Maize yield estimator
Estimate grain yield in t/ha before harvest by counting cobs and kernels in the field.
Use 10 m, or 11.11 m at this row width to sample exactly 1/1 000 ha. Add rows together if you counted several.
Count only cobs that will be harvested; ignore tiny or barren ones.
Count around the middle of the cob. Always an even number, usually 12–18. Average at least 5 cobs.
Count along one row from base to tip, leaving out unfilled tip kernels.
About 2 900–4 000 kernels/kg (0.25–0.35 g per kernel); 3 200 is a middle value; use 3 600–4 000 after drought or heat at grain fill.
Enter the number of cobs you counted in that length of row.
How this is calculated
This is the yield-component method: count cobs in a measured strip, count kernels on typical cobs, and turn the kernel count into mass with an average kernel weight. It works from the dough stage onwards, once kernel numbers are fixed.
Cobs per hectare = cobs counted × 10 000 ÷ (row length × row width). 25 cobs in 10 m of 0.9 m rows is 25 × 10 000 ÷ 9 = 27 778 cobs/ha. Kernels per cob = kernel rows × kernels per row, e.g. 16 × 35 = 560.
Yield (kg/ha) = cobs/ha × kernels per cob ÷ kernels per kg. With 3 200 kernels/kg: 27 778 × 560 ÷ 3 200 = 4 861 kg/ha, or 4.86 t/ha at about 12.5% grain moisture.
Kernel weight is the biggest unknown. A dry or hot grain-fill period gives lighter kernels, so more of them make a kilogram; use a higher kernels-per-kg figure then. Treat the answer as ±15%, and sample several spots across the field, because one strip can be well off the field average.
Read the guide: How to estimate your maize yield before harvest
Results are estimates for planning. Check product labels and local recommendations before you apply anything.