Dry periods during the growing season in Western Australia's grainbelt in recent years have heightened grower interest in improved diagnosis and treatment of micronutrient deficiencies, to better inform decision making.
While decision support packages are common for macronutrients including nitrogen and phosphorus, there is still some uncertainty surrounding micronutrient decision making.
A two-year project with Grains Research and Development Corporation (GRDC) investment, led by the Liebe Group, aims to determine the requirements for and benefits of micronutrient foliar application in medium-to-low rainfall areas of WA's Northern Agricultural Region (NAR).
Liebe Group executive officer Rebecca McGregor said research into micronutrients had previously been conducted in the WA grainbelt, but much of this work had been in medium to high rainfall areas in southern and central cropping regions.
"Establishing a data set for our area would help local growers to make informed decisions about micronutrient fertiliser type, rate, timing and placement, that may improve the yield potential of their crops," she said.
"Many growers believe crop-limiting micronutrient deficiencies are occurring in their paddocks and they want to know why this is happening and what strategies or practices are needed to address this."
Ms McGregor said plant tissue testing remained a critical tool for diagnosing micronutrient deficiencies but was not widely used by growers, and the project also aimed to increase understanding of the benefits of utilising this decision support tool.
A 2018 Liebe Group survey of 25 farm businesses in the region confirmed that many local growers believe their crops have micronutrient deficiencies.
"Of the growers surveyed, 44 per cent believed their crops were deficient in micronutrients, and of these, 90 per cent thought zinc (Zn) and copper (Cu) deficiencies were limiting crop potential, and 33 per cent perceived that Zn, Cu and manganese (Mn) were limiting crop potential," Ms McGregor said.
"Ninety two per cent of surveyed businesses used a compound fertiliser including Zn and Cu in trace amounts, and of these businesses, 24 per cent additionally used foliar-applied Zn and/or Mn, and 20 per cent also used a seed-applied product or a liquid micronutrient product banded at seeding.
"Most of the perceived deficiencies were on deep sandy earths and sandy duplex soil types."
Ms McGregor said the project was collecting and analysing plant tissue data from the region in order to gain a greater understanding of the actual scale and impact of micronutrient deficiencies.
She said 100 wheat paddocks, comprising a total of 400 sites, had been sampled across the region in 2018, a year in which most farms in the area had received good growing season rainfall.
"Plant sampling, conducted at the mid tillering stage, showed 17 per cent of plant samples had Zn levels considered to be marginal, with only 5 per cent considered deficient, and 6.75 per cent of samples had marginal Mn levels, with 2.25 per cent considered deficient," she said.
"No copper deficiencies were identified in the plant sample survey."
In 2019 the project will establish a demonstration site which will explore the impact of timing and rates of foliar micronutrients (Zn, Mn and Cu) on a wheat crop in the Latham region
Information about monitoring plant nutrition levels, including micronutrients, is available on the DPIRD website
