Vegetation indices as rapid, non-destructive tool to assess nitrogen status in irrigated rice.
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The use of optical radiation sensors is a promising strategy for nitrogen management as it reduces the costs of chemical analyses and allows quick decision-making in the supplementary application of N to irrigated rice. By combining three spectral reflectance bands (red, far-red, and near-infrared), 22 vegetation indices (VIs) were computed and assessed for their effectiveness in estimating the nitrogen status of rice crops. The results indicated that the selected VIs considerably underestimated dry leaf biomass (DLB) and did not efficiently estimate N status parameters, such as leaf N concentration (LNC) and leaf N uptake, at the vegetative stage. The large variations in these N status parameters can be explained by the VI in subsequent stages. The VI selected in the parametrisation process was promising for explaining variation in DLB and leaf area index at the reproductive and grain-filling stages. However, the VI showed low performance in estimating LNC at the reproductive stage. The modified red-edge soil-adjusted VI and normalised difference red-edge index showed high performance in estimating the N nutrition index in the growth stage and across the whole crop cycle. These results show the importance of using active sensors for effective crop N status estimation.
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Irrigated rice, Low-altitude, Radiation bands, Ecofisiologia, Arroz Irrigado, Oryza Sativa, Sensoriamento Remoto, Rice, Spectral analysis, Remote sensing, Nitrogen, Vegetation index, Radiation use efficiency, Ecophysiology