Pollinating insects can increase bean yields by up to 50%. Emma Gillbard visits a farmer who is using beetle banks and grass margins to boost yield and cut chemical use.

Scottish farmer John Seed is using the power of pollinators to grow 6t/ha spring bean crops with zero insecticides, purchased P and K or pre-harvest glyphosate.

Pollinating insects are vital to successful field bean production, which is why John has established a range of flowering grass margins and beetle banks to encourage beneficial insect populations on the farm.

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According to the Processors and Growers Research Organisation (PGRO) pollinators can promote field bean yield by 17 to 30%.

This can rise to over 50% when crops are affected by heat stress.

“There is more to be done to improve yield by looking after pollinators than there is by applying fertiliser and other chemicals. The less chemical inputs, the better,” says John.

Biodiversity boosts yield

In a drive to increase biodiversity and encourage pollination at Woodend Farm in the Scottish borders, John and his wife Louise established 5m multi-species grass and flower-rich margins around every field perimeter and seven beetle banks across the 180ha farm.

Breaking up large fields up to 40ha in size created a habitat haven and highway for insects to easily move around the farm.

The biodiversity boost not only increased pollinators, and consequently bean yield, but also eliminated the need for insecticides across the farm, as natural predator populations thrived.

“Bean crops grown next to the beetle banks are noticeably thicker with more than 15% higher yields. There really is a clear difference.

“However, this yield benefit is not so apparent in other crops which highlights the fact beans are so reliant on pollination as a yield factor,” says John.

This is because pollinating insects – particularly bees – set seed in field beans via cross-pollination and help facilitate self-pollination.

The proportion of seed produced by each mode of pollination varies with variety, level of cross-pollination and with crop stress and disease.

Yields of bee-pollinated bean crops can also be 20% less variable, with greater harvest index, shorter straw, and earlier ripening.

Shorter straw length means crop canopies are less likely to lodge, while faster ripening means an earlier harvest and reduced reliance on pre-harvest glyphosate sprays – something which is particularly important for John.

John Seed © Emma Gillbard

Cutting chemical use

John now grows a total of 40ha of winter and spring beans, destined as animal feed for his flock of 32,000 laying hens, in a bid to increase home grown protein.

Growing crops with as little chemical input as possible is a key objective of his, in order to promote soil health and keep costs to a minimum.

Last year, spring beans averaged 5.5 to 6t/ha, with just the one pre-emergence herbicide and a single chocolate spot spray.

John previously used pre-harvest glyphosate to desiccate the crop and destroy weeds lurking beneath the bean canopy, but he now lets crops naturally senesce with the help of disease and pollinators.

“We apply one chocolate spot spray early in the season to protect the crop and maximise green leaf area, but that’s it.

“An influx of disease later in the season is not necessarily a bad thing as this can help the crop naturally die off,” says John.

Together with the benefit of pollinators bringing crops to maturity earlier, John has now successfully stopped using glyphosate for the last two years. 

This has also been made possible by having an on-floor biomass-fired grain drying system that will dry beans from over 20% moisture to 13% in less than a week.

P and K fertiliser

John’s ambition to cut chemical use at Woodend Farm does not stop there. The inclusion of chicken litter in the arable rotation has hugely improved soil fertility and organic matter levels.

There have been no applications of purchased P and K fertiliser or lime for the past seven years.