Variability and spatial correlation of soil micronutrients and organic matter with macadamia nut production

ABSTRACT Soil fertility is the key to agricultural production. The spatial correlation and location of nutrients may significantly affect the yields. The objective of this work was to evaluate the variability and spatial correlation of iron (Fe), copper (Cu), manganese (Mn), zinc (Zn), and organic matter (OM) with macadamia nut yield. The study was conducted in an Oxisol cultivated for 20 years with macadamia nut in Sao Mateus, state of Espirito Santo, Brazil. A 100 point grid was used comprising an area of 144 × 140 m with a minimum distance between points of 5 m, in which a single composite soil sample was collected from 0-0.20 m layer for chemical analysis of Fe, Cu, Mn, Zn and OM. Nuts under the canopy’s projection were harvested from February to June, 2015. The data were evaluated by geostatistical analysis using semivariograms, and kriging was used to map spatial distributions of nutrients and nut yield. All evaluated attributes showed strong or moderate spatial dependence structure. The OM was correlated positively with micronutrients, but only Zn was positively correlated with nut yield. Crossed semivariograms adequately explained the maps of Zn and Mn; and Fe showed opposite tendency for macadamia nut yield.