Spatio-temporal aspects of brown eye spot and nutrients in irrigated coffee

Abstract

Brown eye spot is one of the most common and important diseases of coffee in Brazil. Using geostatistics, this study evaluated the spatio-temporal aspects of the disease and how they relate to plant nutrition and soil fertility in plots irrigated by center pivot and drip irrigation. The experiments were conducted in Carmo do Rio Claro City, in southern Minas Gerais state, southeast Brazil. The sampling grid was georeferenced with 50 points in 17 ha and 52 points in 11 ha for center pivot and drip irrigation, respectively. Disease incidence was assessed at 60-day intervals from August 2012 to March 2015. Yield, plant mineral nutrition, and soil fertility were evaluated at each point annually. Weather data were obtained from climatological stations with sensors for temperature, relative humidity, wind velocity, leaf wetness duration, and total precipitation that were located inside and outside the coffee canopy in both experimental plots. Climate data were correlated with disease incidence. Disease progress curves were plotted, and semivariogram models were fitted for assessments with a high disease incidence over time. Then, the data were interpolated by ordinary kriging, and maps of disease, yield, and leaf nutrients (B, P, and K) were constructed. The average temperatures and accumulated rainfall rates were lower in periods of higher incidence, but relative humidity was high. All variables exhibited space-time variation in both plots. There was a correlation (p < 0.01) between disease incidence and leaf nutrients (B, K and P). The disease incidence in the center pivot and drip irrigation plots ranged from 0 to 23% and 0–25%, respectively, and varied over space, showing spatial dependence and the presence of disease foci with outward gradients. Areas with high intensity changed over planting years along with yield and nutrient availability.