In Summary
  • Hermetic storage bags or silos keep oxygen out.
  • Poor grain drying also predisposes it to aflatoxins.
  • Contamination from aflatoxin is a major contributor of qualitative losses during storage.
  • Chronic dietary exposure to low doses of aflatoxins is a known risk factor for liver cancer and other health-related issues.

As maize farmers harvest their produce, a good chunk of the grain could be lost, especially due to the ongoing rains.

Brian Okinda spoke to Dr Jane Ambuko, a senior lecturer at the University of Nairobi’s Department of Plant Science and Crop Protection, and a Principal Investigator of UoN’s YieldWise Postharvest Project, which is funded by the Rockefeller Foundation, on measures farmers and the government can take to safeguard the staple crop.

What is the level of postharvest loss in the maize supply chain?
There are two kinds of losses that occur in maize namely quantitative (lost kilos/volume) and qualitative. Quantitative losses are easy to determine and report since they constitute a physical reduction in the marketable volume and can be easily measured.

In Kenya, the figure may range from 10–20 per cent of the total volumes. Qualitative are due to loss of aspects such as nutritional, safety or grade and are hardly considered a loss or reported as such.

What factors contribute to the losses in maize?

The two losses begin from the field and continue through the other postharvest handling stages. Some farmers cut their maize and leave it in the field for too long, exposing the crop to fungal rots leading to qualitative losses.

Poor traditional processing practices like where sticks are used to ‘beat’ grains off the cobs results in lots of broken grains (qualitative loss) and also predisposes the grain to other deteriorative agents including aflatoxins.

Poor grain drying also predisposes it to aflatoxins. There are other loss agents such as spillage.

During storage, the key agents of postharvest losses are pests, mainly weevils which can lead to 100 per cent loss. Rats also contribute to high storage losses.

Contamination from aflatoxin is a major contributor of qualitative losses during storage. Aflatoxin contamination is predisposed by other factors such as poor drying, damaged (broken) grain and dump or not well-aerated storage.

What measures should farmers take to reduce postharvest losses in maize?
Farmers should not delay harvesting their maize once it is mature; prolonged stooking in the field exposes the grain to rot. Farmers should also be assisted to access simple processing technologies such as shellers instead of the common traditional methods used.

After shelling, the maize must be dried properly to the recommended moisture content level of about 13 per cent before storage. There is a special tarpaulin that farmers should use to dry maize and other grains. Using the tarpaulin makes the grains dry faster.

After drying, the maize should be stored properly in a clean, dry and well-aerated store to avoid contamination and infestation by pests.

One of the storage technologies recently introduced in the Kenyan market are hermetic bags. The principle behind hermetic storage (bags or silos) is keeping oxygen out of the bag or storage container. This suffocates the storage pests such as weevils which cannot survive without oxygen.

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