This project was made possible due to GRDC investment.
Western Australia’s southern cropping regions have a need for further diversification in crop rotations for disease and weed management and for the development of more robust and sustainable farming systems. Current rotations revolve around cereal grains with break crops being heavily reliant on canola. The key objectives of this project were to determine if:
- linseed can be successfully grown under dryland farming conditions in southern WA,
- if any investment is required into machinery and infrastructure by growers to grow linseed,
- to develop basic agronomic guidelines and to assess the yield potential of three commercially available linseed varieties grown under dryland conditions in WA, Croxton, Glenelg and Bilton.
All these outcomes were successfully achieved within the project.
In 2021 the canola and linseed stubbles were tested for soil borne pathogens (PredictaB) and the following crops yields were measured to determine if there was a benefit to the following crop from the potential drop in disease pressure.
Over the three grower demonstration sites there was a considerable drop in nematode pressure and overall soil borne pathogen pressure. P. neglectus and P. quasitereoides disease pressure in particular was reduced from medium to medium to low disease risk down to low to zero disease risk.
The results from the crop yields in the season following the linseed or canola crops were mixed. The PredictaB results certainly demonstrated a reduction in soil borne disease pressure however this didn’t always able to translate into final yield. The Katanning site did demonstrate an advantage in growing lupins after linseed compared to canola however due the very wet season a large portion of the canola area was damaged by water logging which impacted the validity of the findings. The Darkan site gave mixed results with one Linseed variety stubble producing a higher barley yield than canola stubble and the other variety lower.
Overall 2021 was an exceptional season with good rainfalls received across the entire season. In good seasons it is difficult for soil borne pathogen trials to show differences in results as roots that may be impacted by disease are still able to access enough moisture to grow a healthy crop. It is in poorer seasons that the benefits of reducing soil disease can be shown in crop yields as better developed root systems are able to access more moisture.
This project was made possible due to GRDC investment.
Wheat is traditionally not grown in large areas throughout the Great Southern Western area primarily due to the high risk of frost damage. There are several key outcomes that were realised from the project and will aid in bringing long season wheats into rotation into this region, which are:
Reaching yield potential – Yields in the Western Great Southern region due to the seasonal conditions have been considered to have room for improvement. Long season wheats are generally higher in yield potential than spring wheats. The project has demonstrated the superior yield potential that can be reached through the use of these crops eg 8.40 MT/Ha of Accroc.
Early sowing strategy – Spring wheats are often delayed in sowing to avoid the frost window at flowering. This delay in sowing can reduce yield potential and increase the reliance on a good finish. Long season wheats offer the option for early sowing with a reduced risk of frost damage by pushing out the time of flowering.
Increased herbicide options – Wheat increases the options available to growers in terms of herbicide options which will be important to producers who are 100% dropping or increasing there cropping.
Reduced frost risk – Frost risk remains the main driver for growers not wanting to grow wheat. Long season wheat varieties have been shown to reduce the susceptibility of wheat to frost throughout the project. Long season wheats will increase growers’ confidence in growing wheat in this region in future seasons.
Eastern Albany Zone – Offers a good early season wheat option which allows growers to capture yield potential in seasons with an early break with a reduced frost risk.
The project has seen very good interest from growers throughout the region and growers have expressed intentions to increase the area of long season wheat in coming seasons. As the production knowledge gaps are narrowed and grower confidence in the long season wheat packages improve it is expected long season wheats will be a key part of growers rotation.
There has been a considerable amount of work conducted into the place of long season wheats in
to the rotation in the south western regions of WA. Typical of any project, while this project has provided some answers, it has also generated the need for further work which includes:
Agronomy Package – Seeding rates, nutrient packages and time of sowing (germination) all require further understanding and more work across different seasons.
High yield suites – The project demonstrated the yields these wheats can achieve, which is very exciting for growers in this region. There is a requirement for developing a best practice high yielding agronomic package that growers can use to maximise the yield potential of these wheats within their rotation.
Frost risk comparison to other crop types – Oats and barley are grown in low lying frost prone areas. While long season wheats are less frost prone than spring wheats, it remains unknown their fit compared to alternate crops, especially when sown early.
Claying has become a vital amelioration tool within the Great Southern region on WA, where the soils are typically sandy, low in organic matter and have a prevalence for non-wetting issues. Claying has shown to be most effective at increasing yield performance on sandy duplex soils, where the clay is incorporated in to soils with an extremely high sand percentage in the top 30-50cm of the soils profile, to lift the overall clay content within crucial area of the soil profile. However, there is an increasing desire form farmers to investigate the potential for claying to increase yield potential and alleviate non-wetting issues on other soil types such as the forest gravels and loamy sands common to this area.
Claying as an amelioration technique is the process of adding clay enriched (>20%) subsoil into clay deficient and water repellent topsoils. Claying topsoils reduces repellence, water and wind erosion risk, increases water holding capacity, and has the potential to increase organic matter.
The best practice for alleviating non-wetting and repellence issues is to target a clay fraction of 5% clay in the topsoil. However, there are quite a few variables that impact the ability of a grower to achieve this benchmark. Firstly, it is unlikely that a paddock has a consistent soil type, let alone a consistent soil texture. To establish how much clay a grower should spread to achieve the best practice benchmark, you need to know three key details:
- What is the current clay percentage in the soil?
- What is the clay percentage in the product you plan to spread?
- What depth will you incorporate the clay in the soil?
To determine your current soil’s clay percentage, you need to take soil samples from a representative area in the paddock and to the planned depth of clay incorporation. Ideally, growers would take multiple soil samples within the paddock at different depths to your target incorporation depth.
You then need to determine the percentage of the clay fraction of the “clay” you are going to spread. “clays” can range anywhere from 15 to 40%, which will significantly impact the amount of clay that need to be applied to achieve best practice results.
Lastly you need to determine what implement you will use to incorporate your clay, and to what depth that will incorporate the clay too? Implement selection will ultimately be based around what the farmer has available to them, and what the desired outcome of the claying is. For example if you are looking to alleviate non-wetting then it is unlikely that you will need to incorporate your clay as deep as you would if you were looking to improve water holding capacity.
Once you have selected your implement and you know your incorporation depth you can use the following formula to determine how much clay is required to shift your top soil form its current clay % to 5% clay.