With the development of protected cultivation of vegetables in China, it is necessary to study the water requirements of crops in greenhouses. Lysimeter experiments were carried out to investigate tomato （2001） and ...With the development of protected cultivation of vegetables in China, it is necessary to study the water requirements of crops in greenhouses. Lysimeter experiments were carried out to investigate tomato （2001） and cowpea （2004） crop evapotranspiration （ETc） in an unheated greenhouse in Eastern China. Results showed remarkably reduced crop evapotranspiration inside the greenhouse as compared with that outside. ETc increased with the growth of the crops, and varied in accordance with the temperature inside the greenhouse and 20-cm pan evaporation outside, reaching its maximum value at the stage when plants’ growth was most active. Differences between the variation of crop evapotranspiration and pan evaporation inside the greenhouse were caused by shading of the pan in the later period when the crops were taller than the location where the pan was installed, 70 cm above ground. The ratio of crop evapotranspiration to pan evaporation was not constant as reported in previous studies, and the variation of the inside ratio αin lagged behind that of the outside ratio αout. Simulation of crop evapotranspiration based on 20-cm pan evaporation inside the greenhouse is more reasonable than that based on 20-cm pan evaporation outside, although pan evaporation outside is more consistent with ETc than that inside. The value of αin, calculated based on air temperature, relative humidity, and ground temperature inside, plays a dominant role in the calculation of ETc. As the crop height increases, altering the location of the inside pan and placing it above the canopy, out of the shade, would help to achieve more reasonable values of crop evapotranspiration.展开更多
Greenhouse gas emissions,nitrogen and phosphorous losses through ammonia volatilization,leaching and surface drainage from rice paddy under efficient irrigation and drainage were analyzed based on field experimental d...Greenhouse gas emissions,nitrogen and phosphorous losses through ammonia volatilization,leaching and surface drainage from rice paddy under efficient irrigation and drainage were analyzed based on field experimental data in order to reveal the eco-environmental impacts of efficient irrigation and drainage on rice paddy.The results showed that total methane emission from rice paddy under the controlled irrigation was reduced by more than 80%and total nitrous oxide emission increased by 15.9%compared with flooding irrigation.Seasonal comprehensive global warming potentials(GWP)of methane and nitrous oxide were 62.23 gCO_(2)m-2 for rice paddy under the controlled irrigation,reduced by 68.0%compared with flooding irrigation.Due to large reduction in seepage and surface drainages,nitrogen and phosphorous losses through leaching were reduced by 40.1%and 54.8%,nitrogen and phosphorous losses through surface drainage were reduced by 53.9%and 51.6%from rice paddy under efficient irrigation and drainage compared with traditional irrigation and drainage.Nitrogen loss through ammonia volatilization was reduced by 14.0%.Efficient irrigation and drainage management is helpful to mitigate greenhouse gases emission,nitrogen and phosphorus losses and their pollution on groundwater and surface water.展开更多
基金supported by the National High Technology Research and Development Program of China (Grant No 2006AA100202)the Foundation of Excellent Doctoral Dissertations of China (Grant No 200546)
文摘With the development of protected cultivation of vegetables in China, it is necessary to study the water requirements of crops in greenhouses. Lysimeter experiments were carried out to investigate tomato （2001） and cowpea （2004） crop evapotranspiration （ETc） in an unheated greenhouse in Eastern China. Results showed remarkably reduced crop evapotranspiration inside the greenhouse as compared with that outside. ETc increased with the growth of the crops, and varied in accordance with the temperature inside the greenhouse and 20-cm pan evaporation outside, reaching its maximum value at the stage when plants’ growth was most active. Differences between the variation of crop evapotranspiration and pan evaporation inside the greenhouse were caused by shading of the pan in the later period when the crops were taller than the location where the pan was installed, 70 cm above ground. The ratio of crop evapotranspiration to pan evaporation was not constant as reported in previous studies, and the variation of the inside ratio αin lagged behind that of the outside ratio αout. Simulation of crop evapotranspiration based on 20-cm pan evaporation inside the greenhouse is more reasonable than that based on 20-cm pan evaporation outside, although pan evaporation outside is more consistent with ETc than that inside. The value of αin, calculated based on air temperature, relative humidity, and ground temperature inside, plays a dominant role in the calculation of ETc. As the crop height increases, altering the location of the inside pan and placing it above the canopy, out of the shade, would help to achieve more reasonable values of crop evapotranspiration.
基金supported by the National Natural Science Foundation of China(Grant Nos 50839002 and 50809022)the National Key Tech-nologies R&D Program of China during the 11th Fiveyear Plan Period(Grant No 2006BAD11B09)
文摘Greenhouse gas emissions,nitrogen and phosphorous losses through ammonia volatilization,leaching and surface drainage from rice paddy under efficient irrigation and drainage were analyzed based on field experimental data in order to reveal the eco-environmental impacts of efficient irrigation and drainage on rice paddy.The results showed that total methane emission from rice paddy under the controlled irrigation was reduced by more than 80%and total nitrous oxide emission increased by 15.9%compared with flooding irrigation.Seasonal comprehensive global warming potentials(GWP)of methane and nitrous oxide were 62.23 gCO_(2)m-2 for rice paddy under the controlled irrigation,reduced by 68.0%compared with flooding irrigation.Due to large reduction in seepage and surface drainages,nitrogen and phosphorous losses through leaching were reduced by 40.1%and 54.8%,nitrogen and phosphorous losses through surface drainage were reduced by 53.9%and 51.6%from rice paddy under efficient irrigation and drainage compared with traditional irrigation and drainage.Nitrogen loss through ammonia volatilization was reduced by 14.0%.Efficient irrigation and drainage management is helpful to mitigate greenhouse gases emission,nitrogen and phosphorus losses and their pollution on groundwater and surface water.
