New legumes for drier environments

With experts predicting global warming will increase temperatures in Australia, plants that can cope with hotter, dryer and more variable conditions will become even more important.

A national program is now under way to identify new earlier maturing and drought tolerant pasture legumes for grazing and grain-based crop rotations that will adapt to climate change.

Options include legumes that flower early, thereby increasing the chances of avoiding drought, and deep-rooted legumes, which make greater use of rainfall events as they occur.

NSW Department of Primary Industries researcher Graham Crocker said the first alternative is to breed and select shorter season annual legumes that flower and set seed earlier to allow them to regenerate in the drier conditions.

“There are at least 14 cultivars of 10 annual species with early maturity currently available, including barrel, spineless burr, button, snail and hybrid medic, balansa, gland, Persian and sub clover, yellow serradella, and Lotus,” Mr Crocker said.

“While they were designed to extend the growing range into more marginal areas, they could be grown in the present zones if the low rainfall margins move eastwards.”

“The disadvantage of earlier maturing lines is they generally produce less herbage and often cannot respond to late season or out of season rainfall.”

He said another approach is to select perennial legumes that are deep rooted and therefore possess better drought tolerance.

Once established, such perennial legumes can respond to rain at any time of the year.

These characteristics also make them valuable in addressing the effects of rising water tables and associated salinity problems.

While lucerne is the obvious legume for the slopes and plains of northern NSW, there are alternatives such as sulla and sainfoin.

Mr Crocker said these winter-growing, non-bloating legumes prefer alkaline soils and can produce large quantities of feed.

“Sulla has other advantages – the characteristics that make it non-bloating also give it a drench-like effect to reduce worm burden and the protein protection in the rumen allows it to increase animal production.

“It is also very tolerant of aphids which are expected to increase in number with increasing temperatures. “

Other alternative perennial legumes include the summer growing sub-tropical species burgundy bean, desmanthus and butterfly pea.

Although these are affected by frosts, they regenerate in spring, giving much faster production than annuals in the second and later years.

Mr Crocker said that with the continuing dry conditions farmers and advisers are showing an increasing interest in identifying adaptable legumes to improve pasture quality for animals and to increase soil fertility for crop rotations.
The 160 farmers who attended field days to showcase legumes being evaluated by Mr Crocker this spring were impressed with the growth of most varieties despite the dry season (where current annual rainfall is 200 mm below average).

The collaborative legume evaluation project involving State Departments of Primary Industries and CSIRO is funded by the Grains Research and Development Corporation and Australian Wool Innovation.

The field days were held at Tamworth, Somerton (near Gunnedah), Barraba & Warialda.