基于植被指数时序动态的冬小麦氮素营养诊断方法

为构建冬小麦冠层临界植被指数时序模型,探究实时、无损诊断冬小麦全生育期氮素营养状况的可能性,基于冬小麦不同生育时期氮营养指数(nitrogen nutrition index,NNI)与相对产量的关系确定NNI临界值,并利用归一化红边植被指数(normalized difference red edge,NDRE)与NNI的定量关系确定临界NDRE值,进而以累积生长度日为时间驱动因子,利用双Logistic函数构建临界NDRE时序模型并用于诊断,且对诊断结果进行了验证。结果表明,NNI与冬小麦相对产量在不同生育时期均呈现明显的线性加平台关系(R²在0.76以上),在开花—灌浆期表现最好;NNI与NDRE呈显著的幂函数关系(R2在0.76以上),在孕穗—开花期表现最好;临界NDRE时序诊断模型在拔节后期、孕穗期、开花期的诊断精度较高;适期播种时冬小麦在180 kg·hm^-2施氮水平下整个生育期均处于轻微氮亏缺或氮适宜状态,为较优施氮量。适期播种时冬小麦氮素营养状况主要受施氮水平的制约;过晚播时受播期的影响,不同施氮水平下冬小麦全生育期均处于氮亏缺状态。综上,依据氮营养指数与相对产量所构建的临界NDRE时序模型能够较准确地实时诊断冬小麦不同生育时期的氮素营养状况,并为作物氮肥精确管理提供技术方法。

Diagnosis Methods for Nitrogen Status Based on the Time-Series Vegetation Index in Winter Wheat

This study aims to construct the time-series dynamic model of winter wheat canopy critical vegetation index,and to explore the possibility of real-time and non-destructive diagnosis of nitrogen nutrition status of winter wheat during the whole growth period. The critical values of nitrogen nutrition index(NNI) were determined based on the relationship between NNI and relative yield. The quantitative relationships between NNI and normalized difference red edge(NDRE) were used to determine the critical NDRE value. Time-series dynamic model of the critical NDRE was further constructed using the double logistic function driven by accumulated growing degree days. The nitrogen nutrition status was diagnosed. The diagnosis results were further validated,which showed that NNI and relative yield have an obvious linear plus plateau relationship at different growth stages(R was above 0.76),with best performance at flowering and filling stages; NNI and NDRE showed a significant power function relationship(R was above 0.76),with best performance at booting and flowering stages. The diagnostic accuracy of critical NDRE time-series diagnostic model was higher at late jointing,booting,and flowering stages. For the treatment of suitable sowing date,at the level of 180 kg N·hm^-2,the nitrogen nutrition status of winter wheat was in mild deficiency or suitable,which was an optimal nitrogen application rate. The nitrogen nutrition status of winter wheat was mainly restricted by nitrogen application rate. For the treatment of late sowing,the growth and development of winter wheat was severely restricted by the sowing date,and wheat remains in nitrogen deficient status over whole growth stages under different nitrogen application rates. In summary,the critical NDRE time-series dynamic model constructed based on the nitrogen nutrition index and relative yield allows accurate and timely diagnosing of the nitrogen nutrition status for winter wheat at different growth stages,and provides a technical method for precision nitrogen management of crops.