Even the best bean grower would have struggled to achieve high yields last season in the worst combination of conditions possible for the crop, which saw yields 23.4% below the five-year mean in variety trials.
Although bean seed is sparse this season, the usual rotational benefits of pulses in lowering inputs while providing a break crop are bolstered by relatively high market prices, meaning growers should not be too hasty to drop beans from their rotation.
“Last season’s weather was quite extreme. If the weather is completely different this season the result is going to be completely different,” says the Processors and Growers Research Organisation’s (PGRO) principal technical officer Becky Howard, adding there are many lessons that can be learned from last year’s poor performance.
Late drilling penalty
Prolonged cold and wet conditions, as was the case in spring 2018, only serve to reinforce why the optimum time for drilling winter beans is from mid-to-late October.
In a wet spring, growers are forced to keep a close eye on disease levels, particularly for chocolate spot, in any early, lush crops which were drilled early.
“If we get any severe cold period in January to February, and there is frost damage to any lush beans, then disease levels tend to be a bit higher on those crops,” says Ms Howard.
The ideal time to drill spring beans is from the end of February to March, with the key factor being to wait for the right conditions rather than trying to force beans into cold, wet soil.
Bean seed will not get away quickly, and drilling in such conditions also results in damage to soil structure, which beans are sensitive too, says Ms Howard.
However, if drilling is left until April then growers will incur yield penalties. “After the middle of April and certainly by May there is always a drop-off in yield, although it varies depending on soil type,” says Ms Howard.
PGRO trials have shown the yield penalty of a mid-April drilling date compared to the ideal mid-March timing is between 0.2-0.5t/ha.
Last year growers who patiently waited for the right conditions were not rewarded with an opportunity until April, with a lot of beans going in then.
Had the reasonable May weather not been followed by a heatwave in June, growers should have produced a decent crop, despite this yield reduction, as crops have a great capacity to recover.
Instead, the wet spring quickly shifted into drought-like conditions – the worst combination for achieving bean yields, leading to the smaller-than-normal bean crops quickly running out of moisture.
Although there is little farmer can do to mitigate such poor growing conditions for pulses, anecdotal evidence from bean growers has shown moisture retention in soils to be better using min-till methods, says Ms Howard,
Soaring temperatures in June last season coincided with the beans starting to set pods, and meant growers saw much higher levels of bruchid beetle damage than normal – up to 80% in some cases.
This is far above the 3% necessary for human consumption and the maximum 10% required for animal feed, with the pest also being suffered in higher levels further north than usual.
“The problems experienced with bruchid beetle were very much due to the temperatures in June and July,” says Ms Howard.
“There are a limited number of active substances that can be used during flowering, and the products that growers do have available are not as effective.”
Managing the pest relies on reducing egg-laying at early pod set. Once you see yellow eggs on the bottom pods, it is too late which is why timing is so important.
Becky Howard’s top spring bean tips
- Aim for the idea drilling date of late February to March
- Don’t force crops into poor seed-beds, wait for the right conditions
- Reducing soil disturbance can help preserve moisture if conditions turn dry
- Signing up for bruchid beetle alerts means the available products can be used at the key time of early pod set
This makes signing up for bruchid beetle forecasting alerts, available on the Syngenta pest-monitoring site, even more important to ensure growers are using what actives are available at the key times.
Emails are sent twice a week starting in May to notify when temperatures are expected to reach over 20C and, therefore, make the beetle a threat.
There is an indication of resistance developing in beans to pyrethroids, but last season growers had another option thanks to the approval of Biscaya (thiacloprid) in November 2017.
Although it is difficult to assess its effectiveness so far, unlike pyrethroids, thiacloprid’s persistency is not reduced as temperatures increase.
A new season offers a new start, but there is some carry over from the poor season last year for beans as both bruchid beetle damage and low moisture content at harvest has affected seed quality and lowered germination rates.
Those growers who can find seed will likely need to use a higher seed rate to combat this lower germination, but those that can’t could look instead at peas.
While vining peas are usually grown on contract, the price for combinable peas such as marrowfat is good – about £220/t for animal feed and £250/t for human consumption.
Peas can be sown much later than beans, from the end of February to May, and combinable peas are much more tolerant of dry soils, although not of poor soil structures.