Research On Ecological Groundwater Depth And The Optimum Irrigation Amount For Different Crop Planting Patterns In Hetao Irrigation District

Soil salinization of Inner Mongolia Hetao Irrigation District has become a major obstacle to the sustainable development of agriculture. Durning the agricultural production process, irrational irrigation and flood irrigation methods, combined with drainage project is not complete, so irrigation groundwater depth become light, beyond the critical depth, the evaporation lets salt remain in the soil, the main reason leading to soil salinization. This paper studied the innerreaction between regional groundwater depth and soil salinity, combined with crop tolerance, initially proposed the ecological groundwater depth that could maintain crops grow normally; Determine the canal scale irrigation water use coefficiency under the comprehensive agricultural water conservation condition with head and tail estimation method, using different methods to determine the minimum irrigation water under different cropping patterns, results could offer theoretical reference for irrigation system determining, rational use of water resources, prevention of soil salinization. The main conclusions are as follows:(1) The study area groundwater table fluctuations during the year was large, divided thaw period, irrigation period, autumn irrigation period, average groundwater depth in the year was 1～2m, individual wells depth always shallow, surrounding arable crops can not grow normally.(2) groundwater condition closely related to the degree of soil salinization, groundwater depth and soil salinity meet good exponential relationship (R2= 0.7153); groundwater salinity and soil salinity also satisfies an exponential regression relationship (R2= 0.6533). That is to say:more shallow groundwater depth, the higher the groundwater salinity, soil salinization more severe.(3) combine the salt tolerance of crops, initially identified different crops ecological groundwater table. the maximum appropriate ecological groundwater depth control of wheat durning growth period is more than 1.4m; that of corn is more than 1.6m; oil sunflower appropriate ecological groundwater depth is greater than 1.2m; while that of food sunflower is more than 1m.(4) The use of field experiments measured data, to obtain the optimum amount of water for irrigated wheat intercropping maize:wheat irrigated four times durning the growth period, The total irrigation water amount is 2900 m3·hm-2; corn irrigated four times durning the growing period, the total amount of irrigation water for maize was 3625 m3·hm-2; minimum irrigation water amount for single crop durning growing period corn 3000m3-hm"2, sunflower 2100 m3·hm-2, irrigation frequency determined according to local conditions.