Factors influencing the sodium content of meadow grass.

Sodium content of grass was largely determined by Na content and K number of the soil. At a given Na content of soil, the Na content of grass decreased with increasing K number of the soil but the decrease was small where K number was >30. Na content of grass increased with increasing soil Na; the increase was higher at low- than at high soil-K status. K fertilizing lowered grass Na at low soil-K status. Soil-Na content can be used in the Netherlands as a basis for Na-fertilizer recommendations, since K number has generally reached a level at which it has an almost constant effect on Na content of grass. Influences of the K and Na status of the soil on the Na content of grass can be expressed as the ratios (15 X K number)/(Na2O+6) for sandy soils and (25X K number)/(Na2O + 14) for clay soils, the numerator at K numbers > 30 being the same as that at K number=30. With increasing ratios, the Na content of grass decreases. The influence on herbage -Na level of a given amount of Na in K fertilizers is correlated to these ratios. The influence of N fertilizers on Na content of grass was not clear and the influence of Mg fertilizers was negligible. Chile nitrate and Nad affected the Na of grass similarly, but Chile nitrate differed from NaCl in decreasing the Ca content; both fertilizers slightly lowered the Mg content of grass. Herbs and clovers contained more Na than grass does. (Abstract retrieved from CAB Abstracts by CABI’s permission)