Spring bean growers drilling crops in the coming weeks can gain up to 1.2t/ha extra yield by using wider row widths and higher plant populations, according to researchers.
Findings from the first year of a study suggest there is scope to increase drilling row widths to 24cm and establish up to 60 plants/sq m, without any adverse effects on yield from plant competition within the rows.
In the absence of published recommendations, current Processors and Growers Research Organisation (PGRO) guidance is to drill narrower row widths of down to 15cm.
However, Steve Belcher, principal technical officer, said this gave the lowest yields in the 2016 study.
At 15cm rows, the yield was 6.2t/ha with 60 plants, compared with the highest yield of 7.1t/ha from 24cm row widths (see graph below).
“The traditional view was that crops with higher plant populations established using wider rows were more likely to compete with each other and underperform, and that better yields came from situations where there was a very even distribution of seeds,” he said.
Neither proved to be the case in the PGRO work, he reported.
“Going up from 15cm to 24cm wasn’t a problem at all, although 36cm rows proved to be too wide and yields dropped off significantly at these greater widths with 60 plants/sq m.”
One possible explanation for the 2016 results is that beans produce an upright plant, with leaves growing all the way up the stem.
“Where plants are evenly spaced, a canopy tends to form over the top of the crop,” said Mr Belcher. “But when you widen the rows, sunlight can get down into the canopy and reach all of the leaves.”
These early results will be well received by growers planning to direct drill their bean crops, as most of these drilling systems work on wider rows, he pointed out.
“At the moment, growers are using all different kinds of approaches, ranging from 12cm right up to 36cm. Some are trying blocking off every other coulter.”
In 2017, the work will be repeated with a few more treatments included, following grower feedback.
“In 2016, we had three row widths – 15cm, 24cm and 36cm, with two plant densities – 40 and 60 plants/sq m.”
This year, he is planning to add an 18.75cm and a 30cm width, as well as looking at a pair of rows with a 15cm spacing, followed by a gap of 30cm, before repeating the pair of rows again.
While results to date indicate 24cm is about right in UK conditions, going up to 36cm doesn’t fare as well with higher plant densities, he added.
“It’s early days, but these results are interesting and they reflect what some growers are finding in the field.”