Mapping hailstorm damage on winter wheat (Triticum aestivum L.) using a microscale UAV hyperspectral approach

Hailstorms pose a direct threat to agriculture, often causing yield losses and worseningfarmers’ agricultural activity. Traditional methods of hail damage estimation, conducted byinsurance field inspectors, have been questioned due to their complexity, partial subjectiv-ity, and lack of accounting for spatial variability. Therefore, remote sensing integration inthe estimation process could provide a valuable aid. The focus of this study was on winterwheat (Triticum aestivum L.) and its response to damage in the near-infrared (NIR) spec-tral region, with a particular emphasis on the study of brown pigments as a proxy for yielddamage estimation and mapping. An experiment was conducted during two cropping sea-sons (2020–2021 and 2021–2022) at two sites, simulating hail damage at critical floweringand milky stages using a specifically designed prototype machinery with low, medium, andhigh damage gradients compared to undamaged conditions in plots with a minimum of 400m 2 area. After the damage simulation, hyperspectral visible-NIR reflectance was measuredwith Unmanned Aerial Vehicle (UAV) flights, and measurements of chlorophyll and of leafarea index (LAI) were contextually taken. Final yield per treatment was recorded using acombine. An increase in absorbance in the NIR region (780–950 nm) was observed andevaluated using a spectral mixture analysis (SMA) after selecting representative damagedand undamaged vegetation spectra to map the damage. The abundance of damaged end-member pixels per treatment resulted in a good relationship with the final yield (R2 = 0.73),identifying the most damaged areas. The absorbance feature was further analysed with anewly designed multispectral index (TAI), which was tested against a selection of indicesand resulted in the highest relationship with the final yield (R2 = 0.64). Both approacheswere effective in highlighting the absorbance feature over different dates and developmentstages, defining an effective mean for hailstorm damage mapping in winter wheat.