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Lentil Harvesting

Under Alberta conditions, long-season varieties seldom mature naturally. Some varieties will mature, but unevenly, resulting in shatter losses as some pods become over-dry while others are still green.

To drydown the crop quickly and evenly, a producer can either chemically desiccate or swath. Crop staging is the same for either desiccating or swathing, but crop staging cannot be accurately determined from a distance. Fields must be thoroughly checked and sampled.

The crop is ready for desiccation or swathing when the bottom third of the pods are yellow to brown, and seeds inside the pods rattle when shaken; upper pods will still be green but should be filled. Delay beyond this stage can result in excessive shatter losses.

Pre-harvest Questions

Before harvesting your lentils, ask yourself these questions.

  • Does the value of the crop dictate whether a desiccant is used?
  • What machinery is available for harvest?
  • Is the equipment ready, with any necessary modifications completed?
  • Is the storage space ready?
  • Should additional resources be secured?
  • How variable is the crop’s maturity?
  • Is there any other variability of crop readiness in the field?
  • What are the current weather patterns?

Swathing

Swathing will hasten drydown and prevent shattering. Lentil must be cut close to the ground to get the bottom pods with an angle of 20° to 30° suggested for the cutter bar. Spring rolling lentil fields is recommended for proper swathing, since bottom pods are only a few inches off the ground. Swathing during periods of high humidity will reduce shatter losses. Swather modifications including pick-up reels and vine lifters are usually needed to do a good job and keep soil from being mixed in with the seeds.

To reduce shatter cut under conditions of high humidity. Swaths can be susceptible to wind movement (especially if cut later than the recommended stage). Under good drying conditions, the quality of the swathed seed is usually better than if chemically desiccated, especially for green varieties. If the swath is subjected to heavy and/or prolonged rain, quality loss can be high due to sprouting, wrinkling and disease build-up compared to a standing crop.

Some key points to consider prior to swathing lentils:

  • cutter bars must travel near the ground surface at an angle of between 20˚ and 30˚
  • swathers should have a pick-up reel and vine lifters for cutting lentil
    • pick-up reels should be adjusted ahead of the cutter bar and run at ground speed
    • vine lifters will provide maximum lifting action but should not be cultivating the soil
    • dirt in the swath can result in earth tag and sample downgrading
  • if the crop is lodged, cut across or at an angle to the lean to increase the effectiveness of the pick-up reel and vine lifters
  • swathers with a floating or flexible cutter bar and/or adjustable gauge wheels will increase swathing speed and minimize damage to the cutter bar, especially on uneven land – a narrow swather can be more successful on uneven land
  • a clean cutter bar works best – to improve cutting action, use soapy water and a scraper or a power washer to wash the cutter bar
  • lentil stubble provides little for swaths to anchor to, so to avoid wind damage to swaths, ensure the crop is cut at the correct stage – swaths should be cut in the direction of the prevailing wind (a swath roller will usually cause an unacceptable amount of shatter loss)
  • a swathed crop is more vulnerable to weather damage than a standing crop, and rain is a serious concern because it can cause quality loss due to sprouting and wrinkling of seed and the spread of disease to pods and seeds. Wet swaths can flatten out, making them harder to pick up (the use of swath turners or side-delivery rakes is not recommended due to excessive shatter losses)

Chemical Desiccation

Lentil desiccation with approved products can speed up drydown when crop maturity is uneven or when green weed growth is a problem and reduce the time from maturity to threshing readiness, reduce shatter losses, and result in improved quality if the seed is harvested before being exposed to wet weather. But a desiccant will not assist in maturing immature seed. Always speak with your input supplier prior to choosing a harvest aid to ensure you will not be limited when it comes time to market your crop.

Following application of desiccants, lentil plants can be ready to thresh in four to seven days if hot, dry, sunny weather follows (although the time period is more commonly seven to 10 days). Application in the evening and into the night, using high water volumes and the using the high end of the recommended rate will result in quicker and more consistent drydown. Days to threshing following application will increase under wet, cool conditions. Reglone® (diquat) has been the most consistent and widely used desiccant through the years. More recently Heat (saflufenacil) and Good Harvest (glufosinate ammonia) have been registered for use as desiccants in lentil.

Glyphosate can be used as a harvest aid but is not a desiccant. It is registered in lentil for control of perennial weeds. It may provide some dry-down effect if conditions are warm and dry. Do not apply glyphosate to crops to be used for planting seed, as it may affect germination and seedling development.

CleanStart® (carfentrazone and glyphosate) is a combination of desiccant and harvest aid. Observations to date suggest crops having CleanStart® applied will take longer to be ready for threshing compared to Reglone®. It should however be faster and more thorough compared to glyphosate alone.

Other products registered for pre-harvest application in lentil include Roundup Original®, Roundup Transorb® and Roundup Fastforward® – these products are not desiccants, but are intended for perennial weed control (Roundup Fastforward® is also intended to hasten crop drydown relative to untreated crop but does not function as quickly or in the same manner as a desiccant).

Following desiccation, straight-cut or swath immediately in front of the combine.

Combining

At 16 per cent seed moisture content is considered ideal for harvesting lentil – acceptable seed moisture contents for threshing range from 16 to 20 per cent, provided adequate drying or aeration facilities are available.

  • while lentil is considered dry and safe to store at 14 per cent seed moisture, it should only be threshed at 14 per cent by producers who do not have drying or aeration equipment available (threshing at 14 per cent moisture will result in higher shatter losses and quality losses from seed damage)
  • the moisture content of lentil seed can change quickly in warm and windy conditions, so to obtain high-quality seed, the crop should be carefully and frequently monitored before combining

Lentils can be straight combined when seeds and pods are fully mature, or after desiccation. Threshing equipment equipped with flex header, automatic height control, pick-up reel or air reels and vine lifters are an asset.

Excessively dry seed will chip and peel during threshing. It is preferable to thresh at about 18 per cent moisture and use aeration to dry the sample to 14 per cent for green varieties and 13 per cent for red varieties for safe storage. The red lentil splitting industry prefers product with moisture content below 13 per cent to improve the efficiency in their splitting plant. Check with your red lentil buyer for any seed moisture content requirements.

During combining, remember that lentil is a food product. The seed’s appearance is a major factor in determining quality and, therefore, price.

  • for a mature standing crop, straight-cutting or swathing in front of the combine is recommended
  • straight-cutting is preferred, since swathing at this time will increase shatter losses
  • both operations demand specialized equipment including pick-up reels, vine lifters and flex headers – air reels have also been effective in straight-cutting operations
  • rotor or cylinder speed is usually a compromise between a slow speed to prevent seed damage and a faster speed to prevent cylinder plugging – the ideal is usually between 250 and 500 RPM
  • set concaves to allow good threshing and separation, with minimal seed damage – since the crop threshes easily, concave settings will usually be wider
  • chaffers should be set at 3/4” and cleaning sieves at 3/8” and then adjusted accordingly; tailings should be kept to a minimum, and grain and return elevator chains should be adjusted correctly to avoid splitting or cracking seed: fan speed should be increased only to the point where an acceptable clean sample is produced; excessive fan speed will blow lentil seed out the back of a combine

Grain Storage

Seed moisture higher than 18 per cent results in longer drying times and as lentil moisture approaches 20 per cent, the crop is difficult to thresh without smashing the seed. Storage at 13-14 per cent moisture and temperatures below 15°C is considered safe for longer term storage.

Lentil seed containing green weed seeds and other high moisture materials should be cleaned as soon as possible to prevent heating. Lentil seed at 14 per cent moisture or less and 15°C or less can be stored safely for up to 40 weeks.

If heated grain drying is needed, air temperatures should not exceed 45°C to preserve germination, and the sample should not be dried more than four to five percentage points per pass through the dryer. Lentil seed can be easily damaged in the drying process, so caution is needed.

Lentil varieties with green seed coats will discolour with age, thus reducing the grade. Producers should store lentil in dry, dark conditions. Seed from successive years should not be mixed, as the oldest seed will cause downgrading of the entire sample. Green lentils should not be stored through a second summer season to avoid excessive discolouration and downgrading.

Lentil seed is susceptible to increased chipping and peeling if handled in temperatures colder than -20°C. Avoid unnecessary handling and invest in conveying equipment that is gentler on the lentil seed when moving. Belt conveyors cause much less damage than steel flighting augers. Lentil can also be damaged when dropped into a bin from significant height and it may be necessary to use equipment (i.e. bean ladders) to soften the drop.