Darle Elkin used to man Air Force nuclear weapon guidance systems, so it's probably not surprising that his tractor cab looks like Houston Mission Control.

Since his days of launching missiles from bunkers in the 1970s, he's replaced his sextant and celestial navigation with GPS and databases. On his Webster City, IA, farm, his 14 years of field data are a treasure trove of cause and effect.

His agronomic records drive decisions such as corn hybrid selection, fertility programs, variable-rate plant populations, crop rotation, nitrogen stabilizer use, and where and when to use corn fungicides. He uses his data to select offensive and defensive soybean varieties, and plants each bean in the area of the field that it fits best.

Variable-rate planting as well as crop nutrient applications have been the norm on his farm for five years. Elkin doesn't like to make decisions based solely on intuition. “I have this data,” he says, “and I use it.

“Ben Rahe, our Premier Crop advisor, and I define A,B,C management zones on our farm based on GPS yield data, soil type, drainage, fertility, organic matter ? any of the factors we can measure that affect our profit potential,” Elkin says.

“The A zones are where we aggressively push plant populations, fertility and spend more money to make money. Our corn population there might be 36,000-38,000/acre. The B zones are the current field average values. We might plant corn there at 34,000. By contrast, the C zones are where we use inputs conservatively, not wasting money where there's a drainage problem or sandier soils. We free up inputs to put on the A zones, and preserve the profits across all zones,” he says.

THIS APPROACH OF variable-rate inputs is like knowing how many people are coming to dinner, so that you prepare enough food.

Elkin lives to experiment. His maps show him how variable-rate inputs and seeding rates affect his profits. This year he added nitrogen (N) stabilizers as another variable in the mix. He uses a 1-2-acre check within field zones to contrast his experimental seeding and fertility rates with “standard” practice.

“We use checks on almost all the fields, experimenting with populations from 28,000 to 40,000, and variable-rating the N,” he says.

All these variable-rate treatments make for a large number of map layers, each representing areas within fields with different soil characteristics, input treatments, seeding rates, hybrid placement and yield histories. “That's where Premier Crop's database helps me out,” Elkin adds. “Their system helps make studying my fields and using my information efficient.