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Cui S.,China Agricultural University | Yin X.,China Agricultural University | Chen F.,China Agricultural University | Tang H.,Hunan Soil and Fertilizer Institute | And 2 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2011

Tillage affects the nitrogen leakage by changing soil physical and chemical properties. The effects of tillage on soil permeability and nitrogen leakage were studied for increasing utilization efficiency of nitrogen in paddy field. Long-term field experiments were established from 2005 in a double rice cropping region, Ningxiang county, Hunan province of China. Treatments included no-tillage with straw returning(NT), rotary-tillage with straw returning (RT), conventional tillage with straw returning (CT) and conventional tillage without straw returning (CT0). Constant-head method was used to analyze soil hydraulic conductivity in the soil layer 0-80 cm. Results showed that there was an increase in soil hydraulic conductivity in NT, which was 63.14% and higher than that in CT. Higher leakage of NH4 +-N and NO3 --N (p<0.05) were found in NT than in other treatments. Straw returning enhanced the leakage of NO3 --N, especially in the period of early rice cultivation. The annual leakage of NH4 +-N was almost two times than that of NO3 --N among each treatment. Compared with other tillage treatments, NT could increase nitrogen leakage, and more attention should be focused on NH4 +-N leakage in long-term flooding paddy fields. Source

Liu S.,China Agricultural University | Xue J.,China Agricultural University | Zhang R.,China Agricultural University | Chen Z.,China Agricultural University | And 3 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2015

Global warming is a concern for policy makers, scientists and farmers around the world. It is widely accepted that climate change has had great impacts on agricultural production and farmers' income. Thus, there is a conundrum of how to balance the tradeoffs between food demand, increasing population, and scarce agricultural resources in the changing climate. Sensitivity and vulnerability of crop production to climate change are highly important for agriculture adaptation, but uncertainty still exists in previous research among diverse regions. Rice production may face huge risk because of the frequent extreme weather in China, therefore, a sensitivity analysis of rice production under the impacts of climatic change in different growth stages will contribute to optimizion of rice cultivation management for adapting to the changing conditions. In this study, we selected the recorded rice phonological observations at 10 agro-meteorological experiment stations, and the corresponding weather and statistical yields from 1980-2012 in Hunan Province, China. These data were used to analyze rice sensitivity to climate change using a panel model combined with multiple regression methods. The relationship of climate and yield trend was computed with the least square method, and the possible relationship between climatic factors and double-rice yield was analyzed by partial correlation analysis. The results showed that the double-rice region in Hunan Province experienced a warming trend over the last three decades, and the average temperature during the early rice and late rice seasons were 0.47 and 0.33 oC/(10a) higher. An increase in temperature of 0.76 oC/(10a) was observed during the vegetative stage of the early rice season, while the late rice season experienced a relatively slower increase in temperature. Precipitation and radiation during the growth stage of early rice tended to increase unnoticeable, but radiation in the vegetative stage and the reproductive stage of early rice changed with the trend -0.40 and 0.40 MJ/(m2·d·10a), while the trend was opposite for the late rice. Yield changes in the early rice were significantly correlated with precipitation and radiation during the ripening stage and the whole growth stage (P<0.01), but only the average temperature was significantly correlated to the yield for the late rice (P<0.05). Whatever the model adopted, the yield sensitivity of double-rice to climate change showed great differences among different growth stages, ranging from -280.11 to 118.20 kg/hm2. Temperature, precipitation and radiation in the vegetative stage were most sensitive to the yield for both the early rice and late rice. The rising temperature increased yield of the early rice, while we observed the opposite effect for the late rice. From 1980 to 2012, temperature increase, decrease of precipitation and radiation changed the early rice yield by -0.24% to 3.18%, and temperature increase during vegetative stage increased the early rice yield by 2.63%, and even accelerated the early rice yield by 157.10 kg/hm2. The late rice experienced a severe yield decrease by -4.98% with only temperature change in consideration. The historical climatic change impacted the yield of the early rice and late rice by 2.59% and -6.02%, respectively. These results suggest that the historical climate change during different rice growth stages has changed yields of double-rice in Hunan Province, especially if temperature rose during the growth stages. There is a strong need to assess historical climate change to project possible impacts in the future and identify adaptive technologies for double-rice production in this region. ©, 2015, Chinese Society of Agricultural Engineering. All right reserved. Source

Chen Z.-D.,China Agricultural University | Wu Y.,China Agricultural University | Ti J.-S.,China Agricultural University | Chen F.,China Agricultural University | Li Y.,Ningxiang Agricultural Bureau
Chinese Journal of Applied Ecology | Year: 2015

Improving the carbon efficiency of crop production systems is one of the important ways to realize low-carbon agriculture. A life cycle assessment approach and input-output calculation method was applied for a double-rice production system in the Hunan Province. Based on statistical data of crop yield and investment in the production system in the period from 2004 to 2012, carbon emission, carbon absorption, carbon efficiency and their dynamic changes of the double rice production systems were estimated. The results showed that the average of annual carbon emission from 2004 to 2012 was 656.4×107kg CE. Carbon emissions from production and transport of fertilizer and pesticide accounted for a majority of agricultural input carbon emissions, approximately 70.0% and 15.9%, respectively. The carbon emission showed a decreasing trend from 2004 to 2012 in the Hunan Province, with an annual reduction rate of 2.4%, but the carbon emission intensity was in a trend of increase. The average of annual carbon absorption was 1547.0×107 kg C. The annual carbon absorption also showed a decreasing trend from 2004 to 2012 in Hunan Province, with an average annual reduction rate of 1.2%, and the carbon absorption intensity showed a trend of increase. Furthermore, production efficiency of carbon showed a slow upward trend. The economic efficiency of carbon showed a larger increasing rate with time, with an average annual growth rate of 9.9%. Ecological efficiency of carbon was stable and low, maintained at about 2.4 kg C • kg-1 CE. It indicated that the integrated carbon efficiency of Hunan double rice crop production system improved slowly with time and the key to improve the carbon efficiency of double rice production systems lies in reducing the rates of nitrogen fertilizer and pesticide, and improving their use efficiencies. ©, 2015, Editorial Board of Chinese Journal of Applied Ecology. All right reserved. Source

Bai X.,China Agricultural University | Zhang H.,China Agricultural University | Chen F.,China Agricultural University | Sun G.,China Agricultural University | And 2 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2010

Greenhouse gas emission is becoming a very important issue with the continuous increasing in the global temperature. In order to evaluate carbon sequestration potential of paddy and reducing emission of greenhouse gas, tillage effects on CH4 and N2O emissions from paddy soil and the trade-off relationship between CH4 and N2O were explored. The closed chamber method was used to measure the CH4 and N2O emission from the paddy field with the treatments of conventional tillage (CT), rotary tillage (RT), no-tillage (NT) at Ningxiang County, Hunan Province. The results show as following. 1) CH4 emission mainly comes from the late rice paddy, which accounted for 69%, 67%, 73% of the studied period under CT, RT and NT, respectively; 2) CH4 emission of all treatments attributed to less than 1% in the winter-fallow season, while the differences of the emission among three treatments are significant with RT>CT>NT; 3) N2O emission shows highly temporal variability that N2O emission in early rice paddy is RT>NT>CT, while in late rice paddy is NT>RT>CT, and the N2O is absorbed in winter-fallow season; 4) CT is beneficial to decreasing N2O emission during the studied period, while NT is beneficial to decreasing CH4 emission; 5) During the studied period, correlation between CH4 and N2O shows negative significantly, but the correlation between CH4 and N2O in winter-fallow season is not significant. In general, though increasing N2O emission appreciably, NT is beneficial to decreasing CH4 emission, and the comprehensive greenhouse effect of N2O and CH4 is also decreased. Source

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