| Saving irrigation water in fields has been more and more paid attention to in agricultural development of Hexi irrigation area and been the key point of experimental study. Due to the huge investments, methods such as drip irrigation and sprinkler irrigation are not suitable for grain crops such as maize with relatively low economic benefit. Thus, we applied the technology of double ridges mulched with wide plastic film extensively used in semi-arid rain feed region to the maize culture in Hexi irrigation area. The studies on the soil moisture, temperature, nitrogen, phosphorus and nitrogen and phosphorus of leaf, maize yield and agronomic traits were conducted. The results demonstrated that:1. Looking from the whole growth period, soil moisture (%) from 80 to 100 centimeter soil layers had little change and had remained at a higher level. This shows that in soil with higher sediment concentration, such as Minqin, a part of irrigation water unused by plants was leaked to 80 centimeter soil layer without roots distribution and returned to groundwater circulation. Eight measuring results showed that five treatments had the same or similar dynamic changes of moisture in 0-100 centimeter soil layers, which indicated that the state of plant growth was similar and had similar water use mode. After June, soil water content of SL 1/2G with the least irrigation water in 0-60 centimeter soil layer was minimum. In the middle of July, each treatment had the lowest soil moisture in 40-60 centimeter soil layer, SL 1/2G was the best minimum, was 5.40%. Except SL 1/2G, soil moisture of all treatments in all soil layers varied slightly and SL/G was slightly higher than other treatments. But we could see that, in 80-100 centimeter soil layer, four treatments with double ridges mulched with wide plastic film were higher than the whole film tile, which illustrated that furrow-ridge design of double ridges mulched with wide plastic film could increase irrigation water pressure, so water could infiltrate rapidly to the soil, which met the crop growth and development, as well as the surplus water infiltrated to deep soil layer. But QP had relatively lower irrigation water pressure, so water stopped on the film for long time and had higher evaporation losses than SL. 2. Diurnal change of soil temperature under different treatments in different time had the same tendency, namely it began to rise gradually from 7:00 in the morning, soil temperature reached maximum at 15:00-16:00 o'clock, then began to decline. Comparing SL with QP, measured on June 4, diurnal average temperature of SL was 0.84℃greater in 0-5cm,0.9℃greater in 5-10cm,0.52℃greater in 10-20cm than QP. On July 15,crops had fully covered ground, this time SL had higher average diurnal temperature than QP, SL was 0.63℃greater in 0-5cm,0.76℃greater in 5-10cm,0.69℃greater in 10-20cm than QP. This indicated that SL had better effect on increasing temperature, which could have a positive effect on protecting maize seedling from cold, shorten the emergence time and improve the emergence rate.3. Mulching mode and irrigation water size both had significant effect on leaf N quantity in crop development period. It could be seen from testing results sampling on July 22 that SL was the highest, was 28.97g/kg,3.8% greater than QP/G,6.1% greater than SL 3/4G,8.7% greater than SL 2/3G,9.0% greater than SL 1/2G. In the harvest period, all leaf total N content decreased, and the differences among treatments disappeared. The order of leaf total N from high to low was SL/G> SL 2/3G>SL 3/4G>SL 1/2G>QP/G. SL/G had the highest leaf total P measured in two growing periods. The difference was not significant among all treatments.4. Seen from the soil profile, soil total N from 0 to 60 centimeter soil layer under each treatment reduced with soil depth increasing, but from 60-100 centimeter soil layer, soil total N increased gradually with soil depth increasing. All treatments had little difference. When harvested soil total N in each soil layer had slightly lower, but to change slightly, which indicated that soil total N content in each layer maintained a relatively stable level, also show that in the same fertilization conditions, effect of mulching and irrigation on soil total N was not obvious. Soil total P remained stable in the whole growth period, and each treatment appeared different differences in different soil layer, but had no significant correlativity with mulching and irrigation. Mineral N was composed with NH4+- N and NO3+- N. Time variability of NH4"-N plus spatial variation of NO3-N in all treatments led to the time and spatial variability of soil mineral N. Compared to the middle growth of crop, NO3-N content of deep soil (60-100cm) increased, especially 60-80cm soil layer, its NO3+-N content was higher significantly than the middle growth of crop. Guessed that from the later growth stage of crop to harvest period, crop used less and less nutrient and moisture, then surface soil enriched more mineral N which infiltrated to deeper soil with soil moisture. This hadn't big effect on NH4+-N, but made NO3-N content increased, thus increasing the mineral N content of deep soil.5. There had no difference among treatments on plant height, ears height, ears length and ears diameter, but SL/G is relatively higher. QP had relative longer bald top length than SL and longer significantly than SL/G. SL 2/3 G had the most kernel rows, for 17.33, the difference with other treatments was less than one line. The order of kernels per row from high to low was SL/G>SL 3/4G>QP/G>SL 2/3G>SL 1/2G. The kernels per ear of SL/G was the most, for 679.73,5.86 more than QP/G,3.86 more than SL 3/4G,15.86 more than SL 2/3G,22.27 more than SL 1/2G. The variance analysis showed that the kernels per ear were very significant positive correlation. The order of 100 grain weight from high to low was SL/G> SL 3/4G>QP/G> SL 1/2G> SL 2/3 G. Grain moisture content varied slightly among treatments. The grain moisture content of SL/G was the highest, for 23.8%,2.2% greater than QP/G,0.8% greater than SL 3/4G,2.3% greater than SL 2/3G, 2.4% greater than SL 1/2G.6. The difference of grain yield and aboveground biomass among five treatments were not significant, and SL/G had the highest yield under the same irrigation. QP/G's harvest index (HI) was 0.35, and the other treatments with four different irrigation quantity were 0.36. Five treatments not differed quite. The energy distribution ratio of SL was better than QP. With the decrease of irrigation water quantity, crop grain yield did not reduce significantly, which led to higher irrigation use efficiency (IUE) in treatments with lower irrigation water. So the IUE of SL 1/2G was the best, for 4.00,86.05% greater than QP/G,78.57% greater than SL/G,44.40% greater than SL 3/4G,29.87% greater than SL 2/3G.As known from study, the technology of double ridges mulched with wide plastic film can gain high yield and save irrigation water by changing soil water content, increasing soil temperature, and then affecting soil nutrient availability, changing energy distribution ratio at later growing period. Looking from the whole growing period, irrigation water of SL 3/4G and SL 2/3G was 1350 m3/hm2 and 1800 m3/hm2 less respectively than QP, grain yield was 384.07kg/hm2 and 480.62kg/hm2 less respectively than QP; when they had the same irrigation water, the grain yield of SL was 512.03 kg/hm2 higher than QP. From yield and saving water benefits consideration, SL 3/4G and SL 2/3G is feasible irrigation and mulching mode of cultivation, which is low in cost, high in yield and good in ecological benefit, and can be demonstrating and promoting in oasis irrigation areas.
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