materials.

Raw material of water-washed hydrochar was critical for the mitigation of GHGI in infertile paddy soil:a column experiment

Water washing is a meaningful method to improve the surface’characteristic of hydrochar produced using hydrothermal carbonization and minimize the negative effect on crop growth.However,the greenhouse effect resulting from water-washed hydrochar application was unclear in agricultural ecosystems.Hence,the effect of water-washed hydrochar on methane and nitrous oxide emissions was analyzed in an infertile paddy soil based on a soil-column experiment.Sawdust-derived hydro-char(WSH)and wheat straw-derived hydrochar(WWH)after water washing were selected and applied with low(5‰,w/w;8.5 t ha^(−1))or high addition rate(15‰,w/w;25.5 t ha^(−1)).The study indicated that water-washed hydrochar could increase the grain yield;the difference between WWH with 5‰application rate and CKU treatments was significant.WSH signifi-cantly decreased CH4 and N2O emissions in comparison with WWH addition treatments.For the same material,there were trends in reducing greenhouse gas(GHG)emissions at low application rate,although the differences were not significant.Compared with all treatments,WSH with 5‰application rate achieved the lowest seasonal emissions for both GHGs.The mcrA gene was the critical factor affecting CH4 emission;soil NO_(3)^(−)-N concentration and the copy numbers of nirK,nirS,and nosZ jointly affected N2O emissions.Benefits from the high yield and low global warming potential,GHG emission intensity(GHGI)at low application rate was lower than at high application rate for WSH.Overall,the response of GHG emissions to water-washed hydrochar varies with the derived feedstock;WSH is a good additive for the mitigation of GHGI.