Effects Of Groundwater Depth And Irrigation-Herbicides Limited On Soil Environment And Maize Growth In Salinized Irrigation District

Hetao Irrigation District is an important food production base,shortage of resources and deteriorating farmland water and soil environment are the key factors that severely restrict the sustainable development of Hetao Irrigation Formulate a pesticide application model suit-able for the sustainable development of the Hetao irrigation area.Therefore,in the Hetao Irrigation District,taking into account the local saline-alkali land conditions,the main pur-pose is to save water,control salt and increase production,and strive to reduce the utilization of herbicides applied,ensure the effectiveness of weed control,vigorously improve the qual-ity of crops,and improve the production environment of agricultural products.Formulate a irrigation-herbicide mode suitable for the sustainable development of the Hetao Irrigation District;rationally use groundwater for replenishment and seek better groundwater depth.In this paper,the research is carried out through the plot test and field positioning monitoring.This paper adopts 2 application levels(Name of herbicide:24%Nicotin·Atrazine):P1(the local application rate is reduced by 30%,1.313 L/hm~2)and P2(the local application rate is reduced by 10%,1.688 L/hm~2),3 irrigation quotas:W1(0.8ET),W2(1.0ET),and W3(1.2ET),and 5 different groundwater depths(DGW:1.25 m,1.50 m,1.75 m,2.00 m,and2.25 m),using the lysimeter and large weighing lysimeter to carry out the test in 2019 and2020.The main findings are as follows:(1)The groundwater recharge at five different groundwater depths(1.25 m,1.50 m,1.75m,2.00 m,and 2.25 m)during the growth period were 179.60 mm,139.17 mm,119.98 mm,68.62 mm,and 48.38 mm.The depth of leakage was 45.97 mm,33.25 mm,17.59 mm,3.00mm,and 2.17 mm.When the DGW was greater than 1.75 m,the deep leakage of each treat-ment was significantly reduced,the irrigation water use efficiency increased,and the stress of salinized soil to crops decreased.(2)The soil electrical conductivity value has a good exponential relationship with the groundwater depth,and the soil salt content in the 0-20 cm soil layer of the surface layer decreases with the increase of the groundwater depth.The soil depth of 20-60 cm and 60-120 cm Soil EC is less affected by the depth of groundwater.When the buried depth of the groundwater is greater than 1.75 m,the surface soil conductivity value is significantly re-duced,and the variation range of the soil conductivity value affected by the buried depth of the groundwater decreases.(3)The low irrigation quota W1P2 treatment has less nutrient leaching loss,but the salt leaching effect is poor,which is not conducive to crop growth and development.The W3P2treatment with the high irrigation quota had the same desalination effect as the W2P2 treat-ment with the medium irrigation quota,but the W3P2 treatment reduced the organic matter content by 29.53%compared with the W2P2 treatment.The W3P2 treatment caused the nu-trient loss,and the growth period caused water stress to the maize and reduced the water use efficiency.(4)At the same application level P2,the high irrigation quota(W3P2)is better than the medium irrigation quota(W2P2),which makes it easy for herbicides to be leached into the deep soil.The buried depth of groundwater has an impact on the amount of herbicide residues in the soil by affecting the content of organic matter.A shallower buried depth of groundwater will increase the migration of herbicides and increase the risk of groundwater pollution.The atrazine content of the DGW1.25m treatment is 0.065 mg/kg and the other 4 groundwater treatments are significantly different(p<0.05).There was no significant difference between DGW2.00m treatment and DGW2.25m treatment(p>0.05).(5)When the application rate is P1(the local application rate is reduced by 30%,1.313L/hm~2)and P2(the local application rate is reduced by 10%,1.688 L/hm~2),the residual con-tent of atrazine and nicosulfuron in mature maize kernels is lower than the national standard,and both are safe to use.However,W2P1(1.0ET,the local application rate is reduced by30%,1.313 L/hm~2)has a poor weeding effect and is likely to cause weeding.Compared with W2P2(1.0ET,the local application rate is reduced by 10%,1.688 L/hm~2),W2P1,W1P2(0.8ET,the local application rate is reduced by 10%,1.688 L/hm~2)and W3P2(1.2ET,the local application rate is reduced by 10%,1.688 L/hm~2)caused a reduction in maize produc-tion.Therefore,the recommended irrigation system and application level are W2P2 treat-ment and the groundwater depth is 2.00 m-2.25 m.