Influence of fertiliser nitrogen on nitrogen fractions and nonstructural carbohydrates in grazed grass-clover herbage

摘要

Abstract Contents of N and nonstructural carbohydrate fractions were measured over a year in herbage from a grazed ryegrass-white clover pasture, which had been fertilised with limeammonium nitrate at an annual rate of 0 (N0), 112 (N112), and 448 (N448) kg N/ha. Total N content of the mixed herbage was often greater than 4% dry weight, and was highest in early spring and lowest in late summer. Levels in many cuts were increased significantly by the N448 treatment; the N112 treatment had little effect. The non-protein N and nitrate N contents were also highest in the N448 herbage, particularly in early spring; the level of nitrate N was also high in autumn. Most of the nitrate N occurred in the grass component. Total water-soluble carbohydrates, and those soluble in hot water but insoluble in cold water, usually comprised less than 12% and 1% dry weight respectively of the mixed herbage. Total water-soluble carbohydrates were negatively and significantly correlated with both total N and “protein” N content...