White clover: loss in drought and subsequent recovery

Abstract

There are limitations to the production and persistence of white clover in drought prone regions. We report on the population dynamics of white clover during the summer/autumn drought of 2000. Seventeen paddocks were selected from Marlborough, Mid Canterbury, South Canterbury and North Otago on the east coast of the South Island, and Wairarapa in the North Island. The pastures were sown in 1998/99 and are comprised of ryegrass, tall fescue, cocksfoot or combinations of these as the grass base, with white clover included in the mix. White clover populations were monitored pre- and post-drought using tiller cores. The percentage of each region's long-term mean rainfall received during the 6-month "drought period" had the largest influence on the presence of white clover in these pastures. Marlborough, with only 73 mm of rainfall during November 2000-April 2001 (23% of its expected rainfall) suffered a 95% reduction in white clover. Mid Canterbury, South Canterbury and North Otago, at 53-61% of expected rainfall had a 40-78% loss. In contrast, Wairarapa, with 303 mm of rainfall, lost only 8%. The rate of recovery was closely related to the magnitude of white clover loss during drought. In regions where large losses occurred, further sampling after 18 months showed little increase in white clover presence. Key words: drought, persistence, populations, seedling, Trifolium repens, white clover

Productivity and seedling recruitment of naturalised annual clovers versus sown clovers Trifolium repens and Trifolium subterraneum

“…These NAC species have the ability to grow to maturity and produce viable seed in most years before the onset of late spring-summer soil moisture deficits, followed by autumn regeneration every year from the large soil seed reserve. White and sub clover were not dominant at any time over the 19-month period, adding further support to the contention that white clover (Knowles et al 2003) and sub clover (Power et al 2006) struggle to persist and make a valuable contribution to summer dry hill pastures of north-facing aspect.…”

“…However, long term abundance of white and sub clover is limited. Poor establishment on summer dry slopes with annual soil moisture deficits limit production, survival, and thus persistence of white clover (Knowles et al 2003;Power et al 2006) which phenologically exhibits optimum growth and stolon propagation during summer when soil moisture stress is greatest. Additionally, white clover is as a highly productive legume species adapted to high soil fertility conditions (high P, S and pH levels) for optimum growth (Haynes & Williams 1993;Moir et al 1997).…”

Achieving persistence and productivity in white clover

“…Summer moisture is the greatest non-genetic determinant of white clover persistence in many cases. Knowles et al (2003) and Dodd et al (2001) demonstrated the direct relationship between severity of drought and the loss of white clover from pasture. Modified grazing management can offer protection under some dry circumstances.…”

Insect populations of six dryland pastures grown in Canterbury

“…These species are suited to summer moist environments and moderate to high soil fertility (Brock et al 2003). However, their persistence is shorter in dryland regions where annual rainfall is <750 mm (Knowles et al 2003).…”