Why N-fixing seed treatment may benefit pulses this spring
© Syngenta A novel nitrogen-fixing bacterial seed treatment could prove especially beneficial this spring in pulse crops with lower levels of soil nitrogen (N).
Syngenta technical manager Simon Jackson says the wet autumn and winter will have depleted soil nitrogen reserves.
In addition, pulse crops are typically grown as a break after successive nutrient-depleting cereal crops, when reserves in the soil are at a low point in the rotation.
See also: Arable Insights Farmers’ strategies to optimise nitrogen use
Simon Jackson © Syngenta
Simon, who spoke at the PGRO Pulse Potential Roadshow, says: “In some instances, soils simply don’t have sufficient background bacteria to initiate productive root nodule formation in pulse crops, or where the existing nodules have been damaged by pea and bean weevil activity.”
One solution, he believes, is to use an endophyte seed treatment such as Nuello iN.
The seed treatment supplies two bacteria capable of atmospheric nitrogen fixation, one of which also helps to release phosphate from the soil to enhance plant establishment.
Importantly, the bacteria get into the root during germination and colonise the plant, to source nitrogen in a form that can be used by the seedling long before root nodulation.
Simon highlights that pulse crops are particularly well suited to take advantage of novel nitrogen-fixing bacteria biofertilisers, since they are already adept at utilising naturally fixated nitrogen.
© Syngenta
Improved performance
Combining the seed treatment with a foliar applied version (Vixeran) later in the season has been shown in trials to add consistency and certainty to performance in both peas and beans.
That’s because pulses are particularly greedy for nitrogen at certain points in the growing cycle, especially seed development as pods fill.
If they draw on the green leaf area to fulfil that demand, the photosynthetic activity of the plant, and consequentially its yield, will be adversely affected.
Therefore, he believes nitrogen fixation from applied nitrogen-fixing bacteria can help to fill the gap and keep plants actively growing to increase yield.
Trial results
Trials in vining peas in 2024 saw that using the microbial seed teatment Nuello iN resulted in better rooting and stronger early growth.
Five trials across the eastern counties and Scotland all recorded a positive increase in yield from the treatment, with an average improvement of 0.95t/ha.
The seed treatment supplies the equivalent of about 30kg/ha of artificial N.
Syngenta’s Simon Jackson says pulse crops can get the same atmospheric nutrient boost from a foliar application of Vixeran fixating bacteria later in spring.
Timing recommendation for peas and beans is around six true leaves.
At this point there is good growth to get the bacteria taken up into the plant, but there is still sufficient bare soil so that some bacteria reach the ground and fix nitrogen in the biosphere around the roots.
He says the field bean trials in 2024, which were badly hit by the widespread onset of rust, achieved a 0.9t/ha yield increase from the fungicide programme, and an additional 0.26 t/ha when combined with the Vixeran treatment – achieving 4.82t/ha.
There was also an increase in the thousand seed weight with the foliar application.
In combining peas last year, a grower’s field scale trial, with Vixeran at the six true leaf stage in May, produced a 1.47t/ha increase at 6.9t/ha, compared with 5.4t/ha in the farm standard control.
