Dynamic Optimization Of Greenhouse Tomato Irrigation Schedule Based On Water,Fertilizer And Air Coupled Production Function

Aerated subsurface drip irrigation（ASDI）,based on the integration of drip irrigation and water fertilizer,utilizes water fertilizer air coupling equipment to break air（oxygen）and mix it evenly with water fertilizer solution.Through the underground drip irrigation system,the gas-liquid two-phase flow formed is transported to the crop root zone,and unlock the high yield potential of greenhouse crops.And crop water production function is one of the important parameters to improve the water use efficiency and economic benefits of greenhouse agriculture.To explore the water consumption law of greenhouse tomatoes under the coupling of water,fertilizer and air,and quantitatively evaluate the influence of water,fertilizer and air management mode on tomato yield and quality.A coupling production function of water,fertilizer and air was put forward to optimize the irrigation schedule during the growth of greenhouse tomatoes.Two seasons of greenhouse tomato experiments were conducted under ASDI.There were three nitrogen application rates（N₁,120 kg/hm²;N₂,180 kg/hm²;N₃,240kg/hm²）and three aeration rates with dissolved oxygen（DO）in irrigation water（A₂,15 mg/L;A₃,40 mg/L and A₁,5 mg/L in the control treatment）in the first season potential yield experiment,while three irrigation rates with soil moisture content（W₁,50%–60%field capacity;W₂,60%–70%field capacity;W₃,70%–80%field capacity）and two aeration rates with DO in irrigation water（25 mg/L and 5 mg/L）in the second season water deficit experiment.In this experiment,the production function and quality function of greenhouse tomato under the condition of water,fertilizer and air coupled irrigation based on Jensen model were constructed,and the water distribution scheme under multiple irrigation quotas was optimized by dynamic programming method.The main results were presented below.（1）The water consumption intensity and water consumption modulus of greenhouse tomatoes under adequate irrigation are 7.3–8.5%at seedling stage and 1.6–1.8 mm daily.The water consumption modulus during flowering and fruiting period is 49.9–53.9%,and the daily water consumption is 4 mm The water consumption modulus at maturity is 37.6–42.8%,and the daily water consumption is 3.5–4.3 mm.Water deficit will reduce water consumption and intensity,and the higher the deficit degree,the more obvious the effect.（2）The Water,fertilizer and air coupled production function of tomato under subsurface drip irrigation based on Jensen model has good accuracy,which can predict the tomato yield coupled with water,fertilizer and air.The best aeration rate and nitrogen application strategies obtained from the model are the DO value of 24.5 mg/L and the nitrogen rate of 281.4 kg/hm²in irrigation water.Under the irrigation quota of 420 mm,the irrigation amount of 5,50,85,100,95 and 85 mm every 20 days is suggested to maximize the yield.The expected yield of ASDI in a single season is 79 t/hm²,which is 26.13%higher than that of control treatment.The net income in a single season increased by 74,712 yuan/hm².（3）The multiplication model is the best fitting model for the"water-quality"model,and the quality sensitivity index（compared with absolute value）is listed as follows:seedling stage(λ_q1=-0.6444)>mature stage(λ_q2=-0.2570)>flowering and fruit-setting stage(λ_q3=-0.0605).（4）Considering the influence of fruit quality on the unit price,the scheme to maximize the production benefit is given as follows:for conventional non-aerated drip irrigation,the irrigate quota is 420 mm,and the irrigation amount of 5,50,85,100,95 and 85 mm every 20days after transplanting.For the ASDI,the irrigation quota is 320 mm,and the irrigation amount are 5,50,75,85,65 and 40 mm every 20 days after transplanting.,The crop yield in the irrigation quota of 320 mm under ASDI will decrease by 11.71%,but the fruit quality is better and the output value will increase by 13.52%,when compared with that in the quota of 420 mm under the control treatment.