Autumn water use and yield performance of caucasian and white clover in east coast pastures: A dissertation submitted in partial fulfilment of the requirements for the degree of Bachelor of Horticultural Science with Honours

The production and water use of irrigated Caucasian clover and white clover pastures with or without ryegrass was studied at Lincoln University, Canterbury. The experimental period extended from late summer to early spring 2004. Irrigation did not affect the total dry matter yield of pastures from 1 March to 9 September, 2004. However, irrigated swards produced 115% more dry matter than dryland pastures from 1 March to 2 June. Caucasian clover (Trifolium abiguum M. Bieb.) yield during the summer (3060 kg DM/ha) was higher than the yield of white clover (Trifolium repens L.) (2390 kg DM/ha) and ryegrass (Lolium perenne L.) (2910 kg DM/ha). During the winter, white clover and ryegrass pastures produced 40% more dry matter from April to June than Caucasian clover combined with ryegrass. This increased production in white clover swards was due to the ryegrass producing 50% more yield in the white clover pastures than in the Caucasian clover and ryegrass pastures. In January Caucasian clover and ryegrass pastures were 25-43% clover compared to 5-15% in white clover and ryegrass pastures. The clover content declined in both white clover Caucasian clover pastures to less than 10% by June. Dryland white clover pastures contained more bare ground than dryland Caucasian clover pastures (30% and 20% respectively). Water use from March to September was higher in irrigated (205 mm) pastures compared to dryland pastures (110 mm). White clover used 35 mm more water than Caucasian clover over the same period. Caucasian clover extracted water from a greater depth than white clover (1.7 m and 1.5 m respectively). Less water in the soil profile beneath Caucasian clover pastures below 1.0 m suggested that Caucasian clover has the ability to extract more water from greater depths than white clover.