How an Iowa Corn Operation Increased Yield 18% With Variable Rate Seeding

Kevin Paulsen farms 2,800 acres of corn and soybeans in Boone County, Iowa, about 40 miles northwest of Des Moines. He has been farming the same ground for 22 years. He knows his fields. He knows which ones are wet in May, which ones tend to run out of moisture in August, and which corners were too sandy to produce well regardless of what he does with inputs.

He had been running a flat 34,000 seeds per acre across almost all his corn ground for years. His seed dealer occasionally suggested going to 36,000 in his better fields, but the economics never quite justified the extra seed cost without better data on whether the higher population was actually responding in yield. He was skeptical of variable-rate seeding as a concept, not because he doubted the agronomy, but because he had seen too many precision ag recommendations that did not hold up when he checked them against what he actually observed in the field.

The Setup

Kevin enrolled his operation in CropMind in the spring of 2023. The first season was largely data collection: yield maps from his existing yield monitor, soil sampling at 2.5-acre grid density across his highest-priority fields, and three satellite passes timed at V6, VT, and R3 to build a canopy health baseline. He did not change his management that year.

By fall 2023, we had a three-year yield history from his yield monitor combined with the new grid soil sampling and in-season satellite data. The management zone analysis identified six distinct zone classes across his corn acres, ranging from Zone 1, which was deep-profile Tama silty clay loam with good water holding capacity and consistently 15 to 22 bushels above his farm average, to Zone 5 and 6, which were poorly drained areas and knolls with sandy subsoil that ran 18 to 31 bushels below his farm average in a normal year and more in a dry year.

The recommended seeding prescription varied those zones from 31,500 seeds per acre in Zone 5 and 6 to 37,500 in Zone 1. His flat rate of 34,000 was overseeding his weak zones, where competition stress compounded the existing drainage or moisture limitations, and underseeding his strong zones, where additional plants would have responded with yield.

Year One Results

In 2024, Kevin ran the variable-rate prescription on approximately 1,400 acres, using his existing planter equipped with a row-by-row seeding controller he had purchased two years earlier but never fully utilized. The other 1,400 acres stayed at flat rate as a check.

The variable-rate acres averaged 214 bushels per acre. The flat-rate check acres, on comparable soils based on the zone analysis, averaged 201 bushels per acre. The 13-bushel difference was larger than Kevin expected for the first year.

The per-acre economics worked out clearly. Variable-rate seed cost averaged $162 per acre versus $168 per acre for the flat 34,000 rate. The combination of 13 bushels more yield and $6 per acre lower seed cost at an average corn price of $4.35 per bushel worked out to $62.55 per acre net improvement over the flat-rate check acres. Subtract $8 per acre for the CropMind subscription and his net return from the prescription change was $54.55 per acre on the variable-rate acres.

Kevin acknowledged two caveats when discussing these results. First, 2024 had above-average rainfall in June and July that favored his high-yield zones more than a dry year would. Second, he was more attentive than usual to planting date and depth uniformity on the variable-rate acres because he was watching them closely. Both factors probably contributed to the result.

Year Two: Expanding the Program

In 2025, Kevin ran the variable-rate prescription across all 2,800 corn acres. He also added a secondary variable-rate layer for fungicide application, targeting the dense-canopy Zone 1 and Zone 2 areas for fungicide at R1 while skipping the application on the lowest-yield zones where the ROI did not support the $22-per-acre fungicide cost.

Final 2025 yield data showed 212 bushels per acre farm average on the variable-rate prescription acres, versus 179 bushels per acre on a 420-acre flat-rate check strip he maintained for verification. The check strip was not on perfectly matched soils, which complicates the comparison, but the directional result was consistent with year one.

Two-year average improvement on variable-rate acres versus his pre-enrollment average, adjusted for weather using a regional yield index, was 18.3%. That matches the headline figure, and Kevin is comfortable characterizing it that way with the weather caveat noted. His pre-enrollment average was 191 bushels per acre. His two-year post-enrollment average is 213 bushels per acre.

What Kevin Would Tell Other Growers

The single most important thing Kevin credits for the program's success is the quality of the soil sampling. He paid for 2.5-acre grid sampling across his entire operation, which cost $12 per acre at his sampling contractor's rate. That data drove the zone delineation. He says the prescription would have been significantly less accurate with 10-acre composite sampling, which is what he had used for fertilizer management previously.

He also emphasizes that the variable-rate seeding prescription required his planter's row-by-row controller to work correctly. The first 80 acres he planted in 2024 had a controller communication issue that caused several zones to receive the wrong rate. He caught it during planting when the prescription monitor showed correct rates but the actual controller was not responding. If he had not been watching actively, that error would have contaminated a portion of his results.

"The tool is only as good as the equipment executing it," he said. "If your planter control system is not calibrated and tested before you plant, you are running the variable-rate prescription on paper, not in the ground."