Índice de Vegetação por Diferença Normalizada (NDVI) visando estimativa de fitomassa de adubos verdes

Abstract

Normalized Difference Vegetation Index (NDVI) to estimate green manure phytomass Fabaceae are the most commonly used species in green manure due to their ability to fix atmospheric nitrogen from the process of symbiosis with diazotrophic bacteria. Estimating its yield allows the producer to correctly manage fertilization for crops in rotation or succession. The present work aimed to monitor the vegetative development of green manures over time, through the Normalized Difference Vegetation Index (NDVI), to estimate its phytomass production. The experimental design was in randomized blocks with subplots; the plots were composed of six green manures, Crotalaria juncea L. (Sunn hemp), Crotalaria spectabilis Roth. (Showy crotalaria), Crotalaria ochroleuca L. (Sunn hemp), Cajanus cajan (Pigeon pea), Canavalia ensformis (L.) D.C. (Jack bean) and Panicum maximum Jacq. and the subplots were the evaluation times production phytomass (30, 40, 50, 60, 70 and 90 days after emergence-DAE), with four replicates. Green manures were conducted during the vegetative phase-until 90 DAE, NDVI evaluations were performed twice a week. The green manures showed satisfactory development within the cultivated period with NDVI values obtained over time presenting maximum values between 55 and 69 days, ranging from 0.77 to 0.91. C. spectabilis, P. maximum, C. cajan and C. ochroleuca showed a strong correlation between NDVI and phytomass production, while C. ensiformis and C. juncea presented moderate correlation with NDVI and phytomass. The active optical sensor allows to estimate its production, with precision varying according to the species.