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Professor calls for shift to diversified farming to boost profit and sustainability

Melbourne University Professor Tim Reeves has called for changes to Australian farming systems.
Photo: Nicole Baxter

Melbourne University Professor Timothy Reeves says building soil carbon and nitrogen is critical.

An experienced agricultural research and extension specialist has outlined the need for major changes to Australian farming systems to secure the industry's long-term profitability and sustainability.

Melbourne University Professor-in-residence at Dookie Campus, Timothy Reeves, told growers, researchers and advisers gathered at the 2020 GRDC Update at Wagga Wagga that global population was growing at rate of 150 people a minute.

"To nourish a global population still growing, our current and future agri-food systems must provide more nutritious food from less land, less energy-rich inputs, less greenhouse gas emissions and all of this under the spectre of the multiplier effects of climate change," Professor Reeves said.

"Clearly, business-as-usual will not be acceptable and the world is now looking to the sustainable intensification of agri-food systems to produce more with less."

Our farming systems need to be more diverse and resilient, he said, and soil nitrogen and carbon levels need to be rebuilt.

Twin goal

Professor Reeves outlined the concept of 'sustainable intensification', saying it involved simultaneous increases in agricultural productivity and ecosystem health.

It is characterised by:

  • conservation agriculture: minimum soil disturbance, mulches, integration of crops, forages, livestock, trees and shrubs;
  • healthy soils: integrated soil nutrition management, building soil carbon and nitrogen;
  • improved crops, varieties, livestock and breeds: high productivity, input-use efficient, resistant or tolerant to abiotic and biotic stress, more nutritious products;
  • efficient water management: 'more crop per drop', reduced water use, system or landscape efficiency; and
  • integrated pest management: diverse systems, genetic resistance, judicious use of safer pesticides at the system, farm and landscape levels.

Professor Reeves said a fundamental step in moving towards sustainable intensification involved more diversification within the farming system.

"The canola/wheat rotation which dominates cropping farms is not a diverse system," he said.

"Research has shown fertiliser nitrogen losses can be reduced by the use of more biologically fixed nitrogen from pasture legumes and pulses."

The advantage of pasture rotations, he said, is they help rebuild soil carbon and in doing so also sequester carbon dioxide.

Professor Reeves said Australia had a dependency on nitrogen-based fertilisers and yet nitrogen losses from fertiliser were a major cost.

During the 1960s, he said, a rule-of-thumb was that for every kilogram per hectare of nitrogen applied as fertiliser, about 19 to 20kg/ha was supplied from pasture as biologically fixed nitrogen.

"Now, the ratio is about 4:1, which means we are using more nitrogen fertiliser than biologically fixed nitrogen," he said.

"That is a huge change, but is that where we want to be in a risky climate and marketplace?"

Nitrogen deficit

Professor Reeves said a consequence of less biologically fixed nitrogen was a growing soil nitrogen deficit.

"We are mining enormous amounts of nitrogen from our systems and we are not taking note of this in our financial calculations," he said.

To arrest the decline, he encourages growers to consider planting 'double-break' crops which may involve sowing canola after a brown-manured pea.

"If we want to build soil nitrogen more dramatically and sustainably, growing a clover-ley pasture will enable soil nitrogen to spiral upwards. This is in contrast to the spiralling-down trend we are now seeing on many farms."

Genetic focus

Professor Reeves said greater emphasis needed to be given to genetic attributes to boost the success of sustainable intensification. These include the continuing development of crops with resistance to biotic stresses such as fungi, bacteria, viruses, parasites, weeds and insects.

Going forward, this would mean developing crops with:

  • enhanced tolerance to frost and heat stress;
  • greater input use efficiency (water, nutrients and elevated carbon dioxide);
  • improved adaptability to mixed farming systems (grazing and grain crops); and
  • added nutritional value.

Water use

Although water use efficiency was already high on many Australian farms, he said there was significant scope for improvement.

"An excellent example of system adaptation to achieve efficient water management is summer weed control," he said.

"Another example is the re-introduction of long fallows."

Pest management

Professor Reeves said another component of sustainable intensification was the use of integrated pest management.

"Resistant weeds, pests and diseases are telling us we need to do things differently," he said.

"GRDC's investments in harvest weed seed control, better rotations and cover crops are examples of non-chemical ways of getting on top of herbicide resistance."


Professor Reeves outlined the work of Melbourne University Associate Professor Graham Brodie at Dookie Campus, who has been developing microwave weeding technology for the past 12 years.

He said significant investment from GRDC and private sector partners had seen the technology move toward commercialisation with the hope of developing a broadacre machine.

The microwave weeding technology aims to kill emerging weeds and weed seeds in topsoil. Research is also underway to measure any soil changes after microwave treatment.

Critical juncture

Professor Reeves said he believed the grains industry was at a critical decision point.

"Sustainable intensification is the sensible scientific pathway to building more efficient and diverse systems to help rebuild soil carbon and nitrogen levels," he said.

"The scientific pathway to more regenerative agriculture involves a focus on 'incremental transformation' as described by CSIRO's Dr John Kirkegaard."

Implementation of sustainable intensification, he said, might initially involve adding a pulse to the system, using a brown manure crop or growing a double break.

The next step, he said, might be adding a pasture legume and livestock into the system, and incorporating perennials to take advantage of summer rain.

"Well-structured soil facilitates improved nutrient cycling and water holding capacity, which in turn results in a more resilient system for crops and livestock," he said.

"We need to develop our soils so they can store summer rainfall. Compaction is an issue on many farms, as is acidity, and if we don't address these now they may become too costly to remediate down the track."

More information: Timothy Reeves, 0439 452 377,

Further reading: GRDC Update Paper: Is sustainable intensification of cropping systems achievable?

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