The potential use of vegetation index to estimate crude protein on natural grasslands of Southern Brazil

The aim of this study was to analyze the potential use of the Normalized Difference Vegetation Index(NDVI) to estimate the crude protein content on natural grasslands. The experiment has been performed since 1986 in the Experimental Station of the Federal University of Rio Grande do Sul, Brazil, in an area of 64 ha of natural grassland. The experiment was arranged in randomized blocks with two experimental units (EU) by treatment. The EU has been managed under forage allowances (FA): 4, 8, 12 and 16 kg of dry matter (DM) per 100 kg of the animal's live weight (LW) per day (% LW). For defining the model accuracy, the first step was to fit a model for forage quality, using NDVI data collected in the experimental area in 2013, 2014 e 2015 (n=164) using the handheld crop sensor 'Greenseeker'. The NDVI index was considered accurate (R2 = 51.16%, P2 = 49.81%, P