Managing different parts of a field with varying input rates doesn't have to be expensive or high tech. John Kramer, Milford, KS, began varying seeding rates long before global positioning systems (GPS) were commercially available.

“We were doing it for quite a few years on a manual basis, because we have center pivots,” explains Kramer, who farms in a partnership with his brother, Larry. “We wanted to seed different rates for dryland corn than for irrigated corn.”

The brothers started out variably applying seed by using an electromagnetic clutch on the transmission of the corn planter. The planter was equipped with a Duo-Rate seed population controller that could reduce the seeding rate 20-40% with the flip of a toggle switch.

“That technology has been around for about 15-20 years,” says Kramer. “Now we use a Rawson hydraulic drive that we manually control from the cab. You dial in the population you want as you drive down the field.”

Yet GPS and yield mapping equipment have also become increasingly important in helping Kramer and his brother pinpoint where and how much ag inputs pay their way. They've been using yield-mapping tools since 1998.

“John uses yield monitor data to make good management decisions,” says Scott Staggenborg, a Kansas State University (KSU) agronomist, who has conducted on-farm seeding rate studies there. “He takes data, looks at it over time and adjusts inputs to match high- and low-producing areas.”

KSU researchers recently helped Kramer make a prescription plant-population map, which he now uses to vary seeding rates for no-till corn. “It's great to be able to vary seeding rates throughout the field,” says Kramer. “Now we can test to see if the guidelines for seeding rates are accurate.”

Varying rates can be particularly important where soil conditions differ. “John has fields with two very contrasting soil types: a high-yielding silt loam and a low-yielding sandy soil,” says Staggenborg. “He wants to know how much we hurt yields, if at all, by dropping the seeding rates in the low producing soils to save seed input dollars.”

The per-acre savings in seed costs could be fairly substantial on lower producing ground, particularly if planting transgenic hybrids that come with a high technology fee, points out Kramer. “I don't feel comfortable dropping 29,000-30,000 seeds/acre on dryland or poor-quality ground that will typically only yield 140 bu./acre,” he says. “I feel like it would be throwing away our money.”

Kramer adds that switching from drilling soybeans on dryland acres to planting them on 30-in. rows has helped to both ensure better seed placement and to significantly reduce the need to plant as much seed. “We've been able to cut seeding rates by one third on some fields and still maintain yields,” he says. “If the cost per unit on seed is $30, then dropping the seeding rate by one third is in excess of $10/acre savings.”

Fine-tuning ag inputs such as seed and fertilizer may promise as much or more payback as efforts to maximize yields. “John focuses on maintaining or increasing yields at the most economically beneficial level,” says Staggenborg. “He wants to know at what level agronomic inputs are at their economic optimum.”

Variety selection and equipment preparation are also key ingredients for making lower seeding rates work, emphasizes Kramer. “We spend quite a bit of time on variety selection and getting planting equipment set up,” he says. “We pay attention to the seeding units and the openers to make sure they're in good condition and planting at the appropriate depth. You only have one chance to get it right.”

After harvest, the Kramer brothers check to make sure they did get it right. “We try to make good use of our input costs,” says Kramer. “We look carefully at performance and not just the cost of the seed.”