| To systematically reveal the regulation effect of mulching from the changes of maize leaf area index and root growth dynamics,"Ningji 198" was used as the experiment material in this study.There were 5 nitrogen fertilizer application rates and the treatment of no application of nitrogen fertilizer and no mulching as control(CK)in this experiment.The experiment plot was in farm of Pingjibao which is located in Yinchuan City,Ningxia Province,Northwest China.The leaf area index,root indexes and yield of maize were measured,and the LAI model and root-length density model of maize under drip irrigation.To analyze the effects of different nitrogen application rates on the leaf area index,root growth and yield of maize under drip irrigation with film mulch,it reveals the response mechanism of the maize leaf area index,root index and yield of the film-mulched drip irrigation to different nitrogen application rates and the optimal nitrogen fertilizer application rate gradient,providing theoretical reference and technical support for rational nitrogen application and sustainable agricultural development of mulching drip irrigation maize.The main findings are as follows:1.Simulate RLAI and RGDD after normalization,The LAI dynamic model y=(a+bx)/(1+cx+dx2)was established,and the model was tested.The results showed that the overall accuracy of this model was above 0.933,and the accuracy was between 0.972-0.974,The dynamic model of maize LAI can accurately predict LAI dynamics from the seedling stage of maize,providing new ideas and effective methods for the study of simulating dynamic characteristics of maize LAI changes in Ningxia.During the whole growth process,maize MLAI presented an increasing trend of quadratic function model with the increase of nitrogen application amount,but the ratio of MLAI to LAImax decreased with the increase of nitrogen application amount,indicating that different maize nitrogen application amount had a regulatory effect on the entire growth period LAI,which provided theoretical basis for further research on maize yield increase.2.Using the experimental data obtained in 2019,the relative root-length density model was established under different nitrogen application rates.It was found that the distribution of relative root-length density met the third-order polynomial function model,and the correlation coefficient of the simulated curve was(R2=0.951).Take advantage of the group in 2018 to provide the data validation relative root length density model under different n application rate,inspection results R2 is 0.845,RMSE is 0.248,the fitting effect is good,but cannot guarantee that the polynomial model relative root length density values in the maize root depth reaches 0,so for maize relative root length density distribution polynomial model is optimized and inspection,The results showed that RMSE of each nitrogen treatment was less than 0.308,nRMSE was 0.242,0.193,0.184,0.226,0.208 and 0.273,and R2 were 0.903,0.953,0.920,0.944,0.962 and 0.898,respectively.It not only had a higher fitting degree,but also solved the problem that the value of NRLD(Zr=1)reached zero at the rooting depth.It is more suitable to simulate NRLD distribution of drip-irrigation under plastic film on maize for different nitrogen rates.3.Under different nitrogen application rates,the root surface area,root volume,root dry weight,root length density,root biomass and root diameter of maize under different nitrogen application rates all showed a trend of increasing first and then decreasing with the growth process of maize.The total root surface area,root volume,root dry weight,root length density,root biomass and root diameter were significantly higher under N3(270 kg/hm2)than under other treatments.4.Increasing nitrogen application significantly increased the number of kernels,100-grain weight and yield of maize.Harvest yield showed N3>N4>N2>N1>NO>CK,nitrogen application rate of 270 kg/hm2 can get about 17135 kg/hm2 yield,if continue to increase nitrogen fertilizer the production will not be significant. |
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