Mesurement and mapping the apparent soil electrical conductivity in pastures

Abstract

The general objective of this study was to test a non contact electromagnetic induction probe to evaluate the soil and pasture variability in a precision agriculture project. Assessment of the variability of soil and vegetation in a permanent pasture are the basis for management of variable rate fertilization, which is the main instrument used by farmers for improvements in permanent pasture in Portugal. The traditional process of sampling and evaluation of the soil and pastures is very demanding in terms of time, labour and reagents, and can derail a project of precision agriculture. This paper describes the major steps followed by the author to simplify the methodology of soil evaluation in a permanent pasture based on measuring the apparent soil electrical conductivity. Tests were carried out in a parcel of approximately 6 hectares, which was subdivided into 28m by 28m squares. The soil and pasture samples and the evaluation of apparent electrical conductivity were georeferenced with a Global Positioning System. The geospatial data were processed by ARCGIS 9.3 software and Geographically Weighted Regression analysis, resulting in significant correlation coefficient values for apparent electrical conductivity and altimetry, soil pH and pasture dry matter yield.