Application of fuzzy logic and geostatistic in the analysis of the fertility of a soil under pasture

Abstract

The objective of this research was to generate a representation of the chemical attributes of the soil, using fuzzy logic and geostatistic analysis as procedures of appropriate mapping to the representation of continuous phenomena. The area in study is located in the south of Espírito Santo state, county district of Alegre. The experiment was done in an Ultisol Yellow-Red loamy texture under cultivation of pasture Brachiaria decumbens. The soil was sampled in the depth of 0-0,2 m, in the 64 points of a regular grid, with dimension of 90 x 90 m. The studied chemical attributes were K, Ca, Mg, Al, SB, T and V. It took place a continuous classification of the attributes, using the fuzzy logic. The data were submitted to the descriptive analysis and, soon afterwards, the geostatistic analysis, through the semivariograms adjustment. The attributes presented moderate and high variability measured by CV. All of the attributes presented spatial dependence, demonstrated by the adjustment of the spherical and the exponential semivariogram. The maps in study presented a mild representation of the limits of variation of the degrees of pertinence of the chemical attributes of the soil, turning them more representative. The fuzzy logic associated to the geostatistic analysis is a suitable technique to be applied to generate a representation of soils attributes, which naturally present a gradual variation in the land.