Lentil Yield, Harvest, and Storage

Lentil Yield - What is the average yield of lentils?

Lentil (Lens culinaris) is a grain legume valued for its nutritional quality and adaptability. In 2021, lentils were cultivated on more than 5.5 million hectares (more than 13.5 million acres) globally, and the average yield ranges from 300 to 1100 kg/ha (267 to 981 lbs/ac). Growers say that they usually expect 1000 kg/ha (892 lbs/ac).

Timing and Management of Harvest - When and How to Harvest Lentils

Harvest timing is one of the most crucial factors for lentil production. Lentils usually are ready to harvest 100-110 days after planting, when the plants are fully mature and the pods are dry and crisp. At this stage, leaves begin to fall, and the stem turns brown. As soon as lentils reach physiological maturity, typically when the seed moisture content is around 30% or less, harvest management processes such as desiccation, pre-harvest glyphosate application, or swathing should start to ensure consistent moisture levels in the crop.

Delaying harvest increases the risk of pod shattering, lodging, and quality degradation due to weather exposure. If lentils are left in the paddock after maturity, they are more vulnerable to adverse weather conditions like rain and strong winds, which may cause the pods to split and the seeds to drop. Additionally, the grain becomes more susceptible to mechanical damage, particularly as the moisture content decreases below optimal levels. This can lead to significant financial losses due to reduced yields and downgraded grain quality. The economic losses associated with a 1–3 week delay in harvest can range from $150 to $450 per hectare ($60 to $180 per acre), primarily due to pod loss, shattering, and quality degradation. Ideally, lentils should be harvested when the seed moisture content is between 12% and 14%, minimizing cracking during harvest.

Early harvesting ensures better grain quality. These imperfections caused by delayed harvesting lower the grain's marketability and can make the seed more susceptible to mechanical damage during processing. Seed coat darkening, triggered by oxidation of polyphenol compounds (tannins), can also reduce the visual appeal of the lentil, a crucial quality criterion in many markets. Rain, humidity, and fluctuating temperatures exacerbate these issues.

Lentils left in the field for too long are also at risk of mold infection. Molds like Alternaria, Aspergillus, and Penicillium thrive in humid, wet conditions, leading to darkened seed coats and further downgrading the crop. Insects such as native budworms may also attack senescing lentil pods, causing further grain damage.

Lentil Harvest management processes

Desiccation is a common strategy that dries down both the crop and the surrounding weeds, allowing for faster harvesting and reducing the likelihood of grain shattering. However, care must be taken to avoid early application, which can cause seed shrinkage and lead to pesticide residue issues. If applied correctly, desiccation can prepare the crop for combining within 7 to 10 days under favorable conditions.

Swathing offers another approach by allowing lentils to dry naturally in windrows, which can reduce shattering losses compared to standing crops. However, swaths are more vulnerable to heavy rain and wind damage, which can cause seed wrinkling and sprouting, diminishing quality. Swathing typically provides better results in regions with good drying conditions and is especially advantageous for green lentils. While swathing reduces weather risk, it requires careful handling and proper equipment like crop lifters and pickup reels to ensure minimal losses.

Machinery Adjustments for Harvest

Lentils are relatively easy to thresh, so harvester settings must be adjusted to avoid mechanical damage to the grain. Flexi-front harvesters are ideal for lentils, allowing the harvester to follow the ground closely, reducing losses from low-lying pods. Threshing speed should be reduced to minimize cracking, particularly in lentils with lower moisture content. Adjustments such as opening concave clearances (10-30 mm or 0.39-1.18 inches) and reducing rotor speeds (300–600 rpm) help protect the delicate lentil seeds during harvest.

Combine Timing and Settings

The moisture content of lentils is a key determinant in both harvest timing and combine settings. For green lentils, a seed moisture content between 16% and 18% is considered ideal for combining, with drying to around 14% post-harvest. Red lentils, on the other hand, should be combined when moisture levels are closer to 13%. Harvesting lentils when they are still "tough" ensures that they are less likely to crack or split, which is essential for maintaining grain quality.

Combine settings need continuous adjustment to ensure minimal grain damage. Low cylinder or rotor speeds are necessary to prevent chipping and splitting, with recommended speeds ranging between 250 and 500 revolutions per minute (RPM). Concave clearances should be set wide enough to allow proper threshing without causing damage to the grain. Proper fan speed adjustment is also essential, as excessive airflow can blow lentil seeds out of the back of the machine. Careful attention must be given to sieve settings to ensure a clean sample with minimal debris.

Lentil Harvesting Challenges

Handling Lodged Crops

Lodged lentil crops present a unique challenge. Crops that have fallen should be harvested in the opposite direction to the lodging. Crop lifters may be required in severe cases, as they lift the plants to ensure cleaner, more efficient intake into the harvester. However, care must be taken when using crop lifters, especially in fields with stones or wheel ruts, to avoid excessive soil intake into the machine, which can damage the equipment and reduce grain quality.

Managing Snail Contamination and Fires

In some areas, snails are a major pest in lentil fields, contaminating grain samples and clogging harvesters. Effectively managing snails requires a multifaceted approach, including pre-harvest baiting, reducing snail habitat in stubble, and modifying harvester settings (e.g., adjusting sieves and slowing grain elevators) to minimize snail intake. Lentil harvesting can also increase the risk of harvester fires due to the flammable dust produced by the crop. Regularly maintaining and cleaning harvesters, particularly around the engine and exhaust areas, is crucial to minimize fire risk. Growers should keep fire extinguishers on hand and be vigilant in high-risk conditions.

Post-Harvest Handling and Storage of Lentils

Moisture Content and Temperature Management

The moisture content of lentil seeds plays a key role in determining how long they can be safely stored. For green lentils, a moisture content below 14% is considered dry, while red lentils are deemed dry at 13% or less. Moisture levels above these thresholds are classified as damp, making the seeds more susceptible to spoilage and damage. For safe long-term storage, lentil moisture content should ideally be kept between 12% and 14%, as buyers prefer this for dehulling and splitting.

The temperature during storage is just as important. Cooler temperatures significantly extend the safe storage period. For example, lentils stored at 5°C (41°F) with 12% moisture can remain viable for up to 370 weeks (approximately 6 years), but the storage period drops to just 23 weeks if the temperature rises to 20°C (68°F), and the moisture content is 14%. A general recommendation is to aim for temperatures below 15°C (59°F) and monitor the bins regularly to prevent moisture migration, which can occur with seasonal changes. Higher temperatures, particularly above 25°C (77°F), should be avoided as they accelerate oxidation, especially in green lentils, leading to browning and a reduction in quality.

Drying

Aeration or drying is necessary before storage if lentils are harvested at high moisture levels. Aeration can help reduce both the seed moisture content and temperature. When using natural air aeration, ambient air lowers moisture levels and cools the seed. This method is particularly useful as lentils are often harvested in warm and dry conditions. Cooling the grain with aeration can greatly extend the storage period, allowing seeds with a moisture content of 14% and a temperature of 25°C (77°F) to be stored for 13 weeks, whereas cooling them to 15°C (59°F) prolong this to 40 weeks.

If artificial drying is necessary, the air temperature should not exceed 45°C (113°F). Drying should be done cautiously, ensuring no more than 4-5% moisture is removed in each pass through the dryer, as excessive drying or high temperatures can severely damage the seed. Between drying passes, a cooling period of up to eight hours is recommended to prevent further damage.

Handling Considerations

Lentils are prone to mechanical damage during handling, especially when dry. If handled roughly, they can chip and split easily. Belt conveyors instead of augers are advised, as belt systems are gentler on the seed. If augers must be used, they should be run at reduced speeds and kept full to minimize seed damage. Moreover, handling should not be done in temperatures below -20°C (-4°F), as the risk of chipping and peeling increases significantly.

Special care is required to prevent unnecessary handling and ensure the seeds are dropped gently into storage bins. For instance, bean ladders or similar equipment can be used to reduce the impact when lentils are moved into storage. Also, gently handling lentils helps avoid physical damage that can downgrade the seed during grading.

Storage Pests of Lentils

Bruchus ervi and Bruchus lentis are common in Europe, North Africa, and Southwest Asia. These small beetles (3 to 3.5 mm long or 0.11-0.14 inches) lay their eggs on young lentil pods. Once hatched, the larvae bore into the pods and feed on the seeds. The larval period lasts about six weeks, after which they pupate inside the seed, leaving only a thin exit window in the seed coat. This damage compromises the integrity of the seeds and can severely affect yield. Adults hibernate in the dry seeds or in protected environments, emerging during the next growing season to infest new crops. Since bruchids do not reproduce in stored seeds, fumigation with phosphine before storage is an effective method of control. Sprays of insecticides like endosulfan, alpha-cypermethrin, or methyl parathion during flowering and pod-setting stages also provide protection from these pests.

Callosobruchus spp., particularly Callosobruchus chinensis and Callosobruchus maculatus, are widespread in subtropical and tropical regions, infesting lentils during storage. The adults of C. chinensis have distinct rust-colored bodies with two brown spots on their elytra, while C. maculatus has black-tipped wings with a large round spot. These beetles lay eggs on the seed coat, and upon hatching, the larvae bore into the seed, developing and pupating inside. With their rapid reproduction cycle, Callosobruchus species can cause extensive damage within a short period. Integrated control measures include maintaining clean storage facilities, fumigating seeds with phosphine, and using botanical pesticides such as neem seed oil to protect the seeds for several months. Biological control using the parasitic wasp Dinarmus basalis can also be highly effective against C. chinensis, completely controlling infestations in stored lentils.

Adopting responsible pesticide practices is important when managing pests like Bruchus sp. and Callosobruchus spp. Farmers are encouraged to consult agronomists for tailored pest management strategies that minimize environmental impact and reduce the risk of resistance. Biological practices should be preferred whenever possible, such as introducing natural predators or using botanical insecticides.

It is highly advised that farmers consult a licensed agronomist before applying agrochemicals and always use certified and suitable products. Farmers should always strictly follow label instructions and recommend dosages. Over-application or misuse of pesticides can harm beneficial insects, contaminate the environment, lead to pest resistance, and harm consumers' and users' health. With responsible pesticide use, farmers can protect their crops effectively while protecting the ecosystem's health.