Geostatistical analysis of coffee leaf rust in irrigated crops and its relation to plant nutrition and soil fertility

Abstract

Occurrence and intensity coffee leaf rust (Hemileia vastatrix) depend mainly on the irrigation system, soil fertility and plant nutrition. The aim of this study was to evaluate the spatial distribution of coffee leaf rust relative to soil fertility and plant nutrition in coffee plantations irrigated by drip and center pivot using geostatistics. The experiment was installed in two experimental areas, with a drip and center pivot irrigation system of 11 and 17 ha and 52 and 50 georeferenced sampling points, respectively. The incidence of the disease, soil fertility and plant nutritional status were evaluated at each point. For the drip system, there was no significant correlation between disease incidence and leaf contents of N, P, K, and Ca. Regarding fertility, there was a positive correlation only for P and the disease incidence. For the center pivot system, there was a positive correlation between coffee leaf rust and Ca, P, and K, and negative for P and K in the leaves, varying according to the assessment date. In soil, only Ca correlated negatively whereas K positively correlated with incidence. The spatial distribution of the disease and nutrients varied over the years, being observed a gradient from foci in the kriging maps elaborated after the adjustment of the exponential model.