Global Agriculture

$3.5M national project to examine ways to boost soil organic matter

11 April 2023, AU: An innovative new $3.5 million farming system project is underway to investigate how Australian grain growers could increase the level of their soil organic matter and return carbon to the soil.

The five-year investment by the Grains Research and Development Corporation (GRDC) in partnership with Australia’s national science agency CSIRO and industry partners Kalyx Australia and Delta Agribusiness, is expected to generate international interest with its focus on improving soil organic matter through effective nutrient management using a whole-of-system approach to increase soil microbes.

This investment builds on GRDC’s commitment to support grain growers to understand and incorporate sustainable farming practices through research, development and extension (RD&E).

A 2022 independent assessment of GRDC’s RD&E portfolio determined that more than a quarter of projects worth approximately $200M were supporting the grains industry to adopt improved practices or technologies with direct environment benefits.

Looking forward, GRDC is finalising a new RDE Plan 2023-28 within which one of the four proposed pillars is ‘Thrive For Future Generations: Australia’s grains industry remains a global leader in sustainability, for people, the planet & our long-term ability to farm’.

This CSIRO-led project will identify the most effective ways to increase soil organic matter from crop residues in a dryland cropping systems and detail the cost-benefit analysis of a range of nutrient and residue management strategies for grain growers. The project will also conduct a lifecycle assessment of inputs for carbon accounting purposes.

Soil organic matter contributes to a range of biological, chemical and physical properties of soil and is essential for supplying nutrients to crops, preserving soil structure and maintaining water infiltration. Lower organic matter levels reduce soil resilience and function.

Good soil organic matter levels support higher grain yield and quality, but Australian soil organic matter levels are declining under continuous cropping cycles. Although plant residues are very high in carbon, nutrients, such as nitrogen, phosphorus and sulphur are required to break it down to build healthy soils with high levels of humus.

GRDC Sustainable Cropping Systems Manager – North, John Rochecouste says an approach to nutrient management that takes into account soil biota function and nutrient requirements could avoid the continued long-term rundown of soil organic matter.

“Retaining carbon via stubble on the ground through no-till farming practices does not always lead to an increase in soil organic matter in the ground,” according to Dr. Rochecouste.

“Additions of nutrients, such as nitrogen, phosphorus and sulphur, beyond that used by the crop, are needed to support the soil biota to ‘break down’ the stubble carbon into humus.

“This research is necessary because it offers a way to increase soil organic matter and will provide quantitative measures of the carbon benefits and the costs of achieving changes in soil carbon.

This research will test the cost and yield benefits of 10 different nutrient supply strategies at 8 sites across Australia.

CSIRO Chief Research Scientist, Dr John Kirkegaard says that the research showed a holistic approach was needed which followed a new paradigm to ‘fertilise the system, not just the crop’.

“We’re discovering that providing carbon via no-till and stubble retention practices is only part of the process and what we actually need to do is provide the microbes with the nutrients they need to grow their populations while they use the crop residue as the energy source,” he says.

“This new joint GRDC and CSIRO research project aims to find the best individual nutrient supply strategies for growers depending on their individual soil needs,” Dr Kirkegaard says.

“We’ll look at a number of factors such as nutrient types, timing and rates, positioning, and even whether we can create a nutrient supply option that targets and uses existing nutrients in soil and residue to reduce costs.

“No commercial fertilisers currently target these nutrient ratios to build soil organic matter from residue, so there’s potential for fertiliser companies to innovate in product development too.”

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