Vetch Agronomy and Management

Take home messages

• Choose the species and variety of vetch depending on your end goals, or desired end-use.
• Get initial management and agronomy decisions right to enable flexibility of end-use.
• There is no “one size fits all “approach with vetch, the diversity of end-uses and environments vetch is grown in require different agronomic approaches and tools.

Background

Vetch has long held a place in the low rainfall mallee cropping areas of southern Australia, particularly with farmers looking for a reliable legume. Recently there has been an increased use of vetch in a variety of farming systems, leading to growing interest in   agronomic practices to get the most out of the crop. Being a crop with a diversity of end-uses means there is no one right way to manage it, 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 watching how the season develops.

The most important point to remember is to treat vetch as a crop, not a break. The more you put into the crop the better your potential return, be it yield, in any form, 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 dictate many subsequent decisions. Vetch can be used to fill in, provide extra feed or just replace fallow as well as for hay and grain production, but if you are looking to maximise benefits and outputs 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, these can be found online.

Choose disease resistant varieties wherever possible, all varieties released from the National Vetch Breeding Program 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 which will assist areas with acidic soils get the best out of legumes.

All legumes benefit from phosphorus but do not require significant amounts of nitrogen, so choose appropriate fertiliser. Vetch can usually “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) plays 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, early growth is vital for this end use. This also applies to using the crop for green or brown manure, the bigger the biomass the better and early canopy closure to out compete weeds is preferred.

For hay production TOS helps dictate when the cutting and drying window will occur. There is a balance to be struck between getting the best growing conditions and timing drying for when the weather warms in late September. In Victoria in 2020 several areas had excellent rains in March enabling very early sowing (mid-March-early April), this resulted in large dense crop canopies developing early. Canopy closure occurred in some cases in early-mid June, 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.

Chemical selection, particularly for broadleaf weed control is still limited in vetches. Pre 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 they can set the crop back for a period of time. It is recommended to talk to local agronomists for chemical advise specific to your soil type and region.

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

Growth regulators are becoming more commonly used to control and influence plant development. In Vetch, gibberellic acid (GA) is the most common used. GA elongates the plant cells and stretches the plant out by artificially increasing the natural occurring hormone (gibberellins) in the plant, promoting elongation of plant cells=. The aim of used GA is to increase plant height to facilitate cutting for hay, to promote growth and development after grazing and to delay onset of flowering, which helps to delay the cutting window for hay production. It should not be seen as essential, but as a tool to use in specific situations.

As part of the GRDC investment Southern Pulse Agronomy, SARDI conducted trials in 2020 looking at the interaction between GA and vetch. They found it had a significant impact on plant height for up to 6 weeks after application but did not significantly increase fodder yields and was found to have a negative impact on grain yield (personal comms. Sarah Day), this data has been published in the 2021 Eyre Peninsula Farming Systems Summary and will be loaded to Online Farm Trials (https://www.farmtrials.com.au/).

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 for this must be just prior to the commencement of flowering, 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 has a much smaller part of the market. These different species all have different characteristics, need different management and suite different conditions, but all produce good fodder and can return significant amounts of nitrogen to the soil. The hard seed levels of woolly pod vetch and purple vetch should be a major consideration when choosing the species of vetch to sow.

Common vetch (CV)

Varieties include Studenica, Morava, Timok, Volga, Rasina, Blanchefleur and Languedoc. Common vetch is the most widely grown species, predominately grown in low rainfall areas in SA, Vic, WA and 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 nitrogen 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, whereas older varieties like Blanchefleur and Languedoc are highly susceptible to this disease. This is important because rust can drastically reduce yields and may induce abortions in pregnant livestock if they are fed heavily infested plant material.

Management issues to consider

Grow rust resistant varieties whenever possible. In higher rainfall areas monitor for Botrytis symptoms, this disease can greatly reduce yields. In all vetches regrowth after grazing is very dependent on seasonal conditions, good moisture and favourable environmental conditions.

Woolly pod vetch (WPV)

Varieties include Capello, Haymaker, RM 4 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 flower later than the common vetch varieties, flowering 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 (yields between 5-12t/ha can be achieved), however grain yields are much lower (0.8t/ha average) and it can be difficult to thresh at harvest.

WPV grows well in mixed crops situations and can tolerate some shading from 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. WPV varieties 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 considered to be safe levels of this grain in a dietary mix. Care should be taken when grazing, as this species is susceptible to over grazing early 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 this crop and WPV is a poor competitor for weeds in early growth stages. Herbicide options are limited for broadleaf weed control, especially in crop. The best option is to use registered herbicides post sowing pre-emergent. Don’t graze early (before 15 nodes), ensure you cut hay or graze before pod start to set seed.  Be aware this species has hard seeds (RM 4, 5-7%, to Namoi > 30%) and can appear as volunteers in subsequent crops. This species is cross pollinated, and if you are producing or/multiplying seeds from RM 4 which has a low hard seed level, isolate from higher hard seed varieties like Namoi by over 1 km.

Purple vetch (PV)

Varieties include Popany, Benatas and Barloo. This species is similar to WPV or later in flowering time (>125 days) and is suited to medium to high rainfall (>480 mm annual average rainfall) areas with a good finish. PV is a high fodder producer in these higher rainfall areas but is not suited to areas of lower rainfall. PV can tolerate some waterlogging compared to other vetch species, grain cannot be used to feed 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, these can be found online.

Method

In 2020, four trials were conducted by the NVBP across lower rainfall areas at Werrimull, Koolooonong, Curyo and Speed in Victoria. These trials were designed to include four varieties and eight advanced lines to demonstrate varietal performance and assess the potential of the advanced lines in specific regions. The four trials were individually designed as randomized complete block designs. All trials were assessed for emergence, vigour, time to flowering, dry matter production and grain yield. The trials at Werrimull, Koolooonong and Speed were sampled for dry matter production twice, first in early autumn and again at early flat pods. This was done to assess early grazing potential in mixed farming/livestock systems. The Curyo trial was sampled for dry matter at late flowering/early flat pod. All trials were harvested for grain yield at full maturity.

Results and discussion

Table 1. 2020 growing season rainfall (mm) at Speed, Kooloonong, Werrimull and Curyo.

Table 2. Biomass yields (tDM/ha) of common vetch varieties and an advanced line at four sites in the Victorian Mallee in 2020

Table 3. Grain yields (t/ha) of common vetch varieties at four sites in the Victorian Mallee in 2020

The results above give an excellent example of the regional potential of the released varieties.

Studenica demonstrated its early growth and vigour, showing potential for use as an early fodder production or winter grazing option in mixed farming systems. Studenica has very early flowering and maturity, so does not always suit spring hay production unless sown later.

Biomass cuts conducted at the more traditional hay timing showed the mid maturity varieties, Volga, Timok and SA 37107, have the ability to continue growth through September and increase fodder production. Morava can produce excellent hay yields but requires adequate soil moisture late in the season, in October, to fulfill its potential for fodder production.

Breeding line, SA 37107, is a likely candidate for release in the future. It flowers at a similar time to Timok, as a mid-maturing line and has shown improved adaption to low pH soils, consistently topping trials of both hay and grain at sites with <5.5 pH. SA 37107 achieved hay yields consistent with other varieties across these sites, as well as topping the grain yields across all sites.

With the increase in vetch use across the Mallee areas it is important to choose varieties aligned with your initial end use goals. Time to flowering and maturity are important considerations when targeting specific end uses and will dictate the optimum seeding window. With the increased diversity of maturity in vetch varieties, it is now possible to swap varieties if you can’t sow vetch until later in the seeding program or if it is to be the first in the ground. Like other crops, choose varieties with end goals in mind, not as a one size fits all approach. For specific varietal details see the 2021 Victorian Field Crop Sowing Guide.

Conclusion

Vetches have 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, the focus is not solely on grain production. Vetch can be used as a tool to combat herbicide resistant grass weeds and still produce a return with hay, grazing or grain and have an impact on subsequent cereals with increased levels of soil nitrogen.

A successful vetch crop can:

• 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 combat herbicide resistance, green/brown manuring can be used with vetches to control competitive weeds which are difficult to control in other crops, e.g. brome grass and barley grass.
• Available soil nitrogen is maintained and can be improved by an average of 56, 92 and 145kg/ha after grain, hay and green manuring, respectively (data from three years x five sites) helping to increase grain yield and protein of subsequent cereal and oilseed crops.
• Grain and hay/silage from Common vetch varieties can be used to feed ruminants without limit.

The key to a successful vetch crop and achieving the maximum benefits from vetch 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.

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 nitrogen applications. This can have a significant impact on profitability and the stress levels associated with these decisions.

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

Acknowledgments

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

Useful resources

NVT Crop Sowing Guide

Contact details

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