Vetch agronomy and management

Take home messages

• Choose the species of vetch and variety depending on your end goals, or desired end-use.
• Each vetch species requires different management and agronomy to achieve optimum production.
• There is no ‘one size fits all’ approach with vetch, the diversity of end-uses and environments in which vetch is grown, require different agronomic approaches and tools.

Background

Traditionally vetch has been a low rainfall legume best suited to sandy, neutral to alkaline soils. However, trials conducted by the National Vetch Breeding Program (NVBP) and others, across a wide range of environments and soils types have demonstrated that vetch can be productive across many farming environments, offering farming systems in many areas all the benefits associated with a productive and reliable legume in their rotations.

Vetch gives growers an extra tool in the fight against herbicide resistant weeds and cereal diseases while still offering the opportunity for a profitable enterprise in the cropping year and benefits that flow on for two to three subsequent crops.

With the increasing use of vetch in numerous different farming systems, an increasing diversity of approaches and agronomic practices are being used to get the most out of the crop. Its diversity of end-uses means that there is no one right way to do everything. However, there are some basic agronomic practices to get right before getting too creative. Your planned end-use does not have to be locked in, flexibility can come with getting the basics right and seeing how the season develops.

The most important point to remember is to treat it as a crop, not a break in the cropping regime. The more you put into the crop the better your potential return, be it yield or the ancillary benefits that come from legumes.

Paddock selection and planning are vital, knowing the weed burden/profile along with the desired/preferred end use, dictates many subsequent decisions. Vetch can be used to fill in, provide extra feed or just replace fallow, but if you are looking to maximise benefits and outputs it’s important that you put the planning in.

Once you have selected the paddock, choose the vetch species and variety that best suits your conditions and major objectives. For specific details on vetch variety characteristics please refer to the 2021 Crop Sowing Guide relevant to your state or area.

Choose disease resistant varieties wherever possible, all varieties released from the NVBP are resistant to rust.

If you have hostile soils or a poor legume history, inoculate seed with appropriate rhizobia. New acid tolerant strains of rhizobia are being released (expected release date 2022) which will assist with inoculation in areas with low pH soils to get the best out of legumes.

All legumes benefit from phosphorus (P) but do not require significant amounts of nitrogen (N), so choose appropriate fertiliser to reflect these requirements. Vetch can ‘make do’ with residual fertiliser from previous cereals but will benefit from well placed P, helping development and vigour.

When looking at different end-uses, time of sowing (TOS) can play an important role in strategic planning. If the crop is to be grazed, early sowing is vital to get the crop up while the soil is warm, as early growth is vital. This also applies to using the crop for green or brown manure; the bigger the biomass the better and early canopy closure is important to out compete weeds.

For hay production, TOS helps dictate when the cutting and drying window will occur. This is a balance between getting the best growing conditions and the timing for drying when the weather warms in late September. In 2020, several areas had excellent rains in March enabling very early sowing (mid-March-early April), this resulted in large dense crops developing early. Canopy closure occurred in some cases in early-mid June, however this resulted in perfect conditions for disease development. As canopy closure occurred so early, fungicide applications could not penetrate the canopy after this point, allowing disease to proliferate and causing significant damage particularly to hay crops. This shows the importance of planning TOS around your preferred end-use, as grazing early may have helped to keep canopies open longer and helped with disease suppression.

For more detailed information on disease management please refer to the paper ‘Vetch Disease Management’ within this publication.

Chemical selection, particularly for broadleaf weed control is still limited in vetch. Pre sowing, incorporation by sowing (IBS) chemicals and post sowing pre-emergence (PSPE) chemicals offer the best options and results. There are now in-crop options for broadleaf control, but their use will set the crop back for a period of time. It is recommended to talk to local agronomists for chemical advice specific to your soil type and region.

Rolling is recommended post sowing, depending upon the tillage system used. Rolling prepares the paddock for hay or grain harvest and can also improve seed to soil contact, but care should be taken with some tillage systems, as it can push soil back into the seed row, concentrating chemicals over the seed, potentially causing issues if there is good rainfall following sowing.

Growth regulators are becoming more commonly used in crop production to control/influence plant development. In vetch, gibberellic acid (GA) is the most common growth regulator that is used. Gibberellic acid artificially substitutes/increases the natural occurring hormone (gibberellins) in the plant promoting elongation of plant cells, it therefore elongates the plant cells and stretches the plant out, with the aim of increasing plant height. It has been used in vetch for several reasons; to increase plant height to facilitate cutting for hay, to promote growth and development after grazing and to delay onset of flowering which helps delay the cutting window for hay production. Its use should not be seen as essential, but as a tool to use in specific situations.

The Southern Pulse Agronomy group (SPA) from Clare conducted trials in 2020 looking at the interaction between GA and vetch. This trial was at two sites in one season, 2020, they found it had a significant impact on plant height for up to six weeks after application, however it did not increase fodder yields significantly and was found to have a negative impact on grain yield (pers. comms. Sarah Day). This data will be published in the 2021 Eyre Peninsula Farming Systems Summary.

For GA to work it requires moisture and nutrients to be available and timing of application is vital, particularly when attempting to delay flowering. Application to achieve this must be just prior to the commencement of flowering, however there is only anecdotal evidence on the length of the delay to flowering caused by GA. This needs further investigation.

Vetch is not vetch.

There are three different species of vetch grown in Australia, common vetch (Vicia sativa) and woolly pod vetch (Vicia villosa) being the two most popular species, and purple vetch (Vicia benghalensis) which represents a much smaller part of the market. These different species all have different characteristics, and therefore, need different management and suit different conditions, but all produce good fodder and can return large amounts of N to the soil. The hard seed levels of woolly pod vetch and purple vetch should be a major consideration when choosing this species of vetch to sow.

Common vetch

Varieties of common vetch (CV) include Studenica, Morava, Timok, Volga, Rasina, Blanchefleur and Languedoc

Common vetch is the most widely grown species of vetch, predominately grown in low rainfall areas in South Australia (SA), Victoria (Vic), Western Australia (WA) and New South Wales (NSW), where it is seen as a good, reliable legume option in farming systems. It offers flexibility to the grower and is an excellent tool in a grower’s fight against issues like soil borne diseases and herbicide resistant grass weeds, while still offering good returns in the form of fodder/grazing, hay, improved soil N and organic matter levels.

Common vetches are generally shorter season than the other species (varieties flower between 85 and 115 days) and are more tolerant to grazing. They are palatable at any growth stage, either green or dry, and the grain is a high protein feed (on average 29% crude protein and 12.5MJ/kg DM metabolisable energy) that can be used for all ruminants.

The Australian bred and released varieties Studenica, Morava, Timok, Volga and Rasina are all resistant to rust. Older varieties like Blanchefleur and Languedoc are highly susceptible to this disease. Rust can drastically reduce yields and may induce abortions in pregnant livestock if they are fed heavily infested plant material, it is therefore important to grow rust resistant varieties whenever possible.

In higher rainfall areas monitor for Botrytis symptoms, this disease can greatly reduce yields.

In all common vetches regrowth after grazing is very dependent on seasonal conditions, good moisture and favourable environmental conditions.

Woolly pod vetch

Varieties of woolly pod vetch (WPV) include Capello, Haymaker Plus, RM4 and Namoi.

These varieties are better suited to medium-high rainfall areas, doing best in regions receiving a minimum of 450mm annual rainfall. All the varieties of WPV are later developing than the CV varieties, not flowering until around 125 days after sowing. Regions looking for later hay varieties should consider WPV. They have superior hay yields to CV, on average yielding approximately 1.5t/ha more dry matter in the same environment compared to CV (yields between 5-12t/ha can be achieved). However, grain yields are much lower than CV (0.8t/ha average) and the grain can be difficult to harvest/thresh.

Woolly pod vetch grows well in mixed crops situations and can tolerate some shading from plant competition, which makes it a good companion plant in forage mixes.

The grain of WPV varieties should not be fed to any livestock, as it contains high levels of toxin and can cause death in ruminants if consumed at high levels. These varieties/species should not be grazed before 15 nodes of growth or after pods have formed seed, due to the toxicity of the grain. There is no data available on what is a safe level of this grain in a dietary/fodder mix.

Care should be taken when grazing, as this species is susceptible to over grazing early in its development due to its slower growth through winter.

Management issues to consider

Make sure paddocks are relatively free of broadleaf weeds as there are limited options for control in WPV, especially in-crop and it is a poor competitor for weeds in early growth stages. The best option is to use registered herbicides post sowing pre-emergent.

Don’t graze early (before 15 nodes) and ensure you cut the hay or graze before pods start to set seed.

Be aware this species has hard seeds, with hard seededness percentage of common varieties ranging from 5-7% RM4 to >30% Namoi and they can appear as volunteers in subsequent crops. This species is cross pollinated, and if you are producing or/multiplying seeds from RM4, isolation from higher hard seed varieties like Namoi needs to be >1km.

Purple vetch

Varieties of purple vetch (PV) include Popany, Benatas and Barloo.

Crop development of this species is similar to WPV, with later flowering time (>125 days) compared with CV. It is suited to medium to high rainfall areas with a good finish and is a high fodder producer in these areas. It is not, however, suited to lower rainfall zones. Purple vetch can tolerate some waterlogging compared to other vetch species. Similar to WPV, grain cannot be fed to ruminants but there is a small market as birdseed.

Management issues to consider

Like WPV this species has very slow winter growth and does not compete well with weeds early. One advantage is that Broadstrike® is registered for use in the variety, Popany allowing for control of a range of broadleaf weeds in crop. It should not be grazed before 10 nodes or grazed/cut for hay after pods start to set seed.

For specific details on vetch variety characteristics please refer to the 2021 Crop Sowing Guide relevant to your state or area.

Conclusion

Vetch has the ability and potential to fit into modern farming rotations in most areas, particularly in mixed farming systems where growers are looking for a versatile break option that still allows for strategic action against specific cropping problems. Unlike pulses and other break crops, its end use is not solely focussed on grain production.

A successful vetch crop can:

• Increase yields and grain protein of following cereal and oilseed crops.
• Allow an extended phase of cropping.
• Decrease many cereal diseases – grass-free vetch crops can break the life cycle of root diseases, preventing multiplication and build-up of disease levels.
• Provide an opportunity to control grass weeds especially in forage use; hay is cut before many grasses set seed providing a chemical free option to avoid weed resistance. Green/brown manuring can be used with vetch to control competitive weeds which are difficult to control in other crops, e.g., brome grass and barley grass.
• Available soil N is maintained and can be improved by an average of 56, 92 and 145kg/ha after grain, hay and green manuring, respectively (data from 3yrs x 5 sites).
• Grain and hay/silage from CV varieties can be used to feed ruminants without limits.

The key to a successful vetch crop and achieving the maximum benefits from its growth is to treat it as a crop, not as a set and forget break option. Inoculate with appropriate rhizobia, control weeds where possible and monitor for insects and disease.

When successfully grown, vetch can be an effective risk management tool on farm. Allowing for a reduction in fertiliser and chemical use in following crops, reducing costs and the risks involved with in-crop N applications. This can have a large impact on profitability and the stress levels associated with input application decisions.

Acknowledgments

The research undertaken as part of this project is made possible by the significant contributions of growers through trial cooperation, consultation and support of the GRDC, the author would like to thank them for their continued support.

Useful resources

2021 Crop Sowing Guide

Contact details

Stuart Nagel
SARDI
stuart.nagel@sa.gov.au

Varieties displaying this symbol  beside them are protected under the Plant Breeders Rights Act 1994.