Post-Harvest Management in Kenya: Drying, Storage and Aflatoxin Control

Post-harvest management in Kenya is where many farmers quietly lose a large part of the crop they worked all season to grow. Grain that survived drought, pests, and disease in the field can still be destroyed after harvest by poor drying, weevils, rodents, and — most dangerously — aflatoxin. Yet the fixes are well known and affordable. This guide covers drying to safe moisture, hermetic PICS bags, aflatoxin prevention, and clean storage, so you keep more of your harvest and sell it for more.

Why Post-Harvest Losses Matter

Every kilo lost after harvest is a kilo you already paid to grow — seed, fertiliser, labour, and land all spent, then wasted. Post-harvest losses hit farmers in three ways:

• Quantity — grain eaten by insects and rodents, or rotted by moisture.
• Quality — discolouration, mould, and damage that cut the price buyers will pay.
• Safety — aflatoxin contamination, which can make grain unfit and unsellable to formal buyers.

Good post-harvest handling turns these losses back into income, and just as importantly lets you store safely and sell later when prices rise, instead of selling into the harvest-time glut when prices are lowest.

Step 1: Harvest at the Right Time

Timing sets up everything that follows. Harvest maize when it is physiologically mature — husks dry and browning, kernels hard, and a black layer formed at the base of the kernel.

• Too early: grain is wet, hard to dry, and prone to mould.
• Too late: grain is exposed to rain, field pests, and aflatoxin-forming fungi, and can shatter or lodge.

Step 2: Dry to Safe Moisture

Drying is the most important post-harvest step. The target for safe storage is about 13% moisture (13.5% or below) for maize and a similarly low level for pulses.

How to dry well:

• Dry on raised tarpaulins, cribs, or clean surfaces — never on bare ground, which adds moisture, soil, and fungi.
• Turn the grain regularly for even drying.
• Protect from rain and night dew — cover or bring under cover.

Checking moisture:

Method	How it works
Moisture meter	Most accurate; gives a direct reading — worth sharing one within a group
Salt-in-a-bottle test	Put dry salt and grain in a sealed jar, shake; salt sticking to the glass means grain is still too wet
Bite/crack test	Mature dry kernels crack sharply and are hard to dent — rough guide only

Grain stored above safe moisture is the single biggest cause of both weevil explosions and aflatoxin.

Step 3: Shell, Clean, and Sort

Once dry, shell maize and then winnow and sort:

• Remove broken, discoloured, mouldy, and insect-damaged kernels.
• Remove chaff, stones, and trash.

Damaged and mouldy grains are exactly where aflatoxin and storage pests concentrate. Taking them out protects the entire batch and improves the grade you can sell.

Step 4: Choose a Storage Method

Method	Cost	Chemical needed?	Best for
Hermetic bags (PICS)	Moderate per bag, reusable	No	Most smallholders; chemical-free grain
Metal silo	Higher upfront, long-lasting	No	Larger, longer-term storage
Ordinary bags + approved treatment	Low bag cost + chemical	Yes	Short-term, budget storage
Traditional granary/crib	Low	Sometimes	Cobs; needs good pest/rodent control

For most Kenyan farmers, hermetic bags such as PICS offer the best balance — strong protection, no chemicals, and reusable for several seasons.

How Hermetic (PICS) Bags Work

PICS bags are triple-layer: two airtight plastic inner liners inside a woven outer sack. When sealed with dry grain inside, any insects present quickly use up the oxygen and die — no pesticide required — and no new pests can get in.

To use them correctly:

1. Only bag properly dried grain (wet grain still spoils, even sealed).
2. Fill the first inner liner, press out excess air, and tie it tightly.
3. Tie the second liner, then the outer sack.
4. Stack bags on pallets or timber, off the floor and away from walls.

Handle bags gently — a puncture breaks the airtight seal. Inspect for holes before reuse.

Preventing Aflatoxin

Aflatoxin is produced by fungi that thrive on stressed, damaged, and moist grain, and it is both a health hazard and a barrier to selling into formal markets. Prevention is straightforward and comes from doing the earlier steps well:

• Harvest on time and don't leave mature grain in the field.
• Dry fast to safe moisture — the fungus needs moisture to produce the toxin.
• Sort out damaged and mouldy kernels.
• Store dry, clean, and airtight, off the ground.
• Keep the store dry — fix leaks, control rodents, remove old residues.

Grain that is dry, clean, and sealed simply gives the fungus no opening.

Step 5 and Beyond: Store Clean and Monitor

• Clean the store before a new harvest — remove all old grain residues that harbour pests.
• Keep it dry, cool, and ventilated, rodent-proof and leak-proof.
• Monitor every few weeks for moisture, insects, heating, and any mouldy smell, and act fast on anything you find.

Common Storage Pests and How to Beat Them

Even well-dried grain can be attacked if the store is dirty or the grain was infested before bagging. The main culprits in Kenya are:

• Maize weevil and larger grain borer — bore into kernels, turning grain to powder; hermetic bags suffocate them without chemicals.
• Grain moths — larvae web grain together near the surface; good hygiene and sealed storage stop them.
• Rodents — eat and contaminate grain; a rodent-proof, well-maintained store is essential.

The pattern is clear: dry grain, clean store, airtight or protected bags, checked regularly. Do those and pest losses fall dramatically.

A Simple Post-Harvest Checklist

Stage	Key action
Harvest	At full maturity, black layer formed
Dry	To ~13% moisture, on raised surfaces
Shell & sort	Remove damaged, mouldy, foreign matter
Bag	Dry grain into hermetic (PICS) bags
Store	Clean, dry, ventilated, off the ground
Monitor	Check every few weeks; act on any problem

Running through this every season turns post-harvest handling from an afterthought into a reliable routine that protects both the quantity and the value of your crop.

Store Well, Then Sell at the Right Time

The reward for good post-harvest management is twofold: you keep more grain, and you can hold it safely until prices recover from the harvest-season low. Watch the market so you sell at the right moment — check current maize and pulse prices on Agrisoko market intelligence — and when you are ready, list your grain on Agrisoko to reach serious buyers directly. For selling maize specifically, see our guide on how to sell maize in Kenya. Grow it, save it, and sell it well.