SPECTRAL VEGETATION INDEXES APPLIED TO NITROGEN SUFFICIENCY INDEX: A STRATEGY WITH POTENTIAL TO INCREASE NITROGEN USE EFFICIENCY ON TOMATO CROP

ABSTRACT The tomato crop is one of the most demanding of nitrogen fertilizers. This element on soil has an elevated mobility that can represent danger to the environment and reduces its efficiency. Therefore, the purpose of this study was to evaluate the methodology for recommending nitrogen fertilizer for tutored tomatoes with a variable rate based on nitrogen sufficiency index. The treatments consisted of a reference plot and five treatments with the nitrogen sufficiency index calculated on spectral indexes NDVI, GNDVI, MCARI, PSSRa and the SPAD value. The productivity was evaluated considering the fruits size and viability. The descriptors of quality, color, soluble solids, total acidity, titratable acidity and flavor were also evaluated. All the indexes evaluated decreased significantly with the applied nitrogen during the cycle, the only exception being MCARI, which resulted in a similar nitrogen quantity to the reference. The NDVI, GNDVI, PSSRa and SPAD value indexes presented a total applied nitrogen decrease varying from 25.2% to 43.8%, neither reducing significantly the productivity nor the fruits quality. The marketable fruits productivity varied from 2332.9 to 2773.8 g.plant−1 among treatments. Only the NDVI and the SPAD value presented significant improvements on the partial factor of nitrogen productivity, among the applied treatments.

摘要 番茄是对氮肥需求量最高的作物之一。土壤中的氮素移动性较强，不仅会对生态环境造成潜在危害，还会降低其利用效率。为此，本研究旨在评估基于氮素充足度指数（nitrogen sufficiency index）的变量施肥方法，用于番茄氮肥的推荐施用。试验设置1个对照区，以及5个分别基于光谱指数NDVI、GNDVI、MCARI、PSSRa和SPAD值计算氮素充足度指数的处理组。试验通过果实大小与商品合格率评估产量，同时测定了果实品质相关指标，包括色泽、可溶性固形物含量、总酸度、可滴定酸度及风味。在番茄生育周期内，除MCARI外，其余所有评估的光谱指数均随施氮量增加呈显著下降趋势；MCARI对应的推荐施氮量与对照区无显著差异。基于NDVI、GNDVI、PSSRa及SPAD值的处理组总施氮量较对照降低了25.2%~43.8%，且未显著降低番茄产量与果实品质。各处理组的商品果产量介于2332.9~2773.8 g·株⁻¹之间。在所有施氮处理组中，仅基于NDVI与SPAD值的处理组氮肥偏生产力得到了显著提升。