Nitrogen fertilization is a cultural practice usually used by common bean farmers. The objective of this study was to evaluate the use of chlorophyll meter as an instrument of indicating the necessity of topdressing nitrogen fertilization in winter common bean crop irrigated by sprinkler irrigation with central pivot. The study was conducted in two stages, at Embrapa-Centro Nacional de Pesquisa de Arroz e Feijão, Santo Antônio de Goiás, GO, Brazil. The first stage, in 2000, consisted in planting two bean cultivars, Pérola and Jalo Precoce, submitted to four rates of nitrogen topdressing, i.e., 0, 30, 60 and 120 kg ha-1 of N, with the purpose to establish response curves between chlorophyll reading obtained with the model Minolta SPAD-502, in each N rate, and grain yield. The second stage, in 2001, verified, in the field, if the established reading values were an indicative of adequate N level in the plant. Cultivar productivity and chlorophyll reading increased with the increase in N rates. At the same N rate, values of reading were higher in the cultivar Pérola. Chlorophyll meter showed efficiency in indicating the necessity of N fertilization as topdressing for common bean.
Phaseolus vulgaris; sprinkler irrigation; chlorophylls; measuring instruments; topdressing
