PA—Precision Agriculture: Use of Electromagnetic Fields for the Determination of the Dry Matter Content of Chopped Maize

A commercially available radio-frequency (RF) application unit was used to estimate the dry matter (DM) content of chopped maize. Chopped maize with a known DM content was placed in the application chamber of the RF unit and a defined power was applied until there was no more power reflected due to an automatic matching network. At this point, the voltage between the capacitor plates and the device-specific parameters, load position and tune position, were recorded. By means of regression analysis, it was possible to clearly explain the variance of the DM content with the parameters measured. However, the relations developed were especially unsatisfactory when different sample weights and densities were included in the analysis. A good adaptability of the model was achieved by using the mass of water as a dependent variable. Calculating a regression equation with data from one farm and estimating the water mass in the samples from another farm using this equation, the correlation coefficient between the real and estimated water content was 0·98.