Calibration and validation of an electronic capacitance meter in a pasture precision agriculture project

Abstract

The general objective of the study was calibrate an electronic capacitance meter to estimating the pasture dry matter in a precision agriculture project. The standard method of assessing pasture requires great effort and farmers are not willing to make this effort in day-to-day management of pastures. The field tests for carrying out in different dates of 2007 and in three dairy farms, represents the typical pastures in Alentejo region (grasses; leguminous; and bio divers mixture). Regression techniques are used to relate the weight of the herbage in kg of dry matter for hectare to the meter reading of capacitance. The estimation of dry matter of the herbage mass, in kg ha^-1, based in capacitance was relatively good in two sites, with overall coefficients of determination of 0,90 in grasses and 0,67 to 0,75 in bio divers mixture. In the leguminous the coefficients of determination obtained varied between 0,27 and 0,59. In 2008, the regression equations were validated in two sites and the results showed a gap between the mass effectively cut and the estimated mass of less or equal to 20%.