| Located in the arid and semi-arid area,Inner Mongolia Hetao Irrigated District is facing many problems that restrict the healthy development of agriculture,such as severe soil secondary salinization,low water and nitrogen utilization,high non-point source pollution and low crop yield problems.And how to solve the above problems is very practical and urgent.In the thesis,a field experiment was carried out to optimize the irrigation system of summer maize under optimum straw mulching in salinized farmland.The optimization of straw mulch tillage mode based on crop root regulation was studied.The rules of soil water-salt migration under straw mulch and irrigation amount were analyzed.Based on the deep learning algorithm,the Progressive Salt-Water Embedded Neural Network model(PSWE)was built to simulate water and salt migration and crop benefits,and the irrigation quota of summer maize under straw mulch was optimized.To explore the response of crop and soil habitat under straw mulching and nitrogen application coupling,and optimize the nitrogen application quota of summer maize under straw mulching.The innovation of the thesis was to use Deep Learning coupling algorithm to construct salt-water migration model and optimize summer maize irrigation system under straw mulching in salinized farmland.Through system analysis,reveals the control process and the mechanism of the salt suppression-regulation water and fertilizer-drug reduction-yield increase under straw mulch coupled with water and nitrogen in Hetao Irrigation District salinization,to achieve the optimum summer maize under straw mulching irrigation system optimization,aimed at rich theoretical system of straw returned,to ease the non-point source pollution,and water saving irrigation area salinization production.At the same time as Deep learning theory and technology in the application of soil water and salt migration model to provide the reference.The main results are as follows:1.Different straw mulching and tillage methods significantly affected the root distribution and production efficiency of summer maize.Straw mulching significantly increased the horizontal root length density of summer maize,and the root distribution layer was shallow,forming"wide and shallow"root system,and the root length density increased by 24.7%compared with conventional tillage.Straw deep buried tillage significantly increased root length density in the soil layer greater than 40cm,promoted the development of deep roots,formed"narrow and deep"root system,and improved the spatial distribution of summer maize root system.Compared with conventional tillage,the root length density in deep roots was increased by 23.8%.The third order polynomial function relationship between summer maize root length density and relatively standardized root setting depth can better describe the distribution of root length density under different tillage patterns.Compared with the conventional tillage,the water use efficiency of summer maize under the straw deep buried tillage mode increased by 32.2%and the yield increased by 19.5%,which was the preferred farming mode.2.The soil salinity accumulates under the straw covering surface,and salt accumulates in all soil layers at the mature stage.They were accumulate salt in the surface layer and the layer below the inter-layer under straw deep buried.Under the treatment of90 mm and 120 mm under straw deep buried,the water holding capacity of the inter-layer increases by 20.3%and 17.2%respectively,and the desalination rate were 7.6%and 7.1%,respectively.The inter-layer plays a role of salt suppression and water storage,and desalinize the root environment.Soil salt content and single irrigation amount were significantly correlated with summer maize yields and water use efficiency.Summer maize yields under straw overlying increased with the increase of irrigation amount.The highest yield was obtained under 135 mm irrigation amount,which was only 1.6%higher than that under conventional tillage.With the increase of irrigation amount,the yield of summer maize under straw deep buried increased firstly and then decreased,and the yield under90 mm straw buried deep was the highest,which increased by 5.2%compared with conventional tillage.Under the straw deep buried tillage model,the water saving and yield increasing effect were significantly.Under the experimental field scale,the optimal irrigation quota was 82-111mm,the water saving was 17.8%above,irrigation was 3 water during the growth period,and the salt content in the surface layer was controlled between1.45-1.48 g·kg-1,which was slightly salinized land,and the salt content of the cultivated land was 5.7%-10.2%lower than that before the experiment.3.The PSWE Neural Network model based on Deep learning has high precision,with root mean square error of 0.029,mean absolute error of 0.570 and determination coefficient of R2of 0.981.Based on the PSWE model,the multi-factor synergistic simulation results of straw deep buried effectively simulated the double-layer progressive causal relationship among the comprehensive conditions of natural growth of summer corn,soil water and salt migration and the production benefit of summer maize.The PSWE model further optimized the summer maize irrigation quota of salinized farmland to be89.3-96.8mm,irrigation 3 water in the growth period,and the salt content of the cultivated layer to be 1.38-1.55 g·kg-1.4.The variation of soil Atrazine residue with time under straw mulching and nitrogen application coupling conforms to the first-order kinetic equation.Soil nutrient content of different treatments promoted the digestion of Atrazine to different degrees,and the contents of soil organic matter,total nitrogen and alkali-hydrolyzed nitrogen in the soil layer of 20-40cm had a greater effect on the half-life of Atrazine digestion.The straw deep buried with medium nitrogen could actually promote the goal of Atrazine digestion.Its digestion rate increased by 5.3%,and the half-life was the shortest,shortening by 3.9d.5.The coupling of straw mulching and nitrogen application improved the spatial and temporal distribution of soil nutrients.The soil nutrient surface concentration on straw covering surface,and the soil nutrient increased with the increase of nitrogen application rate.With the increase of nitrogen application rate,the nutrient of soil layer near inter-layer was increased firstly and then decreased.At the summer maize mature period,the treatment of the middle nitrogen(180 kg·hm-2)combined with straw deep buried reduced deep nitrate accumulation quantity 56.8%,and reduced 84.7%ammonium nitrogen accumulation amount.The straw inter-layer formed the interception of nitrogen migration barriers.Before autumn water,the ground water to?class,and reduced the risk of ground water nitrogen pollution effectively,and the treatment promote the deep root growth.Compared with conventional tillage,straw deep buried combined with 180-193.7kg·hm-2nitrogen application rate could achieve the synergism improve among nitrogen application reduction,pollution reduction and plant nitrogen application use efficiency increase.The contribution rate of plant nitrogen assimilation products to yield increased by32.1%,plant nitrogen use efficiency increased by 66.8%,and crop yield increased by9.3%.In conclusion,the best tillage mode for salinized land in Hetao Irrigated District was straw deep buried combined with deep plowing.The optimized summer maize irrigation system was:irrigation quota was 89.3-96.8 mm,and Irrigate 3 times during growth period.Under the optimized irrigation system,the salt content of cultivated layer could be controlled in the range of 1.38-1.55 g·kg-1,which was slightly salinized.The optimal nitrogen application rate was 180-193.7 kg·hm-2. |
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