Second helpings for canola

Profit from increased yields more than covers the cost of liming...

Farmers growing canola on acid soils could receive a bonus of up to $90 per hectare with a second application of lime on land treated within the past 10 years, according to WA trials.

Long-term trials, supported by growers through the GRDC, also found that canola yields remain high for years with the carryover impact of lime.

Trials at Cunderdin, Kojonup and Mingenew that received lime between 1987 and 1989 showed significant improvements in subsurface acidity into 1996.

According to University of Western Australia researcher, Mark Whitten, the benefit which accrued without re-liming was partly due to an improvement of subsurface acidity from lime moving down in the soil profile.

"Newly applied lime at 1.8 t/ha increased canola yields at Kojonup from the baseline 0.7 tlha by 24 per cent, 29 per cent and 37 per cent. This was on plots that received zero, 1 t/ha and 3 t/ha of lime respectively in 1987.

"This increase is equal to an extra return of $60-$901 ha based on a price of $360/t which would more than cover the costs of liming and improve the long-term value of the land," Mr Whitten said.

Trace element question

Farmers have raised questions about the effect lime may be having on trace elements, specifically boron, copper, iron, manganese and zinc. Trace elements levels, particularly manganese in crops, should be monitored, particularly after liming.

Mr Whitten said the jury is still out on whether raising the soil pH to manage sub-surface acidity in low nutrient soils will eventually cause deficiencies. He said test services are widely available to WA growers and deficiencies can be remedied with foliar spraying so growers can maximise the benefits of liming.

When is the best time to apply lime?

Lime can be applied during the less busy times of the year, provided there is sufficient ground cover to prevent physical loss before the lime is mixed into the soil by the next cultivation or seeding operation.

Subprogram 3.4.3 Contact: Mr Mark Whitten 08 9380 2503