Ionic relations in tropical pasture grasses

Ionic relations in the tops of nine tropical pasture grasses were studied by using K‐Na and K‐Mg nutrient replacement series in sand culture. Rhodes grass, green panic, and pangola grass accumulated Na when K supply was low and Na was available. Sorghum, kikuyu, paspalum, speargrass and setaria accumulated very little Na but considerable quantities of Mg when the K supply was low and Mg was available. There were smaller increases in the amounts of Mg accumulated by rhodes grass, green panic, buffel grass and pangola grass than in the other five species when grown in solutions of low K/Mg ratio.

Concentrations of K, Na, Ca, Mg, P, Cl, NO , and SO. in the plant tops are presented. Although experimental treatments resulted in considerable variations in the concentrations of individual elements, cation‐anion balances (C‐A) remained relatively constant when nutrient deficiency did not depress yield in rhodes grass, green panic, pangola grass, sorghum, kikuyu, paspalum and speargrass. C‐A values in setaria and buffel grass increased as the concentration of K in the nutrient solutions increased.

These results are used as a basis for suggesting management practices that will improve the chemical composition of plant material and avoid a number of nutritional disorders that can occur in animals grazing these grasses.