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Zhang Y.,Jiangsu Academy of Agricultural Sciences | Chen L.,Jiangsu Academy of Agricultural Sciences | Zhang C.,China Agricultural Machinery Testing Center | Yang H.,Jiangsu Crop Cultivation Technology Guidance Station | And 3 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2015

Methane (CH4) and nitrous oxide (N2O) are 2 important long-lived greenhouse gases (GHGs) that contribute to global warming. Paddy soils have been identified as a dominant source of atmospheric CH4 and N2O. Little information is available on the impacts of rice mechanical planting methods on CH4 and N2O emissions and rice yield in high production rice-wheat double cropping system. A field experiment was conducted with super rice cultivar Nanjing 44 as materials during the rice growing season from 2011 to 2012 in Suzhou, Jiangsu Province. By using static chamber/gas chromatographic techniques, in this two-year field experiment CH4 and N2O emissions were simultaneously measured under 3 rice planting methods: mechanical direct-seeding (MD), mechanical transplanting (MT) and artificial transplanting (AT). Each planting treatment was combined with either wheat straw retention or wheat straw removal. The results indicated that all treatments exhibited comparable seasonality in CH4 fluxes, showing an increase at the beginning and a decline later on. High N2O emissions were triggered by the midseason drainage episode during the rice growing season in 2011 and 2012. CH4 accumulative emissions from transplantation to critical stage of effective tillering accounted for 76.49%-91.13% of the total emissions during the rice growing season. N2O accumulative emissions from critical stage of effective tillering to elongation stage represented 33.56%-49.41% of the seasonal N2O emissions. Compared with wheat straw removal, wheat straw retention significantly increased seasonal total CH4 emissions by 125.96%-138.31% in 2011 and by 108.63%-127.10% in 2012 (P<0.05), respectively, and reduced the seasonal total N2O emissions by 2.83%-12.50% in 2011 and by 3.39%-18.19% in 2012 (P>0.05), respectively. The MT slightly decreased CH4 emissions during the rice growing season by 3.25%-9.50% compared to the AT (P>0.05), while both treatments were significantly higher than that from the MD (P<0.05). The seasonal total CH4 emissions in the MD were respectively 15.69% and 18.43% lower than those in the MT and AT with wheat straw removal, and 14.54% and 22.66% lower than those with wheat straw retention in 2011. And in 2012, the seasonal total CH4 emissions in the MD were correspondingly 26.63% and 32.12% lower than those in the MT and AT with wheat straw removal, and 30.51% and 36.75% lower than those with wheat straw retention, respectively. Compared with the AT, MD significantly increased N2O emissions during the rice growing season by 0.16-0.97 kg/hm2 in 2011 and 2012 (P<0.05). The seasonal total N2O emissions were comparable between the MT and the AT (P>0.05). For the years of 2011 and 2012, the rice yields under the AT were the highest, followed by the MT, and the yield under the MD was the lowest. Compared with the AT, the MD significantly decreased rice yield by 8.43%-10.79% (P<0.05), while the MT slightly decreased yield by 1.27%-3.49% (P>0.05). CH4 was more important in the 2 GHGs in that the effect of the seasonal CH4 emissions from rice-wheat double cropping system on climate was approximately 4 times greater than that of N2O emissions. The global warming potential (GWP) of CH4 and N2O emissions in the plots with wheat straw retention was 116.23%-130.35% higher than that in the plots with wheat straw removal in 2011 and 87.72%-118.04% in 2012 (P<0.05). The GWP in the MD was significantly lower than those in the MT and the AT (P<0.05). The GWP per yield in the MD was respectively 12.02% and 28.71% lower than that in the AT with wheat straw retention in 2011 and 2012 (P<0.05). The overall results indicated that the MD could effectively decrease total CH4 emissions during the rice growing season; with wheat straw retention, the conversion from AT to MD would reduce the comprehensive greenhouse effect resulting from the CH4 and N2O emissions in high production rice-wheat double cropping system in the downstream of the Yangtze River in China. ©, 2015, Chinese Society of Agricultural Engineering. All right reserved. Source


Liu C.,China Agricultural University | Ma C.,China Agricultural University | Wang P.,China Agricultural University | Zhao S.,China Agricultural University | And 2 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2015

The thermal insulation properties of solar greenhouse thick cover are affected by many factors, due to the complexity of heat transfer process which include conduction, convection and radiation. There have been some studies on the effects of the outdoor wind speed and infrared characteristic parameters of cover surfaceon the thermal insulation performance of thick cover. However, it is difficult to obtain accurate results due to the site conditions are not easy to control, and there are limited systematic studies on impact factors, which include heat preservation performance of greenhouse thick cover, using heat transfer theory. To master the effects of main influence factors on heat transfer coefficient of thick cover, we analyzed the relationship between surface emissivity of thermal insulation covers, thickness of thick cover, coefficients of insulation materials, wind speed of outside and the heat transfer coefficient of thermal insulation covers using heat transfer theoretical model on thermal thick cover. While the relationship between one factor and heat preservation performance of thick cover was being analyzed, other factors should be considered as constants to eliminate the impact of these factors. Thus the variation trend of relationship between single factor and heat transfer coefficient K can be gained. The results showed that the effect of up surface emissivity of thermal insulation covers on K value was more than 8.9%, and the effect of down surface emissivity of thermal insulation covers on K value was less than 4.5%, when there was fixed film under the thermal thick cover. When there was without fixed film, the effect about down surface emissivity of thermal insulation covers on K value would increase, but it was still lower than that of up surface emissivity on heat transfer coefficient. The increase in thickness and the decrease in conductivity coefficient of thermal thick cover would increase the heat transfer resistance substantially. So the K value would be decreased with thickness increasing or heat conductivity coefficient of thick cover materials reducing. It also showed that all the thermal insulation materials could meet the heat preservation performance requirements of horticultural cover, when the thickness was between 40 mm and 50 mm, based on the analysis of the relationship between K and thickness of thermal thick cover, conductivity coefficient of thermal insulation materials. K value of thermal thick cover was decreased with wind speed increasing (neglecting the heat loss of thick cover overlap joints) when emissivity of the upper surface was high and the heat transfer coefficient was low; K value of thermal thick cover was increased with wind speed increasing when emissivity of the upper surface was low and the heat transfer coefficient was high. An empirical formula on heat transfer coefficient was promoted based on the analysis of the relationship between influence factors and heat transfer coefficient. And the parameters in the formula were obtained by regression method. The empirical formula about K provides theoretical foundation for development and application of thermal thick cover. ©, 2015, Chinese Society of Agricultural Engineering. All right reserved. Source


Huang C.,China Agricultural University | Huang C.,Chinese Academy of Agricultural Sciences | Han L.,China Agricultural University | Liu X.,China Agricultural University | Ma L.,China Agricultural Machinery Testing Center
Energy Sources, Part A: Recovery, Utilization and Environmental Effects | Year: 2011

Rice straw can be used for biochemical conversion for energy production. The use of near infrared spectroscopy was explored to estimate the contents of cellulose, hemicellulose, and lignin in this study. A total of 172 samples from 17 provinces of China were collected and scanned using NIRSystem 6500 spectrophotometer. Different spectra pretreatments and regression methods were adopted to optimize the models. When evaluated on independent validations, the standard errors of validation and determination coefficient of validation were 1.49%, 1.59%, 0.65% and 0.82, 0.71, 0.78, respectively. It was concluded that near infrared spectroscopy can be used to roughly analyze the contents of cellulose and lignin, and can only distinguish high contents and low contents of hemicellulose in rice straw. Copyright © Taylor & Francis Group, LLC. Source


Mengtao Y.,Chongqing University of Science and Technology | Hongwei J.,China Agricultural Machinery Testing Center | Xiaomei W.,Chongqing University of Science and Technology | Yonggang Y.,Chongqing University of Science and Technology
Applied Mechanics and Materials | Year: 2012

Based on the development practice of the pump performance test bed for the agricultural sprayer, a new program is proposed to cover the integrated mechanical structure of the pump performance test bed. Analysis was given to the various performance parameters of the pump test with regard to their testing methods, and specific methods of work performance test and inhalation performance test were also discussed to explore the test results. Finally, the issues that need to be focused were raised on the design and manufacture of pump performance test for the sprayer. © (2012) Trans Tech Publications, Switzerland. Source


Chai L.,China Agricultural University | Ma C.,China Agricultural University | Zhang Y.,China Agricultural University | Wang M.,China Agricultural Machinery Testing Center | And 2 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2010

In order to study the feasibility of the application of ground source heat pump (GSHP) in greenhouses, experimental research on groundwater-style ground source heat pump system was carried out in greenhouse heating in Beijing. Experimental result showed that the coefficient of the system performance in greenhouse heating had reached 3.83 during the heating period of Oct.15, 2007-Mar.10, 2008, about 42% energy had been saved compare with conventional coal-fired hot water heating system, which its merits of energy-saving and greenhouse gases mitigating of the system were distinctive. The total electric consumption and the heating cost of the system was 0.15 kW·h/(m2·d) and 0.12 Yuan/(m2·d), respectively. The comparison among the heating systems of GSHP, natural gas, coal and light diesel oil were made, which the relative heating cost were 1.20, 1.31, 1.00 and 3.36, respectively, and the heating cost of ground source heat pump was higher than that of coal slightly, but was lower than that of natural gas and light diesel oil apparently. Source

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