基于临界氮浓度的滴灌棉花氮素营养诊断模型研究

摘要

A critical nitrogen concentration in plant above-ground biomass,which is defined as the minimum nitrogen concentration required for maximum plant growth,can be found at any time in the growth cycle.To determine the critical nitrogen (N) concentration dilution curve with different nitrogen levels for drip-irrigation cotton in the Manas County of Xinjiang.Field experiments were carried out with cultivars of Xinluzao 45 and five nitrogen rates (0 kg/hm2,120 kg/hm2,240 kg/hm2,360 kg/hm2,and 480 kg/hm2) were applied.Results showed that N concentration in above-ground biomass was declined with accumulated physiological development time after emergence.The relationship between the above-ground biomass and critical N concentration can be described by the power equation (Nc =3.91 Wmax-0.24),with a =3.91 and b =0.24.The relationship between the correlation coefficient was 0.906.Through the root mean square error (RMSE) to verify this model,validation results showed that the model had a good simulation performance.Based on the critical N concentration model,the model of nitrogen nutrition index (NNI) was developed.According to the NNI under critical N concentrations,it was concluded that 240 ～360 kg/hm2 could be used as the optimum N application rate of drip-irrigation cotton in Xinjiang.%在新疆滴灌棉田,选择新陆早45号作为试验材料,设置5个施氮水平(0、120、240、360、480 kg/hm2),研究滴灌棉花各器官氮素吸收分配规律及生物量和氮浓度的动态变化,并建立滴灌棉花的临界氮浓度稀释模型,确定临界氮营养指数,实现对滴灌棉花氮素营养丰缺程度的诊断.结果表明,滴灌棉花生物量随施氮量的增加而增加,氮浓度随滴灌棉花的生长进程而降低;滴灌棉花临界氮浓度与地上部生物量间符合幂函数关系,其相关系数为0.906.通过均方根误差RMSE对模型进行验证,验证结果表明,所得模型的模拟性能较好.基于临界氮浓度建立的氮素营养指数模型(NNI)可作为滴灌棉花氮素营养状况的判别指标,由氮营养指数得到滴灌棉花的适宜施氮量为240 ～ 360 kg/hm2.