| The experiment of corn's regulated deficit drip irrigation under plastic film mulched for seed was carried out from April to October in 2006 at key experimental station in an arid area of Northwest China (Zhang ye). Three gradients of soil moisture content were designed on this experiment, which compared with corn's border and furrow irrigation under the condition of sufficient water supply. The purpose was to study optimal regulated deficit plastic mulched drip irrigation scheme according to the analysis of soil water content, soil temperature, biomass characteristic and dry matter accumulation of corn, grain yield and water use efficiency. The main results as follows:1. The effect of emitter flow on the saturation area of soil, plane and vertical moist area was obvious. The relationship between radius of saturation area and emitter flow was regressed by Rs=4.21q+8.35. The relationship between radius of plan, vertical moist distance and irrigation quota can be described by Rh=14.687(qt) 0.35 and Rv =7.9(qt) 0.56 respectively. There was no significant difference between single emitter's plan moist distance and more emitter's, which was linearly collocated with the same distance (d=28cm).2. The diurnal change of drip irrigation corn's soil temperature in 0-10cm was very acute, and the changes became smooth along with the increase of soil depth. Irrigation can lower the soil temperature, especially in 0-10cm. The volume of irrigation water had significant impact on soil temperature, the more irrigation water, the more significant dropping of soil temperature.3. The curve of drip irrigation's soil moisture content with corn's stage was smoother than that of border and furrow irrigation. The moisture content of drip irrigation soil was lower than border and furrow irrigation below 40cm. The soil moisture content increased with depth of soil before sowing, but reversed after harvest. Drip irrigation had no influence to deep (deeper than 55cm) soil moisture content.4. The growing speed of the height and leaf area index leaf is most fast in jointing-heading stage, and that was stable in heading stage, but the leaf area index of corn lowered after filling stage. The accumulation of corn's dry matter was very little, and the rate of dry matter accumulation became fast after jointing stage. The dry matter accumulation showed a rising trend after sowing and achieved maximum in autumn stage. The lowest yield under water stressed in jointing-heading stage (Y2) had significant difference with the sufficient drip irrigation in the whole stages (Y8).5. The corn's daily water consumption of drip irrigation was 1mm/d which was the smallest in sowing-jointing stage. After jointing stage, the water consumption increased to 3-4mm/d rapidly, and achieved maximum in filling stage, then it lowed to about 2mm/d speedily after un-fully mature stage. The evaporation intensity around plant was lowed from 0.23 mm/d(sowing-jointing) to 0.003mm/d (heading-filling), after filling stage it was increased, and achieved maximum in autumn stage, the maximum evaporation intensity was 0.37mm/d,which accounted for 17% of water consumption.6. The highest water use efficiency (WUE=2.28kg/m3) of drip irrigation corn was Y4, which was lack of water in filling stage to mature stage. The next was Y8 (WUE=2.01kg/m3). The lowest water use efficiency (WUE=1.18kg/m3) of corn was CK3, which was furrow irrigation corn. The WUE of Y4 that was lack of water in jointing to heading stage was second lowest (WUE=1.32kg/m3). The highest irrigation water use efficiency (IWUE) was Y4, and which was 3.77kg/m3, the second was Y5 (IWUE=1.18kg/m3). The lowest was CK3 (IWUE=1.54kg/m3), and second lowest was Y2 (IWUE=1.82kg/m3).7. The yield of drip irrigation increased with the increase of total water consumption. The regression model between yield and total water consumption was y = 1.72x+501.95. The drip irrigation corn's sensitive coefficients of Blank model in sowing–jointing, jointing-heading, heading-filling, filling- mature stage were 0.11, 0.60, 0.18, 0.07 respectively, and the sensitive index of Jensen model were 0.05, 0.70, 0.19, -0.03 respectively.8. The economic irrigation quota of drip irrigation was 2400 m3/hm2, which was calculated according to the principle that forming maximum WUE and IWUE. Irrigation quota in sowing–jointing, jointing-heading, heading-filling, filling- mature stage were 273, 1090, 692, 345m3/hm2 respectively, which was achieved by linear programming, but the irrigation quota that was calculated by dynamic programming were 240, 1440(1200), 720(960), 0 m3/hm2 respectively.9. Furrow irrigation corn's economic effectiveness was lower than border irrigation corn under the full irrigation condition, and there was significant difference between them. There was no significant difference between drip irrigation corn with border irrigation and furrow irrigation under the full irrigation condition. The highest economical benefit of drip irrigation was Y8 (full irrigation), and the next was Y4, and there was no significant difference between them. The economical benefit of drip irrigation was low both in Y2 and Y5, Y6, Y7 (lack of water in several stages) and their economical benefit were significant difference with Y8. The total irrigation water of drip irrigation corn was lower 17.5% and 34% than border and furrow irrigation respectively, and 23.6% fertilizer was saved by drip irrigation.
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