By Helen Olsen
As the practice of no-till continues to spread, some researchers are turning their attention to more accurately measuring cost versus benefits.
Peter Ridge, technical director of DIRT Management in Toowoomba, has recently carried out a field study in Hopetoun, Victoria, to investigate the costs and benefits of no-till.
"I am satisfied that we can demonstrate we have higher water use efficiency than our neighbouring conventional farmers," says Mr Ridge.
However, he believes a longer time frame is needed to validate other purported benefits, including improved soil structure, which could lead to greater yields and profits for growers. "The Canadian experience is that this might take closer to 20 years to demonstrate - so it"s early days yet."
Mr Ridge agrees there are substantial short and long-term environmental benefits of no-till. It reduces soil water evaporation before crops have reached full ground cover and increases soil moisture retention after summer storms. In the longer term, it can result in the reduction of nitrogen fertiliser use. The stubble left by the no-till method can also diminish soil erosion.
The question for Mr Ridge is whether notill offers real economic benefits for graingrowers when costs are taken into account.
Increased costs of no-till can occur through a greater need for herbicides, the need to reduce the amount of stubble in some years, and having to buy spraying equipment that allows rapid weed eradication over large areas after summer rains.
The field study led to estimates that the short-term financial gains of no-till are $94 a hectare, with additional costs of $19/ha.
This includes costs for increased fertiliser application and sowing losses for stubble that is too difficult to sow through. It does not account for any investment in machinery that may be needed to sow through heavy stubble.
The longer-term cost benefits of no-till are more difficult to quantify. The figure calculated based on the field study and the climate history of Hopetoun is a net gain of $52/ha.
"The cost benefit analysis is somewhat theoretical - that is it"s my interpretation of the literature and what it means for practice," Mr Ridge says.
He also emphasises these figures assume best practice on the part of the grower, in terms of getting the times right for sowing and weed control, and the rotation of crops for disease and weed management.
The stubble left by no-till channels water away from the surface and into the soil, reduces runoff after heavy rain and reduces waterlogging. This is enhanced by macropores (old root channels and earthworm burrows), which increase over time.
Surface stubble also reduces soil erosion, particularly important for areas that suffer from high winds, such as Victoria"s Mallee region. Mr Ridge estimates that wind storms soon after the sowing in the Mallee occur in 25 percent of years, carrying away soil and nitrogen fertiliser and costing growers about $11/ha. Resowing up to 20 percent of the crop represents additional costs.
According to Mr Ridge, about 50 percent of the nitrogen applied to the cropping area is initially retained in the surface stubble, with the rest being incorporated into the crop. This results in extra fertiliser being needed in the first few years after the start of no-till, meaning an increased cost in this area.
However, the nitrogen is gradually absorbed into the soil, lessening the need for fertiliser in the longer term. Mr Ridge estimates the absorption will take five to 10 years, but points out that since most long-term studies show no-till increases the turnover rate of nutrients, including nitrogen, it could be in the soil more quickly.
In summary, his study confirms no-till"s short-term benefits, particularly for cropping areas where water and soil conservation are crucial. However, the definitive economics of no-till may take another two decades to gather.
For more information: Mr Peter Ridge, 0419 661 539, firstname.lastname@example.org
"Assessing risks to encourage farm change"
North, South, West