Time right to test for copper deficiency
Date: 02 Jun 2016
Copper deficiency is one of the most damaging micronutrient deficiency issues in the WA grainbelt.
Department of Agriculture and Food WA (DAFWA) scientist Ross Brennan, who is leading a Grains Research and Development Corporation (GRDC) funded micronutrient project in WA, said grain yield losses from copper (Cu) deficient soil could be up to 20 per cent.
“While we are not seeing the severe Cu symptoms of 30 to 40 years ago, slight Cu deficiencies are now common in WA agricultural soils due to today’s intensive cropping systems,” he said.
“Although Cu lasts a long time in the soil, slight to mild deficiencies of this nutrient are often diagnosed and result in many growers losing several thousand dollars’ worth of crop annually.”
Dr Brennan said wheat and barley were more susceptible to low soil Cu levels than crops such as canola, which was more efficient at accessing the nutrient.
“Also, nitrogen (N) application where there is a marginal supply of Cu in the soil will exacerbate Cu deficiency in wheat and barley,” he said.
Dr Brennan said symptoms of slight Cu deficiency included the leaf tip of younger leaves – frequently the flag leaf – dying back and sometimes forming a ‘needle tip’.
“For tissue testing, analysis of whole tops and/or youngest emerged leaves – at the five to eight-leaf stage of wheat – allows Cu status to be assessed,” he said.
Dr Brennan said tissue testing at this stage of crop growth provided enough time for Cu foliar sprays to be applied before flowering, when Cu was needed for pollen and grain formation.
He recommended the following management for Cu tissue testing results:
- Cu concentrations less than about 1.5 milligrams per kilogram (mg/kg) parts per million (ppm) mean the crop is deficient in the nutrient and a foliar Cu spray should be applied before flowering, followed by a soil application of granular Cu fertiliser for next year’s crop
- Cu concentrations greater than 1.5mg/kg and less than 2mg/kg mean the crop is highly likely to develop Cu deficiency before maturity. A foliar Cu spray should be applied before flowering, followed by a soil application of granular Cu fertiliser for next year’s crop
- Cu concentrations of 2-2.5mg/kg in the young tissue is usually acceptable at the booting stage of crop development. But if the sample was taken before the five-leaf stage, high levels of N have been applied and growing conditions are excellent, Cu deficiency may develop. If conditions of high N and excellent growing conditions have occurred up to the late booting stage, then arrange for further leaf tissue testing and apply a foliar Cu spray if there are low to marginal Cu levels
Dr Brennan said early season foliar sprays were highly effective in correcting micronutrient deficiencies.
“However, unlike soil-applied Cu, foliar Cu applications have little or no residual effect, so where there is deficiency it is still important to follow up with a granular Cu fertiliser for next year’s crop,” he said.
Dr Brennan said tissue testing should be conducted by laboratories accredited by the Australasian Soil and Plant Analysis Council (ASPAC).
More information about diagnosing and managing Cu deficiency is available in the GRDC western region Wheat and Oats GrowNotes via this link, in the GRDC Hot Topic Micronutrients in the western region via this link or by searching ‘copper deficiency’ on the DAFWA website via this link.
The research project ‘Managing micronutrient deficiencies in cropping systems of WA’ is part of the More Profit from Crop Nutrition (MPCN) II program and aims to address concerns that micronutrient deficiencies may be increasing in the WA grainbelt.
Dr Ross Brennan, DAFWA
08 9892 8444
Natalie Lee, Cox Inall Communications
08 9864 2034, 0427 189 827
GRDC Project Code DAW00239