Use of nitrogen sufficiency index to estimate topdressing doses for common bean

Abstract

Portable chlorophyll meters can be used to improve the prediction of nitrogen (N) doses for common bean. This study aimed to evaluate two chlorophyll meters (Minolta SPAD-502 and ClorofiLOG CFL 1030) to predict topdressing N doses for the Pérola, TAA Gol and BRSMG Uai cultivars and for the VR 20 line. Eight field experiments (four genotypes and two devices) were carried out in a randomized blocks design, with four replicates, being the treatments topdressing N applications corresponding to four nitrogen sufficiency indices. There were discrepancies between the indices obtained by the different devices for the same genotype, as well as among those obtained with the same device for the different genotypes studied. Thus, when the index is used to define the N doses, the genotype and the chlorophyll meter used must be considered. In addition, the recommended index of 95 % should not be generalized to all the cultivars and should be reduced.