Testing for micro nutrients to optimise yields

A wheat head (foreground) with discoloured and shrivelled grain from a copper deficient crop. Growers with good crops have been encouraged to test for trace element deficiencies before it is too late to take action.

A wheat head (foreground) with discoloured and shrivelled grain from a copper deficient crop. Growers with good crops have been encouraged to test for trace element deficiencies before it is too late to take action.

Grain growers on the south coast and lower Great Southern experiencing good seasonal conditions have been reminded to tissue test for micro nutrients to optimise crop yields.

Micro nutrient or trace element deficiencies, such as copper, manganese and molybdenum, have been reported in Western Australia and can result in significant yield losses.

Department of Primary Industries and Regional Development principal research officer Ross Brennan urged growers to test their crops soon so they would be in a good position to apply a foliar application late winter.

Dr Brennan said testing was important, as crops often showed few symptoms of micro nutrient deficiencies.

“A series of 25 department trials across the Great Southern to the Esperance region in the past three years showed that although there were few crop symptoms of deficiencies, micronutrient applications frequently resulted in yield increases of 25 to 30 per cent,” he said.

“This was particularly so for copper, one of the most damaging micro deficiencies, where leaf symptoms were observed infrequently but grain yield losses of up to 30 per cent were recorded.”

Dr Brennan said crops might be at risk of deficiencies if micro nutrients had not been applied in the past 15 years.

“Some paddocks have been continuously cropped with compound fertilisers that have low levels of copper in the fertiliser mix,” he said.

“There is also a risk that copper deficiencies in wheat and barley crops could be exacerbated by the application of nitrogen in paddocks with marginal supplies of copper in the soil.”

Dr Brennan urged growers with high yielding crops to take plant samples as soon as possible and send them to a laboratory accredited by the Australasian Soil and Plant Analysis Council.

“Tissue testing assesses the status of micro nutrients of the plant by examining the whole tops and-or the youngest emerged leaves, taken at the five-to- eight leaf stage of wheat,” he said.

“While it is cheaper to take a sample of the top of the crop, the most accurate result is achieved from sampling the youngest leaves on the plant.

“Then growers can be well armed with information to determine whether they need to act to ensure their crops have adequate plant nutrients to achieve yield potential.”

Dr Brennan said foliar sprays were highly effective in correcting micronutrient deficiencies.

“Unlike copper applied to the soil, foliar applications have little or no residual effect so it is still important to follow up foliar treatments with a granular copper fertiliser for next year’s crop,” he said.

Dr Brennan said micro nutrient applications were well worth the investment, as they had a long residual value that will last for at least 20 years.

“Having adequate supplies of the micronutrients in soils that are moist is the best insurance that the current crop will have adequate supply for grain yield,” he said.

“If growers know their crop is likely to be deficient it is best to apply micronutrients as a solid fertiliser at seeding.”

For more information about tissue testing for micro nutrients visit agric.wa.gov.au and search for ‘monitor plant nutrition levels.’