Soil project eyes 1t/ha gain

Headshot of Cally Dupe
Cally DupeCountryman
The $22 million project will initially focus on cereals before expanding into other local crop rotations.
Camera IconThe $22 million project will initially focus on cereals before expanding into other local crop rotations. Credit: Cally Dupe

Researchers driving a $22 million soil amelioration research project have set the ambitious target of boosting farmers’ grain yields by at least one tonne per hectare.

Subsoil compaction, acidity, and water repellance are the bane of fertile soil, leading to shallow crop root systems and poor access to subsoil water for plants.

Those specific constraints could lead to a 50 per cent gap between potential and actual grain yield, according to Grains Research and Development Corporation.

GRDC and Department of Primary Industries and Regional Development are trying to work out the most profitable and long-lasting strategies to manage these constraints in sandy, gravel and duplex soils, which are common in WA’s Central, Great Southern and South Coast grain-growing areas.

The new, five-year project will explore combination techniques and full soil re-engineering, including liming, deep ripping, spading and soil inversion.

Titled, “re-engineering soils to improve the access of crop root systems to water and nutrients stored in the subsoil”, the project was announced in February as part of a $48 million partnership between the State Government-funded DPIRD and GRDC.

Researchers plan to build on previous DPIRD and GRDC findings which identified the benefits of soil amelioration, but the main focus is on how re-engineering the soil profile could optimise water use and nutrient supplies.

Project leader Stephen Davies, who works at DPIRD, said soil amelioration in WA was most common on deep and sandy soils, up to a depth of 40cm, “with good results”.

“The potential benefits of re-engineering the profile to a depth of 80cm is unknown,” he said.

“This project will assess whether the fundamental redesign of the soil profile through soil re–engineering can achieve dramatic improvements in critical measures of cropping performance.

“This includes water and nutrient efficiency, grain yield and grower profitability.”

Dr Davies said if soil re-engineering could overcome a one to 1.4 tonne per hectare yield cap on just 20 per cent of the 12 million hectares of sandy, gravel and duplex soils, it would generate an extra $600 million to $840 million a year in yield benefits for WA grain growers.

Soil amelioration work at the project sites started in April, with seeding in May and June. Plot sizes vary from 0.5ha to 2ha, initially with cereals before later including other local crop rotations.

The work will include at last 10 field trials across WA’s grain-growing areas, as well as glasshouse and laboratory experiments at DPIRD’s Northam Grains Research Facilities.

Dr Davies said not all of the trial sites had been determined, but duplex soils were common through the Central, Great Southern and South Coast grain-growing areas.

Some existing, long-term soil amelioration trials will be re-ripped and re-limed, to provide data on crop and soil responses, and financial returns over an extended period.

Dr Davies said a key aim was to upgrade DPIRD’s Ranking Options for the Soil Amelioration financial modelling tool to incorporate the economic benefit of soil re-engineering.

“ROSA is a valuable tool to help growers understand the costs and benefits of soil amelioration and re-engineering strategies,” he said.

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