COMPATIBILITY ANALYSIS OF THE SOIL CALCIUM CONTENT BY MULTIFREQUENCY EC SENSORS

Nowadays in precision agriculture, the on-the-go measurement of soil nutrients is an important research topic in the sustainable nutrient management practices. Determining the nutrient content of soils and the judicious and site-specific replacement of missing mineral compounds of soil has a major impact on production costs in terms of current fertilizer prices. Soil sensors currently on the market can only determine total soil salinity. Therefore, selective soil salinity testing is only possible using laboratory methods. However, these methods are rather expensive, slow, and cumbersome. Growers often need faster and cheaper soil sampling process and immediate results. We believe that by developing measurement models of soil sensors, the data delivery process could be significantly shortened, so that measurement results could be processed and used even in real time. In this paper, we prove that electrical conductivity measurements can be a suitable tool for the determination of the selective salinity of soil. In our experiments, the calcium cation content of soil was measured by conductometry in laboratory conditions. In our model, we investigated the effect of a reasonable and well-considered variation of the measuring current frequency on the measurement output variable, i.e. the electrical conductivity (often abbreviated as EC) value. Our experiments have shown that with multi-frequency, solutions containing predetermined concentrations of Ca2+ ions, the EC obtained as an output parameter follows different functions.