Can vetch play a role in your farming system?

Key messages

• Vetch can provide an alternative source of nitrogen, as well as feed for livestock
• It is suited to either being sown on its own, or in a companion cropping system, alongside cereals or canola
• Farmers appreciate it’s early growth and flexibility, which provide opportunities for green/brown manuring, hay, grazing and grain production
• A Riverine Plains demonstration is trying to determine the “sweet spot” for vetch termination in a wheat crop, to maximise both nitrogen fixation and wheat yield

Vetch was a focus of conversation at our recent alternative nitrogen sources field day at Sanger, both because of its potential for nitrogen fixation and its role in producing high quality feed for livestock.

So, what did farmers have to say about it, and what’s the potential for vetch in the Riverine Plains?

Vetch in companion cropping systems

Farmers often sow vetch on its own for brown or green manuring and hay, but it can also be sown alongside cereals or canola in a companion cropping mix (where two crops are sown and grown at the same time in the same paddock).

Compared to other legumes in a companion cropping scenario, vetch’s growth habit means that it doesn’t out-compete wheat or oats for early moisture, nutrients and light, grows quickly and can be terminated from the mix (desiccated), or taken through to grain as needed. This adds flexibility to farming systems, making it easier for farmers to adapt to seasonal conditions and market opportunities.

Ideally, vetch is sown early (i.e March or April), to maximise biomass production and nitrogen fixation, however this is not always possible, especially when conditions are dry. 

Vetch is often preferred over other legumes because it provides:

• early feed for livestock, including lambs, especially when sown early with cereals such as oats, wheat or barley
• system flexibility, because it can be terminated before it impacts on wheat yield
• nitrogen fixation (alternative nitrogen source)
• can be used on its own in a fallow or brown manure situation, to reduce weed competition (break crop)
• vetch only or vetch/cereal hay is popular, because of its good protein and energy levels

Farmers also noted that vetch seed can be tricky to harvest because it sets pods close to the ground. Several farmers had used wheat or canola in a companion cropping mix to provide a trellis for the vetch to climb, to make harvest easier. A key learning from this was that wheat or canola sowing rates need to be high enough to ensure the vetch plants are supported through to harvest. The group also heard how rolling could improve harvest efficiency, by flattening clods and other debris. Read more in GRDC’s vetch GrowNote (southern).

Consider also that if both the vetch and the main companion crop is taken through to harvest, seed will need to be separated using a seed grader.

Some farmers expressed concern that vetch’s hard-seededness can make it hard to remove from paddocks, however newer varieties such as Morava are soft-seeded, making this less an issue.

In a wet spring, vetch also requires fungicide applications to prevent leaf disease.

Trial looks at termination timing of vetch in wheat crop

As part of a GRDC National Grower Network project, Riverine Plains established a demonstration trial at Sanger to investigate the amount of nitrogen fixed by vetch as a companion crop with wheat and the optimal timing of its termination. 

The trial aims to find the “sweet spot” for vetch termination, where nitrogen fixation from vetch is maximised, but wheat yield in unaffected, and is also looking at the costs of sowing and desiccation. In 2024, the trial was sown in June, with termination occurring either in July, August, September or October. 

The 2024 results showed:

• No significant differences in wheat yield or quality when grown on its own compared to being grown as a companion crop with vetch (except when a companion crop with 50 percent nitrogen was terminated in September, which yielded significantly less).  
• Vetch and wheat biomass both increased as the season progressed, with vetch biomass highest at the September termination, while wheat was highest at the October termination, suggesting wheat was better able to compete for resources.
• Vetch biomass production was relatively low when sown as part of a companion cropping mix with wheat, likely due to factors relating to the dry season in 2024, as well as competition by the wheat. 
• The estimated nitrogen benefit of the vetch varied between 0.4 kg–6 kg N/ ha, with the highest nitrogen benefit occurring at the end of September.
• Vetch sown in a monoculture yielded poorly in this trial (approximately 0.1 t/ha), likely due to seasonal conditions. 

The trial is being repeated in 2025. Read the full results in Companion cropping for lower cost nitrogen supply from Research for the Riverine Plains, 2025.

Vetch as a source of nitrogen

The amount of nitrogen returned to the soil from a vetch crop depends on the amount of biomass produced (a rule of thumb is that legumes can fix 20 kg N/ha per tonne of dry matter produced, with a potential range of 7–60 kg). For this reason, vetch will perform best when sown early. 

After termination, it will take some time for the plants to break down and for nitrogen to become available to subsequent crops, with responses often not seen until the season after.

The nitrogen fixed by legumes such as vetch can reduce farmer reliance on synthetic fertilisers such as urea, which can be expensive and difficult to source at peak times. Read more on the economic benefits of pulses (GRDC). 

However, when using legumes such as vetch to provide nitrogen, consider that successful nodulation by rhizobia involves using the correct strain, as well as the removal of soil constraints, such as acidity. 

Brown manuring with vetch 

Brown manuring vetch can provide mulitple soil health benefits, by adding organic matter and improving soil structure, as well as nitrogen.

Brown manuring vetch in low-rainfall zones has also been shown potential to increase crop resilience by suppressing weeds and managing soil moisture effectively (a study by Birchip Cropping Group confirmed brown manuring with vetch can reduce weed seed banks by up to 90%, reducing herbicide dependence). 

Vetch as a brown manure can be particularly useful in seasons where moisture conservation is critical.

Summary

Vetch offers potential in the Riverine Plains as alternative source of nitrogen when sown on its own or in companion cropping scenarios, as well as other soil health benefits. Further research is needed to identify the sweet spot for termination, to maximise both nitrogen fixation and yield. 

Acknowledgements

This article was produced as part of the GRDC NGN project Companion cropping legumes for lower cost nitrogen supply in farming systems.