Estimativa do coeficiente de cultivo (kc) da cana-de-açúcar a partir do nível de cobertura do solo com uso de drone

Abstract

Sugarcane is one of the main crops in midwest Brazil, and also an important part of the national scenario, which encourages and shows how important the studies on its productivity are. The crop coefficient (Kc) and the reference evapotranspiration (ET0) are used to estimate the evapotranspiration of a crop. The Kc presents important information for several activities that involve the water balance, for example, irrigation management and climate zoning. Therefore, this work aimed to adjust a mathematical model to estimate, under field conditions, the Kc of sugarcane by the level of ground covered by the leaf canopy. The experiment was happened in an area of 0.42 hectares, in which there is a large weighing lysimeter (7.2 m2 of area, 1 m of useful soil depth and approximately 13,500 kg). The weighing lysimeter was used to measure the evapotranspiration of the variety RB966928 irrigated and cultivated in the spacing of 1.5 m between furrows. The value of Kc was determined daily by dividing the evapotranspiration by the reference evapotransporation, which was obtained from a nearby meteorological station using the Penman-Monteith method. The percentage of land cover (%LC) was also evaluated through aerial images taken with a drone. The fraction of covered soil (fCS) was derived from the LC. The assessments were made from planting to maximum soil cover. There were 13 evaluations in ten months and %LC values ranged from 0 to 99.9%. The quadratic polynomial model 𝐾𝑐 = −0,6613𝑓𝐿𝐶2 + 1,2743𝑓𝐿𝐶 + 0,4688 was fitted with a coefficient of determination (R2 ) of 0.81 and a standard error of 0.096.