After the R4 stage, the final number of grains per ear has been determined. At this point it is possible to estimate final yield. As you measure plant density, open three ears at each sampling spot and count the number of grains per ear. Use the first, fifth, and tenth plant in the measurement row if these have harvestable ears. If the selected plant does not have a harvestable ear, move to the next plant in the row for the count.
It is essential to avoid deliberately selecting plants with large ears, as that will bias your results. Count the number of rows of grain and the number of grains in a representative row. Do not tip kernels which are less than one-half of the size of the kernels in the center of the ear. Multiply number of rows by kernels per row to get grains per ear. You will have to assume a final grain weight, so this is only an estimate of yield. You can assume 3,500 grains per kilo at 15% moisture for many improved varieties. Final yield estimate in kilograms per hectare at 15% moisture is:
Plants/ha x ears/plant x grains/ear x 1/(number of grains per kilo)