A single Kansas State University TAPS farm offers participants more than 1.15 billion theoretical management pathways — and that count excludes repeated weekly irrigation decisions. The figure, drawn from the K-State Testing Ag Performance Solutions program, quantifies the decision burden precision agriculture places on corn growers who manage seed, nitrogen and water on variable fields.

The calculation rests on three planting dates, 27 hybrids, 121 seeding rates, seven at-plant nitrogen rates, seven sidedress rates and seven options for each of four fertigation applications. Irrigation adds another 21 choices every week of the season.

That combinatorial scale frames the core problem Daran Rudnick, irrigation engineer at Kansas State University, wants growers to confront before they touch another rate or build another prescription: without a clearly defined objective, more options do not produce better answers.

"What is truly the limiting factor?" Rudnick said. "Do we want to elevate the low-productivity zones, or do we want to reduce the inputs to match those productivity zones?"

The question carries direct margin implications. A farmer chasing maximum yield will make different seeding, nitrogen and irrigation choices than one chasing maximum profit. A producer working under a limited water allocation may measure success in bushels per inch of irrigation rather than bushels per acre. Another may target nitrogen cuts that save money without erasing the gain through lost yield.

Rudnick's advice: set those goals before the harvest map appears, not after.

Competition results illustrate the spread

In the 2024 Colby TAPS competition, roughly 100 participants on 34 teams selected 22 different hybrids, planted populations ranging from about 20,000 to 36,000 seeds per acre, applied roughly 110 to 280 pounds of nitrogen per acre and used between 2 and 15 inches of irrigation. Every decision fed into the final yield, efficiency and profitability of each team's simulated farm.

"At the end of the day, which was the driving factor?" Rudnick said. "How did the earlier decision influence the second and the third decision?"

When several practices change simultaneously, isolating which one produced the result becomes difficult. That is a data-interpretation problem as much as an agronomic one, and it applies to on-farm trials as readily as to contest entries.

Rudnick recommends keeping some core decisions stable. A grower might lock in a hybrid and seeding-rate strategy at planting, then react in-season through irrigation and nutrient management. Fewer moving variables make the resulting data easier to read and the lessons easier to carry into the next crop year.

Water drives, nitrogen optimizes

A review of about six years of University of Nebraska TAPS sprinkler-irrigated corn data found water acted as the primary production driver, with nitrogen serving as the optimizing factor. Other practices still mattered, but their individual effects became harder to distinguish among the many possible input combinations — a caution for any grower attributing a yield bump to a single product or practice without controlling the others.

Precision agriculture does not require testing everything at once. The useful starting point, according to Rudnick, is one plainly stated question: is the goal higher yield, better profit or more efficient use of a constrained input? Once that goal is set, farmers can select the technology, data and management changes needed to answer it.

Growers can test the framework in person: the University of Nebraska's UNL-TAPS program, K-State's sister competition, will run an interactive crop skills challenge at Husker Harvest Days, Sept. 15-17 in Grand Island, Neb., at Lot 928.