Seasonal variations in chemical composition of pasture

Abstract

Abstract As part of a study of seasonal variations in chemical composition of pasture herbage Ca, Mg, K, and Na concentrations, and the ratios K/(Ca + Mg) and Ca/P, were determined by monthly samplings at seven sites in the lower North Island. Grass and clover components were harvested separately at six sites, and grasses, clovers, and “other species” (herbs) at the seventh. Sub-plots were harvested by hand shears, after which sheep were allowed to graze before the plots were enclosed until the next sampling date. The seasonal patterns in herbage chemical composition were similar at all sites despite wide differences in soil, climate, and dry matter production. For Ca, the highest values occurred in summer and the lowest in mid winter. Calcium concentrations were higher, and the variations greater, in clovers than in grasses, and concentrations were even higher in “other species”. Trends in Mg were seasonally similar to those for Ca but were much less pronounced; and differences between grasses and clover...