Building soil resilience & carbon through plant diversity

WHY THIS PROJECT IS NEEDED

Farmers are looking to improve soil resilience to enable sustained or improved productivity in an increasingly variable climate. Farmers can improve aspects of soil health by increasing the range and diversity of plant species grown in a rotation, either by sowing different species as cover crops, through companion cropping, or by planting different species within a broadacre crop rotation.

This project is measuring the effects on soil function of increasing the diversity of species grown under a range of cropping systems in the Riverine Plains.

In short: The project investigates the impact of using different species in cover cropping, intercropping, and crop rotations on soil resilience, carbon dynamics, and productivity.

Project focus

The project aims to determine the medium-longer term contribution of cover cropping, intercropping and crop rotation to soil resilience and carbon dynamics, and cropping system productivity. It follows on from the Increasing plant diversity project.

The project investigates changes in soil function, soil resilience and carbon stocks under a range of agronomic practices that incorporate plant diversity in cropping systems in the medium term (4-7 years).

The project also investigates how much photosynthate (i.e., carbon from rhizo-deposits) from cover crop and intercrop species is stabilised in soil, and its contribution to soil aggregation.

The project trial is being hosted an existing long-term field site at Burramine, Victoria.

A similar, long-term field site has been established by Central West Farming Systems and at a site established by Birchip Cropping Group. Further, the project will determine appropriate fertiliser reductions in cane crops following mixed species cover crops at Ingham, in conjunction with Herbert Cane Productivity Services.

Project outcomes

The project will determine the long-term impact of plant diversity on soil carbon dynamic, quantify the stability and role of rhizodeposits (e.g. root exudates) on soil carbon, aggregate formation, and soil microbial communities and optimise intercrop mixes to enhance soil resilience. 

Longer term, the project aims to identify agronomic interventions that increase plant diversity in cropping systems that can improve soil resilience and sustain or increase system productivity. The project ultimately aims to increase carbon levels and resilience in Australian cropping soils. 

Interim results from this project have been published in Research for the Riverine Plains, 2025, with the article describing how summer cover cropping, temporary intercropping with vetch and synchronous intercropping with beanola and peola, are affecting soil nitrogen, biomass and yield, as well as soil fertility and carbon.

Key messages from the trial are that:

• Temporary intercropping, (when two crops are sown in the same paddock at the same time, before one is terminated) and synchronous intercropping (when two crops are sown and harvested at the same time) are promising methods for building diversity in cropping systems, especially where traditional cropping practices such as tillage or monocultures have led to a decline in soil fertility and soil carbon.
• Variable summer rainfall at the Burramine trial site highlighted the difficulty in establishing summer cover crops, with overall biomass production highly dependent on follow-up rainfall.
• Summer cover cropping was associated with an emerging trend for declined water availability at the time of winter crop sowing, as well as yield penalties. 
• Temporary intercropping with vetch did not reduce the yield of wheat sown at the same time in this trial.
• While temporary intercropping showed a small additional biomass gain, there has been little-to-no impact on soil health or carbon to date.
• Future work needs to quantify the variability of biomass and yield production in these systems and relate this to soil nutrient and carbon cycling (resilience). 

There's a lot more to this project- learn more by reading the full article: Investigating summer cover cropping and intercropping to improve soil health, productivity.