18 June 2001 Production Benefits in Legume Boost for Dryland Pastures

Research at Lincoln University offers a production-boosting message to dryland stock farmers but many appear reluctant to accept the extra grazing management demands involved.

"The legume content of dryland pastures in Canterbury and North Otago has fallen to a level lower than desirable for maximum animal production," says Lincoln farm management masters degree researcher Stephen Kirsopp, who has just completed a farmer survey of pasture types, sowing rate, management practices and livestock carrying capacities.

"Low quality pastures result in reduced animal production which in tum results in reduced farm profitability. The link is clear and straightforward and the downward spiral inevitable," he says.

"To reverse the process and pull out of the spiral is also straightforward but surprisingly few farmers appear to have made the necessary management commitment."

The key lies in recognising the importance of pasture legumes within New Zealand's pastoral grazing systems and choosing those legumes which do their job the best in the prevailing climatic and soil conditions.

"Legumes fix nitrogen in the soil and enhance the production of companion grasses. Traditionally New Zealand dryland farmers have opted for ryegrass as their grass and white clover as the companion legume. Up and down Canterbury and into Otago that is what you will find," says Mr Kirsopp.

Indeed his survey of 75 Canterbury and North Otago farmers, Mr Kirsopp found that 97 percent of respondents used white clover in their pasture mix, compared to 38% sowing red and the 34% sowing sub clover.

"Unfortunately the choice owes more to tradition than to pasture science and up-to-date climatological knowledge.

"We know that white clover fails to persist in drought conditions yet such conditions have increasingly become a feature of the seasonal cycle along the east coast of New Zealand. Doesn't it make sense then to look at more drought-tolerant pasture species? Subterranean clover, for example, the backbone of Australian pastoralism, is also very well adapted to summer drought conditions in New Zealand.

"Similarly, lucerne has distinct production advantages over ryegrass and white clover as rainfall levels become more erratic.

The advantages of both these species in dry conditions have been well known for many years, with Lincoln University leading the work in New Zealand as far back as the 1940/50s.

Today modern pest and disease resistant cultivars of lucerne are capable of producing at least 50 percent more feed than traditional ryegrass/white clover swards which, in dry seasons with high evapotranspiration and frequent dry winds, will grow only minimally.

Most of the survey respondents derived their income from sheep and relied on good quality spring pastures to finish lambs prior to the onset of drought. Ewes require high protein intake over the early lactation period to minimise the post-parturient breakdown in their natural resistance to intestinal parasites.

The lambing percentages (survival to tailing) were greater on all the lucerne farms compared with the no-lucerne farms – 123% against 117% – and this may be attributable to the ewes enjoying better nutrition over the summer.

"Subterranean clover and lucerne clearly have a role in this regard," says Mr Kirsopp, "with the choice of lucerne more appropriate for the better free draining soils and subterranean clover more suited to the poorer drained areas, soils with non-permeable pan or shallow soils over rock where it is not practical to plant the deep rooted lucerne."

While 50 of Mr Kirsopp's farmer respondents grew lucerne, with the average area being 17% of the pasture, the majority were still using the old Wairau variety despite new cultivars offering greater productivity, disease and pest resistance resulting in increased longevity.

Lincoln University's production-boosting message to dryland farmers is contained in Mr Kirsopp's recommendations, based on his research. He modelled several pasture species alternatives and the results indicated that to achieve the maximum pasture production from dryland farms up to 40 percent lucerne should be grown, with 50 percent or more in ryegrass/ sub clover and pastures plus 10 percent in winter feed.

"The improved nutrition and higher protein forage resulting from the sub clover will help reduce the early spring metabolic disorders in ewes carrying multiple lambs.

"Lambing should commence on the pastures but the ewes and lambs should be transferred on to lucerne in the last week of September, with all sheep rotationally grazed until they are finished.

"By growing up to 40 percent lucerne the stock will be better fed and the need for conserved food will be reduced, provided overall pasture management is good. The aim is to sell all the lambs by early January and is made possible by achieving increased lamb growth rates."

Sadly, Mr Kirsopp says, many farmers appear to be reluctant to accept the extra management burden that lucerne requires and they are continuing to sow traditional pasture species. This is despite the clear evidence that they can have additional feed, lambing percentage increases and improvement in animal liveweight gains with lucerne and subterranean clover.

Previous teachings and recommendations from the pasture seed companies and researchers have been that ryegrass/white clover is a suitable pasture mix for all the agricultural regions of New Zealand. It appears that these recommendations are not ideal for the many summer drought prone areas such as Canterbury, North Otago and elsewhere and that pasture production and longevity can be greatly improved by sowing alternative species.

Ian Collins, Journalist, Lincoln University, Canterbury, New Zealand

Steve Kirsopp, Farm Management Group, Lincoln University, Canterbury, New Zealand