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Liming is a common practice to alleviate soil acidification in agricultural systems worldwide. Because liming affects soil microbial activity and soil carbon (C) input rates, it can affect soil greenhouse gas (GHG) emissions as well. However, little is known about the effect of liming on GHG emissions from rice agriculture, one of the main sources of anthropogenic methane (CH 4 ). Here, we report on the first experiment to measure the effect of liming on GHG emissions from rice paddy fields. We studied a double rice cropping system in an acid paddy for two years and measured the impacts of liming on GHG emissions and rice growth with or without straw incorporation. We found that liming reduced CH 4 emissions in the early rice season, but it did not affect nitrous oxide (N 2 O) emissions. Over the two-year study, lime application reduced total CH 4 emissions by 12.5% and 15.4% in plots without and with straw incorporation, respectively. Lime application significantly enhanced rice aboveground biomass, while reducing the area- and yield-scaled global warming potential of CH 4 and N 2 O emissions. Lime application stimulated soil respiration during the fallow season and reduced the abundance of methanogens during the early rice growing season. Together, these results suggest that liming reduces CH 4 emissions by promoting the decomposition of organic matter during the fallow season, thereby reducing C availability for methanogens. We conclude that in the short term, liming is an effective practice to reduce greenhouse gas emissions from acidic paddy soils. [ABSTRACT FROM AUTHOR]

Great attentions have been taken to the effects of climatic warming on crop production, however, fewer were known about the actual impacts of nighttime warming under different cropping systems. Therefore, a three-year field experiment with a passive nighttime warming (PNW) facility and a one-year field experiment with free air temperature increase (FATI) facility were conducted in major Chinese rice cropping systems. Four-year field observations from different rice cropping systems all showed that nighttime warming less than 1.0 °C could shorten the length of crop pre-flowering phase period while prolonged the length of post-flowering phase period, resulting in insignificant reduction in the length of crop entire growth period. The temperature increase caused significant increments in grain yields by 16.2, 12.7 and 12.0% for late rice in the rice–rice cropping system, wheat in the rice-wheat cropping system and rice in the single rice cropping system, respectively. However, this warming declined grain yields significantly by 4.5 and 6.5% for early rice in the rice–rice cropping system and rice in the rice-wheat cropping system, respectively. Since warming-induced yield reduction was less than warming-induced increment in each cropping system, the annual yields was higher in the warmed plots than the non-warmed under all systems. Our findings can provide important references to cropping system adjustment for coping with global warming in China and other regions. [ABSTRACT FROM AUTHOR]

Abstract: Recently increasing studies suggest that a comprehensive assessment of cropping practices impacts on greenhouse gas (GHG) emissions at yield-scale will benefit cropping technique innovation and policy selection for higher-yield with less-emissions. In this paper, we conducted a meta-analysis to quantify the impacts of rice cropping practices on the global warming potential (GWP) of GHG emissions at yield-scale rather than area-scale in China. The results showed that the yield-scaled GWP of Chinese major rice cropping systems during rice growing season was in the order: double rice cropping system (1188.9kg CO2 equiv.Mg−1)>rice-upland crop rotation system (777.0kg CO2 equiv.Mg−1)>single rice cropping system (346.7kg CO2 equiv.Mg−1). Nitrogen fertilization (50–300kgNha−1) significantly increased rice yield with slight increments in the GWP of CH4 and N2O emissions, resulting in significant reductions in the yield-scaled GWP. The greatest reduction occurred at the application rate of 150–200kgNha−1 by 37% as compared to the non-fertilization control. For organic amendments, biogas residue application had no significant effect on the yield-scaled GWP, while manure application and straw recycling significantly increased the yield-scaled GWP by 54% and 154%, respectively. Intermittent irrigation significantly reduced yield-scaled GWP by 59% largely because of a significant reduction in CH4 emission and a significant increment in rice yield. No-tillage showed lower CH4 emission with similar rice yield in comparison with the conventional tillage, resulting in a reduction in yield-scaled GWP by 20%. These results indicate that there is a great potential to meet the new objective of higher-yield with less-GHG emissions through innovating rice cropping technique. More efforts should be paid on the field observations of GHG emissions during non-rice growing season, so as to perform a life-cycling assessment of GHG emissions from rice fields at yield scale under different cropping systems. [Copyright &y& Elsevier]

Abstract: To learn the historical response of cropping system to climate change will benefit the strategy decision of future cropping adaptation. In this paper, we conducted an integrated analysis of the climate records of seventy-two meteorological stations and the records of crop yields over the period 1970–2009 in Northeast China. It was found that over these forty years, the daily mean, maximum and minimum temperatures during crop growing season increased on average by 0.34°C, 0.28°C, 0.43°C every ten years, respectively. No significant change in the precipitation was found, although the differences between years were large. After de-trending the agronomic technique contributions to the increments of crop yields, the historical warming had led to great annually increments of 16.6kgha−1, 15.5kgha−1 and 3.2kgha−1 in rice, corn and soybean yields, respectively. According to the historical warming level, present cropping boundaries can be theoretically extended northward about 80km with a prolonged growing period by 10 days compared to the 1970s. Actually, the growth durations of newly approved varieties of rice, corn and soybean have really prolonged by 14.0 days, 7.0 days and 2.7 days since the 1950s, respectively. The actual growing periods of rice and corn have also respectively prolonged by 6 days and 4 days due to the adjustment of sown and harvest dates by the farmer since 1990s. The existing rice cropping region has been extended northward 80km in the 2006 compared to the 1970. These actual responses were consistent with the theoretical calculation according to the historical warming trends. Our results demonstrate that cropping system owns the potential to progressively and actively adapt to the global warming for high yield through a comprehensive strategy. [Copyright &y& Elsevier]