ACCORDING to Agriculture Victoria, most of the state has experienced an extremely dry autumn and now even when rain has fallen, soil temperature may have become the main factor limiting pasture growth.

Agriculture Victoria Livestock Industry development officer, Nick Linden said soil temperature, like moisture and fertility, plays a major role in controlling plant growth.

“Covers will stop fixing much nitrogen below about nine degrees which can provide some opportunities for response to urea,” he said.

“Research in Tasmania shows that perennial ryegrass continues to grow down to about five degrees, while annual ryegrass as low as two degrees.

“Australian phalaris has been shown to also grow down to about five degrees and a ‘guesstimate’ for more winter active cultivars is between one-and-a-half and two degrees lower.”

Mr Linden said urea and gibberellic acid (GA) provide options to increase pasture growth when nitrogen and/or soil temperature is limiting, on the proviso that good soil fertility, perennial pasture species and soil moisture are present.

“GA is made naturally in plant roots during spring and stimulates shoot and cell elongation, promoting plant growth.

“The application of manufactured GA in winter stimulates plant growth and increases winter feed availability. 

“GA should be applied when air temperature is between five and fifteen degrees, when natural levels of GA are low. 

“Several producer groups have trialled using GA with or without urea and results have varied across sites and years, so it may be worth talking to a local group or agronomist for advice on what to expect.

“The response to urea will be slower than when pasture growth is optimal (i.e. spring) but may be worthwhile,” he said.