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Spring Peas and Beans – Pre-harvest dessication options

7 August 2019

Combine peas

Due to the indeterminate nature of combining peas, most combining pea crops in Scotland benefit from desiccation, unless it is an exceptionally dry harvest.

Diquat (e.g. Reglone): The recommended dose is equivalent to 2-3 litres of Reglone in 200-300 litres of water/ha.  A wetter, such as Agral, should be used but if peas are intended for human consumption consult with your processor first.  The optimum time of application is once the lower pods are yellow-brown parchment-like but not shedding, while the middle pods are yellow crinkled and becoming parchment-like.  At this stage the average moisture content is likely to be below 45%.  Early desiccation tends to reduce yield, produce shrivelled peas and weaken the straw; if desiccation is delayed, lodging tends to become more extreme and spray penetration can be inadequate.  A period of at least seven days is required between desiccation and combining.  Although combining can take place as soon as 7 days after desiccation, the norm is closer to 12-14 days.  Straw from desiccated crops may be fed to livestock from 4 days after spraying.

Glyphosate (various): Glyphosate is recommended as a pre-harvest herbicide and any desiccating effect is an additional benefit.  Crops grown for seed should not be treated with glyphosate.  As the crop is almost mature when glyphosate is applied, this treatment does not accelerate the natural rate of crop maturity; it should not be used to even up or desiccate peas.  The recommended dose of glyphosate for weed control in peas varies according to the product used, weeds that are present and their density.  The average moisture content of the seeds should be below 30%.  The target weeds should be healthy with green leaf to intercept the spray.  Harvest may take place 7 days after application of glyphosate but 10-14 days is more likely.

Field beans

Field beans for animal feed can be treated pre-harvest for control of most grasses and broad-leaved weeds with many glyphosate products.  It is applied when the seed has below 30% moisture, the bean stems are usually green/brown and the pods are black. Generally about 10-14 days before harvest, but can be a lot longer.

Diquat is a quicker crop and stem desiccant, and controls or checks many weeds.  It is applied when the crop is mature and the majority of pods have turned black.  Harvest after 4-7 days.

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