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Pea Post-Harvest

Western Canadian research into the nutritive levels and value of field pea straw is limited, but it is believed that field pea straw has considerable nutrient value when used as an alternative feed source and as a nutrient when returned to the soil.

Value as a Feed Source

Results from a three-year study on 469 field pea straw samples from various locations in south central Alberta show large variability in nutritive value between years and sites. This variability may be a reflection of soil fertility, moisture and environmental (growing) conditions.

Overall quality is usually better than cereal straw. Field pea straw can be significantly higher in protein, but high fibre levels limit digestibility and expected feed intake.

  • field pea straw is primarily useful for beef cattle rations where high quality roughage is not as important as for other classes of livestock – when pea straw is fed with higher quality roughage and/or grain, it can produce a very cost-effective ration (the higher protein levels generally make pea straw a better match with grain than cereal straw)
  • palatability studies (how well an animal will consume the feed) with field pea straw have not been conducted – anecdotal evidence with beef cattle suggest a wide range in field pea straw palatability (cattle devouring the feedstuff versus complete rejection)
  • processing the straw (such as grinding or chopping it with machines like mix mills or hay busters) and mixing the straw with other feeds may help with palatability
  • farmers thinking of using field pea straw in rations should have their feed tested

Nutrient Value of Straw Returned to Soil

It is questionable whether benefits derived from removing straw from the field through baling are greater than incorporating it into the soil. Field pea straw contains nutrients, which once broken down by the soil micro-flora, can be made available to the following year’s crops. However, the total value of nutrients varies considerably depending on total pounds per acre of straw produced, When assessing the benefits of baling versus incorporating, the cost of baling straw ($7.25 to $10.25/tonne ) and hauling it ($3 to $10.25/tonne) must be taken into consideration (source Alberta Machinery Guide 1998). Given these factors (taking baling and hauling to the customer’s yard into account) and the value of the nutrient contained in the straw, a break-even return of $22.12 to $32.37/tonne is required.

The decision to work straw back into the soil or bale and feed it is entirely up to each individual operation. It’s important to recognize field pea straw’s worth and not under-value it. Farmers thinking of removing field pea straw should test it for protein, phosphorus, potassium and sulfur to determine the nutrient content. A feed analysis of a representative sample of pea straw for protein, phosphorus, potassium and sulphur is needed to do the calculations.

Making the Grade

The lowest grade for human edible green pea, Canada No. 2, requires a sample with no more than 1 per cent other classes (off-types or admixtures), 3 per cent or less bleached seed and 5 per cent or less total damage, with minimum earth tag. Other quality factors or standards are also used in the grade table, but off-types, bleach and earth tag are the three most important factors that can downgrade green pea samples to feed.

Following these next tips can help producers achieve the all-important Canada No. 1 or 2 grade for the premium, human edible green pea market.

Off-types & Admixtures

  • don’t use seed that contains admixtures of yellow or maple pea (pea characterized by a dark brown seed coat) – maple pea (distinguished by its purple-coloured flower) can be rogued in the field
  • if you’re growing both yellow and green pea on your farm, eliminate contamination at seeding and harvest
    • keep machinery clean
    • clean augers before moving from one type/colour of pea to another
    • use belt conveyors rather than conventional augers, if possible

Minimize Bleaching

Green pea bleaching occurs when harvest is delayed, and maturing seed is exposed, over time, to wet and drying conditions as well as sunlight. Bleach is defined as the discoloration of more than 1/8 of the pea seed cotyledon. If more than three pea seeds in 100 have a bleached area (that is, a white or yellow color larger than 1/8 of the seed), the sample will grade less than Canada No. 2. The longer the crop stays out, the greater the likelihood of bleaching. In other words, every day in the field costs you money.

Here’s how you can minimize bleach:

  • select uniform fields and seed early
  • seed green pea FIRST
  • control perennial weeds the year before with a pre-harvest application of Touchdown® or Roundup®
  • scout fields before harvest to determine when the crop is ready for harvest
  • use Reglone PRO® desiccant with high water volumes when most of the field is ready for desiccation
  • green pea will be ready for harvest five to seven days after desiccation – ensure maximum combine capacity for rapid harvest, and use a second combine if available

Earth Tag Management

To reduce earth tag in green pea, follow these management tips:

  • select a green pea variety with a good harvest rating
  • roll your pea field just after seeding, to eliminate ridges and an uneven seed bed, as this approach will minimize dirt entering the combine (normal plant dust will not adhere to a dry pea seed coat, but combined soil will)
  • use Reglone PRO® at the proper desiccation stage to even out crop drydown and eliminate green weed material – green material (either green weeds or green pea plant material) will increase the level of earth tag on the seed
  • combine when seed moisture content reaches 18 to 20 per cent for the first time – properly tuned aeration bins are essential for a green pea harvest
  • field pea combined at 18 to 20 per cent moisture will require aeration conditioning for short-term storage

Green Pea Bleach Study Results

A three-year project, involving nine green pea varieties at a site north of Edmonton, was conducted to study different desiccation practices and their effects on green color retention of the seed. The study concluded that quality green pea crops can be produced profitably in Alberta.

  • all nine green pea cultivars graded Canada No. 2 or better when desiccated with Reglone PRO® at the correct time and with high water volumes (combining occurred six to seven days after desiccation in all three years)
  • green pea varieties vary in their susceptibility to bleaching, with smaller seeded varieties being slightly less susceptible (in this study, seed size differences did not affect final grade)
  • one treatment in the study – which included natural drydown, no desiccation and late harvest – resulted in all varieties being downgraded to a Canada No. 3 or feed quality
  • natural drydown resulted in pea harvest occurring about two weeks later than the desiccated plots
  • natural drydown produced seed with more bleach as well as an increased number of pea seeds with a dull, less intense green colour