THE WATER-USE EFFICIENCY OF WINTER-WHEAT AND MAIZE ON A SALT-AFFECTEDSOIL IN THE HUANG-HUAI-HAI RIVER PLAIN OF CHINA

This paper deals with the water-use efficiency of winter wheat (Tritic um aestivum L.) and maize (Zea mays L.) on a salt-affected soil in the Huang Huai Hai river plain of China. A strong linear relationship was found between the dry above ground biomass and evapotranspiration (ET ) for winter wheat (48 kg ha-1 mm-1) and maize (38 kg ha-1 mm-1). A si milar result was obtained for the grain yield of winter wheat (10 kg h a-1 mm -1). The harvest index of winter wheat decreases at increasing evapotranspiration: i.e. from about 0.4 down to 0.3 when evapotranspir ation increases from 200 to 380 mm. Application of the yield-decrease - evapotranspiration-decrease model of Stewart et al. (1977) to divide evapotranspiration in soil evaporation and transpiration resulted for winter wheat in a total soil evaporation of 9 mm (3% of total evapotr anspiration) and for maize of 62 mm ( 17.5% of total evapotranspiratio n). The relationship between grain yield of winter wheat and irrigatio n depth could be approached by a quadratic curve indicating that with increasing amount of irrigation water yield increase becomes less. Soi l salinity increased during the dry season mainly due to capillary ris e and decreased during the rainy season in summer by leaching. The cap illary rise during the dry season was estimated from the chloride conc entration of the soil water at a depth of 2 m and the increase of the chloride content in the layer 0-2 m and amounted to about 55 mm. The d ecrease in chloride content in the layer 0-2 m during the rainy season counterbalances the chloride increase in the dry season.