Sesame (Sesamum indicum L.) is a short-duration oilseed crop valued for its high oil content and nutritional quality. Although sesame is relatively hardy, its cultivation during the rainy season poses special challenges, particularly at the time of harvesting and threshing. Unlike cereals, sesame capsules dehisce (split open) upon maturity, leading to seed shattering losses if not handled carefully. Moreover, high humidity and frequent rains during the monsoon make harvesting, drying, and threshing operations difficult. Proper management practices are therefore essential to minimise losses and ensure good-quality produce.
1. Maturity Signs and Optimum Harvest Time
- The sesame crop is usually ready for harvest 80–100 days after sowing, depending on the variety and season.
- Maturity signs include:
- Yellowing and drying of leaves.
- Browning of stems.
- Lower capsules are turning yellow to brown.
- In the rainy season, harvesting should be slightly earlier than complete maturity to reduce shattering losses caused by sudden showers or strong winds.
2. Harvesting Methods in Rainy Season
- Plants are cut 5–10 cm above ground level using sickles when about 70–75% capsules have turned yellowish-brown.
- To prevent seed scattering during handling, care must be taken not to disturb mature capsules excessively.
- Staggered harvesting is recommended for varieties with non-synchronous maturity, ensuring that mature capsules are not left in the field for long.
- In areas with prolonged rainfall, harvesting during sunny intervals should be prioritised, even if labour has to be mobilised quickly.
3. Drying and Bundling Practices
- Immediately after cutting, plants should be tied into small bundles and placed upright (capsules facing upward) in the field or on raised platforms.
- In the rainy season, field drying is risky. Instead:
- Bundles may be stacked under temporary shelters or thatched structures to avoid direct rain.
- Tarpaulins, plastic sheets, or ventilated sheds can be used for safe drying.
- Adequate air circulation must be ensured to prevent fungal growth on moist capsules.
4. Threshing Techniques
- Traditional method: Bundles are sun-dried for 7–10 days, then beaten with sticks or threshed by shaking to release seeds.
- In rainy weather, mechanical threshers or tarpaulin-assisted manual threshing is preferred to reduce moisture absorption.
- After threshing, seeds should be winnowed to remove dust, capsule fragments, and other impurities.
5. Post-Harvest Drying and Storage
- Freshly threshed sesame seeds contain high moisture and are highly prone to fungal infestation and aflatoxin contamination during the rainy season.
- Seeds should be dried to 8–9% moisture content using sun-drying (on clear days) or mechanical dryers if rain persists.
- Storage must be done in moisture-proof bags (polyethene-lined gunny bags) placed on wooden pallets in well-ventilated, dry stores.
- For long-term storage, seeds may be treated with inert dusts (like diatomaceous earth) or stored under controlled conditions to prevent insect attack.
6. Challenges and Solutions in the Rainy Season
- Challenge: Frequent rainfall delays drying.
Solution: Use covered drying structures, solar dryers, or mechanical dryers. - Challenge: Seed shattering due to untimely harvesting.
Solution: Harvest slightly early and store plants under shelter until final drying. - Challenge: Fungal infestation.
Solution: Rapid drying, proper aeration, and safe moisture levels before storage.
Conclusion
Harvesting and threshing of sesame during the rainy season require special care to avoid heavy losses from seed shattering, excess moisture, and fungal contamination. Timely harvesting, sheltered drying, careful threshing, and scientific storage are crucial steps for maintaining seed quality and maximising profits. By adopting improved techniques and using mechanical aids where possible, farmers can significantly reduce post-harvest losses and ensure better returns from sesame cultivation in the monsoon season.
Siraj Ahmed, Wajeeh Ur Rehman, Fiaz Hussain, Asmat Ullah, Sana Ullah
Agronomic Research Station, Karor-Layyah
