Scouting makes it possible to compare the actual stand with the desired plant population, says McWilliams. Estimating plant population involves counting the number of viable plants in a length of row that equals one one-thousandth of an acre in several spots across the field. Six to eight spots across 20 acres provide a good sample. Average these counts and multiply by 1000 to get the plant population.
The length of row that equals one one-thousandth of an acre varies with planting width, notes McWilliams. In 22" rows, the length is 23.8'; in 30" rows it’s 17.4'.
In relating stand loss to yield loss, McWilliams cites figures from the National Crop Insurance Service corn loss instruction book. These figures show how a 75% stand will result in a 10% yield loss, a 50% stand in a 26% yield loss and a 25% stand in a 43% yield loss. Yield losses may increase with uneven distribution or large gaps or skips in the stand.
"The stand isn't the only factor to consider in a replant decision," adds McWilliams. "Crop insurance requirements may be a consideration. There are likely to be yield losses from planting at a later date. There are costs for the replant seed and other replanting and pest control costs. The grower has to evaluate these factors carefully to determine if replanting is worth the time, money and effort."