Effect of rice cultivar on greenhouse-gas emissions from rice-fish co-culture

In aquaculture,co-culturing rice with fish may mitigate greenhouse-gas emissions.In this study,co-culture of four rice cultivars in a laboratory-scale rice–fish system reduced CH_(4)and N_(2)O emissions relative to fish monoculture.Differences in CH_(4)and N_(2)O emissions among rice cultivars primarily stem from the differential effects of rice plants on plant-mediated CH_(4)transport,CH_(4)oxidation and nitrogen absorption.

The impacts of conservation agriculture on crop yield in China depend on specific practices, crops and cropping regions

For smooth and wide application of conservation agriculture(CA), remaining uncertainties about its impacts on crop yield need to be reduced. Based on previous field experiments in China, a meta-analysis was performed to quantify the actual impacts of CA practices(NT: no/reduced-tillage only, CTSR: conventional tillage with straw retention, NTSR: NT with straw retention) on crop yields as compared to conventional tillage without straw retention(CT).Although CA practices increased crop yield by 4.6% on average, there were large variations in their impacts. For each CA practice, CTSR and NTSR significantly increased crop yield by 4.9%and 6.3%, respectively, compared to CT. However, no significant effect was found for NT. Among ecological areas, significant positive effects of CA practices were found in areas with an annual precipitation below 600 mm. Similar effects were found in areas with annual mean air temperature above 5 °C. For cropping regions, CA increased crop yield by 6.4% and 5.5%compared to CT in Northwest and South China, respectively, whereas no significant effects were found in the North China and Northeast China regions. Among crops, the positive effects of CA practices were significantly higher in maize(7.5%) and rice(4.1%) than in wheat(2.9%). NT likely decreased wheat yield. Our results indicate that there are great differences in the impacts of CA practices on crop yield, owing to regional variation in climate and crop types. CA will most likely increase maize yield but reduce wheat yield. It is strongly recommended to apply CA with crop straw retention in maize cropping areas and seasons with a warm and dry climate pattern.

Cropping system innovation for coping with climatic warming in China

China is becoming the largest grain producing and carbon-emitting country in the world,with a steady increase in population and economic development.A review of Chinese experiences in ensuring food self-sufficiency and reducing carbon emission in the agricultural sector can provide a valuable reference for similar countries and regions.According to a comprehensive review of previous publications and recent field observations,China has experienced on average a larger and faster climatic warming trend than the global trend,and there are large uncertainties in precipitation change,which shows a non-significantly increasing trend.Existing evidence shows that the effects of climatic warming on major staple crop production in China could be markedly negative or positive,depending on the specific cropping region,season,and crop.However,historical data analysis and field warming experiments have shown that moderate warming,of less than2.0 °C,could benefit crop production in China overall.During the most recent warming decades,China has made successful adaptations in cropping systems,such as new cultivar breeding,cropping region adjustment,and cropping practice optimization,to exploit the positive rather than to avoid the negative effects of climatic warming on crop growth.All of these successful adaptations have greatly increased crop yield,leading to higher resource use efficiency as well as greatly increased soil organic carbon content with reduced greenhouse gas emissions.Under the warming climate,China has not only achieved great successes in crop production but also realized a large advance in greenhouse gas emission mitigation.Chinese experiences in cropping system innovation for coping with climatic warming demonstrate that food security and climatic warming mitigation can be synergized through policy,knowledge,and technological innovation.With the increasingly critical status of food security and climatic warming,further efforts should be invested in new agricultural policy,knowledge and technology creation,and popularization of climate-smart agriculture,and more financial investments should be made in field infrastructure development to increase cropping system resilience in China.

Source attributions of heavy metals in rice plant along highway in Eastern China

Air and soil pollution from traffic has been considered as a critical issue to crop production and food safety, however, few efforts have been paid on distinguish the source origin of traffic-related contaminants in rice plant along highway. Therefore, we investigated metals （Pb, Cd, Cr, Zn and Cu） concentrations and stable Pb isotope ratios in rice plants exposed and unexposed to highway traffic pollution in Eastern China in 2008. Significant differences in metals concentrations between the exposed and unexposed plants existed in leaf for Pb, Cd and Zn, in stem only for Zn, and in grain for Pb and Cd. About 46% of Pb and 41% of Cd in the grain were attributed to the foliar uptake from atmosphere, and there were no obvious contribution of atmosphere to the accumulations of Cr, Zn and Cu in grain. Except for Zn, all of the heavy metals in stem were attributed to the root uptake from soil, although significant accumulations of Pb and Cd from atmosphere existed in leaf. This indicated that different processes existed in the subsequent translocation of foliar-absorbed heavy metals between rice organs. The distinct separation of stable Pb isotope ratios among rice grain, leaf, stem, soil and vehicle exhaust further provided evidences on the different pathways of heavy metal accumulation in rice plant. These results suggested that further more attentions should be paid to the atmospheric deposition of heavy metals from traffic emission when plan crop layout for food safety along highway.