Developing a nutrient calculator for organic soil amendments

Farmers to benefit from cross-industry decision support tool

Compost application at a field demonstration site at Laidley. Picture: Supplied.

Compost application at a field demonstration site at Laidley. Picture: Supplied.


A new nutrient calculator will provide farmers with the true nutrient and fertiliser replacement value of organic soil amendments.


New research is being conducted to develop an integrated nutrient calculator that provides farmers with the true nutrient and fertiliser replacement value of organic soil amendments.

Led by the Queensland University of Technology, and working with agronomists and researchers from the University of Queensland, Deakin University and La Trobe University, the project will develop a cross-industry, user-friendly decision support tool.

QUT Associate Professor David Rowlings said while there is general agreement within the farming and agronomic communities on the benefits of applying organic soil amendments, there is little understanding on how to effectively integrate the plant nutrient value of these products into existing farm nutrient budgets.

"Being left to their own devices, it can be difficult for growers to determine on which soil types, for which crops or in which situations across their farm they may gain the most advantage from using a particular manure or compost type," Assc Prof Rowlings said.

"Year on year application of set rates of organic amendments, without consideration of soil nutrient content and crop nutrient use, can result in soil nutrient imbalances and are not consistent with the principles of good farming practices and precision agriculture.

"Animal manures, even from within the same industry and production cycles, are diverse in their age, nutrient composition, density, moisture content, organic matter quality and decomposition rates, so it is difficult to develop prescriptive management recommendations.

"To complicate matters even further, composted or digested products have very different characteristics to raw manures, and exhibit very different nutrient release patterns."

These barriers, which are preventing farmers from accounting for the value of the nutrients in animal manures and other organic amendments, such as composts, are being addressed via a new, $3.5 million national research program funded through the federal Department of Agriculture's Smart Farming Partnerships Program and Meat and Livestock Australia, together with a consortium of farming, composting and state government project partners.

Director of the Centre for Recycling of Organic Waste and Nutrients at University of Queensland, Johannes Biala, said the farmer-ready tool will calculate not just the total amount of nutrients contained in these products and supplied at a given application rate, but also provide the timing of nutrient supply over time and the subsequent potential for reducing mineral fertiliser inputs.

"The aim of this work is to investigate the integrated use of aged and composted feedlot manure, aged chicken litter, aged dairy manure, composted layer manure, composted piggery pond sludge and urban derived compost within conventional crop nutrient programs," Mr Biala said.

"Field demonstration sites are focusing on the fertility and soil conditioning gains various organic amendments may offer, and, in combination with laboratory incubation trials, provide best nutrient supply estimates for these products.

"Furthermore, gaseous nitrogen losses during a cropping cycle are also determined in intensively researched field sites where vegetables, cotton and grain are grown."

Commenced in late 2018 and running until 2020, Mr Biala said the recommendations generated by the calculator are being demonstrated at 12 on-farm sites using 15 different commercially-available organic amendments.

"The trial and demonstration sites are located in some of Australia's most productive agricultural regions and close to ready supplies of organic amendments," Mr Biala said.

"The field sites encompass Australia's major agro-ecological climatic zones, soil types and industries, with Queensland farm sites located in the Lockyer Valley, on the Darling Downs and in the central south-west.

"The farm types include intensive vegetables, broadacre cropping, fodder crops and cotton, and the efficacy of organic amendments is being assessed using a standardised treatment and data collection protocol.

"These sites provide comprehensive on-farm demonstration to farmers on how to reduce mineral fertiliser input costs, while improving yield and soil health outcomes and reducing environmental impacts."

Additional sites are located in the Murrumbidgee Valley, NSW, greater Melbourne and Geelong region of Victoria, and Limestone Coast, South Australia.

The project will include a series of demonstration days and workshops on managing various organic amendments in each region.


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