MODELS FOR ESTIMATING POTASSIUM AND NITRATE TO CHANGES OF ION CONCENTRATION IN SOIL SOLUTION

The adequate fertigation use bases on the application of nutrients by water according to crop needs throughout its cycle. The evaluation of nutrients in the soil solution may be faster if based upon soil electric conductivity and moisture by using parametric models. The objective of this study was to evaluate the sensitivity of two parametric models for estimating nitrate and potassium concentration in the soil solution under changes of ion concentration during a crop cycle. One model was that from Vogeler et al. (1996) in which ion concentration is a function of soil moisture and electrical conductivity; the other was the potential in which the concentration is a function of the electrical conductivity of the soil solution. The potential model presented a better performance compared to that of adapted from Vogeler, as for estimation of ion concentrations as for the sensitivity of this model to changes in concentration of this ion in the soil solution. The models showed greater sensitivity when fitted to data corresponding to all possible occurrences in the soil during the crop cycle. The model should consider a range of concentrations with the possible values of the soil solution along crop cycle.