Hyperspectral Vegetation Indices To Assess Water And Nitrogen Status Of Sweet Maize Crop

Water and nitrogen (N) have long been known as two primary restricting inputs for crop production. Matching N supply to water availability is essential to accomplish an optimal crop response and satisfactory use efficiency levels for those input resources. Proximal sensing methods enable rapid, non-destructive water and nutrient deficiency determination, and they are widely used in precision agriculture. Narrow-band vegetation indices use reflectance in red and near-infrared to collect the red-edge section of the spectrum, thus they have been favourably included in studies aiming to estimate crop nitrogen concentration and to detect water stress. In this study, the sensitivity of narrow-band vegetation indices to describe the response of sweet maize under different water and nitrogen management approaches was investigated. To this aim selected structural, red-edge and water-band indices were chosen, and their performance was evaluated. The results demonstrated the importance of red-edge based vegetation indices for assessing the sweet maize status. In particular, the red-edge indices had the high sensitivity to nitrogen levels, especially NDRE, CIred-edge, DATT and MTCI that showed great discrimination capability. In addition, among the studied indices, NNDVI and WBI/NDVI were the only indices affected by the interaction of water and nitrogen, with the ability to separate low nitrogen regimes. Our study highlighted the crucial importance to choose appropriate narrow-band vegetation indices for monitoring plant eco-physiological response to water and nitrogen stresses.