| In order to search for good water-saving cultivation measures in Guanzhong Plain., Shaanxi province, where with relatively favorable agricultural conditions but water resource is a potential restraint factor for sustainable development of agriculture, field experiments (2000 ~ 2001) were conducted on the red-oil soil in Yangling area, Guanzhong plain, Shaanxi province, where annual precipitation is about 550 ~ 600 mm with semi-humid prone to drought area. The cultivation method was carried out by means of applying plastic mulching on the ridge and rain harvest and winter wheat (Triticum aestivum) and summer maize (Zea-mays) (the most important two grain crops in local area) were adopted as indicate crops, and winter wheat was the first crop, the summer maize was the next, the rotation was practiced. During the experimental period, irrigation was not implemented, the growth of crops only depended on the stored water in the soil before sowing and the rainfall at the growth period. The effect of cultivation method on WUE and yield of winter wheat under cultivation of mulching and rain harvest were studied, in addition the nutrient accumulation in different organs, the changes of dry matter amount, nutrient uptake, NOa'-N and NtLi+-N contents in soil profiles, accumulation amount of mineral N and nitrogen efficiency of crops- etc were also investigated. The main results obtained from the experiments are as follows:1. Cultivation through plastic mulching on the ridge and rain harvest improved soil water status, at turning green stage of winter wheat, in 0~20 cm and 20~40 cm soil layer, under plastic mulching conditions the average water contents were 19.3%, 18.2%, respectively, under no mulching conditions, they were 18.2%, 16.9%, the former increased 1.13%, 1.26%, respectively. At later growth stage, the average water storage amount was lower 28.7 mm in depth of 100~200 cm comparing mulching with no mulching. It indicated that plastic mulching collected and conserved more water more effectively at the seedling stage and effectively utilized soil water in deep soil layer at the vigorous growth stage.2. Under plastic mulching conditions, the yield increase effect was very significant. Plastic mulching increased significantly biological and economical yield of winter wheat by 15.86%, 22.6% under two of high N treatments conditions than that of two low N treatments. Among the all treatments the grain yield of high N, low density treatment was highest. Comparing with no mulching, mulching greatly increased yield, under the low N, low density conditions (treatment 3 and 5), biological yield and economical yield increased 9.5%, 14.4%, respectively; and under high N, high density conditions, biological yield and economical yield increased 39.5 %, 28.9 %, respectively.In the case of summer maize, under mulching and high N rate conditions, biological yield and economical yield were 6591 kg/hm2 > 11997 kg/hm2, respectively, that was higher 22.1 %% 13.3% than that under low N rate conditions. Under the conditions of plastic mulching on the ridge, wheat straw mulching in ditch and rain harvest and high N rate, the maize biological yield and economical yield were 6005 kg/hm2 > 11826 kg/hm2, respectively, which was higher 7.4 %> 12.1% than that low N rate, biological yield and economic yield. Among the all treatments, mulching was higher than CK, high N, low density mulching yield was the highest, that was higher 60% and 58% than CK. Mulching and rain harvesting cultivation can enhance output notably.3. Plastic mulching and rain harvesting cultivation improved soil water status and increased output, therefore also increased WUE. In this experiment the WUE was high up to 22 kg/mm.hm2 under high N, low density treatment of winter wheat, whose economic efficiency was the best, that was higher 1605 yuan/hm2 than that under CK, the income ratio reach 32.3 %, the other treatments only increased yield but did not improve income .4. Plastic mulching and rain harvesting cultivation harmonized the relationship between...
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