The content and yield of six elements in four grasses as affected by nitrogen application and interval between harvests

Abstract

Effects of three levels of applied nitrogen and 4- and 8-week intervals between cuts on the nitrogen, phosphorus, potassium, calcium, magnesium and sodium content and yield of four grasses grown in field swards were studied in three full harvest years. Concentrations of elements in herbage lower than those required by some classes of livestock were found as follows: in the case of phosphorus, where high yields of grass were obtained without any very recent application of phosphorus; in the case of calcium, mainly at harvests in late April/early May; in the case of magnesium, in most of the grass harvested in April, May, June and July; in the case of sodium, where no nitrogen or the intermediate level was applied, except at the October/November harvests; in the case of nitrogen, at harvests in May and July with the 8-week interval and no applied N. Suggestions are made as to ways of raising the concentrations where necessary. The concentration of potassium in herbage was greatly in excess of animal requirements; possible ways of economizing on potassium application are considered. Applied nitrogen (as ‘Nitro-chalk’) greatly reduced extractable soil potassium, reduced soil magnesium, and had little or no effect on soil calcium, sodium or pH.