Kikuyu over-sown with ryegrass and clover: dry matter production, botanical composition and nutritional value

Abstract

The seasonality of growth and low nutritional value of kikuyu (Pennisetum clandestinum) pasture restrict milk production. The aim of the study was to determine the dry matter yield, botanical composition and nutritional value of irrigated kikuyu over-sown with annual ryegrass (Lolium multiflorum var. westerwoldicum), white clover (Trifolium repens) and red clover (T. pratense) or a mixture of perennial ryegrass (Lolium perenne) with white and red clovers under intensive grazing conditions with dairy cows. The incorporation of annual ryegrass, perennial clover or perennial ryegrass–clover into kikuyu pasture changed the seasonal fodder flow and increased the spring dry matter (DM) production. The over-sowing of kikuyu with annual ryegrass had no effect on the DM production of kikuyu during the summer and autumn. Kikuyu and kikuyu–ryegrass, fertilised with nitrogen fertiliser, had a higher DM production rate than kikuyu–clover pastures. Kikuyu–ryegrass pasture transformed from ryegrass-dominant in spring to kikuyu-dominant in summer and only kikuyu in autumn. This led to a decrease in metabolisable energy (ME) and increase in neutral detergent fibre (NDF) content of the pasture during spring, summer and autumn as kikuyu became more dominant. The clover content of kikuyu over-sown with clover decreased annually but was still higher than 30% at the end of two years after establishment. As the kikuyu content of the kikuyu–clover pastures increased, the seasonal growth rate changed from a low autumn growth (37.9 kg DM ha−1 d−1) in the first year to a higher autumn growth (48.5 kg DM ha−1 d−1) in the second year. The over-sowing of kikuyu with clover resulted in lower DM production and NDF values and higher crude protein (CP), ME and calcium (Ca) values. The lowest CP content in kikuyu–ryegrass pasture was during summer and autumn when kikuyu was dominant. The Ca content of the grass pastures (kikuyu and kikuyu–ryegrass) was low. The phosphorus (P) content of both the kikuyu–clover and grass pastures exceeded the requirement needed for dairy production (0.38%). The mean Ca:P ratio of the kikuyu–clover pasture meets the 1.6:1 ratio needed by dairy cows. The kikuyu and kikuyu–ryegrass pasture had a Ca:P ratio lower than 1:1 and Ca supplementation would be needed for dairy cows. The incorporation of annual ryegrass, perennial clover or perennial ryegrass–clover into kikuyu pasture improved the seasonal DM production and nutritional value of the pasture.