Effects Of Nitrogen Application Rate And Plastic Film Mulching On Maize Root Nutrients,Root Morphology And Yield Under Drip Irrigation

In order to explore the regulating effect of combined application of nitrogen fertilizer on the dynamic change of maize root system growth and yield formation under the condition of drip irrigation with film mulching.With "Tianci 19" as the test material,4 nitrogen application level treatments and blank control CK under 2 kinds of mulching film were set up.The soil nutrients,maize root system indicators and grain yield were measured,and a maize root biomass model and a root biomass-based critical nitrogen concentration model were constructed in the Ningxia Yellow River Irrigation Area,and four different nitrogen fertilizer rates were applied respectively with mulching biodegradable film and ordinary mulching film.Effects on corn root soil nutrients,root morphological characteristics,root biomass,root nitrogen absorption and utilization efficiency,and grain yield.Compare the differences and advantages and disadvantages of biodegradable film and ordinary mulching film,and find out the best nitrogen fertilizer application rate,which is Ningxia The rational nitrogen application and green sustainable development of agriculture in the irrigation area of the Yellow River irrigated areas with film mulching and drip irrigation provide a theoretical reference for maize.The main findings are as follows:1.Effects of nitrogen application rate and plastic film mulching on soil nutrients in corn root layer under drip irrigationIn the maize seedling and harvesting period,the soil organic matter content,total nitrogen content and soil C/N decreased with the deepening of the soil layer,and increased with the increase of nitrogen application rate.The content of available potassium and available phosphorus in the soil decreased with the deepening of the soil layer and the growth process of corn.After a certain level of nitrogen application,the content of soil organic matter will not increase,the total nitrogen content of the soil will accumulate too much,and the absorption and utilization of soil available phosphorus and potassium by corn plants will decrease.Covering with biodegradable film is conducive to the accumulation of soil organic matter in the 0-20cm soil layer,increasing the absorption and utilization of soil C/N and total nitrogen,and covering the ordinary mulching film is conducive to the accumulation of soil organic matter in the 2040cm soil layer,increasing soil C/N and total nitrogen.2.Effects of nitrogen application rate and plastic film mulching on corn root morphology under drip irrigationWith the advancement of corn growth period,the morphological indicators of corn root length,root diameter,root surface area and root volume of different treatments showed a dynamic trend of increasing first and then decreasing,and each treatment reached the peak in the corn silking period.Under the same nitrogen application level,covering with ordinary plastic film is more conducive to the increase of root length,root diameter,root surface area,root volume and other morphological indicators of corn roots.Under the same film mulching condition,the change rule of root morphological characteristics under each treatment was N2>N3>N1>N0>CK.N2 treatment was more conducive to the increase of corn root length,root diameter,root surface area,root volume and other morphological indicators.3.Model construction of maize root biomass and critical nitrogen concentration under drip irrigation in Ningxia Yellow River irrigation areaThe corn root biomass of each treatment was concentrated in the 0-30 cm soil layer;the fitting results of nonlinear regression model found that the combined variable(D2H)as an independent variable can significantly improve the estimation accuracy of corn root biomass,and the coefficient of determination reached 0.89 respectively;The residual analysis results found that the model has heteroscedasticity.After using the logarithmic transformation method to eliminate the heteroscedasticity,the power function model constructed by the combined variable(D2H)is the optimal model:W=0.07(D2H)1.17,R2 is 0.90.As a result of the model test,the coefficient of determination of the estimated and measured root biomass was 0.94,and the MAE,SEE and ME were 0.04kg,0.06kg and 0.02kg,respectively.The model can better fit the morphological indexes and biomass allocation dynamics of corn root system under drip irrigation.The root system critical nitrogen concentration dilution curve model was constructed,the model expression was Nc=1.91W-0.74,and its determination coefficient R2=0.95.To further verify the critical nitrogen concentration dilution curve of corn root biomass,R2 is 0.85,RMSE is 0.07 g·kg-1,and n-RMSE is 4.16%.The model has good accuracy and stability.The root system nitrogen nutrition index model was constructed based on the critical nitrogen concentration dilution curve of drip irrigation maize,and the results obtained were consistent with the fitting curve of yield and nitrogen application level.The optimal nitrogen application range of drip irrigation maize in Ningxia Yellow River irrigation area is recommended to be 240-270 kg·ha-1.4.Changes of nitrogen application rate and plastic film mulching on corn grain yield and component factors of drip irrigationWith the increase of nitrogen application rate,the number of ears,grain weight,ear weight and yield can be significantly increased.Under different nitrogen application rates,the yield of maize is N2>N3>N1>N0>CK.Covering with ordinary plastic film is more effective than covering with biodegradable film.Conducive to the formation of output.When the nitrogen application rate is 240kg·hm-2,the yield is the highest.