Spreading the tropicals

A number of farmers in central NSW, from western as well as inner slopes areas have already shown tropical grasses can be persistent long term, as well as fill vital feed gaps such as summer and autumn.

In drought years such as the last three in many areas, tropicals grasses have also stood up well to heatwaves and provided valuable quality green feed when annual species have dried off and temperate perennials have failed to respond to rain outside their normal main growth periods, late autumn to mid-spring.

DPI tropical grass variety trials have been established across central and southern NSW including Cowra, Orange, Condobolin and Yanco, with more sites planned.

All sites have high interest. The Orange trial shows promise in higher altitude tableland areas. Also, western stands have shown how some species are especially persistent in harsh conditions, given suitable management.

Project leader and NSW DPI senior research scientist Dr Suzanne Boschma says trials have generally established well with many varieties at or above acceptable plant densities with several species producing high drymatter production in their first spring/summer and autumn.

For example, some species produced 7000 kilograms per hectare drymatter or more at Orange this past season with one reaching over 9000kg/ha.

Some varieties at Cowra produced around 4000kg/ha, good for a difficult spring/summer/autumn.

Dr Boschma says a focus of the trials will not only be to measure productivity and quality, but, importantly, long-term persistence.

Already farmers have found species like Premier digit grass have long-term persistence if well managed in areas as far south as Koorawatha (between Young and Cowra) and as far west as Nyngan, Nymagee, and north of Condobolin. Some other species have shown poorer persistence, hence variety choice is likely to be critical, as it is in the north.

One promising tropical grass cultivar recently released is panic Megamax 059. It has been persistent and productive in northern NSW and is so far showing excellent promise in some of the trials.

It was released from an MLA WA and NSW tropical grass development program involving NSW DPI (research scientist Carol Harris led it in NSW).

My feeling is tropical grasses will suit many central and southern NSW areas and should follow the lead from northern districts where suitable varieties grow well with winter annual legumes.

Winter legumes germinate in autumn, provide winter-spring feed, and then set seed and dry off until the next autumn.

They also provide nitrogen for the tropical grasses.

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While higher-altitude environments, like the Orange experimental site, will have a shorter tropical grass growing period (close down earlier in autumn and restart later in spring) this should improve their compatibility with winter growing legumes.

There will be more soil water for legume use because of the earlier cessation of tropical growth and later start. But tropicals should be able to supply more reliable vital green feed over the summer/early autumn.

Occasionally higher tableland areas receive an out of season summer frost.

Our experience indicates such frosts can check tropical grass growth, and in more extreme cases burn off growth (which is still edible). But regrowth can be relatively fast.

Tolerance to autumn frost was seen this year in the Orange trial where growth continued, although slowed, in several of the tropical grass varieties after a few early to mid-May frosts.

In western areas tropical grass compatibility with winter legumes can be more difficult because of competition for autumn and spring moisture.

Some landholders have accepted this reality and supplement lack of legume contribution to nitrogen by adding fertiliser (urea) ahead of good rain forecasts from early spring onwards.

Next week. New pulse and canola varieties boost yield and protection from disease.