An 18-month trial of summer cover crops, including sudan grass, astro forage sorghum, millet, cow pea, sun hemp and mixed pastures, is showing promising results in Western Australia, with plans to extend the work once the trials are complete.
‘Multispecies summer cover crops for Western Australian cropping systems’ is one of eight projects under the $2.5 million Soil Extension Program, supported by the Regenerative Agriculture Alliance (RAA) at Southern Cross University and funded by the Department of Agriculture, Fisheries and Forestry (DAFF).
These industry-led projects will quantify the benefits of regenerative agricultural practices in restoring degraded soils across Australia over a three-year period.
The WA project, led by not-for-profit agribusiness organisation Facey Group, was “very successful” over the 2021/22 summer period and the 2022 growing season, according to the organisation’s chief executive officer, Dr Kelly Pearce.
Measuring success
Success was measured by the timely establishment of the crops – including sudan grass, astro forage sorghum, millet, cow pea, lab-lab, sun hemp and mixed pastures containing sunflower, buckwheat, tillage radish, brassica and chicory – in September and October. Staff also assessed their survival over the summer and autumn period on minimal rainfall. The majority of the species survived until the sites were terminated prior to seeding of the 2022 winter crops in April/May.
In the absence of summer rainfall events, the local landscape is barren over summer, but the summer crops were continuing to grow and produce biomass, thereby protecting and shading the soil and promoting microbial activity.
“Facey Group staff and producer members have increased their knowledge regarding the life cycles and suitability of various summer cover cropping species that were grown through this project,” Dr Pearce wrote in her latest progress report.
With the project now continuing towards harvest and final data collection, technical reports will be distributed early 2023.
Dr Pearce said the data analysis would provide further insight into the benefit on soil factors including health, moisture, compaction and nutrient cycling.
“Facey Group is particularly interested in understanding the benefit of multispecies summer cover cropping options compared to single species, and the subsequent production and economic benefits to the following winter cash crops,” she said.
Challenges
The key challenge for this project has been securing contractors to undertake time-critical tasks, such as soil sampling immediately prior to seeding, and seeding under the right conditions. The ideal time for seeding was in September/October when there was adequate soil moisture for establishment. Warmer soil temperatures allowing the species to germinate, without the temperatures being too high and causing heat stress in the emerging summer crops.
Facey Group invested in a soil sampling unit and drying oven to reduce the reliance on external contractors, and to improve oversight on the timing of sampling and assessments.
Other challenges included a diamondback moth infestation at one demonstration site, a result of the lack of greenery in the landscape early last summer, but pest control measures, such as spraying, were quickly implemented.
The moths were particularly attracted to the brassica species in the project, however due to the regular monitoring of sites by Facey Group staff and the host growers the infestations were noticed and treated before much damage was done, allowing the crops to quickly recover.
Potential outcomes
Dr Pearce said the preliminary results of the project indicate that summer cover crops may improve soil health and structure for producers in the Wickepin region to, thereby improving the productivity and profitability of subsequent winter crops.
Summer cover crops may also provide stock nutrition over summer and during the autumn feed gap, when stubble reserves have been used.
The rapid recovery of various species following grazing indicates the potential for multiple grazes during the summer and autumn prior to termination.
“This research is novel in the Wickepin region, so it has attracted a lot of interest from local producers and industry,” Dr Pearce said.
“We have been approached by farmers throughout the duration of this project who have trialled summer cover crops in one or two paddocks on their property and are interested in the scientific results from these experiments.
“There has also been a lot of interest in the species selection, which was supported by local specialist Dr Neil Ballard.”
“In response to the success of this project and the value that has been provided to local producers, Facey Group has plans to continue and extend on the findings from this project.”
Facey Group is planning to continue research into summer cover cropping in the Wickepin region over coming seasons, further evaluating time of sowing and species selection.
The 2021 season had extremely high rainfall for the area (approximately 540mm, compared to annual median of 398mm) which encouraged successful establishment of the summer cover crops. The ability of summer crops to establish and grow locally under a range of seasonal conditions should be evaluated.