Strategies for Reducing Post-Harvest Losses in Agriculture

The term “postharvest loss” refers to measurable quantitative and qualitative food loss that occurs in the postharvest system. With the renewed focus on investment in agriculture, there is growing interest in effective interventions to reduce postharvest losses.

This article discusses strategies for reducing post-harvest losses in cereal grains, roots and tubers, as well as fruits and vegetables.

Strategies for Reducing Post-Harvest Losses in Cereal Grains

1. Harvesting
In tropical countries, most grains are harvested once a year, though some areas with bimodal rainfall may have two harvests annually (e.g., Ghana and Uganda). African farmers harvest grain crops when they reach physiological maturity.

At this stage, the grains are highly susceptible to pest attacks. Poor farmers sometimes harvest crops prematurely due to food shortages or the urgent need for cash. Premature harvesting reduces both nutritional and economic value, and the food may become unsuitable for consumption.

Quality cannot be improved after harvest; it can only be maintained. Therefore, it is crucial to harvest at the correct maturity stage and peak quality.

2. Drying
Most farmers in Africa rely on natural drying using sunlight and air movement. However, damp weather at harvest time can cause significant postharvest losses.

Grains should be dried to minimize damage and reduce moisture content to levels below 13-15%, which is necessary to prevent mold growth during storage. This helps prevent fungal species that may be present on fresh grains from thriving. Crops may be dried in the yard or a crib.

3. Threshing/Shelling
For some grains like millet and sorghum, threshing may be delayed for several months after harvest, with the unthreshed crop stored in open cribs. In the case of maize, the grain may be stored on the cob with or without sheathing leaves, or the cobs may be shelled and the grain stored.

4. Winnowing/Cleaning
Winnowing is usually done before storage or marketing if the grain is to be sold directly. For most smallholders, this process is done manually, which is inefficient from a commercial perspective since grain purchased from smallholders often requires additional cleaning to remove stones, sand, and extraneous organic matter. Smallholders have little incentive to provide well-cleaned grain for marketing, limiting profits from sales.

5. On-Farm Storage
Post-harvest losses during storage are linked to both poor storage conditions and inadequate storage capacity. Stores must be constructed to ensure dry, well-ventilated conditions that allow for further drying when drying before storage is incomplete.

Stores should also protect the grain from rain, groundwater, rodents, and birds, and minimize temperature fluctuations.

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Strategies for Reducing Post-Harvest Losses in Roots and Tubers

Root and tuber crops remain living organisms after harvest, and losses during storage primarily arise from their physical and physiological conditions.

The main causes of loss are mechanical damage, physiological conditions (maturity, respiration, water loss, sprouting), diseases, and pests. To ensure effective storage, these factors must be understood and properly managed, taking socio-economic conditions into account.

1. Harvesting
The harvesting phase is crucial. If roots and tubers are bruised or damaged during harvesting, later attempts to prevent food loss will be ineffective. Molds and viruses will infest the crop, leading to early rotting.

Correct harvesting practices provide a greater opportunity for the introduction of better postharvest methods. Providing proper tools, equipment, and training for harvesters should be prioritized.

2. Handling
The skin of roots and tubers is an effective barrier against bacteria and fungi that cause rotting. Breaking the skin stimulates physiological deterioration and dehydration. Handling roots and tubers carefully reduces postharvest losses significantly.

3. Packing
Roots are often packed in the field, with farmers placing larger roots at the top to attract buyers. Packing should minimize deterioration by cushioning the roots against impact and compression. Care should be taken to avoid physical damage during packing, such as bruising from stacking, overfilling, or vibration. Containers should allow for good aeration to prevent bruising during transport.

4. Transportation
Temperature management is critical during transport. Loads should be stacked to allow proper air circulation, dissipating heat from the produce and the surrounding environment. In many developing countries, traditional baskets or trays are used for short-distance transport, but they have limitations over long distances.

In such cases, using suitable containers such as natural and synthetic fiber sacks or molded plastic boxes is ideal for transporting roots and tubers to distant markets.

5. Storage
For successful storage of fresh roots and tubers, the following steps must be taken:
i. Select only high-quality roots and tubers free of damage or pest infestations.

ii. Store them in specially designed stores.

iii. Regularly check the stores for pests and damage. Many farmers do not routinely store roots and tubers but leave them in the ground. However, successful storage can be achieved using specially constructed pits or mounds.

For example, a field storage clamp is a low-cost technology for storing potatoes using locally available materials for ventilation and insulation.

6. Processing
Root and tuber crops, such as cassava, sweet potato, and yam, are vital for food security and income generation in many developing countries. Processing these crops helps overcome perishability issues and adds value. Techniques include peeling, washing, grating, pressing/fermentation, sieving, and frying/drying.

Dehydration or sun drying is the simplest and most affordable preservation method, extending the shelf life of perishable crops. This also facilitates transport and opens new markets for farmers. Dried products are often stored in metal bins or water tanks made from galvanized metal sheets.

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Strategies for Reducing Post-Harvest Losses in Fruits and Vegetables

Some varieties of the same crop store better than others, so careful selection is essential.

1. Harvesting
Harvesting should be done carefully to minimize mechanical injuries such as scratches, punctures, and bruises. The time of day when harvesting is done can also affect product quality and shelf-life.

Harvesting in the cool early morning is recommended to avoid exposure to heat, and to ensure better work efficiency. If harvesting during hotter parts of the day is unavoidable, crops should be kept shaded to minimize weight loss and wilting.

2. Handling
Mechanical injury creates entry points for pests and accelerates physiological deterioration. Fruits and vegetables should be handled gently to avoid bruising and skin breakage. The skin acts as a protective barrier against bacteria and fungi, and breaking it promotes rotting. Reducing handling minimizes mechanical damage and preserves product quality.

3. Sorting and Cleaning
Systematic sorting and grading, combined with appropriate packaging and storage, can extend shelf life and reduce losses. Sorting is done to separate poor-quality produce from good-quality ones and further classifies the good produce by size or other quality factors.

4. Transportation
Proper packaging is essential to maintain freshness during transportation. Containers should be clean, smooth, ventilated, and appropriate for the specific crops. Ventilated packaging helps reduce deterioration during transportation, storage, and marketing.

5. Storage
Only high-quality crops should be stored. Storage conditions must maintain optimal temperature, humidity, and environmental conditions to extend shelf life. Regular inspection of stored crops is essential to prevent spoilage.

6. Processing
Processing plays a critical role in stabilizing and diversifying food supplies, creating employment, and improving the nutritional value of products. It helps reduce the high perishability of leafy vegetables, making them more stable and offering improved digestibility. Processing methods include drying, salting, fermenting, and pickling.

To reduce food loss and maximize shelf life, only varieties known for better storage should be kept. The strategies discussed in this article should be implemented to reduce postharvest losses and improve food security.

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