Nitrogen fertiliser effects on nutritive characteristics of perennial ryegrass during late autumn, and mid- and late winter in western Victoria

Abstract

A study determined the effects of differing rates of nitrogen fertiliser [0 (N0), 25 (N1), 50 (N2) and 75��kg N/ha (N3)] during late autumn (T1) and mid- (T2) and late (T3) winter on the nutritive characteristics of perennial ryegrass over a 28-day period after each application. All nitrogen applications were made to pastures with a post-grazed residual mass (dry matter) of 1400 kg/ha. Changes in metabolisable energy followed similar patterns for all treatments within a given period. Metabolisable energy was highest in T1, ranging from 11.8 to 13.1 MJ/kg dry matter, followed by T2 (11.5-12.3 MJ/kg dry matter) and T3 (10.6-11.5 MJ/kg dry matter). Changes in crude protein for all treatments at each application time were similar, irrespective of rate of nitrogen application. At the commencement of treatment application times, the existing crude protein content (%DM) was highest in N3 (T1��19, T2 23, T3 22), followed by N2 (T1 18, T2 21, T3 21), N1 (T1 17, T2 20, T3 20) and N0 (T1 16, T2 17, T3 18). During both T1 and T2, neutral detergent fibre content decreased by 4 percentage units and increased by a similar amount during T3. Generally, neutral detergent fibre content (%DM) was highest during T3 (53-58%), followed by T2 (45-54%) and T1 (43-49%). Water-soluble carbohydrate content (%DM) increased during all treatment periods with the highest level observed during T1 (18-31%) followed by T2 (3-14%) and T3 (1-6%). Nitrate content (measured as nitrate-nitrogen) decreased throughout T1, primarily due to dry conditions, while during T2, levels for N3 and N2 were significantly (