A review of red and white clovers in the dryland environment

Red and white clovers are best adapted to areas with good soil fertility and adequate soil moisture (750 mm annual rainfall), particularly over summer (150 mm), and are therefore restricted to small areas such as the more fertile valley floors and lower shady slopes in dryland environments. To extend their range and aid survival in dry environments, grazing management and cultivar selection are critical. Continual grazing (set stocking) during spring leads to a dense grass pasture, providing protection from desiccation for white clover stolons in the following summer. White clover cultivars have an inbuilt plasticity that allows morphological adaptation to changes in grazing management. For instance, set stocking in combination with a small-leafed cultivar results in a reduction of plant size but an increase in the stolon population, leading to better plant survival through drought periods. Where drought leads to stolon death, reseeding becomes a viable mechanism for clover persistence, and grazing management has a major influence on survival of new seedlings. For red clover, there is evidence that 'creeping' types survive better than 'crown' types in hill country, but the scope for extending red clover into drier areas is more limited. Key words: cultivars, drought, dryland, grazing management, morphological adaptation, persistence, red clover, reseeding, summer rainfall, Trifolium repens, T. pratense, white clover