Anions and cations in plants, but why do we care?
All this positive-negative, cation-anion, high CEC-low CEC stuff comes into play when applying nutrients and water. Table 1 gives the soil-borne elements necessary for plant growth, the form taken up by the plant and the element’s mobility in the soil. Note that most mobile elements have a negative charge and the somewhat mobile and immobile elements have a positive charge. Over application of a (-) charged element followed by excessive water will quickly move that element through the system. Likewise, over application of most (+) charged elements on a low CEC soil can move that element through the system since there are not enough (-) charges on the soil particle surface to bind to the cation.
The odd anion is phosphorous. Even though it has a (-) charge, it is not mobile in soil because phosphorous forms are not very soluble. It can, however, still move – not as the anion, but bound to soil particles as the particles move. Therefore, minimizing runoff is helpful in reducing phosphorus pollution.
Understanding nutrient movement in soils helps producers apply nutrients and water to maximize economic effectiveness while minimizing environmental impact.