Drying techniques are agricultural practices applied to assist with the balance of moisture in grains post-harvest, determined by a combination of ambient temperature and relative humidity. Spoiling due to insufficiently dried grain is one of the main causes of grain deterioration, loss in grain quality, and thus market value. Grains have the capability to absorb or evaporate moisture, and a balance of moisture content in the air and grains should be sought to achieve an Equilibrium Moisture Content (EMC). EMC prevents the formation of moulds that may affect the quality of grains, spread of pests and germination of grain seeds. After harvest, transportation and threshing, grain needs to be further dried to be preserved. Natural drying techniques are based on ambient air circulation to reduce the moisture content of the grain before storage. Artificial drying techniques apply fans and/or heating elements to move air and maintain constant temperatures .Natural drying (sun drying) is the preferred, commonly used agricultural technique in southern Africa and does not require use of machinery. Drying techniques preserve the contents of seeds thus assuring sustainable agricultural productivity and the practice as climate smart.
To effectively implement Drying Technique practices:
- Step 1: Harvest crops.
- Step 2: Consider the number of different crops that need to be dried.
- Step 3: Dry the crops naturally using air temperature or direct sunlight or artificial drying through using fans or other mechanical means.
- Step 4: Never place crops directly on the soil but rather on a cement area, woven mats or a layer of sacks.
- Step 4: Livestock should be kept away from drying grains to prevent contamination and loss.
- Step 5: Farmers should consult storage life charts that will help determine dry crop characteristics and approximate times for drying.
- Step 6: Cover all drying grain at night to prevent loss or damage.
- Step 7: Sorghum should be left on the seed, maize should be de-husked and left on the cob, grain and pulses are normally left in their pods.
- Step 8: Monitor the stored grain by checking at least every two weeks.
- Food and Agriculture Organisation (FAO), 1994. Agricultural engineering in development. Italy, Rome.
- Food and Agriculture Organisation (FAO), 2001. Rural structures in the tropics. Design and development. Chapter 16 Grain crop drying, handling and storage. Italy, Rome.
- World Food Programme (WFP), 2012. Training Manual for Improving Grain Postharvest Handling and Storage. Italy, Rome.
Benefits
- Prevents loss in grain quality.
- Outside on a flat surface, drying system costs less.
- The drying crib system can be used for many years.
- Forced air/hot air dryer systems are not weather dependent.
Drawbacks
- Imbalanced EMC leads to low quality seed, possible mould/decay and possible germination of grain seeds.
- The natural drying technique is not suitable for humid climates as EMC is difficult to achieve without artificial drying.
