Effect of nitrogen fertilisation during the cool season on daily growth rate, botanical composition and selected nutritive characteristics of a mixed grass-clover pasture in the Winelands sub-region of the Western Cape

摘要

Nitrogen effects the productivity, botanical composition and quality of grass-clover pastures. Responses to N fertilisation are area and season specific and must be quantified to ensure optimal economical pasture production. A grass-clover pasture mixture was established under irrigation at Elsenburg Research Farm with the aim of developing nitrogen fertiliser management strategies for grass-clover pastures during the cooler months. The mixture consisted of perennial ryegrass (Lolium perenne L.), tall fescue (Festuca arundinaceae Schreb.), cocksfoot [Dactylis glomerata L), red clover and white clover (Trifolium pratense L and Trifolium repens L). The effect of different fertiliser N rates (0, 20, 40 or 60 kg ha1) and season of application (autumn, early winter, late winter and early spring) on daily growth rate, botanical composition and selected nutritive characteristics were evaluated. Autumn applications of 40 and 60 kg N ha 1 during the first year of the study and 60 kg N ha 1 during the secondyear increased primary dally growth rate. Except for autumn in Year 1, N fertiliser application rate did not influence residual daily growth rate. The nutritive characteristics - dry matter content (DM), crude protein content (CP) and in vitro organic matter digestibility (IVOMD) - remained within the expected range. However, pasture CP content was very high in the first year (> 30 %). The low response efficiencies to N fertiliser and resultant high cost of producing the extra pasture render most treatments uneconomical compared to buying in feed barley or oats as grain.