Spatial variability of phosphorus, potassium and liming requirement in an area under pasture

Abstract

The objective of this work was to analyze the spatial variability of phosphorus, potassium and of the liming requirement (LR) of a soil under pasture, sampled by the regionalized method and to compare the results with the values obtained by the conventional method of sampling. It was made a regionalizing sampling of 64  georreferenced points, spaced 10x10m, and another in the conventional way,  at 20 random points, to form a composed sample; for both methods, P, K⁺ and LR were determined. The variables of the soil were analyzed by the descriptive statistics and, soon afterwards, by the geostatistics. The spherical model was adjusted for all the variables in study. The ratio of spatial dependence (DR) was classified at strong for P and moderate for K⁺ and LR.  It was observed, on the maps, that P and K⁺ presented the highest contents in the center and upslope of the area, respectively, and values of LR were reduced downslope of the area. For the variables P and K, most of the area presents lower contents than suitable, for the conventional sampling method. It was observed for LR that in 63.80% of the area, the need for correction of acidity is larger than recommended   in the conventional method. The used technique provided means to compare the conventional sampling method with the regionalizing method, suggesting that this kind of study be done, mainly in areas of larger extension, where the results tend to be more evident.