The effect of the function type for describing the soil buffer power on calculated ion transport to roots and nutrient uptake from the soil

The relationship between amount of a nutrient in soil and its concentration in solution, the buffer curve, is usually non-linear. However. most models that calculate nutrient transport in the soil and nutrient uptake by the p lant often assume a linear buffer curve because of simpler programming. In this paper a model is presented that uses the Freundlich function to descri be the non-linear buffer curve in the soil. It has been shown that calculat ed uptake and depletion curves were not influenced by the shape of the buff er curve. In a sensitivity analysis the buffer capacity, soil solution conc entration, soil water content, soil impedance factor, maximum influx and th e curvature of the Freundlich function were varied and the influence on cal culated uptake was studied. The buffer capacity in general had a minor infl uence and the linearity or non-linearity of the buffer capacity had under n o circumstances an influence on calculated uptake. Thus, the use of a linea r buffer curve in transport models does not lead to a significant error in the results.