Why it matters more each year
Aflatoxin is a toxin produced by Aspergillus flavus. It is a serious health hazard, it is regulated, and buyers — exporters, processors, organised retail — test for it. A consignment above the limit is rejected outright, and the farmer usually has no idea why.
You cannot see it, smell it or taste it.
Where it comes from
Two windows, and neither is in the growing season:
1. End-of-season drought stress. A crop that goes through moisture stress in the last few weeks develops damaged, shrivelled kernels that the fungus colonises in the soil, before harvest.
2. Drying and storage. This is the bigger one. Pods harvested at high moisture and dried slowly, or heaped while still damp, or stored above safe moisture, allow the fungus to grow and produce toxin.
What actually prevents it
Irrigate at the end if you can. Terminal drought is the field-side driver. Where irrigation exists, one irrigation in the last three weeks matters.
Harvest at the right maturity. Over-mature pods left in the ground, especially in warm moist soil, are where colonisation happens.
Dry fast, and dry properly. Spread thin on a clean raised surface — a tarpaulin or a platform, never bare earth. Turn it. Get the moisture down quickly rather than leaving pods in a windrow for days.
Do not heap warm or damp pods. The centre of a heap stays warm and damp for days and that is where the fungus grows.
Store dry. Below the safe moisture level, in clean bags, off the floor, away from walls, in a ventilated store. Re-dry if the monsoon raises the moisture again.
Discard the damaged, shrivelled and insect-bored kernels. They carry most of the toxin. Sorting them out lowers the level of the whole lot substantially, and it is manual work rather than an input.
Control storage insects. Insect damage opens the kernel to the fungus.
The commercial point
If you sell into any organised channel — export, oil mills with quality systems, branded processors — this is not optional and it is where the price premium lives. A farmer who can demonstrate proper drying and storage is selling a different product from one who cannot.
