Criteria to Nitrogen Management On Common Bean Crop Using Portable Chlorophyll Meter.

The chlorophyll meter is a device which allows obtain relative chlorophyll index (RCI) which correlated with the chlorophyll and leaf Nitrogen (N) concentration, therefore, determination of RCI by chlorophyll meter can be an alternative used to predict to necessity N by common bean, however, there are questions about which leaf is the most appropriate to define need for N by the crop. Thus, the aim of this study is establish the leaf diagnosis most appropriated to define N necessity of common bean, through chlorophyll indirect readings through the use of portable chlorophyll meter. The experiment was carried out with cultivar Perola during dry growing seasons of the agricultural year 2011, with purpose of establishing witch the best leaf diagnostic (first, second and third fully expanded trifoliolate leaf from the top), to define the necessity N of common bean, using the chlorophyll meter (Minolta SPAD-502). The experimental design is a randomized block with five N rates (0, 50, 100, 150 and 200 kg ha^-1) in the form of ammonium nitrate and four replications. Chlorophyll meter readings were first taken 14 days after emergence (DAE) and then weekly until 35 DAE on five randomly selected plants per experimental unit. Linear correlations were calculated on the mean relation between RCI in first, second and third fully expanded trifoliolate leaf, leaf N concentration, N accumulation and grains yield. Third trifoliolate leaf fully expanded from the top shown to be more adequate for evaluating the nutritional status of nitrogen in common bean cultivar Perola from the RCI effect at 28 and 35 DAE, according to the best correlation between RCI and leaf N concentration and aboveground N accumulation. There was no significant correlation between grain yield and RCI values at 28 and 35 DAE.