基于根系生物量的宁夏滴灌玉米临界氮稀释曲线构建

Construction of critical nitrogen dilution curve for maize under drip irrigation in Ningxia based on root biomass

为了探究利用玉米根系指标精准施氮的问题,借助于作物临界氮浓度模型思路,调查玉米根系生物量与植株氮浓度动态变化规律,明确宁夏引黄灌区滴灌玉米最佳施氮量。本研究开展6个不同施氮水平试验,采用统计分析与建模方法,建立基于根系生物量的滴灌玉米临界氮浓度模型,并计算根系氮素营养指数,分析不同处理下滴灌玉米产量效益。结果表明:滴灌玉米根系生物量、根氮累积量以及产量受施氮水平的影响差异明显;随着玉米生育进程的推进,各处理根系生物量呈逐渐上升趋势,根系氮浓度则呈下降趋势;整合前2年数据,构建基于根系干物质滴灌玉米临界氮浓度稀释曲线为N_(c)=1.97W~(-0.59),R^(2)=0.92;第3年数据验证结果R^(2)为0.91,RMSE和n-RMSE分别为0.15 g·kg^(-1)和7.49%,模型精度相对较高;通过氮营养指数NNI计算和产量效益分析,判断出宁夏引黄灌区滴灌玉米最佳施氮量推荐范围为270~311 kg·hm^(-2)。此结果可为宁夏水肥一体化条件下玉米精准施氮提供理论指导。

To explore precision nitrogen application by using maize root index,we investigated the dynamics of maize root biomass and plant nitrogen concentration by means of crop critical nitrogen concentration model,and revealed the optimum amount of nitrogen application to maize under drip irrigation in Ningxia Yellow River Irrigation Area.There were six nitrogen application levels.The critical nitrogen concentration model of maize under drip irrigation based on root biomass was established by statistical analysis and modeling method.The nitrogen nutrition index(NNI)of roots was calculated to analyze the yield benefit of maize under drip irrigation across different treatments.Results showed that root biomass,root nitrogen accumulation,and yield of maize under drip irrigation were significantly affected by nitrogen application level.Root biomass of each treatment showed a gradually increasing trend but root nitrogen concentration showed a downward trend with maize growth.By combining the data of different nitrogen levels in the first two years,the critical nitrogen concentration dilution curve of maize based on drip irrigation of root dry matter was constructed as N_(c)=1.97W^(-0.59)(R^(2)=0.92).The model validation results with the test data in the third year showed that R^(2) was 0.91,RMSE and N-RMSE were 0.15 g·kg^(-1) and 7.49%,respectively,indicating high accuracy of the model.Based on the NNI calculation and the analysis of yield benefit,the optimum nitrogen application rate of maize under drip irrigation in Ningxia Yellow River Irrigation Area was estimated to be 270-311 kg·hm^(-2).Our results could provide theoretical guidance for precise nitrogen application of maize under drip irrigation in Ningxia.