Nutrient diagnosis of coffee-tree by DRIS using different sensitivity constants according to the nutrient yield response

The objective of this study was to test the use of standard scores to reduce the dependence among nutrients on DRIS indices. Different scores were attributed to nutrients with common (R), intermediate (M) and rare (I) response to coffee crop. The study was conducted using data of leaf analysis from plantation farms at Matão and Franca, State of São Paulo, Brazil. Leaves were taken from bearing branches during the summer, from 1999 to 2001. DRIS indices were calculated using the original formula defined in 1981 by Jones with a sensitivity constant k = 30 for all nutrient relations. The tested method attributed different values for the constant k, depending on the type of response of coffee-tree to each nutrient. When the methods were evaluated by comparison of the relations between the nutrient balance index (NBI) and yield, the use of scores in the order I<M<R showed to be more efficient then the usual method using the same score for all nutrients. The methods had about the same efficiency when evaluated by comparing the leaf nutrient diagnosis by DRIS with the sufficiency range method.

coffee; DRIS; leaf analysis; nutrient status