Future-proofing our soils

July 21, 2020

New research from the Soil CRC is showing how we can naturally care for the fragile soils of Australia, the mainstay for our food, biodiversity and water future.

Australian soils are subject to many kinds of stress, such as compaction, erosion and low rainfall. Poor soil can have a huge impact on our agricultural productivity.

The CRC for High Performance Soils (Soil CRC) is bringing together scientists, industry and farmers to research practices that help farmers to improve their soil. The CRC includes university, farmer group and state government partners.

“The CRC is bringing new technologies and ideas into farming systems with the goal of making them more resilient,” says Dr Lukas Van Zwieten, who leads a Soil CRC program focusing on applying research to solve multiple soil issues at once. “This means farms may function for a longer period going into water stress and when the drought breaks, they bounce back more quickly.

“Water is the main limiting factor for crop and pasture productivity in Australia,” adds Van Zwieten. Compaction due to large machinery used on farms can compound these issues, as can soil chemical constraints such as sodicity, which make it harder for water to penetrate the soil.

Natural improvements

Once farmers harvest their crops, farmland can remain fallow for months or even years. Soil CRC researchers — including Professor Terry Rose at Southern Cross University, one of the project leaders within the program — are looking at using that time to grow plants specifically selected to improve soil resilience. They have trial plots for sugar cane and grain crops across Australia, including in northern Queensland, New South Wales and South Australia.

“Sugar cane production in northern Queensland is often affected by pests called nematodes, which eat the sugar cane roots,” says Van Zwieten. “So CRC researchers are trialling the use of a kind of mustard plant that has biofumigant activity to decrease the amount of these nematodes in the soil.”

The researchers are also trialling using cover crops that add extra nutrients to the soil when they break down. One of these plants is a large legume called Sunn Hemp or Indian Hemp (Crotalaria juncea) which can fix its own nitrogen from the atmosphere. It also has a large root system that creates a lot of biomass, becoming food for microbial life.

“Like any other animal, microbes have to eat,” says Van Zwieten. “And what they eat is organic material. Like you or I might eat a piece of bread, microbes eat organic compounds exuded from roots and the biomass from plant matter left over from the harvest. 

By growing cover crops, farmers can maximise organic inputs into soil, increasing microbial abundance and biodiversity, and potentially increase plant-available nutrients for future crops across Australia.”

CRC researchers are also using plants to physically open the soil to reduce compaction. “The tillage radish has a large taproot which basically opens the soil. As it breaks down, you get large holes in the soil, so when it rains you’ve got an easy pathway for water.”

The CRC researchers will test the soil in a lab to see how it performs when exposed to water stress. “We are hoping these mixed-species cover crops will result in bigger, better yields and yields that might be more resilient to weather variability,” says Van Zwieten. “That’s what farmers need.

“Where farming systems or chemical inputs are becoming more difficult to use due to restrictions and cost, these types of alternative management practices are becoming more important.” 

— Cherese Sonkkila


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