Summary

New forage and dual purpose field pea varieties provide growers with an alternative break crop to vetch. However agronomic management to reduce blackspot disease risk and maximise biomass production will be essential to make the most of these new options.

Background

With field pea and vetch making up about 120,000 ha of South Australia’s cropping area, the introduction of these new varieties offers an alternative to growers looking for a break crop option, particularly in lower rainfall zones.

Research Aims

The research was designed to assess the potential of the forage field peas, as well as providing agronomic management guidelines and assessing the nitrogen fixation and hay quality of the forage field peas compared with grain field peas and vetch.

In The Field

Forage and dual purpose field peas were compared with grain field peas and vetch at four replicated trial sites in South Australia in both 2013 and 2014. This has provided an understanding of their performance and potential for use as a break crop option in SA.

Trials comparing plant biomass and grain yield production of field pea and vetch were completed at Minnipa, Lameroo, Hart and Tarlee in 2013 and 2014. Nodulation and nitrogen fixation assessments were collected at Hart and Tarlee. The hay quality and digestibility of field peas and vetch samples were analysed for samples from the Tarlee site.

Results

The forage field pea variety PBA Hayman agronomically performed very differently to the grain variety Kaspa and dual purpose varieties Morgan and PBA Coogee and will require a different management strategy to optimise production.

PBA Hayman was found to have a higher biomass production potential than the other field pea varieties evaluated and in some situations than vetch. This increase was up to 70% greater than Kaspa and Morgan in some conditions and was more evident when sown early or grown in more favourable environments.

PBA Hayman was found to have an increased susceptibility to the major pea disease “black spot” over all other varieties and, under high disease pressure, biomass production was dramatically reduced compared with Kaspa and Morgan.

PBA Hayman has significantly lower grain yield potential, between 20 and 80% lower, than other field pea varieties and grain retrieval may be difficult due to its late maturity.

The value of PBA Hayman as an alternative to vetch in SA will depend on being able to sow it early and control blackspot disease infection. This may be difficult to achieve in many areas and seasons.

Biomass production of the potential dual forage/grain field pea PBA Coogee was generally only similar to Kaspa and Morgan and grain yield was always lower than Kaspa by 14-54% and equal or lower than Morgan. This suggests Kaspa or Morgan remain the variety of choice for grain yield.

Biomass comparisons between field peas Kaspa, Morgan and PBA Coogee and vetch were complex, varying with site, year, variety and sowing date. Generally, vetch varieties produced equal or greater biomass levels when blackspot was present or in favourable growing environments. The best relative performances by the field pea varieties were at later sowing dates in lower rainfall environments. Field pea varieties generally showed similar or greater grain yields than vetch.

Nodulation studies found that the forage pea and vetch varieties formed an adequate number of nodules per plant with background soil rhizobia. Pea and vetch varieties sown at the early timing of early/mid May fixed on average 15 kg N/ha more than those sown later (late May – early June).

Oat/legume mixtures of more than 20% oats generally reduced metabolizable energy (ME) and crude protein levels similar to those found in 100% oats.