Uso do clorofilômetro e sua relação com o manejo da adubação nitrogenada em cultivares de sorgo granífero e silageiro na região semiárida

Abstract

The rational management of inputs is essential for the efficiency of crops in regions with less water availability. Among plant nutrients, nitrogen (N) is the most complex due to its losses due to edaphoclimatic factors. In the sorghum crop, productivity accumulates linearly with the application of N, which is the nutrient most demanded by the crop. Thus, the objective was to evaluate the use of the chlorophyll meter and its relationship with the management of nitrogen fertilization in cultivars of grain sorghum and silage. The experiment was carried out in a randomized block design in a 4x4 factorial scheme with three replications, four sorghum cultivars, two granifers (BRS310 and 50A50) and two forages (SS318 and BRS655) in four different nitrogen fertilization management systems at sowing with doses of 16, 32, 48 and 64 kg ha-1of N (urea). The fertilizer used for sowing was 90 kg ha-1of P2O5(Super Simple) and 20 kg.ha-1of K2O (Potassium chloride). The cover fertilization was carried out right after thinning, aiming at reaching a total of 110 kg ha-1. The increase in the nitrogen fertilization dose at planting has potential for use in grain and forage sorghum in clay soils in the semiarid region of Minas Gerais, as it reduces the number of operations. The increase in N doses at planting has a positive correlation with the AtLeafindex and with the main agronomic characteristics in the grain sorghum group, whereas in the silage group there is a negative correlation for the AtLeaf index, which indicates different management of this nutrient according to the groupof cultivars.