Proper field pea storage management is important to prevent a grade decrease.
Field pea can be safely stored between 12% to 16% seed moisture content and 15°C for several weeks, but regular bin probing and monitoring is required.
Crops stored under cool, dry conditions can be stored for long periods, but as seed moisture or temperature rises, storage length becomes less. The drier and cooler the grain, the safer it is during storage. The target temperature for all grains is 15°C.
Field peas stored at 12% seed moisture and a low temperature of 6°C maximizes the storage to 370 weeks, whereas a seed temperature of 16% and a temperature of 16°C reduces safe storage time to 20 weeks. See Long-Term Storage of Lentils, Peas, and Chickpeas.
Peas often respire or go through a sweat after being placed in storage. Extra care should be taken to monitor the grain inside the bin for moisture build-up or spoilage, temperature, and for the presence of insects.
It’s important to be cautious of weed seed dockage or green materials (i.e. Canada thistle heads) from volunteer crops, as they can cause heating (hot spots) if you cannot not get proper air flow through the bin.
A variety of manual and automated systems are available to help keep track of seed condition.
If pulses require handling, they should be moved as little as possible, and handled gently to reduce chipping and splits. Use belt conveyors instead of augers. If using augers, run the auger full and at a reduce speeds. Use ladders on equipment to minimize the dropping of seed from more than a few feet.
Pea seed should not be cleaned or handled below –20˚ C because of the increased risk of chipping and peeling.
See PAMI research for more information: Improved Management of Stored Pulses, Research Update, August 2019, PAMI
HEATED GRAIN DRYING OR AERATING DOWN
Peas are considered dry at <16% seed moisture, tough between 16.1% and 18% seed moisture, and damp at >18% seed moisture.
Drying or aerating down to 16% moisture should be done gradually at temperatures at or below 45°C.
Using air for temperature control is known as aeration while using ambient air for drying is know as natural air drying (NAD).
Blowing air through grain is the most common method to control temperature in the bin. If the grain is tough but not wet, then blowing ambient air through grain can also result in moisture removal.
When drying field pea, the time to run your fans will depend on airflow rate, starting moisture content, and ambient conditions.
Run the fans when the average ambient temperature is cooler than the grain.
Latest research: Improved Management of Stored Pulses, Research Update, August 2019, PAMI
If the seed moisture content must be reduced by 5% or more, drying should take place in two stages.
With a hot air dryer, pea seeds should be dried to within 2% of final moisture content and then tempered in an aeration bin for at least 6 hours.
Afterwards, they should be cooled to the outdoor seasonal temperature. The slowness of this process prevents grain cracking.
Another option is to start combining between 18% –20% moisture and then truck the product directly from the field to the seed cleaning plant to have the peas cleaned, this will knock off 1% or 2% moisture. Upon returning to the farm, stick the field peas in an aeration bin and dry down to 16%.
Making the grade
Grading standards are determined by the Canadian Grain Commission. Through the harvest sample program, farmers have the opportunity to send in harvested samples to the Grain Commission for grading. This grade can be compared with local buyer grades and may assist in marketing.
Colour as a grade determinant is assessed after the removal of damaged peas and peas of other colours.
Good – a bright, normal colour, lightly earth tagged or lightly stained.
Fair – moderately immature, moderately earth tagged or stained.
Pink peas – refers to staining caused by the bacteria Erwinia Rhapontici.
Food peas – surface discolouration is to be considered in the overall colour assessment of the sample. Discolouration that extends into the cotyledon is to be considered damaged.
Feed peas – colour is not a factor.
Care must be taken in assessing these pink peas as there are pink seed treatments for peas being used. Questionable samples are to be handled as per the ISO national procedure for handling suspected contaminated seeds.
SIZING OF YELLOW PEAS
In yellow peas only, if size is determined as small or large, then size becomes part of the grade name. If a sample does not meet the definition for large or small, it is graded without reference to size.
Bleached applies to green peas only. Green peas are considered bleached if 1/8 or more of the surface of the cotyledon is bleached to a distinct yellow colour which is in marked contrast to its natural colour.
Damaged peas include:
Split or broken peas with more than 1/4 of the pea broken off.
Splits include split peas, pea hulls, split peas of other colours, broken pieces that are less than 3/4 of the whole seed, and cotyledons that are loosely held together by the seed coat.
Whole peas that are sprouted, heated, shrivelled, damaged by insects, badly deteriorated or discoloured by weather or by disease, or that are otherwise damaged in a way that seriously affects their appearance or quality.
Grade of yellow peas depending on type of damage:
Green peas – considered damaged only if peas are damaged from another cause.
Whole or split peas which are distinctly green throughout as a result of immaturity or variety is considered “Peas of other colours”.
Immature yellow peas are considered damaged only if peas are damaged from another cause.
Immature, but not distinctly green, peas – are not considered damaged, but taken into account in the general evaluation of the sample.
Heated and Binburnt – Heated peas or split peas that have dull seed coats and discoloured cotyledons ranging from light tan to dark brown are considered heated.
If they are lightly damaged, with tan-coloured cotyledons and distinct heated odour, the grading is heated.
Otherwise they are considered damaged.
Binburnt refers to peas that are blackened as a result of severe heating in storage. There is a single tolerance in feed peas for the total of heated and binburnt.
Odour – There is no numeric tolerance for odour. Consider the basic quality of the sample; the type and degree of the odour, and the presence of visible residue causing the odour. If odour is the grade determinant and there is:
An excessive objectionable odour not associated with the quality of the grain, but not heated or fireburnt – then the grade is “Peas, Sample Canada (colour and size) Account Odour.
An excessive heated odour – “Peas, Sample Canada (colour and size) Account Heated”.
An excessive fireburnt odour – “Peas, Sample Canada (colour and size) Account Fireburnt”.
Shrivelled – are distinctly distorted and shrunken, or have a severely dimpled surface.
Marsh spot: this nutritional disorder, caused by manganese deficiency in the soil, results in dark reddish brown spots or cavities on the inner surface of the cotyledons.
Foreign material includes any material other than peas, broken peas or pea seed coats. Foreign material is not a grading factor in feed peas.
Other pulses such as beans, chickpeas and lentils are included in foreign material.
In feed peas, pulses other than green, yellow or orange peas refers specifically to maple and marrowfat peas. These are not considered as part of foreign materials.
Hard earth pellets are pellets or stones that do not crumble under light pressure.
Soft earth pellets are pellets that crumble under light pressure. These pellets can be earth and fertilizer pellets, or any non-toxic material of similar consistency.
Stones are hard shale, coal, hard earth pellets, and other non-toxic materials of similar consistency.
Fertilizer pellets are a manufactured plant nutrient product used by producers in the production of grain. They are typically small, round or irregular shaped and usually white, grey, brown, pink or reddish in colour.
Fertilizer pellets are assessed as stones when constituting 1.0% or less of the net sample weight.
Ergot is a plant disease producing elongated fungal bodies with purplish-black exterior, a purplish-white to off-white interior, and a relatively smooth surface texture.
Excreta is excrement from any animal including mammals, birds, and insects.
Insect parts – refers to pieces of insects such as grasshoppers and lady bugs that remain in the sample after cleaning or processing.
Samples are analysed for the percentage of insect fragments and graded according to established tolerances.
Insects may also result in seed staining and earth adhering to the seed and may result in samples having an objectionable odour.
Samples containing staining will be considered to be earth tagged and grading according to colour definitions.
Sclerotinia sclerotiorum is a fungus producing hard masses of fungal tissue, called sclerotia. The sclerotia vary in size and shape, have a coarse surface texture, vary in exterior color from dark black to gray to white and have a pure white interior.
Contaminated is defined in the Canada Grain Act as; “Contaminated means, in respect of grain, containing any substance in sufficient quantity that the grain is unfit for consumption by persons or animals or is adulterated within the meaning of the regulations made pursuant to sections B.01.046(1), B.15.001 and B.15.002(1) of the Food and Drugs Act.”
Samples deemed to be contaminated by the Grain Research Laboratory in consultation with the Chief Grain Inspector for Canada are graded “Peas, Sample Condemned”.
Fertilizer pellets in excess of 1.0% of the net sample weight are graded Peas, Held IP Suspect Contaminated Grain.
If a sample is suspected of being coated with a pesticide, desiccant, inoculant or if the sample contains evidence of any foreign chemical substance other than fertilizer pellets, the sample shall be graded “Peas, Held IP Suspect Contaminated Grain”.
IMPACT ON GRADING
The lowest grade for human edible green pea, Canada No. 2, requires a sample with:
No more than 1% other;
3% or less bleached seed;
0.5% foreign material;
8% cracked seed cost; and
5% or less total damage.
In green pea, the vein pattern in the upper-most pods should be easily recognizable and 75% to 90% of the pods should have turned to yellow tan.
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.
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 rogue 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
o use belt conveyors rather than conventional augers, if possible.
Care should be taken when harvesting pea for human consumption. Pea seed samples containing excessive amounts of foreign material or seeds that are cracked, peeled or discoloured are suitable only for the feed market.
Soil adhered to the seed is called earth tag and is a common factor in downgrading dry pea. Earth tag may occur during combining when moisture from weeds or heavy dew causes soil or dust to stick to the seed.
The maximum allowable bleach level for green pea destined for human consumption is 3%. No. 1 Canada is 2%, and No. 2 Canada is 3%.
Green varieties are susceptible to bleaching as they near maturity. Bleaching of seed is caused by high humidity, bright sunshine and warm temperatures. For this reason, extra care should be taken to harvest green pea varieties as soon as possible.
The longer the crop stays out, the greater the likelihood of bleaching. In other words, every day in the field costs 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 herbicide.
Scout fields before harvest to determine when the crop is ready for harvest.
Use desiccant with high water volumes when most of the field is ready for desiccation. Refer to Keep It Clean for a list of products of concern and the steps you can take to mitigate risk.
Harvest crop 6 to 7 days after desiccation. (See Green Pea Bleach Study Results below).
Green Pea Bleach study Results
A 3-year project, involving 9 green pea varieties at a site north of Edmonton, was conducted to study different desiccation practices and their effects on green colour retention of the seed. The study concluded that quality green pea crops can be produced profitably in Alberta.
All 9 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 6 to 7 days after desiccation in all 3 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 2 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.
EARTH TAG MANAGEMENT
Earth-tagged seed has dirt attached that cannot be removed.
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. 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 is either green weeds or green pea plant material that will increase the level of earth tag on the seed.
Combine when seed moisture content reaches 18% to 20% for the first time. Properly tuned aeration bins are essential for a green pea harvest.
Field pea combined at 18% to 20% moisture will require aeration conditioning for short-term storage.