Internal temperature is crucial to plant growth in the greenhouse. We investigated the patterns of constructing and managing greenhouses in Chongqing, and developed an algorithm of heating temperature for closed winte...Internal temperature is crucial to plant growth in the greenhouse. We investigated the patterns of constructing and managing greenhouses in Chongqing, and developed an algorithm of heating temperature for closed winter plastic greenhouses under the conditions of no man-made illumination, no ventilation and hot wind machine as the heating equipment, which are the most adopted pattern of greenhouses in Chongqing area. The algorithm includes two functions of temperature outside the greenhouse, which calculate the values of the warming estimation coefficient (WEC) and the gap between temperatures inside and outside the greenhouse with the measured data of outside temperature, and then give the value of internal temperature; the heat rating of heating facilities required by a greenhouse can be determined by this algorithm with given values of floor area and internal temperature, measured outside temperature and calculated WEC. Verification of the algorithm demonstrates a desirable accuracy of estimation. Algorithms of computing heating temperature for greenhouses of different constructing and managing patterns and in different geographic conditions can also be derived in a similar way. This research presents a paradigm for developing a feasible method to fit out greenhouses with appropriate heating facilities, aiming at energy efficient and cost efficient production.展开更多
An efficient water use requires accurate estimations of crop ET （evapotranspiration）. However, an accurate ET estimation is really difficult to achieve when big regions such as irrigation districts or complete water...An efficient water use requires accurate estimations of crop ET （evapotranspiration）. However, an accurate ET estimation is really difficult to achieve when big regions such as irrigation districts or complete watersheds are involved. Satellite images are an alternative that can be used to estimate accurate crop ET for big regions. In the present study, two known methods were used to estimate crop ET, the METRIC model which was developed by the University of Idaho and a Kc-NDVI relationship. In the METRIC model, ET is estimated as a residual of the energy balance equation. The second method uses reference ET, and estimates a crop coefficient （K,.） as a linear function of the NDVI vegetation index. ET was estimated in a section of the Rio Mayo Irrigation District located in Sonora, Mexico using Landsat 7 satellite images. Crop ET of the main crops was estimated. Results show some differences between both methods. An average ET depth of 460 mm for the wheat average growing season was found when using METRIC, while an average ET depth of 421 mm was found when using the Kc-NDVI relationship. A water use total efficiency of 62% and 63% was found for METRIC and the Kc-NDVI relationship, respectively.展开更多
基金a grant from the Major Programs of the Ministry of Science and Technology during the 10th Five-Year Plan Period from (2001BA04A)
文摘Internal temperature is crucial to plant growth in the greenhouse. We investigated the patterns of constructing and managing greenhouses in Chongqing, and developed an algorithm of heating temperature for closed winter plastic greenhouses under the conditions of no man-made illumination, no ventilation and hot wind machine as the heating equipment, which are the most adopted pattern of greenhouses in Chongqing area. The algorithm includes two functions of temperature outside the greenhouse, which calculate the values of the warming estimation coefficient (WEC) and the gap between temperatures inside and outside the greenhouse with the measured data of outside temperature, and then give the value of internal temperature; the heat rating of heating facilities required by a greenhouse can be determined by this algorithm with given values of floor area and internal temperature, measured outside temperature and calculated WEC. Verification of the algorithm demonstrates a desirable accuracy of estimation. Algorithms of computing heating temperature for greenhouses of different constructing and managing patterns and in different geographic conditions can also be derived in a similar way. This research presents a paradigm for developing a feasible method to fit out greenhouses with appropriate heating facilities, aiming at energy efficient and cost efficient production.
文摘An efficient water use requires accurate estimations of crop ET （evapotranspiration）. However, an accurate ET estimation is really difficult to achieve when big regions such as irrigation districts or complete watersheds are involved. Satellite images are an alternative that can be used to estimate accurate crop ET for big regions. In the present study, two known methods were used to estimate crop ET, the METRIC model which was developed by the University of Idaho and a Kc-NDVI relationship. In the METRIC model, ET is estimated as a residual of the energy balance equation. The second method uses reference ET, and estimates a crop coefficient （K,.） as a linear function of the NDVI vegetation index. ET was estimated in a section of the Rio Mayo Irrigation District located in Sonora, Mexico using Landsat 7 satellite images. Crop ET of the main crops was estimated. Results show some differences between both methods. An average ET depth of 460 mm for the wheat average growing season was found when using METRIC, while an average ET depth of 421 mm was found when using the Kc-NDVI relationship. A water use total efficiency of 62% and 63% was found for METRIC and the Kc-NDVI relationship, respectively.
