Nitrogen management in wheat based on the normalized difference vegetation index (NDVI)

ABSTRACT: Biomass production and nitrogen (N) accumulated in wheat shoots may be used for quantifying optimal topdressing nitrogen doses. The objective of this study was to develop and validate models for estimating the amount of biomass and nitrogen accumulated in shoots and the N topdressing dose of maximum technical efficiency in wheat using the normalized difference vegetation index (NDVI) measured by an active optical canopy sensor. Field experiments were carried out in two years and treatments consisted of N doses applied at plant emergence and as topdressing. NDVI, shoot biomass and N accumulated in shoots at the growth stage of six fully expanded leaves and grain yield were evaluated, being determined the topdressing N dose of maximum technical efficiency (DMTE). The NDVI was positively correlated to shoot biomass and N content in shoots and models for the relationship between these variables were developed and validated. The DMTE was negatively correlated with the NDVI value evaluated at the moment of N topdressing application. Thus, NDVI evaluation by an active optical canopy sensor can be used for nitrogen fertilization in variable rate, allowing the adjustment of applied N doses in different areas within a field.

摘要：小麦地上部生物量与氮素累积量可用于量化最佳追施氮肥用量。本研究旨在利用主动式光学冠层传感器测得的归一化差分植被指数（NDVI），构建并验证可用于估算小麦地上部生物量、氮素累积量及最高技术效率追施氮肥用量（DMTE）的模型。本研究连续两年开展田间试验，试验设置不同施氮量，分别于作物出苗期及追肥阶段施加。研究测定了六叶期的NDVI、地上部生物量、地上部氮素累积量与籽粒产量，并确定了最高技术效率追施氮肥用量（DMTE）。结果表明，NDVI与小麦地上部生物量及地上部氮素含量呈显著正相关，本研究构建并验证了上述变量间的关系模型。最高技术效率追施氮肥用量（DMTE）与追肥施氮时刻测得的NDVI值呈显著负相关。因此，利用主动式光学冠层传感器获取NDVI值可应用于变量氮肥施肥，实现田块内不同区域施氮量的精准调控。