Effects Of Water And Nitrogen On Sunflower Growth And Soil Environment Under Drip Irrigation

As a large-scale irrigation area in China,Hetao Irrigation District is an important grain and oil production base.The climate in the irrigation area is dry,less rainy,and has a large amount of evaporation.In addition,the unreasonable irrigation of local farming results in serious salinization and secondary salinization in irrigation areas;salt accumulation,serious nitrogen leaching,and low water and fertilizer utilization are urgently needed,solve.Therefore,in the irrigation area,the field experiment of drip irrigation under the drip of sunflower was carried out to study the law of soil water,salt and nitrogen transport,analyze the growth of crops,dry matter and nitrogen uptake,compare the yield factors,water and nitrogen utilization,etc.,combined with Hydrus.The 1D model,which is suitable for the water-nitrogen ratio of local crops,has practical scientific significance for improving the water and soil environment of the irrigation area,efficient use of water and nitrogen resources,improving crop yield and quality,and providing theoretical support for agricultural production in the irrigation area.The main conclusions are as follows:(1)When the irrigation amount is less than 180mm and the nitrogen application rate is less than 160kg/hm2,the water content is positively correlated with the irrigation amount and nitrogen application rate.When the water content is low,increasing the nitrogen application can reduce the surface evaporation.From the soil profile,the EC value and pH value of each growth period are basically "S" type,which is characterized by first drop,then rise and then fall.Ammonium nitrogen is easily adsorbed by soil particles and is not easy to move and accumulates in the surface layer.During the period of fertility,TN and nitrate nitrogen will move to the middle soil due to soil water movement and water absorption of crop roots;nitrate nitrogen is easily absorbed by crops.It is also easy to leaching with water and has great mobility.The peak value of nitrate nitrogen in the filling stage is 18.47%lower than that in flowering stage.(2)From the seedling stage to the flowering stage of sunflower,with the increase of nitrogen application rate,the growth indexes(plant height,stem diameter,leaf area)increased;from the filling stage to the mature stage,the most value basically appeared in N2 treatment.Taking stem thick as an example,W2N2 treatment was 6.94%,8.96%,and 5.35%higher than W2N3,W3N2,and W3N3,respectively.The dry matter accumulation and nitrogen uptake of the plants showed an "S"-type change with the growth period of the crops;the dry matter quality of each plant in the seedling,bud,flowering,grain filling and maturity stages accounted for the total accumulation.The amounts are 7.22%,16.22%,36.63%,13.85%,and 26.08%.The nitrogen uptake of the plants before the grain filling stage was proportional to the nitrogen application rate,and the maximum value of nitrogen uptake during the mature period appeared in W3N2(225mm,160kg/hm2).The grain yield was between 6592.95 and 8100.12kg/hm2,and the W3N2 treatment was the highest.When the nitrogen application rate was 160kg/hm2,the water use efficiency was the highest.After that,the nitrogen application level was increased,and the WUE and IWUE were basically no increase.The peaks of IWUE of W2 and W3 are both N2;under the same irrigation level,the nitrogen use efficiency increases first and then decreases with the increase of nitrogen application rate,and the nitrogen utilization rate is high during N2 treatment.(3)The Hydrus-1D model was used to analyze the water and nitrogen distribution characteristics of the soil.Combined with the actual conditions of crop growth,yield,water and nitrogen utilization,the optimal water and nitrogen treatment was W2N2(180mm,160kg/hm2).