"To help make seeding rate decisions for soybean, Dennis Bowman and I developed a seeding rate calculator—or rather, we resuscitated one that we had running some years ago," Nafziger said.
The web-based PC version is available here, the Android app is available here, and the iPhone/iPad online spreadsheet is available here.
The calculator asks for both weight and seeds per pound for seed units sold by weight, or for seeds per unit for seed sold by number. It then asks for the percentage of warm germination, which is required to be on the seed tag or container, and for the cost per unit. Field size and row spacing are also requested.
The only subjective information requested by the calculator is an estimate of the percentage of germinable seed expected to emerge and establish plants under the soil conditions and perhaps the weather forecast at planting.
Wet soil can decrease emergence
Nafziger said that under very good conditions it is reasonable to expect close to 100% of good seed to emerge. But if soils are cold or wet (or likely to get wet), this percentage should be decreased. The calculator goes from 100 to 70%, with the idea that expecting less than 70% emergence of good seed should be a signal to wait for better conditions before planting.
"The calculator returns seed spacing down the row, seed requirements per acre and for the field, and the amount of time it will take to plant the field," Nafziger said. "While we developed the calculator for soybean, it works for corn or small-grain seed as well."
Source: University of Illinois