Lentils, a type of pulse or edible legume, are a globally important food crop cultivated for their nutritious, protein-rich seeds. Their delicate, low-growing habit requires a careful, multi-stage approach to harvesting to maximize seed quality and yield. This process involves precise timing, specialized equipment for cutting and gathering, and careful post-harvest handling.
Identifying Harvest Readiness
The precise timing of the harvest is crucial, as it determines the final quality of the seed. Farmers monitor both visual indicators and the seed’s internal moisture content to determine when to begin the process. Lentils are mature enough for swathing or desiccation when the lower pods transition from green to a yellow or brown color and the seeds rattle when shaken.
Moisture content is the most reliable metric for readiness. It is preferable to begin threshing when seed moisture is elevated, ideally between 16% and 18%. Excessively dry seeds are prone to chipping and cracking during handling. This higher moisture content minimizes field shattering losses, which occur when dry pods burst open before collection.
Swathing and Windrowing
A two-step harvest is often necessary to prepare the low-growing crop for threshing. Swathing involves cutting the plants and laying them into uniform rows, known as windrows, to encourage even drying. This method allows the crop to reach the final desired moisture level before the combine collects it.
Specialized swathers, often equipped with floating cutter bars, cut the plants close to the soil surface to capture low-hanging pods. Swathing under high humidity conditions, such as early morning, helps reduce pod shattering losses. Uniform windrows are essential for consistent drying before the second stage of harvest begins.
Combining and Threshing
Once the windrows have dried sufficiently, a combine harvester picks up the material and separates the seed from the plant residue through threshing. Lentils thresh easily, but the seeds are susceptible to damage, necessitating careful adjustments to the combine’s internal mechanisms.
The cylinder or rotor speed must be slowed significantly, typically between 250 and 500 revolutions per minute, to prevent chipping or breaking the delicate seeds. Concave settings are kept relatively wide to allow for good separation while minimizing mechanical impact. Fan speed must also be regulated, providing just enough airflow to clean the sample without blowing the lightweight seeds out with the chaff.
Cleaning, Drying, and Storage
After threshing, the harvested grain often contains foreign material, requiring a cleaning process. Specialized screens and air cleaners remove this debris to prepare the seed for market or storage.
Drying
If the harvested seed’s moisture content is above the safe threshold for long-term preservation, further drying is required. Green lentils are considered dry at or below 14% moisture content, while red lentils are dry at 13% or less. If artificial heat drying is necessary, the air temperature should not exceed 45°C (113°F) to prevent damage to the seed’s quality and viability.
Storage
For long-term preservation, the lentils are moved into storage bins that provide cool, dry, and aerated conditions. Aeration is used to cool the grain and maintain a temperature below 15°C (59°F). This significantly extends the safe storage period and prevents the discoloration of green varieties. Careful handling is maintained using belt conveyors instead of traditional augers to prevent the fragile seeds from cracking or splitting.