As seen in Farm Weekly, 27/04/2023

Growing cover crops in Western Australia can offer many benefits to farmers, such as providing additional forage for livestock, improving soil health, reducing erosion, and providing a source of nutrients for subsequent crops.

It is important to select the appropriate cover crop species for the specific soil and climatic conditions of your area.

Some farmers say cover cropping works, others say it is a waste of time.

What is the difference? Why did it work for one and not the other?

The first step is setting goals. What change do you want to address?

Knowing what is possible is easier with experience and it may be beneficial to research or seek advice.

Maybe the problem is a symptom and not the cause of the issue, meaning the actual problem will not be fixed if not addressed correctly.

With cover cropping it is no different.

Once goals have been set and problems identified, then the process of picking species is easier.

Observation is a key to success.

What plants are thriving? Which plants are suffering? Are they cash crops or are the weeds winning?

Weed pressure can be a symptom that things are not balanced in the soil.

Certain weeds grow in certain conditions.

If the conditions are not right for them, they do not grow.

By having a particular weed issue usually indicates there is a soil condition that is giving that plant an ecological advantage over other plants.

It may be a physical issue such as compaction, or responding to high free soil nitrate in the soil, or rising salinity levels in the soil.

Soil structure is a major issue we face.

Poor soil structure leads to problems such as erosion, low water infiltrations, anaerobic soil conditions, poor root development, low nutrient acquisition, and low water retention, to name a few.

The easiest way of improving soil structure is to have a plant growing in the vegetative stage.

In the vegetative stage it will release up to 80 per cent of the carbon it captures during photosynthesis as a root exudate.

This feeds soil microbes.

These microbes need a home, so they will use some of the exudates to create homes, benefitting soil structure.

Having a healthy soil microbe population is good, but microbe diversity is more important.

One way to increase microbe diversity is to increase plant diversity.

Plants will bring and develop their own soil microbiome, increasing the microbe diversity in the soil.

The key to diversity is using different functional plant groups.

As a quick rule of thumb, grasses, legumes, brassicas, non brassicas and forbs are the quick way to group the different plant functions.

For more diversity each group will have cool and warm season species, annuals, biennials and perennials.

This drives diversity within the soil microbiome and accelerates soil health.

For cash cropping, picking species that will not interfere with harvest is crucial.

Legumes like subterranean clover grow flat on the soil allowing it to grow all season long while fixing nitrogen and supporting mycorrhizal fungi.

Taller species can grow tall enough to be cut while harvesting, meaning having to harvest the green material.

Broadcasting or disk drilling in the taller species after the cash crop gets a couple of weeks head start will normally stunt the taller species, and after harvest the cover crop will continue to grow.

Plantain would be another species not usually viewed in a cropping situation but has merit to add at low plant densities.

Another option is growing early maturing cash crops, leaving a longer period of time that a cover crop can be established after harvest.

This way, after harvest, a cover crop can be seeded and get its roots established before the rain turns off.

Having plants growing and using water has the potential to dry out the soil, but will actually save soil moisture.

Transpiration of a low growing cover crop will be less than having bare soil and allowing water to evaporate.

Once the cover crop has established and created a good cover, there is an option to terminate it.

The cover crop will have fed the soil microbes for extra days as compared to no cover crop, and the cover will help keep the soil cool, reducing the evaporation.

One of the messages that Dr Christine Jones said at a field day in WA was that conventional agricultural science is difficult to transpose into regenerative agriculture because the management and soil conditions are different.

This includes things like the micro-water cycle and once we have an active diverse microbe population in our soils, we are able to do more, like a cover crop to continue to build soil.

Irwin Hunter & Co’s Cover Crop Plus Mix (winter and summer versions) and Green Manure Mix are recommended to farmers looking at doing a cover crop.

Our other mixes such as SouWest Mix, Self Regeneration Mix, Maximix and Interow Mix all have a diverse range of components that can also be used as a cover crop.

Irwin Hunter & Co can also Mix & Match to farmers requirements.

Some cover crop options that are suitable for Western Australia include:

  • Legumes such as Crimson Clover, Paradana Balansa, Parafield peas and Faba beans are all nitrogen fixing and provide good ground cover helping to reduce erosion.
  • Cereal rye tolerates the hot dry conditions of WA and helps suppress weeds.
  • Brassicas like Tillage Radish help break up compacted soils resulting in improved soil structure.

All varieties available from Irwin Hunter & Co.

Overall, planting cover crops can be an effective way to improve the sustainability and productivity of Western Australian farming systems, while also providing a range of environmental and economic benefits.

Written with the assistance of Kevin Elmy CPAg.

Contact your local farm supplier or Irwin Hunter & Co for more information regarding its extensive range of pasture seed and mixes.