Australian growers are removing more potassium (K) from their soils than they are putting back, putting crop performance at risk.
To help address this, the Grains Research and Development Corporation (GRDC) is investing $5.8 million in a project led by The University of Queensland (UQ). The aim is to help growers manage potassium loss and adjust fertiliser decisions accordingly.
GRDC Sustainable Cropping Systems Manager Dr Cristina Martinez said crops often remove more potassium, a nutrient vital for water regulation and nutrient transport in plants, than what is added as fertiliser.
K deficient soybeans. Photo: Mike Bell
"This ongoing loss is making more farmland marginal or deficient in potassium. It's been a known issue in sandy soils, but now we're seeing it in heavier soils too," Dr Martinez said.
Adequate potassium nutrition helps plants withstand stress from drought and disease pressure, while deficiencies can result in stunted growth, reduced root development and overall yields.
"This project will help growers spot potassium deficiency early and apply the right fertiliser, in the right place, at the right time. It's about giving them practical tools and advice to improve fertiliser use efficiency and get the best return on investment."
K deficient sorghum. Photo: Mike Bell
The four-year project, with a total value of $9.4 million, will deliver clear recommendations and testing guidelines for growers, backed by new research to ensure the advice is up to date and reliable.
It will establish a clear understanding of the issue in eastern Australia – measuring how well crops take up potassium fertiliser in different soils over multiple years. It will also look at how soil type and mineralogy affect potassium availability, using lab work, glasshouse studies and field trials.
This project complements research already underway in Western Australia through the Soil Water and Nutrition (SWAN) collaboration, where the focus is on lighter, sand-textured soils.
UQ's Professor Michael Bell, who heads up the project, said potassium is an essential plant macronutrient.
"Even though crops absorb a lot of potassium (similar to nitrogen), only a small amount is actually removed when the crop is harvested. The exception is when crops are harvested for hay which removes nearly all the potassium," Professor Bell said.
Professor Michael Bell, who heads up the project, said potassium is an essential plant macronutrient. Photo: GRDC
"For grain crops, most of the potassium stays in the leftover plant material and returns to the soil. In sandy soils, it can move deeper with water. But in heavier soils, potassium tends to stay near the surface.
"How potassium is spread through the soil affects how well crops can access it, especially depending on when and where the soil is moist."
Professor Bell said the project will test how crops respond to potassium fertiliser in different soil types and regions in the northern and southern grains region.
"The relationship between soil test potassium status and fertiliser responses will be used to improve indicators of deficiency and likely responses to future fertiliser application," he said.
"We'll also undertake more detailed research to explore the effectiveness of different application strategies (broadcast, drilled, deep banded and foliar), the residual value in subsequent crop seasons and the efficiency of recovery of applied K fertiliser."
Project research partners include NSW Department of Primary Industries and Regional Development; Department of Primary Industries, Queensland; University of New England; South Australian Research and Development Institute; and University of South Australia.
