Cover Crop Project Summary 2022
The objectives of the project were to investigate, test and communicate the suitability of multi species cover crops in a range of environments across south-eastern Australia. Activities measured the impacts cover cropping had on soil health. Soil analyses were selected to both test relevant and innovative soil health and biological parameters such as nitrogen cycling pathways and microbial community structure, and place these in the context of more traditionally understood agronomically-important soil properties. In addition, cover species suitable for environments across south-eastern Australia was investigated and cover crop termination methods were compared.
Outcomes achieved were efficient knowledge transfer to growers, facilitating optimum cover crop choice and termination methods suited to their farming systems and environment, and improved understanding of soil fertility, structure, biological health, and invertebrate impacts across south-eastern Australia for improved farm resilience and profitability.
This project was severely impacted by drought, hailstorms, bushfire and the Covid pandemic however the resilience and determination of the grower group network involved in the project meant that alternative methods of extension were developed and delivered including meeting in smaller groups at the local level; becoming proficient in using video conferencing; and using social media platforms and SMS messaging to a much greater degree.
A range of specific practical findings observed from the project for the benefit of farmers in south-eastern Australia include:
- Seed varieties that were certain performers were French white millet, tillage radish, buckwheat and sunflowers.
- Tillage Radish assisted with breaking up soil compaction, by producing ground penetrating tap roots combined with strong lateral roots although it was somewhat limited by soil strength in soils with very low moisture retention.
- Top growth of Tillage Radish produced very good biomass to be used for mulching or stock grazing.
- Tillage Radish carry-over did become a host for cutworm and in the absence of spraying it seemed to become the preferred target to the benefit of other crop types
- It was confirmed that aerial spreading of cover crop seed prior to harvesting a crop in Spring can be successful on Kangaroo Island.
- Glyphosate provided certain termination of the cover crop in the trials whereas the roller crimper was only effective dependent on plant growth, stem thickness and strength.
- Spring sowing showed better results than summer sowing for warm season cover crops, although not viable in every year, could be included when conditions are suited.
- Soil aggregation visually improved at the Waikerie site under multi species by trial’s end. Diversity appeared to have triggering improved soil culture with minimal inputs.
- In some of the multi seed mix trials ryegrass and oats dominated depending on soil depth. The resulting cover crop canopy shaded out competition leading to a reduced winter/spring weed presence.
- Mallee region multi-species plots developed improved soil aggregation and infiltration characteristics over the project duration.
- Summer cropping at the Langhorne Creek site demonstrated that tillage radish, faba beans, wheat, cereal rye, oats and sunflower were realistic options. Rye grass dominance impacted these crops reaching full maturity.
- Crop species linked some isolated observations which demonstrated pest suppression or reduced risk of pest outbreaks.
- Following two years of cover crop treatments, spring barley in 2020 showed up some quite visual biomass differences at the Sister’s Creek site, Tasmania.
Multi Species Demonstration Trials Analysis
The main finding of the soils and agronomy analysis on the cover crop demonstration trials is that whilst expectedly climate driven (the most successful sites generally had the highest rainfall, and the least successful had the lowest).
Whilst at several of the lower-rainfall sites there was a negative impact on crop yield, this was not observed at most sites, and indeed yield increases (where data was available) were observed at a similar number. Whilst growing a summer cover crop likely utilises some soil water which may impact eventual yield of winter crops, reduced soil moisture did not appear to impact yield at most sites in what was mostly a reasonable growing season in 2021.
The main biogeochemical finding we observed was a decrease in nitrate-N at many of the cover crops sites, accompanied by an increase in both dissolved organic N (DON) and microbial biomass N (MBN), as well as proteolysis and amino acid uptake. Taken together, these findings suggest that cover cropping has reduced the concentration of the most lossy form of plant-available nitrogen (nitrate), whilst also increasing the amount of N that is potentially available (DON + MBN), and its rate of delivery (proteolysis and amino acid uptake). Assuming that cover crops can be integrated into systems without imparting either a yield penalty or excessive monetary cost, this finding suggests that they may act to reduce N losses, retaining N in an easily mineralizable form, and increasing the rate of that mineralisation.
Collectively, the demonstration sites can be grouped by rainfall into three categories:
Low rainfall. These sites will typically not benefit from the integration of summer cover crops unless there is either exceptional summer rainfall to support an opportunistic planting that is carefully monitored for water usage. Cover crops may be suitable (single or mixed) when sown in winter in place of a cash crop. However, if biomass is then harvested for hay or grazed, their positive impact on soil function would likely be reduced (whilst noting their contribution to the farm business through the provision of biomass/fodder). For summer cover crops in these environments there is a risk that soil health outcomes may actually regress due to excessive water use curtailing growth and carbon input from the following winter cash crop.
Medium rainfall. These sites may benefit from either summer or winter cover crops, though care would need to be taken when looking towards growth in the summer season to avoid a water penalty for the following winter crop. Nonetheless, it is apparent that within the context of the short study period this project allowed, there are positive, neutral, and negative outcomes across the medium rainfall sites.
High rainfall. These sites (found on the eastern side of the LEP, KI, Vic and Tas in the present study) showed the most consistently positive outcomes, with many suggesting an increase in cash crop yield as well as multiple soil health benefits, even after the relatively short time period afforded by the project. Care would still need to be taken regarding excessive water use.
Out of the higher rainfall sites, the site at Stokes Bay (KI) showed most promise, with a 1 t/ha increase in yield of the oats cash crop following 1½ summers of mixed species cover crop. Notably, even after such a relatively short adoption period, this also resulted in an increase in SOC concentration in the 10-20 cm and 20-30 cm layers (refer to chart below), with the lower of these two depths being a statistically significant increase.
Multi Species Demonstration Trials Invertebrate Analysis
The inclusion of polycultures, such as inter-cropping or cover cropping, may have multiple benefits under Australian conditions where fields are large, and there is a need to diversify crop cultivars, type and flowering time to minimise the risk of crop failures in dryland systems. This is essentially a means of spreading risk by incorporating a diverse mixture containing species that succeed more in wetter and drier conditions, ensuring that a species that can capitalise on prevailing conditions is present regardless of the eventual rainfall. What was clear is management needs to understand the context in which it is being applied and its tolerance to sporadic risk if pest threats are less where plant diversity is increased on farm.
Cover Crop Species Evaluation
The species evaluation trials demonstrated that even in southern Australia’s dry climate, multiple species with differing growth traits were found to tolerate these conditions, either as summer or winter options. At one site (Minnipa), additional work was undertaken to assess the relationship between the winter cover crops, soil properties, and yield of the following winter cash crop after an intervening summer fallow period. This found that mixtures of 3-6 cover crop species resulted in greater wheat yield in the following winter season as a result of greater inputs from the cover crops retaining more soil moisture and increasing the amount of slow-release nitrogen.
Information on potential suitability of cover crop candidates for south-eastern Australia was compiled at the start of the project. This provided information about different plant species to ensure the best outcome planning and implementing cover cropping pursuits. The evaluations were based on a species’ suitability as a cover crop, rather than for its cash crop performance.
Cover CropTermination Summary
The termination trials showed that whilst in certain situations non-chemical (knife roller) means of termination could be effective, chemical means of termination was most successful. In some areas, crops effectively “self-terminated” due to lack of water, which from a disease, weed, and pest management perspective, has the desired outcome without chemical or labour inputs.
Communications & Extension
The extension and communications plan for the project was developed and implemented on a three-tier engagement process, at paddock level through small plots and demonstration trials; then how this translate to the whole farming system through engagement with the farming systems groups; and then to the broader farming community through farmer champions who hosted the demonstration trials and the participating farming systems groups through their existing communications channels and extension activities.
The project steering committee kept a motivating partnership with the collaborators and delivery partners. By being involved with their communication and extension activities enabled the project to deliver an extensive range of activities and reach a broad audience. Project outputs are summarised in the table below.
Baseline and end of project evaluation of knowledge and confidence relating to the science of mixed species cover crops and giving advice was conducted with representatives from the collaborating organisations. The eleven project collaborators have a direct influence on over 2,000 farm group members in south-eastern Australia plus social media connections with over 11,000 account holders.
Monitoring and Evaluation
The project set up a range of mechanisms to monitor the progress and evaluate the success of the project. A baseline and end of project survey was conducted with project collaborators asking the following questions:
- Rate your knowledge of applying multi species cover crops in farming systems (1 – Very poor, 2 – Below Average, 3 – Average, 4 – Above Average, 5 – Very Good).
- How confident are you about giving advice to your peers and/or farmers about incorporating multi species cover crops in farming systems (1 – Would not give advice, 3 – Confident to give some advice, 5 – Very confident to give advice)?
- Rate your knowledge (1 – poor, 3 – average, 5 – very good) of the impacts of cover cropping on:
- Soil health
- Nutrient cycling and stratification
- Organic carbon and fractions
- Soil moisture
- Economic benefits to following cash crops
Results of the evaluation are presented in the table below. For all the project parameters being evaluated, there was an increase in knowledge and confidence.
A range of comments on the value of the project were volunteered by project collaborators including:
- “It has raised my knowledge of comparative regional trials and a range of evaluated approaches – this is valuable and, in my mind, a critical first step towards improving collective understanding of the cover crops system.”
- “Project has produced tangible data that shows the specific pros and cons based on location, system, rainfall, etc.”
- “I feel like I have learned enough to be confident about giving advice.”
Project Progress Summary – March 2022
Challenging weather patterns occurred throughout this winter / spring period with severe thunderstorms, heavy rainfall, and damaging winds recorded across the project sites. Cold fronts, heavy rain, hail events and damaging strong wind gusts continued into the later stages of this reporting period. Rainfall throughout spring was sporadic with November being generally above average rainfall.
Substantial extension and outreach has been undertaken as the project nears the end, greatly raising the profile of the project through strategic social media engagement. Project collaborators continue their ongoing engagement with community groups, with very high attendance numbers reported at field days.
Invertebrate Field Trials
Over ten paired invertebrate field trials have now been conducted during the project, in conjunction with a replicated randomised block small plot trial and ad hoc collection of pest data from larger demonstration sites. This data demonstrates the variable and often unpredictable response invertebrate pests exhibit in response to mixed species cover crops.
When collecting soil cores from the lower Eyre Peninsula demonstration site at Ungarra to survey soil macroinvertebrates, snails and Russian wheat aphid numbers were quantified in the cash crop (Oct 2021). Following cover crop treatments tested the assumption that more pests would be carried over in the mixed species cover crop over summer. This was not the case with no significant differences being detected between treatments. These results are concordant with the literature that pest threats are neither increased nor decreased in response to mixed species cover crops.
A replicated small plot trial was conducted at Warooka on the lower Yorke Peninsula to test if the inclusion of tillage radish in mixes, or by itself, would favour Italian snails. The results from this site indicated that cover crop species have a significant effect on snail numbers (F19,95 = 6.2; P < 0.001), with the most snails observed where tillage radish was grown (as shown by green bars on the graph below), either as a single species or as in a mix.
Soil Analysis of Demonstration Sites
The majority of sample analyses from the farm demonstration trial sites have now been completed by the CSIRO, including several novel soil health metrics (active carbon, proteolysis, and amino acid utilisation), and microbial diversity analysis, as well as more traditional measures of nitrogen and phosphorus availability. This data will be analysed with field management and crop performance data, with the results being presented at the final project workshop to be held in April. Results will also be available on the project web site.
Around the Regions
MacKillop Farm Management Group
Activities delivered have generated considerable interest in the use of winter and summer active multi species crops to produce feed, and for soil health benefits. Two demonstration trials at Pine Hill and Sherwood have been completed, following harvest of the 2021 wheat crop. A targeted project extension event was held with a field day in November 2021. Over 100 people were engaged through project events held in 2021, with most attendees being farmers or land managers, the remainder agronomists, consultants, and contractors. A joint field day held in association with the Coorong Tatiara LAP and Grassland Society of SA (Limestone Coast Branch) on Boosting Soil Fertility Using Compost, Crops and Deep Tillage was held in November at Padthaway and Bordertown. Information on mixed species cover crops and pests was presented to approximately 70 growers and agronomists. Feedback from attendees was positive.
Dr Mel Fraser showing the differences in root systems between buckwheat and barley grass. A rangeof different species can be seen on the bonnet. The benefits of each were discussed.
Southern Farming Systems
Paddock demonstration trials continued throughout this reporting period in their cash crop phases in Victoria (SW Vic and Gippsland). The demonstration trial in SW Victoria had final paddock harvest assessments completed in December including biomass, yield and grain quality sampling and is on track for full completion of project activities by the end of January when data will be provided to CSIRO. The demonstration trial in Gippsland is also on track to fulfil project activities, with harvest and assessments due to be completed in January. The demonstration site in Tasmania has had all cover crop rotation assessments completed prior to being planted into its final cash crop of potatoes from which yield and biomass will be collected in early 2022. The species evaluation trial in Tasmania was terminated in September and sown over with a cash crop of spring barley in late September. The trial established well and will be taken through to harvest in February 2022 to collect yield and grain quality data.
At the Gippsland Spring field day in October, attendees visited the demonstration trial site with an overview given on the project and the trial treatments with 100 people in attendance made up of a mix of farmers and industry representatives.
A spring paddock walk was held at the Tasmania demonstration trial site held in November. The group also visited the species evaluation trial site at Longford. There were two main presentations relating to the project and trial work with two local agronomists focusing on cover crops fit for purpose – targeting cover crops to suit your system, and effective mixed species cover crops for building carbon, preventing erosion and grazing. Twenty people were in attendance with a mix of farmers and industry representatives.
SFS, Tasmania – cover crop was terminated in September, remaining biomass mown off in preparation for sowing of a Spring barley crop at the end of September.
Upper North Farming Systems
The project progressed well with the demonstration trial being sown to wheat for its final year. It was soil tested, biomass cuts taken and was harvested at the end of 2021 for yield and other harvest measurements. The effects from the 2020 mixed species treatments and their effect on the 2021 cash crops yield will be assessed and analysed. Soil sampling for Crown Rot and other root disease inoculum levels and in-crop expression were undertaken in all plots to assess in-trial and regional levels over the trial period. There were minimal challenges this year with good establishment of the wheat and sufficient in-season rainfall.
The annual UNFS Members Expo was held in September in Booleroo Centre for growers, agronomists, resellers, and researchers. Mark Farrell (CSIRO) was one of the keynote speaker, presenting on the cover crop project with specific reference to the UNFS trial site. Mark also presented in a field soil pit to discuss with the attendees the trial and related research in a more “hands on” way. The event was very successful with great attendance and outcomes.
Ag Innovation and Research Eyre Peninsula
AIREP are currently developing case studies for the two farm demonstration sites to be promoted through the AIR EP website, newsletter and social media channels. Further extension is planned in late March including a presentation of the project and results at a Regenerative Agriculture Forum being host by AIR EP and Eyre Peninsula Landscape Board.
SA No Till Farmers Association
Knife roller in action.
Mixed crop knife rolled at flowering.
Result of the herbicide treatment in a termination trial.
The condition of harvested seed after in-season knife rolling treatments.
Stock Journal Article
Bevan and Andrew Smith in a mixed summer cover crop at their Laura property in the Mid North. The mix includes sunflowers, millet,
sorghum, buckwheat, mung beans, corn, vetch, peas, clovers, winter canola and teff.
Increased summer plantings playing key roles despite dry December | Stock Journal | South Australia
Project web site
The project web site provides all the relevant background and resources produced in the project to date. Go to https://research.csiro.au/mixedcovercrops/
Two new SANTFA articles have been loaded onto the website:
Legumes in the Rotation – The combination of nutrients from chicken litter plus nitrogen fixed by the lentils in the previous year provides most of the cereals’ nitrogen requirements and means Brendan doesn’t usually need to apply any ‘starter’ fertiliser at seeding.
Sustainable N use helping Integrated Pest Management, not hindering: Aphids as indicators – Understanding likely Aphid population responses to management, climate, crop type and increased diversity within a crop field, it may be possible to select agronomic practices that limit threats.
Project Progress Summary – October 2021
The project continues to make significant progress in this reporting period (February to July 2021). The new year started with below average rainfall and warmer than average temperatures. This cycle continued throughout much of this reporting stage with rainfall below average for Australia as a whole with April being recorded as among the driest month on record.
The project is due to wind up in early 2022, with results from the demonstration site analysis to be presented at a workshop to be held in mid-March in Adelaide. This workshop will also allow project partners to discuss what worked for them in the project and to identify gaps for future RD&E.
Soil Sampling & Analysis
The project is now at the critical data gathering and generation phase. CSIRO laboratory analysis for over 1000 samples received to date is progressing well. All samples received were processed within 48 hours of receipt, preparing and stabilising them for onward analysis of various soil health metrics.
CSIRO in consultation with the Steering Committee devised and executed a communication plan for all collaborators to ensure that the strict sampling and sample storage protocols were understood and could be adhered to https://research.csiro.au/mixedcovercrops
Guidance was provided to them on alternate approaches, confirmation was received from them all that their commitments were understood. Throughout the next reporting period CSIRO will engage with collaborators to collate all in-field data and prepare final datasheets for analysis and eventual release as open access data.
A field sampling day was held prior to sampling commencing to ensure samples were undertaken correctly. This also presented the opportunities to provide immediate remote support to other collaborators who had site-specific issues to be resolved. Sampling was completed throughout March to May by all collaborators with the exception of one based in Tasmania which was complete sampling in September due to their different farming systems.
Outreach & Extension
Close to twenty workshops and field day events were conducted throughout this reporting period. Good attendances have shown that interest in this project is still very high with extremely positive feedback and requests for further field walks during next reporting period.
Although collaborators were still faced with cancelling or postponing field days and other planned events, maintaining delivery of activities throughout this reporting period has been less challenging.
Attendees at field sites have been impressed with the biomass production at the trial sites, especially after the dry summer experienced across much of the project area.
Substantial extension and outreach has been undertaken by CSIRO greatly raising the profile of the project at the national level. This outcome is mostly due to strategic social media engagement.
Invertebrate Pest and Beneficial Monitoring
Michael Nash attended six demonstration days in early 2021 where information on integrated pest management (IPM), soil engineers and pollinators was extended to growers and industry. IPM support continues to be provided to Ag KI with monitoring of Diamondback Moth (DBM), continuing. Information on beneficial species was extended to growers. Limited pest pressures have been detected during crop establishment in SA this is due to dry conditions which has limited pest sampling to 3 sites during the 1st half of the year. An alternative demonstration site at Rokewood was used to test slug response to cover crops and results were provided to Southern Farming Systems and the collaborating grower. Sampling at Bairnsdale was also undertaken with limited pest pressure detected. Two sites had soil cores taken for analysis of soil invertebrates from demonstration sites to align with CSIRO soil sampling requirements. The other two sites soil sampling for invertebrates and monitoring have been delayed due to the dry start in SA.
Soil cores have been collected from this demonstration site to survey soil macroinvertebrates. No differences between treatments were observed. Pitfall traps set in late January did detect differences between treatments with an increased abundance of ants in the least diverse fallow treatment, which is concordant with the literature. One species of springtail (Hypogastruridae) was also observed to be in greater abundance in the fallow treatment.
Data collected in March 2021 from species evaluation site indicated more pollinators (European Honeybees) were observed visiting Sunflowers and Tillage Radish than the Buckwheat, which contradicts overseas literature that would suggest buckwheat is a good resource for pollinators. Maybe a more suitable buckwheat species needs to be included in mixes to provide resources. Ongoing monitoring of Diamondback Moth (DBM) in brassicas using smart traps indicated lower numbers of moths were attracted to the mixed species demonstration site compared to a paddock of volunteer canola. DTN smart traps (automated “Smart Traps”) to monitor DBM will be re-established in August 2021.
Soil cores have been collected from this demonstration site to survey soil macroinvertebrates. The number of slugs was quantified in the cash crop (June 2021) following cover crop treatments to test the grower’s assumption more slugs would be carried over in the mixed species cover crop over summer. This was not the case with no differences between treatments detected.
Cover Crop Termination Trials
Four termination trials were completed during this reporting stage. Treatments and some early results from two of the trials are summarised below.
The termination trial was set up on the edge of the Stanton Farmer Demonstration site which had been sown on 13/10/2020. There were 3 treatments – roller crimper; chemical; and mowing (ride on lawn mower). The chemical treatment (glyphosate) had the best result on terminating the cover crop. Next effective was the mower with the roller crimper having little effect on terminating the crop.
Termination trial was implemented at Wolseley in a warm season multispecies cover crop that was sown on 6/10/2020. Termination strategies included – Control – nil; Crimp rolled (5 km/ha); Crimp rolled (10 km/ha); Glyphosate; Crimp rolled (5 km/hr) + Glyphosate; Crimp rolled (10 km/hr) + Glyphosate. The crimp treatments were applied on 22/04/2021 and glyphosate applied on 2/05/2021. Results to come in next newsletter.
Cover Crop Species Evaluation Trials
A species evaluation trail was sown in mid July 2020 to 14 treatments. Unfortunately, a mechanical issue with the seeder resulted in inconsistent emergence across the plots. On advice from Mark Farrell and Michael Nash it was agreed that the site would be used as a demonstration of what grows successfully on Kangaroo Island. A report has been composed on which species in this summer cover crop performed best (available from Ag KI). Michael Nash was able to conduct some invertebrate counts on the numbers of foraging bees of the different flowering plant species which includes tillage radish vs buckwheat vs sunflowers. Oats have been sown over the top of the species screening demonstration this year.
The Wangary species trail has been left out to regenerate medic pasture this year. Biomass cuts will be taken in leu of crop grain yields later this year. Further analysis of the data provided from the Minnipa species trial was undertaken in February. The findings showed that when grown as a winter break crop in this dry environment, a sweet-spot of six species grown as a mixture resulted in the highest wheat yield the following season. This appears to be related to higher moisture retention in those treatments which fostered a larger microbial N pool. Preliminary findings have been presented at several seminars including GRDC Updates in Bendigo.
Project Progress Summary – March 2021
The project has made significant progress in this reporting period due to improved growing conditions with good rainfall across south eastern Australia.
A reduction in numbers allowed at gatherings due to COVID restrictions has impacted the way some activities within the project areas have been delivered. In particular cross region restraints (site visit access in Victoria and Tasmania) have prevented project collaborators from meeting up physically to discuss results and reduced the opportunities of providing feedback.
Due to significantly better climatic conditions throughout this project period there has been a considerable improvement in the quality of cover crops. Rainfall Australia wide throughout August was 10% above average and in October was 35% above average across much of the country. October rainfall was the ninth wettest on record for South Australia. The above average start for sowing winter/spring cover crops lead to exceptional results seen in some trials and other summer trials are progressing well.
Project Focus & Activities
The Mixed Cover Crops project started in 2018 and will deliver its final report in April 2021. The purpose of the project is to assess the suitability of mi
xed species cover crops for use in the farming systems of the Southern Region of Australia. The primary focus is the traditional summer fallow, but some cool-season work has also been conducted. There are 20 demonstration trials across the southern region, each evaluating the performance of a mixed cover against a single species or typical summer weed-controlled fallow.
The project has three components:
- Five species evaluation trials to evaluate cover crop species across different soils and climates, established on a small plot basis
- Nine termination trials testing timing and method of cover trop termination
- Twenty demonstration trials which span from Streaky Bay in the West to Tasmania, and cover the Upper and Lower Eyre Peninsula, Upper and Mid North, Mallee, Kangaroo Island, South-East, Gippsland, and Tasmania. These are at least one seeder width scale. In the coming months, soil samples will be analysed from these 20 trials.
What are we looking for?
Ultimately, we need to establish where mixed species cover crops can be successfully established without negatively impacting the following cash crop’s yield. Beyond that, the next most important question is how the treatments have impacted on soil physical, chemical and biological parameters. Soil testing of all 20 sites is being conducted in autumn 2021, prior to establishment of the final cash crop. Entomology surveys are also being conducted at a number of the demonstration sites over the life of the project.
Cover crops have the capacity to alter soil chemical, biological and physical properties. Due to their sensitivity to change, we are placing particular emphasis on factors impacting soil nitrogen cycling and other measures of soil health. We are also investing effort to understand how the cover crop treatments impact the location of water and nutrients within the soil profile.
Early results from the Minnipa winter species selection trial indicate that cover crops may positively impact availability of both water and nitrogen early in crop growth, resulting in significant increases in yield relative to the fallow in some of the mixes. Traditional soil mea
surements including pH, soil moisture and organic carbon are also being quantified. Along with the physical and biological measurements, the entire dataset, which will be unified across the 20 sites, will enable us to interpret the grain yield and quality results as a function of the cover crop treatments (none, single or multi) and their impact on soil function. They will allow us to understand where and why trends differ across the study area. We expect data to start coming available on the project website early 2022.
Demonstration Trial Sites Progress
AIR EP’s demonstration sites being maintained by the farmers, having sown and managed the paddock treatments consistently over the past two years, ensuring all components are documented.
Mixed species trial sites managed by Upper North Farming Systems have performed very well through the whole growing season resulting in the best ground cover and biomass to date. The demonstration paddock was successfully sown on time and with good germination. All treatments have established well in 2020.
Some sites managed by SA No-Till Farmers lacked soil moisture and were not suitable to plant a summer cover crop.
The Lowbank trial site managed by the Murraylands and Riverland Landscape Board is one of the lowest rainfall sites in this project. Aided by a near average rainfall in season 2020 the growth at this trial site has been a vast improvement on previous years. A field day was held at this site with discussion including the visual benefits to the root systems of diversified planting. Highlighting the significant difference in root ball mass where different plant roots were closely intertwined. Discussion also included the role of mixed species over summer and their role in changing the soil rhizosphere through the fostering and proliferation of a wide host of beneficial microorganisms.
There were some challenges surrounding crop rotation and subsequent timing of treatments in the Tasmanian demonstration site. Plans are in place and seed organised for sowing into its cover crop phase following harvest. This paddock demonstration was in its cover crop phase from March through to late August when it was terminated and sown into a spring barley cash crop. Distinct visual differences have been observed in the spring barley crop, with the fallow areas showing up much lighter compared with the cover cropped areas of this trial.
Ashley Amourgis, SFS Research and Extension Officer, has been busy mixing up cover crop blends and inoculating soybeans for a paddock demonstration as a part of the ‘Mixed Cover Crops for Sustainable Farming’ project.
Evaluating how summer cover crops impact weeds and dry matter in the following cash crop for Gippsland’s farmers
Paddock demonstration trials have continued through this reporting period at the two Victorian sites. The SW Victoria and Gippsland sites have both been in their cash crop rotation for much of this period. The trial in SW Victoria was in its cash crop of faba beans which was harvested late December. Two days following harvest, the cover crop treatment was sown directly into the bean stubble and these plants have begun to establish. The paddock demo in Gippsland remains in its cash crop of wheat, with harvest planned for Jan-Feb 2021. The final biomass sampling of the cover crop in paddock demonstrations for SW Victoria and Gippsland will be completed in March 2021, along with the soil sampling post-termination, prior to sowing the final cash crop.
Cover Crop Species Evaluation Trials Progress
Unfavourable climatic conditions early in the project delayed some of these being sown and germinating. Good conditions in 2020 mean all of these trails have either been completed or are under way.
The first AIR EP species trial sown January 2020 failed to establish evenly due to lack of follow up rain, so a second species trial was sown in November 2020. The site has now established much better this time, with ongoing monitoring for pest species being undertaken.
Cover crops species trail at Wangary
Termination Trials Progress
Four termination trials were completed during this stage with some data still being collated and will be reported for the next stage. Two other termination trials will occur as demonstration sites are at the appropriate growth stages over the coming months. Following termination trials in Tasmania, Southern Farming Systems conducted another replicated termination trial at the SFS trial site in SW Victoria in early 2021 using the crimp roller as one treatment. A field day and demonstration of the roller in use is planned.
Knife rolled plots at the Robinson Terminational trial near Hoyleton In October 2020
Invertebrate Monitoring Update
Ag KI is assisting with sticky traps on the island to assess the flight patterns of diamond back moth and native budworm in mixed species versus single species in canola and faba bean resulted in traps having to be changed twice.
Smart traps were deployed at one site to test pest differences between mono and poly cultures in the spring of 2020. However, the lack of telecommunications support in rural areas hindered the use of this technology. Smart traps were ground truthed using delta traps and sweep netting to support local growers adopt IPM. Preliminary analysis from three sites comparing three different pest species suggests no difference in pest numbers between mono and poly cultures. A greater number of beneficial invertebrates was detected in mixed species paddocks, but this result needs to be confirmed with further monitoring next season. Individual reports are being completed.
Once finalised, IPM monitoring data will be incorporated into information regarding invertebrates associated with various cover crop species, which will then be added to the current species review developed by Jenny Stanton.
A pilot study indicated the choice of cover crop termination method may influence ground dwelling invertebrate communities, with spray seed associated with increased Portuguese millipede abundance. This result needs to be repeated.
Winter and spring surveys (pitfall trapping) found lower relative abundance and species numbers of ground dwelling invertebrates in the cover crop paddock in the Mid North. However, a greater number and diversity of ants in the cover crop paddock in spring could provide greater soil porosity.
Smart traps monitoring diamond back moths in mixed species canola
Checking out the invertebrates in establishing #mixedspecies emerging on abundance of spring moisture
Increasing plant diversity enhances the natural control of insect herbivory in grasslands. Species-rich plant communities support natural predators and simultaneously provide less valuable ood for herbivores. This was found by a team of researchers led by the German Centre for Integrative Biodiversity Research (iDiv), who conducted two analogous experiments in Germany and the U.S. Their results were published in Science Advances and show that increasing plant biodiversity could help reduce pesticide inputs in agricultural systems by enhancing natural biological control.
Kangaroo Island Field Day – 11th March 2021
For more information contact Jenny Stanton at firstname.lastname@example.org or 0484 602 946. Field day brochure can be accessed here: Mixed Species Cover Cropping Field Day
Project Progress Summary – August 2020
Over the summer months some project sites experienced good rainfall of up to 50 mm and trials that were sown into good soil moisture in January established well. At other trial sites summer crop emergence failed due to climatic challenges including forecast rain events not occurring, severe heat waves and bushfires. Autumn rainfalls were average and above average in some regions which provided an opportunity to re-sow trial sites that did not progress over the dry summer. These are all real challenges associated with developing resilient and sustainable farming systems. The added value of this project has been to highlight the challenges of incorporating mixed species cover crops into farming systems.
The demonstration sites are still on target for delivery. Twelve demonstration sites were successfully implemented over the past eight months. Demonstration sites in the SA Mallee have presented challenges which are currently being addressed, including soil erosion in the fallows, ryegrass, wild turnip and barley grass.
Cover Crop Termination Trials
Four termination trials have been completed. Other termination trials will occur as demonstration sites are at the appropriate growth stages over the coming 12 months.
Cover Crop Species Evaluation Trials
Trials have been established at Minnipa on the upper Eyre Peninsula, the lower Eyre Peninsula, Kangaroo Island and the SFS Inverleigh site in south west Victoria. A further trial will be sown in Tasmania this year.
Project Case Study – Southern Farming Systems Update
Ashley Amourgis, Ian Herbert and Natalie Jenkins
- Farm demonstration sites have been set-up to monitor year-on-year effects of cover cropping across the same area.
- Favourable conditions over the summer of 2019/2020 resulted in excellent summer cover crop establishment and crop growth.
- A species evaluation trial established at Inverleigh evaluated 13 different treatments, including eight single species and five multi-species mixes.
- A combination of both chemical and mechanical termination was the most effective termination
- technique in a trial at Inverleigh.
- Using a crimper roller has not proven to be a reliably effective termination technique in cover crop trials in Tasmania.
Farm Demonstration Sites
SFS has set up three replicated, paddock scale demonstrations sites, one each in south- west Victoria, Gippsland, and Tasmania. The aim of these sites is to monitor the same area over consecutive years, providing data from more than one season and monitoring the long-term impacts cover cropping can have over successive years. Soil sampling will be undertaken in the final year, just prior to the final cash crop being sown and sent to CSIRO for analysis. The trials all include the same fundamental treatments (as below), with differing species selected for the single and multi, to suit the rotation: Fallow; Single species; Multi species.
This site was sown into a canola stubble on 24-Jan 2020 near Rokewood into good moisture with 50 mm of rainfall falling in January. Decent follow up rainfall in February (40 mm) meant the trial established well and continued to add biomass. The moist summer conditions were favourable for volunteers, and a high level of volunteer canola established in the fallow plots. The fallow was designed to represent ‘as the farmer would maintain the paddock’, so the volunteers were retained for much of the summer period. Volunteer canola was present in the single species and multi species plots as well, however the other brassicas, tillage radish and blue gorilla – rape, as well as the sorghum and millet still established well amongst the volunteers, indicating all are quite competitive species. The multi species plots visually had the highest ground cover and the highest biomass at 3500 kg DM/ha compared with 2700 kg DM/ha for the single species plots and 2350 kg DM/ha in the fallow. These measurements were taken eight weeks post sowing and just prior to termination. The whole trial area was sprayed out in mid-March in preparation for the winter cash crop.
Single species (LHS)– tillage radish + volunteer canola (left) vs multi-species (RHS) – sorghum, millet, tillage radish, blue gorilla rape + volunteer canola at Rokewood cover crop demonstration trial.
This site was established in March 2019 at Sisters Creek in northern Tasmania. The trial was terminated on 24-June.
The mustard in the single species plots grew to a height of approximately 1 m, with much shorter mustard plants observed in the multi species plots. Mustard may be a desirable cover crop because it is a bio-fumigant, reducing growth of some soil-borne diseases, providing additional benefits to the following crop.
Frost had an impact on the buckwheat, eliminating many of the plants in the mixed species plots. The fallow areas were sprayed out prior to sowing. A higher moisture content was observed in the areas where a cover crop has been sown (both single species and multi-species) compared with the fallow.
Plants were dug up to observe differences in root biomass. The crown and root structure of the mustard was quite short and woody, with limited potential for breaking up compacted soils or increasing soil infiltration. The ryegrass plants had excellent tillering and root mass, whereas the roots observed on the vining peas were relatively weak. Following termination, the trial was sown into a cash crop of poppies.
On 25-Mar 2020 the same areas were re-sown to the previous years’ treatments and species. When terminated the area is planned to be sown into maize over summer, before returning to a third cover crop for the final year of the project.
Single species – mustard (LHS) vs multi-species – mustard, ryegrass, vining peas, buckwheat (RHS)) at Sisters Creek cover crop demonstration site in 2019.
The Gippsland site was established at Bairnsdale on 3-Feb 2020 into a barley stubble with good moisture. The site had 70 mm of rain in the second half of January and a further 10 mm within 24 hrs of sowing resulting in excellent establishment. About ten weeks post-sowing, 60 wethers were moved into the trial area for grazing. After five weeks they had grazed each of the treatments to ground level and were removed. Some observations to note was the increased suppression of annual ryegrass in both the single species and multi-species plots. The trial area has now been sown into wheat for the 2020 cash crop. It will be interesting to note the level of ryegrass across each of the treatment areas during this cash crop rotation.
Multi-species seed mix used in Gippsland cover crop demonstration (RHS) and the multi-species plot at the Bairnsdale (LHS) site towards the end of March, about seven weeks post sowing.
Species Evaluation Trials
The species evaluation trials are designed to evaluate current and emerging plant species to assess their suitability to the growing region. Treatments include a combination of both single species and multi-species, plus a fallow area: AGF FArmour Summer Cover (millet, sorghum, buckwheat; tillage radish, leafy turnip & sunflower), AGF SummerMax (sorghum, millet, tillage radish & Blue Gorilla rape); fallow; sorghum; millet; buckwheat; tillage radish; black mustard; lablab; leafy turnip; Sunn hemp/cowpeas/soybean; black oats (Saia)/winter canola (Phoenix CL)/winter wheat (RGT Accroc); Vetch/Black Oats (Saia).
The trials are assessed as the cover crop species grow and effects on the following cash crop. Growth of the cover crop species, weed intensity, ground cover and resilience post-termination are all monitored.
A replicated trail was sown at the SFS Inverleigh site on 21-Jan 2020 following a ryegrass hay crop. Buckwheat had the highest biomass at 1050 kg DM/ha, followed by sorghum and leafy turnip. All biomass was removed when taking plant cuts, including any weeds present, to provide an overall picture of how total biomass impacts soil conditions, including soil moisture. The only weed present in all plots at the time of the score was volunteer ryegrass from the previous hay crop. Both sorghum and leafy turnip had high total biomass but had quite a high weed pressure. Buckwheat appears to be quite a competitive species in this environment with a relatively low weed pressure assessment. Other species that appeared to suppress the volunteer ryegrass quite well were millet, black mustard, the oats/canola/wheat mix and the vetch/oats mix. The trial was chemically terminated on 27-Mar and sown into wheat on 11-May. The wheat plots will be monitored in season and yield data obtained off each plot at the end of the season.
Clockwise from top left: Millet, black mustard, species evaluation plots and buckwheat at the Inverleigh trial site, March 2020
Termination trials have been undertaken in both Victoria and Tasmania to evaluate the effectiveness of different termination techniques including knife rolling, grazing, herbicide application and slashing.
A replicated trial was set up at the SFS Inverleigh site the trial area was sown to the AGF SummerMax mix on 21-Jan 2020. Three different methods were used in termination: chemical, mechanical and a combination of both, as displayed in table 5. The chemical applications went out on 27-Mar on the chemical only and chemical + mechanical treatments. The mechanical only treatment was mown on 27-Mar. Biomass all was transferred back onto the plot behind the mower. Just over two weeks later, the mechanical + chemical treatment was also mown, allowing time for the translocation of the herbicide to occur.
The least effective method of termination was mechanical only. No real plant death occurred through the mowing only process. Chemical only was more effective than mechanical, however there were still some plants that were not fully terminated after one chemical application. The most effective method was a combination of the two. The initial chemical application was able to inhibit plant growth and begin the process of degradation and in combination with mowing to help speed up tissue breakdown; this was considered the most effective method.
Termination trial at Inverleigh trial site, photo taken two weeks post final termination
Soil Macroinvertebrate Monitoring Update
Field monitoring protocols for invertebrates continued to be ground truthed as insect challenges emerged at a variety of sites. Implementing the testing of smart traps was found to be a valid method; however, species level identification still requires morphological verification as pheromones for cotton bollworm/native budworm are not species specific. A number of pest preferences to specific crop species is being observed. This data is being incorporated into information regarding invertebrates associated with various cover crop species that then will be added to the current cover crop species review being developed by Ag KI.
Smart traps sending real time images to the cloud to give information on pests and allowing more accurate pest management plans.
A new endemic genus of springtail was also recorded from the demonstration site at Bairnsdale. Smart traps were deployed in the Autumn of 2020 with two pheromones aimed at attracting males of two moth species. It was found that the pheromones were not species specific, hence spring monitoring using these pheromones will focus on native budworms, the dominant species encountered in southern pulse crops. Winter and spring surveys have been planned for the next stage.
The Seed Treatment Information fact sheet is now available on the this website:
An area of the paddock demonstration site at Sisters Creek was rolled on 24-Jun 2019, about three months post sowing. Both the single species and multi-species areas were trialled with the crimper roller. The roller was modified to a 3-point linkage arrangement due to dirt build up on the roller, reducing its effectiveness. Once rolled the crop was left for a further eight weeks to break down prior to sowing the paddock into poppies. Observations taken eight weeks post termination found the crimper roller was about 70% effective in terminating all plants. One area of the single species paddock was rolled for a second time about four weeks post first crimping and was found to have a better plant termination result. For full termination, the area was sprayed with a knockdown prior to sowing the paddock into poppies.
In January of 2020, the crimper roller was again assessed on a cover crop paddock of buckwheat and annual ryegrass on a property near Sheffield in northern Tasmania. This trial had three treatments: crimper roller, mulching and chemical termination. The paddock was terminated when the buckwheat was at flowering. While all treatments had some level of termination, both the roller and mulching were not 100% effective. The most effective method of termination was the herbicide treatment.
LHS Soil build up on crimper roller 2019. RHS Crimper roller in action in buckwheat/ryegrass cover crop at Sheffield, 2020.
Project Update – March 2020
Tasmania Update (March 2020)
Multispecies generally work as a form of weed control however require the optimum species mix for the site, it will take some time to work out the best species mixes for each site (deep sands versus loam over clay). Loam over clay AGF mix was vigorous and left little room for weed species to invade the multispecies strips. However it should be noted the cereal crops are vigorous and outcompeted the legumes. As the season continues, it may be that the legumes have performed their key task of providing fixed nitrogen to the mix. Some modifications were made to one of the crimping/knife rollers to suit the wetter weather conditions at the Tasmania termination trial site.
Langhorne Creek Demo Site Update (March 2020)
The Langhorne Creek trial site produced some challenges with managing weeds in combination with the multispecies mixes, with no chemical options to control radish and three corner jacks. It was considered to split seeding options to allow for multispecies seeding following the early control of these problem weeds. Waiting for the 2019 winter harvest to finish before re-seeding the summer multispecies demonstration reduced rainfall opportunities to get the summer crop in the ground, however to get the best function from the tillage radish, seeding is best to occur after summer solstice. Additionally, waiting for the winter harvest before proceeding with the summer seeding follows the nature of the true farming system, the reduced sowing opportunities reflect the true opportunities available to this system. The dry hot nature of 2019 and 2020 summer to date has delayed this sowing, it is hoped to make the most of the first opportunity available, and 10mm rain will be required.
Waikerie Demo Site Update (March 2020)
After a significant period of development, a demonstration site at Waikerie was sown in winter 2019 with a blanket mixed species planting. With incredibly dry conditions getting a summer mix and single species crop sown at the correct time was challenging but proved that emergence of at least 2 species is possible. Significant differences were observed in the soil condition going into the spring summer period in the pre-existent multi-species site – there was an abundance of stored soil moisture and this was observed as being predominantly in relation to the proximity of the tillage radish tuber.
Project update (March 2020)
The project is making good progress over the past six months excellent numbers in attendance at field day events, with attendees engaging and expressing interest in how this system could benefit their own farming practices. There have been discussions between agronomists and growers regarding the benefits and possibilities of these systems particularly in the Mallee region and how long these systems would take to see significant change in soil characteristics. All of this was despite the climatic challenges including lack of rain and bushfires that have ravaged the regions, especially on Kangaroo Island.
This project is providing the space for constructive conversations around both the soil health benefits and the possible economic advantages of multispecies cover cropping. Discussions continue in relation to how multispecies might look in a larger cropping business (particularly mixed system), including how to best utilise the opportunities provided by a multispecies crop when the business is continuous cropping. Discussion with some landholders informed there is interest in the role of a multispecies crop as sheep feed and the project is gathering attention from other growers who have expressed interest to try mixed cover copping on a small scale.
Project Update – September 2019
Minnipa Ag Centre Field Day (Sept 2019)
Fiona Tomney from SARDI is managing the Eyre Peninsula Agricultural Research Foundation cover crop species evaluation trial at Minnipa Agricultural Centre one the Eyre Peninsula. A crowd of around 90 listened to Fiona and Mark Farrell from the CSIRO present on the Mixed Species Cover Crop project, and the aims of the species evaluation trial.
Upper North Farming Systems Field Day (August 2019)
Joel Williams presented to 110 farmers and industry at the UNFS Members Expo 1/08/2019 on soil biology and role of diversity at the mixed species cover crop demonstration site at Booleroo Centre in the mid North of South Australia. Presenters were; Matt Nottle (farmers perspective) Marg Evans (SARDI – disease management), Joel Williams ( Integrated Soils – soil function) and Greg Butler (SANTFA – Cover crop project overview). Attendees included ten students from Booleroo Centre Area School Ag Team at both the site visit and presentations. Turn out was the highest ever for the UNFS main field day event and topics presented are believed to be the reason for this.
Soil Health session on Lower Eyre Peninsula (August 2019)
The Lower Eyre Peninsula Agricultural Development Association (LEADA) held a morning session with Joel Williams from Integrated Soils the science behind using multi species plants to improve soils. The Multi Species Cover Crop demonstration site on Morgan’s property at Wanilla was visited following the a presentation by Joel. The paddock is comparing multi-species cover crop vs sown barley for grazing.
Cover Crop Demonstration at Lameroo (July 2019)
The Mixed Species Cover Crop demonstration site at Lameroo has established well. The species mix is the AGF Winter Max made up of tillage radish, Rootmax ryegrass, cereal rye, Forester oats and field peas.
Soil Health on Lower Eyre Peninsula (June 2019)
The Lower Eyre Peninsula Agricultural Development Association (LEADA) in conjunction with Natural Resources Eyre Peninsula held a workshop/field walk morning ‘Exploring Soil Health’ at Ungarra. A good crowd of engaged farmers engaged in discussions on building healthy soils and role of multi species crops in the farming system.
Southern Farming Systems (SFS) Bus Tour (June 2019)
SFS conducted a bus tour to the Sister’s Creek Mixed Cover Crop demonstration site in Northern Tasmania in June 2019. Due to very poor weather on the day the trial itself was not able to be visited. However the works that are being conducted was still discussed during the tour in a nearby shed.
Knife Roller ready to go (March 2019)
The first knife roller to be used in the termination trials has been fabricated and will be shown at the upcoming SANTFA field days.
Project update – November 2018
First cover crop is in the ground (November 2018)
The first multi species cover crop demonstration site has been sown in the last week of November 2018 in the Mid North of SA on a farm near Hoyleton. The species in the cover crop mix included faba beans, vetch, cereal rye and millet.