Claculation Of Crop Water Consumption And Delermination Of Parameters Under Dificit Irrigation

Crop evapotranspiration is the key basis for reasonable irrigation and water resource management, which has important value in the agricultural production. The article made use of the BoWen-ration energy balance system, lysimeter, and micro-lysimeter to measure the evapotranspiration and evaporation of the Winter Wheat in Yangling, Shaanxi province, at the same time, analyzed the replenishments of underground water to crop using 10-year materials of Baoji Gorge irrigation districts. Based on the analysis,the main results showed as follows:1. Using the single time average and dual crop coefficient approach proposed by FAO, we determined the crop coefficient of Winter Wheat. With the value measured by lysimeter and crop evapotranspiration, we modified the crop coefficient. Under the climate conditions of Yangling, Shaanxi province, if the breed not changed, we can get the single crop coefficient of Winter Wheat using time averaged crop coefficient approach, which were: K_cfro(Measured)=0.55;K_cmid(Tab)=1.25;K_cend(Tab)=0.76;meanwhile, we got the dual crop coefficient by the dual crop coefficient approach, which were: K_cbfro(Tab)=0.55 ;K_cbmid(Tab)=1.25;K_cbend(Tab)=0.79.2. Calculated the Winter Wheat crop coefficient day by day with the data measured by lysimeter. The peak value appeared about 200 days after planting, when was during the heading and grain filling stage. We also fitted the equation of the crop coefficient of Winter Wheat and days after planting.3. The method of using water stress coefficient to modify the crop evapotranspiration calculated by crop coefficient was feasible. We calculated the crop evapotranspiration of the wheat field under different water levels by single and dual crop coefficient approach. The results showed that the value calculated by dual crop coefficient approach can accord with the measured data preferably except the plant growth stage, when the calculated value was bigger than the measured data.4. The replenishment rule of underground water to crop in the fields was: the volume of underground water replenishment changed with the depth of it, which had negative correlation relationship. That was, the shallower the buried depth, the more the replenished water; the deeper the buried depth, the less the replenished water; under certain depth, the replenished water was 0, and deeper than it there was no replenished water. Under the conditions of no irrigation, the suitable range of underground water was 1.0～2.5m,the suitable buried depth was 2.5m for wheat growing;the suitable range of underground water was 1.0～2.0m,the suitable buried depth was 2.0m for maize growing in Guanzhong loess region.