Effect Of Deficit Irrigation On Yield,Quality And Water Use Of Gramineae-legume Mixed Sowing Forage Grass In Hexi Irrigation Area

This field experiment was carried out in the Hexi irrigation area during 2019.Under the plastic film mulching cultivation,there were three planting modes:silage maize monocropping?S?,silage maize mixed with fodder bean?SM?and silage maize mixed with lablab bean?SL?.Six irrigation modes were set in each planting mode:irrigation at 6-leaf stage?W1?;irrigation at 6-leaf stage and 12-leaf stage?W2?;irrigation at 6-leaf stage and pollen-shedding stage?W3?;irrigation at 6-leaf stage,12-leaf stage and pollen-shedding stage?W4?;irrigation at 6-leaf stage,pollen-shedding stage and blister stage?W5?,irrigation at 6-leaf stage,12-leaf stage,pollen-shedding stage and blister stage?W6?,each stage was irrigated with 1500 m³hm^-2.The effects of different planting modes and irrigation modes on the maize growth,yield,quality,water use and economic benefits were studied.The main results are as follows:?1?Under the same irrigation mode,SM and SL treatments did not significantly increase the plant height and relative chlorophyll content of maize compared with S treatment,but significantly increased the leaf area index and biomass in the later growth stage.Under the same planting mode,the plant height,relative chlorophyll content,population leaf area index and biomass of W5 treatment were not significantly different from those of W6 treatment at blister and harvest stage,which were significantly higher than those of W1 treatment,but no significant difference was found in irrigation treatment at 6-leaf and 12-leaf stage.?2?Due to the mixed sowing treatments increased legume yield,the total yield of SM and SL treatments was significantly higher than that of S treatment.Compared with S treatment,the total fresh grass yield of SM and SL treatments increased by19.11%and 16.44%,and the total hay yield increased by 12.67%and 9.00%.Under the same planting mode,the maize yield,legume yield and total yield of W4,W5 and W6 treatments were significantly higher than those of W1 treatment,but there was no significant difference between W4,W5 and W6 treatments.The average value showed that the total fresh grass yield of W2,W3,W4,W5 and W6 treatments increased by17.26%,21.25%,39.12%,45.88%and 46.63%compared with W1 treatment,and the total hay yield increased by 13.86%,17.71%,35.75%,44.18%and 43.80%compared with W1 treatment.?3?Under the same irrigation mode,there was no significant difference in crude protein,starch,crude fat,acid detergent fiber?ADF?and neutral detergent fiber?NDF?content of the entire maize plant in each planting mode.Because of the addition of legume,the total content of crude protein increased significantly,and the total content of starch,ADF and NDF in the mixed sowing treatments decreased significantly,so the mixed sowing treatments significantly increased the relative feed value?RFV?compared with the single planting.At the same time,SM treatment significantly increased the total yield of crude protein,crude fat and crude ash.Under the same planting mode,the content of crude protein,starch,ADF and NDF in the entire maize plant under different irrigation treatments were not significantly different,but W5 and W6 treatments significantly increased the total yield of crude protein,crude fat,crude ash and starch compared with W1 treatment.The average value showed that the content of crude protein,crude fat and total RFV of W5 treatment were significantly higher than those of W1 treatment,and the highest yield of crude protein,crude fat,crude ash and starch were obtained under the W5 treatment.?4?Under the same irrigation mode,there was no significant difference in soil water storage,evapotranspiration,precipitation use efficiency?PUE?and water use efficiency?WUE?among different planting modes.The mean value showed that SM and SL treatments significantly increased PUE and WUE compared with S treatment.Under the same planting mode,soil water storage,evapotranspiration and PUE of W5and W6 treatments were significantly higher than those of W1 treatment,while WUE of W6 treatment was significantly lower than that of other irrigation modes.The mean value showed that WUE of W1,W2,W3,W4 and W5 treatments were significantly higher than W6 treatment,which increased by 21.78%,21.32%,22.68%,14.93%and23.64%compared with W6 treatment.?5?The total output and net profit of SM and SL treatments were significantly higher than that of S treatment,the total output increased by 19.87%and 17.64%compared with S treatment,and the net profit increased by 27.37%and 20.11%.Under the same planting mode,the net profit of W5 treatment was significantly higher than that of W1,W2 and W3 treatments,and there was no significant difference with W6 treatment.The average value showed that the net profit of W2,W3,W4,W5 and W6 treatments were 16.46%,21.95%,36.59%,47.56%and 36.59%higher than that of W1 treatment.The SM-W5 treatment achieved the highest net profit(24,700 Yuan hm^-2)among all the treatments.In conclusion,silage maize mixed sowing with fodder bean and irrigation 1500m³ hm^-2 at 6-leaf stage,pollen-shedding stage and blister stage?SM-W5?is a suitable management measure for silage maize production in Hexi irrigation area,which can promote maize growth,improve grass yield,nutritional value,WUE,and obtain the highest net profit.