Why Maize Storage Losses Are Harder to Count Than They Sound

Ask three different sources what share of stored maize is lost to pests and spoilage in a typical season, and you'll likely get three different answers, sometimes a wide margin apart. That's not because anyone is being careless. It's because "storage loss" gets measured at different points, over different timeframes, and by different methods, and those choices change the number more than most published figures let on.

We spent part of this season trying to understand where the disagreement actually comes from, rather than picking a favourite figure and repeating it. What we found is less a single hidden truth and more a set of definitions that quietly don't match.

Three ways of counting the same sack

Some estimates measure weight loss at the point of sale, months after storage began, capturing moisture loss alongside genuine spoilage. Others measure only what's visibly damaged by pests at a single inspection, missing losses that happen gradually and are sold off cheaply before full spoilage sets in. A third approach relies on farmer self-reporting, which tends to run lower, understandably, since nobody enjoys quantifying their own loss.

• Weight-based measurement at sale: captures moisture loss and spoilage together
• Single-inspection pest damage counts: misses gradual or early-discounted losses
• Farmer self-reported estimates: consistently the most conservative figures

None of these methods is wrong exactly. They're just answering slightly different questions, and a published national average rarely says which one it's using.

What we chose to record instead

Rather than adopting one figure as authoritative, we've started noting the measurement method alongside any storage statistic we cite, and flagging plainly where two sources disagree without pretending one is simply more correct. It's a small discipline, but it means a reader comparing our numbers to another source can actually understand why they might differ, instead of assuming one of us made an error.

For farmers deciding whether to invest in improved storage, the honest answer is that the return depends heavily on which kind of loss you're most exposed to, and that's a conversation worth having locally rather than settling with a single national percentage.