Irrigation and drainage development of deserts in China

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This research is composed of the following three subjects of study.1. Water resources utilization for development of sandy deserts :In the experimental field at the Shapotou Desert Experiment and Research Station, evapotranspiration from soybeans was estimated by the water balance method using the drainage type lysimeters under the condition of drip irrigation system. The water holding in the soil, soybean yield and evapotranspiration in a sandy field increased by covering the soil surface with silt contained in the Yellow river. Application of the small amount of water at frequent intervals decreased the deep percolation losses in a sandy field. Feasibility of agricultural utilization of treated wastewater from a rural settlement was proved by the experiments of soybean and corn culture during four years.2. Soil management for cultivation of sandy deserts :The chemical properties of soil at Pingluo upland field were analyzed. In the case of high groundwater level, the salt accumulation of the field was recognized with lower harvesting of wheat. Application of the, large amount of surface irrigation water after the harvesting season decreased the value, of electric conductivity in the soil.3. Drought tolerance and radial growth of woody species in Shapotou.Differences of drought tolerance among nine woody plants were investigated using the p-v curve method. The drought tolerance of Ammopitanthus mongolicus, Caragana intermedia, and Salix gordejevii was remarkable in all of the species. Anatomical studies on radial growth of five woody species maintained by periodic irrigation were also investigated. The periodic cycle of radial growth was observed in Elaeagnus. angustifolia : and Thuja orientalis, whereas Populus alba showed constant growth. In Pinus sylvestris and Salix matsudana the stagnation of growth occurred once in growing season.