Cool season performance of Caucasian clover and white clover in perennial ryegrass pastures

Animal productivity has not been evaluated on Caucasian clover (Trifolium ambiguum M. Bieb.) in pasture mixtures with perennial ryegrass (Lolium perenne L.), and low cool season activity is a fundamental problem in its adaptation to lowland pastoralism. The objectives of this experiment were to compare autumn lamb liveweight gains on Caucasian clover and white clover (T. repens L.) in perennial ryegrass pastures under high (Olsen P 22) and low (Olsen P 11) fertility, and to quantify the temperature requirements for clover leaf appearance. Lambs rotational grazed a first year grazing experiment according to a 2² Latin Square Design over 52 days. White clover pastures had less grass than Caucasian because of difficulties during grass establishment. There was no effect of soil fertility and little appearance of differences in liveweight gain between Caucasian clover (57 kg ha⁻¹, 48 g d⁻¹, 50 g kg DMI⁻¹) and white clover (55 kg ha⁻¹, 56 g d⁻¹, 56 g kg DMI⁻¹). A greater decline in Caucasian clover pasture content relative to white clover as air temperature decreased reflected a higher base temperature (4.2°C) and thermal time (279°Cd) requirement for leaf appearance for Caucasian clover compared to 3.1°C and 173°Cd for white clover. Leaf appearance (LA) was estimated for both clovers using simple linear models: Caucasian clover LA = 0.00358*(Ta-4.2); white clover LA = 0.00577*(Ta-3.1). These results show the different responses to temperature to be species specific and suggests the influence of Caucasian clover winter dormancy on its low cool season production can be quantified in different locations throughout New Zealand by simple modelling.