THERE are numerous agronomic and operational benefits to be gained from delaying soil amelioration until the soil is moist, in addition to minimising the risk of soil erosion, according to the Department of Primary Industries and Regional Development (DPIRD).
Western Australian grain growers have become increasingly interested in the use of rotary spaders, large offset discs, mouldboard and one-way ploughs to mix or invert the soil and reap long term agronomic and production benefits.
But below-average growing season rainfall throughout the grainbelt last year and ongoing dry conditions has led to a lack of ground cover, elevating the risk of losing valuable topsoil from wind and water erosion from soil disturbance.
DPIRD research scientist Stephen Davies said delaying soil amelioration until the soil was moist would both reduce the erosion risk and create several opportunities.
"Tillage equipment works more effectively in moist soil, particularly subsoils," Dr Davies said.
"Sands, in particular, are more cohesive enabling the soil to be carried on the spades of a spader to achieve effective mixing or to 'hold and fold' on discs and plough boards for inversion.
"Implements operating in moist soil are able to work deeper and operate more efficiently at optimum depth."
Reduced resistance from working in moist soil also uses less horsepower and puts less strain and wear on tillage equipment and tractors, saving fuel and maintenance costs and generating efficiencies.
Dr Davies said there were also agronomic advantages to undertaking amelioration in moist soil.
"When water repellent soil is disturbed in dry conditions, the expression of topsoil water repellence increases dramatically," he said.
"While deep mixing and soil inversion can reduce topsoil water repellence, using tillage implements when the soil is dry is often less effective than amelioration undertaken when the soil is moist.
"Waiting until significant rain falls also provides the opportunity to combine non-chemical weed control through tillage, improving the long-term sustainability of the cropping system.
"Sowing a cereal crop immediately after the soil has been ameliorated when the soil is wet can aid rapid crop emergence and provide an opportunity for the seedlings to grow roots into loose, moist soil."
Another strategy is to delay soil amelioration until spring, as part of a fallow or 'renovation year' to prepare paddocks to aid future management and profitability.
"This may involve spreading amendments, weed knockdown followed by deep tillage in spring and sowing a cereal cover or - in some environments - a summer crop," Dr Davies said.
"The renovation year can be a useful weed and disease break and with the stubble residue from a late summer or cover crop there is then opportunity to grow a high value break crop the subsequent season."
While delaying soil amelioration may involve some cost and curtail short-term returns, Dr Davies said it was often worth the compromise in the longer term.
"There are many crop performance benefits to be achieved from delaying soil amelioration, alongside the management advantages to be gained from operating a more sustainable farming system," he said.
With ongoing dry conditions in many parts of the WA grainbelt, coupled with sparse stubble cover, sandy soils are already at risk of erosion and soil amelioration undertaken when the soil is dry would increase the risk.
If erosion was to occur, the Commissioner of Soil and Land Conservation may issue a Soil Conservation Notice to direct a landholder to undertake an immediate action to mitigate the erosion.
Failure to comply with a notice is liable to result in prosecution.
p More information: agric.wa.gov.au
