Spring beans Autumn sown?

Can spring beans  be autumn planted as an alternative to a winter beans? 

A question being asked in the light of an apparent shortage of winter beans due to fewer plantings (wet autumn) and the lower yields of the 2020 harvest. 

Outcomes from trials at PGRO are summarised here.

Out of curiosity PGRO a spring bean was planted in the autumn of 2013 alongside 3 Recommended List trial sites (4 reps the same as the trial). Plots were sown  at  20 plants/m² (same as the winter beans) and at 40 plants/m² (the then recommended density for spring beans). 
The spring beans survived the winter and yields were very high in that year with the spring bean out-yielding the winter bean Tundra at 2 of the 3 sites.  This comparison has continued.

There have been site changes (from fertile silts to sandy loams) and the spring bean varieties have varied.

Below is yield data across all sites from 2014 to 2019, whilst varieties of spring bean have varied, the winter bean Tundra was a constant.

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Yields were variable over the years, with autumn sown spring beans at 40 plants/m² (SB40) giving similar yields (101%) to Tundra at 20 plants/m² (Tundra20) (100%). 
Autumn sown spring beans at 20 plants/m² (SB20) gave lower yields (88%). 
In some years and at some sites, autumn sown SB20 yielded a little higher than SB40.

By following just one site, Stubton, Lincs (2016 to 2019) a comparison with a spring bean sown in the spring can also be made. Whilst there there is a lot of variability with Tundra at 20 plants giving the highest yields (100%).  Autumn sown SB40 (95%) was higher yielding than autumn sown SB20 (89%) or spring sown spring bean at 40 plants/m² (SB40) (93%).

Spring beans may not be as cold tolerant as winter beans. The winters during the trial period have been relatively mild, but there have been cold snaps.

It should be noted that all PGRO winter bean trials are covered with a 1mm mesh ground net after pre-emergence herbicide to protect against crows, rooks etc. It may provide some slight protection against frosts.

Awareness notes:

• If using Farm Saved Seed  testing is considered essential. A seed testing service is available from PGRO   https://www.pgro.org/seed-testing/
• Don’t plant too early, target drilling last week of October through to mid-November.
• Avoid plants being too proud through winter.
• Sowing deep can minimise lush top growth in early winter.
• If autumn planting spring beans, aim to achieve at least 40 established plants/m².
• Spring beans do not branch as well as winter beans and ground cover is less extensive.
• Amongst other traits winter beans are bred for cold tolerance, branching and a high tolerance to Ascochyta  so it important to recognise that they have a different profile to spring beans.
• Be alert to diseases, especially Ascochyta and chocolate spot
• Note that autumn planted spring beans flower earlier and
• Autumn planted spring beans are earlier to mature than either winter beans or spring planted beans.

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For discussion with the researcher contact Steve Belcher at PGRO
email : steve@pgro.org
Office telephone : 01780 782585