Field pea harvesting must be considered in terms of an overall harvest system. Paying close attention to crop and equipment needs will usually result in earlier harvesting, higher quality and optimum yields.
Combining Peas
Pre-Harvest Considerations
CROP MATURITY
Depending on type and variety, seeding date and seasonal moisture, field pea crops require a growing season of approximately 90 to 105 days.
Field pea plants mature from the bottom to the top, and are near maturity when the bottom 30% of pods are ripe, the middle 40% of pods and vines are yellow-coloured, and the upper 30% pods are turning yellow. This is the stage to swath or desiccate if either of these harvest methods is chosen.
Seeds in bottom pods will be very firm and require some force to dent the seed coat with a fingernail.
Seeds from middle pods will flatten somewhat with pressure between the thumb and finger, and the seed coat will dent with a little fingernail pressure.
Seeds from the uppermost pods will be fairly soft and, with a little pressure, will split into two cotyledons.
Pea crops can also be left to straight cut without desiccation.
Pea crops are mature when seeds in the bottom pods are detached and loose in the pods and when the upper pods are turning yellow. Once the crop is mature it can dry down very quickly if the weather is warm and dry.
SEED MOISTURE CONTENT
Seed moisture content of physiologically mature pea will decrease quickly if weather conditions are warm and dry and if humidity is low.
Drought stress in the crop will also result in rapid drydown.
Desiccation or swathing can start when seed moisture content has reached approximately 25% to 30%.
Drydown of the sprayed crop between 16% to 18% seed moisture normally takes 5 to 7 days, depending on weather.
If the crop is to be straight combined, you can begin when seed moisture content has reached approximately 18% to 20%, provided the straw is dry enough to feed through the combine.
Once the crop is combined, a short time in an aeration bin may be required if the grain is not at storable 16% or if the seed is warm. Aeration of straight-harvested pea is generally required to condition the grain for longer storage.
FIELD MONITORING
Pre-harvest field monitoring will help determine which harvest system to consider, if more than one is available, and will greatly assist in determining when to begin harvest operations.
Monitoring pea fields means checking plants in numerous locations for uniformity of stages of maturity.
Most fields will not be 100% uniform in topography – there could be greener conditions in lower, wetter areas and further advanced plants on higher areas.
A decision to begin harvest will hinge on a majority of the field meeting certain criteria. Do not sacrifice the quantity and quality of your crop waiting for smaller greener areas to reach the proper stage to start harvest.
Harvesting too early will result in immature seeds – this is especially important with yellow cotyledon varieties because immature yellow-green seeds will result in downgrading.
Harvesting too late when the pods are dry and brittle may result in shatter losses and will increase the risk of poorer quality seed due to adverse weather. For green pea varieties, harvesting even several days later may result in excess bleach.
The decision to start the harvest process will depend on three factors:
crop maturity (stage of uniformity – how variable is the crop’s maturity?)
seed moisture content
presence of weed growth.
Other considerations may include weather patterns, and marketing considerations (for human consumption, livestock feed or seed).
PRESENCE OF WEED CONTROL
Waiting for green weed growth to drydown will jeopardize quality and yields.
Swathed green weeds are unlikely to dry sufficiently in a few days, so combining will be delayed.
Green weed material in a straight-cut operation will cause extra wetness in the threshing areas of the combine, resulting in moisture on the seed coat and dirt adhering to this moisture (earth tag). Grades will be lowered because of earth tag (see Grading Section).
PRE-HARVEST AIDS (GLYPHOSATE)
Various chemical harvest management tools are available to aid in the preparation for combining. It’s important to select the right product for right crop and the intended outcome.
Crop desiccation and dry down and pre-harvest perennial weed products are not the same. Make sure to select the right product, follow label directions, and timing of application. Harvest aid products vary in speed of activity, efficacy, and pre-harvest intervals.
Apply glyphosate for pre-harvest weed control and not for desiccation. See Desiccation information further below.
Pre-harvest glyphosate must only be applied when the grain moisture content is less than 30% in the least mature part of the field to prevent unacceptable residues in the harvested grains.
To determine if the field pea crop is at less than 30% seed moisture:
The bottom pods are ripe and dry with seeds detached from the pods.
80% of plants are yellow to brown in colour.
Top pods are wrinkled and the seed is firm.
The top of the plant may have a slight green colour.
This treatment will provide some crop dry down, but this benefit may be inconsistent and is unlikely to occur under cool, wet conditions.
The crop and in-crop weeds must have enough green material remaining at application time for the herbicide to be effective.
Glyphosate is not registered for pea crops destined for planting seed because irregular germination and seedling development can occur.
Applying glyphosate too early can reduce yield and seed size, and late-season application may result in levels of glyphosate in the seed that exceed maximum allowable levels.
Growers must take appropriate risk mitigation steps to ensure product residues remain below maximum residue limits (MRLs) set by regulatory agencies.
Prior to applying glyphosate, check with potential buyers. Some companies are NOT accepting peas where glyphosate was used pre-harvest as weed control.
KEEP IT CLEAN
Certain crop protection products can restrict the marketing options for your pulse crop. Before you make your crop management plans, talk to your grain buyer and read the Keep it Clean Pulse Maximum Residue Limits Advisory for a list of products of concern for this year, and the steps you can take to mitigate risk.
More than 85% of Canada’s pulse production is exported to feed the world. Market access is important to the Canadian pulse industry, and growers play a key role in keeping the doors open.
Source: For the latest “Keep it Clean” updates, visit Keep it Clean main website.
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Chemical desiccation is used to burn off crop foliage and weeds, and can be very effective for green pea, reducing the time to harvest and resulting in a good green coloured seed.
Field Pea – Assessing Peas for Maturity to Determine Desiccation Timing
The goal of desiccants or harvest aids is to make sure the crop is dry and goes through the combine efficiently.
Timing of the application is critical because it has immediate dry down effects. Application too early will reduce seed size and yield of pea.
Apply as the crop is approaching physiological maturity – the application can be made when the bottom and mid-area pods have turned tan to yellow colour, and top pods are pitted and starting to turn yellow.
If some areas of the field are immature, it is better to go around those areas when desiccating if the goal is the highest quality seed production.
Apply the desiccant at the same time as the proper swathing stage, wait approximately 5 to 7 days, then straight combine or swath and follow immediately with the combine.
Consult product labels prior to use for final detailed instructions.
BENEFITS OF DESICCATION
The benefits of chemical desiccation include:
The opportunity to have the crop harvested sooner, reduces risk of exposure to wet weather, and eliminates the risk of swath movement from wind.
Standing desiccated crops will also dry more rapidly after a rain, compared to a crop in swath.
Reduces the time from maturity to threshing readiness and reduces shatter loss. However, a desiccant will not assist in maturing immature seed.
A desiccant is a contact herbicide, so green material is killed quickly and drydown begins within a very short time compared to natural drydown. Thus, drydown is faster, more even and can be achieved late in the season when days are shorter and generally cooler.
The use of a desiccant will usually eliminate the need for swathing, thus avoiding potential problems with wind blown swaths, rain-soaked swaths and pick-up losses.
Standing desiccated crops will also dry more rapidly after a rain, compared to a crop in swath.
Germination of seed is not affected unless applied in advance of the recommended stage.
HOW TO APPLY
Spray only as many acres at one time as can be combined in two or three days after drydown.
If the entire crop will take more than two or three days to combine, stagger the desiccant application so that not all the crop is ready at the same time.
Use proper rates, high water volume and spray at the correct crop stage.
OTHER CONSIDERATIONS
Powdery mildew and heavy weed infestations can reduce the effectiveness of the chemicals due to coverage reductions.
Harvest Systems – Swathing
In most conventionally managed systems swathing is not necessary.
In organically managed systems, swathing may hasten drying and prevent shattering, however, pea swaths are extremely susceptible to damage from wind. The swather can also be used to cut the crop at full maturity. Shattering loss can be high using this method.
Field Peas – Almost Ready to be Harvested
WHEN TO SWATH
Swathing can be done when most of the vines and pods have turned to a yellow-tan colour, and seeds are difficult to dent with a thumbnail.
As much as one-third of the vines and pods may still have some lime green colour left, but these plants will cure in the swath.
The fully formed but immature seeds will dry without much shrinking – the overall seed moisture content will be approximately 25%.
Pea crops that are very short and have many pods close to the ground are usually best swathed when partially green – the pick-up reel will have more material to work with, resulting in a better swath.
Swathing should be done during periods of higher humidity to prevent shatter losses.
Lower areas of the field (which remain green) should be ignored when the proper swathing or straight cutting time approaches for most of the field. Delayed cutting to allow these areas to advance in maturity may jeopardize quality and quantity of the remainder of the crop.
SWATH ROLLING
Swath rolling may be necessary to protect the swath from wind damage if the swather lays a dense narrow swath.
A very mature dry crop may result in a fluffy swath, prone to wind damage (rolling drier pea swaths will result in greater seed shattering in the swath).
Lay a wide, shallow swath that will cure and dry quickly – adjust the discharge opening of the swather to as wide as possible to lay a wide swath (avoid piling the swath in bunches).
SWATHER TABLES
Swather tables should be fairly narrow, so the table will follow ground contours as the crop is cut close to the soil surface – a narrow table will also produce a shallower swath (there is usually very little stubble to keep the swath off the soil surface, so rapid drying is important).
Gauge wheels mounted on the swather table will also aid swather operations – gauge wheels help prevent the cutter bar from digging into the soil and maintain uniform cutting height with less operator fatigue.
Swather tables with adjustable pitch should be adjusted to a steep pitch – this angle will help get the cutter bar closer to the ground and will allow the crop to come off the draper more evenly.
CUT, SPEED AND ANGLE
A heavy, taller crop can best be handled with a narrow swather table or by taking a narrow cut (12 ft. to 15 ft.) with a wider table.
Swath the crop slowly –3 to 4 mph (as slowly as it takes to lay an even, uniform swath).
All varieties of field pea have hollow, weak stems and most will lay over or lodge when heavy in pod – the best method of swathing or straight cutting a lodged pea crop is at a right angle to the direction in which the crop is lying.
COMBINE SETTINGS
Picking up a well-formed pea swath is generally not a problem.
Combining is easiest if the width of swather cut is well-matched with combine capacity and the moisture content of the crop is between 16% and 20%. Matching the swath size and density to the combine capacity allows a uniform feed to be achieved.
The combine should follow closely behind the swather, if the crop is to be swathed when it is fully mature.
These conditions require the least combine power, and good separation takes place readily.
Pick-up speed should be carefully matched to the combine ground speed to minimize shatter losses.
If the combine is equipped with a variable speed pick-up, the proper feeding rate of the swath is much easier to maintain.
Sprocket change on the pick-up drive may be needed to reduce the pick-up speed to that suited for pea swaths.
Harvest Systems –Combining
Field Pea – Ready to Harvest
WHEN TO COMBINE
Field pea can be successfully combined as soon as the seed moisture content is down to 20% or less.
Seed damage will increase as the crop becomes drier than 16%. This damage reduces both germination and quality.
Although peas are considered dry at 16% moisture, harvesting at approximately 18% to 20% moisture will reduce the risk of seed cracking or peeling and reduce shatter losses. This also results in an earlier harvest and can reduce weathering loss.
Pea vines that are damp or slightly green will greatly increase combine power requirements and may result in plugging and wrapping problems.
Combining at too high a moisture content (over 20%) will increase the amount of earth tag on the pea seed.
Earth tagging may also occur when combining starts too early in the morning or continues too late in the evening and when dew is present; earth tagging is also common when weeds like thistle or quack grass are present.
Combining at too low a moisture content will cause excessive cracking and splitting losses – cracked and split seed downgrades quality when pea is destined for the seed or human consumption market.
COMBINE SETTINGS
General recommendations for combine settings include:
low cylinder speed
ample concave clearance
maximum wind velocity.
Low combine cylinder or rotor speeds are required to reduce seed cracking. Speeds of 300 to 600 revolutions per minute are normally used, depending on the moisture content of the pea sample.
An initial concave setting of 0.6 to 1.5 cm clearance at the front and 1.2 cm at the rear is recommended.
Combine and grain augers should be operated full and at low speeds to reduce cracking and splitting of seeds.
Keep the combine operating at full capacity to help reduce seed damage in the cylinder and also in the grain elevators.
Combine hoppers should be unloaded at slow speeds to reduce seed damage.
When combining a swathed pea crop, match the pick-up speed to the ground speed of the combine. Keep the swath moving uniformly to match the combine capacity to reduce seed damage and shatter losses.
View from the Combine
NO DESICCATION
Straight combining without desiccation can be successful, however, there is a risk of shatter loss and the crop must be uniformly mature across the field before threshing can be completed.
Shattering can be reduced by harvesting during the humid part of the day, and by reducing the reel or pick up speed to keep the action against the crop to a minimum.
This harvest method can be very successful if the crop is at the same stage through the field, maturity has been reached relatively early, and the weather is hot and dry at harvest.
If using a straight cut header, it should be equipped with vine lifters (pick-up guards) and/or a pick-up reel to ease the harvest of lodged or tangled crops.
STRIPPER HEADER
This is the newest header type for straight combining pea crops.
It incorporates a flail type cylinder enclosed in a shroud and is operated at 1 in. to 2 in. above the soil surface. One advantage to the stripper header is its ability to harvest badly lodged pea crops.
Careful adjustment and maintenance of the stripper header is needed to offer a clean undercarriage to eliminate hang-ups of pea vine and dirt entering the combine.
Some concern exists that operating the machine at very high RPMs in dry pea crops will increase the damage to the seed and increase the amounts of split pea and dockage.
The stripper header width should be properly matched to the combine capacity to both increase efficiency and not overload the combine.
Proper header height control is important to avoid picking up dirt, which will cause earth tag (earth tag is not easily removed from pea seed and will usually lower the grade of the grain).
SPECIAL PICK-UP
Another method for combining a pea crop is to use a special pick-up (manufactured by Sund or Rake-Up), which pulls the standing, very mature dry pea crop into the combine.
Pick-up wheels may be replaced with coulters, which cut the pea vines at the edge of the pick-up.
Pea vines must be very dry because this type of pick-up works by breaking plants off at the soil surface before pulling them onto the draper – this operation leaves most of the green weed material standing in the field, and it prevents dirt from entering the combine.
Special pick-ups may not work well in short or thin crops – they perform best on longer pea vines that have fully matured and have been exposed to some rain, as the stems at the soil surface become weak after a rainy period.
This type of harvest method is not a feasible option for green pea crops for human consumption markets. Green pea usually bleaches too much by the time the crop is ready for this type of equipment.
PICK-UP REEL
VINE LIFTERS
Swathers should be equipped with a pick-up reel, preferably with stiff fingers, and with vine lifters – adjustment of the pick-up reel, backward or forward, may alleviate piling problems.
Many types of vine lifters are available, and most allow for some adjustment to perform well on all headers – lifters should be spaced every 12 in. on the header for most pea crops but may have to be spaced as close as 6 in. for short, thin crops.
Flexible lifters are preferred over the more aggressive rigid lifters for straight cut headers as they reduce the amount of dirt entering the combine.
For extremely short crops, lifters may have to be removed to get the cutter bar below the lowest pod.
Pea Straw Management
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.
BENEFITS OF LEAVING STRAW ON THE FIELD
One of the benefits from growing a pea crop is the positive effect of pea residue in 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.
Improved soil structure, tilth and recycled nitrogen for succeeding crops are all benefits of pea straw incorporation. In fact, most of the nitrogen returned to the soil after growing a pea crop comes from the straw.
Because of these benefits, it is recommended that pea straw remain on the field and not be baled off for feed purposes. Consider the following:
Dry pea straw breaks up and pulverizes quite readily when combined.
Straw that is slightly green or tough will remain almost whole going through the combine.
A good straw chopper and chaff spreader will cut and spread the straw and chaff sufficiently so that tillage or direct seeding is not a problem.
Tough straw will wrap around the chopper drum if the straw chopper knives are dull and worn.
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.
VALUE AS A FEED SOURCE
When assessing the benefits of baling versus incorporating these nutrients into the soil, the cost of baling straw and hauling it must be taken into consideration.
Results from a 3-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 removing field pea straw should test it for protein, phosphorus, potassium and sulphur 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 on value of selling as feed versus improving your soil.
