Winter Maize Seed Storage and Management Techniques for Overwintering
Corn seed storage in northern China presents a significant challenge due to low seed temperatures at the late stage of maturity and high moisture content at harvest, making it difficult to dry and increasing the risk of low-temperature freezing damage. Ensuring safe storage through winter is critical for maintaining seed quality. Based on research and practical experience, effective strategies begin before harvest, taking advantage of the cool and dry autumn conditions in the north. The key is to reduce moisture below the level that can be affected by freezing before cold weather sets in, allowing seeds to survive the winter safely.
The following measures are recommended:
(a) **Stalk Standing Before Harvest**
During the late ripening and early wax ripening stages, opening the husks of corn ears allows them to dry more effectively. This method, widely used in provinces like Liaoning and Jilin, involves leaving the stalks standing before precipitation. The best time for this is 10–20 days before harvest, with tests showing a 9.7% increase in water loss within the first 20 days. The optimal period is during the early wax stage, as doing it too early may reduce yield, while delaying it reduces drying effectiveness. This method is especially beneficial for varieties with longer growth periods and slower dehydration.
(b) **Early Harvest and Sorghum Drying**
Harvesting earlier, particularly during the end of the milk stage, helps maintain seed viability. Research shows that seeds harvested at this stage have good quality and do not affect yield. A common practice is to cut the parent stalks 30 cm above the ground, then tie the mother stalks and hang them for drying. This method ensures efficient moisture reduction.
(c) **Ventilation Storage of Corn Ears**
Storing corn ears in well-ventilated areas allows continued drying throughout autumn and winter. The cob provides natural protection to the embryo, reducing mold and pest infestation. Small quantities can be stored using stakes or wooden frames, while larger volumes require elevated, well-ventilated storage structures. These can be built with bricks or wood at least 30–50 cm off the ground, covered with straw or masonry. Some regions use woven bags for better ventilation before constructing storage bins. Permanent warehouses can also be built using wooden or metal silos, ensuring proper airflow and protection from rain and snow.
(d) **Low-Temperature Sealed Storage**
Once the moisture content drops to around 13%, it’s advisable to seal the seeds after threshing. This is typically done in early spring, using natural low-temperature winds to keep the seeds dry. Sealing methods include using glands, sleeves, or insulation materials like perlite or rice husks. A 20–40 cm layer of insulation is ideal, ensuring the integrity of the sealed environment.
**Key Management Practices:**
1. **Moisture Control to Prevent Freezing**
Seed quality depends heavily on moisture levels. Before winter, seeds must be fully dried to prevent freezing. Moisture should remain below 14% to ensure safe storage. High moisture increases respiration and enzyme activity, leading to potential freezing damage. At 14% moisture, seeds can withstand temperatures as low as -40°C, but at 19%, they may lose viability after just 8 days at -12°C, and at 30%, they could die within 2 days.
2. **Regular Monitoring and Inspection**
Northern corn seeds often stay in storage for long periods. Regular checks of moisture and germination rates are essential. If moisture rises above safe levels, immediate drying is necessary. Germination tests should also be conducted periodically to detect any damage and take corrective action promptly.
3. **Maintain a Clean and Secure Storage Environment**
Storage facilities must be clean, dry, and free from leaks. Outdoor storage should avoid open areas where rain and snow can cause damage. Pest and rodent control are also crucial to protect the seeds.
4. **Proper Storage Methods**
Seeds should be stored at least 30 cm above the ground, with space between stacks. It’s important to avoid sudden temperature changes—seeds stored outdoors should not be moved indoors, and vice versa, as this can reduce germination rates. Cold room storage is generally preferred, but outdoor storage is also possible if properly protected.
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