Effects Of Different Water And Nitrogen Treatments On Growth And Yield Of Spring Soybean Under Mulched Drip Irrigation

Drip irrigation under mulch is an efficient and water-saving cultivation mode.Under this mode,the formation of soybean growth and yield under different water and nitrogen treatments is not clear.Based on this,this experiment adopts two-factor split-plot design(the main area is irrigation water,W₁:1875 m³·hm^-2,W₂:2625 m³·hm^-2,W₃:3375 m³·hm^-2;the secondary area was nitrogen application rate,N₀:0 kg·hm^-2,N₁:120 kg·hm^-2,N₂:240 kg·hm^-2).Under the condition of drip irrigation under mulch,the effects of different water and nitrogen treatments on root growth,photosynthetic characteristics,dry matter accumulation and flower-pod dynamics of spring soybean were preliminarily explored.The main results were as follows:（1）Under the condition of 1875-3375 m³·hm^-2irrigation amount and 0-240 kg·hm^-2nitrogen application,increasing irrigation amount could increase root dry weight,lateral root length and lateral root surface area in 0-100 cm soil layer.The root dry weight increment of W₃N₁treatment reached the maximum(66.41 g·m^-2)during flowering-seeding stage,the lateral root length reached the maximum(1992.60 m·m^-2)during seed-filling stage（August 15）,and the lateral root surface area reached the maximum（July 15）during podding stage,which increased by 0.43-1.34 m²·m^-2compared with other treatments.（2）Under the experimental conditions,the SPAD,net photosynthetic rate and transpiration rate of the top three leaves at the early stage of seed filling（R5）of soybean showed the following trend with the increase of irrigation amount:W₃>W₂>W₁,and the following trend with the increase of nitrogen application amount:N₁>N₂>N₀.Appropriate increase of irrigation amount and nitrogen application amount could increase the leaf area index and photosynthetic potential of spring soybean at each growth stage.Excessive nitrogen application(240 kg·hm^-2)led to the decrease of leaf area index and photosynthetic potential,which was not conducive to the formation of dry matter and resulted in yield reduction.（3）Under the experimental conditions,increasing irrigation and nitrogen application can increase dry matter accumulation.Under W₃N₁treatment,dry matter accumulation reached the maximum fitting dry matter accumulation(1392.4125 g·m^-2),and the maximum dry matter accumulation rate reached the maximum in each treatment(36.47 g·m^-2·d^-1);the distribution ratios of each part of soybean under different water and nitrogen treatments at maturity stage were mostly as follows:grain>stem>leaf>pod bark>petiole.（4）Increasing irrigation amount to 3375 kg·hm^-2could significantly increase the number of flowers,pods and grains per plant under drip irrigation with nitrogen application rate of 0-240 kg·hm^-2;the number of grains in the 7th-15th sections accounted for 60.78%-77.17%of the number of grains per plant under various water and nitrogen treatments,and the contribution rate to the yield per plant reached more than 60%.The treatment W₃N₁obtained the highest yield(6083.10kg·hm^-2),with 100-grain weight of 16.52 g,which was 5.70%-49.76%higher than that of other treatments,and 100-grain weight increased by 0.59-1.76 g.In summary,under the conditions of this experiment,the irrigation amount was 3375 m³·hm^-2and the nitrogen application amount was 120 kg·hm^-2.Spring soybean had the best field performance and the highest yield.Considering comprehensively,the suitable irrigation and nitrogen application combination for drip irrigation under mulch in Yili area of northern Xinjiang is:irrigation amount is 3375 m³·hm^-2,total nitrogen application amount is 120 kg·hm^-2,and the yield is6083.10 kg·hm^-2.