GRAIN growers in the southern Mallee have been urged to take a conservative approach to planting this season's crop.

Yield Prophet figures suggest that in some of the region's paddocks, there is a 20 per cent chance crops will fail without further rainfall between now and sowing.

Birchip Cropping Group research agronomist Simon Craig said growers were facing vastly different conditions to what they encountered last year.

He said unlike this time last year, when the soil profile was full, there is very little plant-available moisture stored in the soil.

At BCG's main trial site for this year, which is just west of Birchip, assessments carried out early this year indicated the soil profile was dry and extremely low in nitrogen.

"The Yield Prophet crop report indicates there is a 20 per cent chance yitpi wheat crops grown at our Birchip site this season will fail or yield less than half a tonne per hectare," Mr Craig said.

"At the current grain prices, you couldn't grow it for that."

Mr Craig said with soil tests revealing basically no soil moisture (down to one millimetre), he was advising growers to be more conservative with their inputs and crop choice than they might have been last season.

"Farmers need to spend their dollars wisely and identify those lower risk paddocks to invest in," he said.

"We're suggesting they look carefully at how their paddocks have performed over the past five years and make input decisions based on how likely it is that a crop grown in a particular paddock will deliver good returns.

"With a limited amount of soil moisture some farmers might even choose not to sow higher-risk paddocks, such as those with low nitrogen and sub-soil constraints."

While there has been some rain in Birchip since the end of the 2011 growing season (33mm for January), Mr Craig said that, generally, only a third of the rainfall received greater than 20mm was stored in the soil profile.

"That's assuming summer weeds are controlled," he said.

"If there are weeds in the paddock, they will use significant amounts of nitrogen and moisture that will substantially decrease yields the following season."

To help farmers plan for the coming season, Mr Craig said soil test results were useful.

According to Mr Craig, last season's harvest results indicated that many crops had failed to reach their full potential because not enough nitrogen had been applied.

"Last year, farmers put out more nitrogen that they are used to and in many cases it was still not enough," he said.

"A lot of Australian Premium White and Australian Standard White wheat harvested had protein levels which were down, which suggests nitrogen was low.

"And paddocks that were low in nitrogen generally had lower than expected yields."

With this in mind, Mr Craig said knowing how much nitrogen was in the soil was a priority when deciding how much fertiliser to order and subsequently apply.

He suggested farmers could group paddocks with similar soil types and conditions and use test results to estimate the soil nutrient levels.

If conditions remain dry in the lead up to seeding, Mr Craig said it was likely farmers would restrict the amount of nitrogen applied to paddocks at sowing time, opting to top-dress prior to forecast rain.

"Especially on the heavy constrained soils around Birchip, I expect farmers will put a small amount of nitrogen up-front and top up during the season according to the conditions," he said. "If anything, we have learnt that no season is the same as the last ... "

• Justine Severin works for the Birchip Cropping Group