Variation And Simulation Of Vegetables And Fruits Water Requirement Under Installation Cultivation

The water demands, water requirement rules and weather effects to the water demands were analyzed, based on the vegetables and fruits water requirement experiments under installation cultivation; the vegetables' crop coefficients outdoor were studied, amended and simulated; greenhouse coefficients were simulated; the water demands were simulated by pan evaporation method and crop coefficients method; cumulative water demands equations were established according to Logistic growth curves; the differences of water demands were researched under different groundwater conditions. The result indicated,The water demands under installation cultivation were less than that under general irrigation condition, whose differences were 50% in vegetables and 30% in fruits. There were similar changes in curves which were one-apex curves in vegetable and fruits water demands, water requirement intensities and modulus coefficients between years. The curve of cumulative water demands was "s" in shape. The water demands outdoor were related with evaporation, air temperature, land temperature and rain, while the water demands in greenhouse were influenced by land temperature.The crop coefficients from FAO-56 were amended by weather parameters. And the growing stages plotted by Logistic curves were substituted for that from FAO-56. The result showed that correlation coefficients between corrected crop coefficients and measured values were in the range, which were from 0.80 to 1.0.The greenhouse coefficients were introduced. When the value was smaller than 1, that's to say, the water demands in greenhouse were less than that under outdoor conditions. In other words, it distinguished water demands in greenhouse from outdoor.The water demands equations were established by synthesis factor including pan-evaporation and weather parameters, whose correlations were significant. The water demands were calculated in two different ways: one used coefficients recommended by FAO-56, and the other one adopted amended coefficients. The results showed that the later one was closed to the actual water demands than former.According to the Logistic curves and depths of ground water, cumulative water demands equations of vegetables were built under installation cultivation, based on using growing stages and depths of groundwater as parameters.The deeper groundwater was, the less water demands, enhancement of cumulative water demands, the use of groundwater and the crop coefficients were. These could be found on spinach water demand experiment, and the right groundwater depth which adapted to the growth of spinach was from 0.6m to 0.9m.