When Chris Armstrong came back to farm the flat ground of Nebraska's Platte River Valley in 2009, he found a 210 bu/acre corn average across the farm.
But data analysis revealed a larger challenge.
Corn yields varied from 140 to 260 bu/acre across dryland and irrigated fields. Organic matter ranged from 1.4% to 4.2%, and pH from 6.2 to 8.2.
In 2015, Chris persuaded his father-in-law Steve Arneal to make some big changes. They traded in a disk for a 16-row Gladiator strip-till machine, which they share with a neighbor. The two also decided to shift to split nitrogen applications on every field. They had been applying nitrogen in the fall at different levels, based on yield goals for each field. In the new split scenario, they apply a base rate of anhydrous with a stabilizer in the fall, then add more N in-season, based on Encirca algorithm inputs.
“We went into strip till thinking the machine would be more of a fertilizer applicator that would put fertilizer close to the corn plant,” Armstrong says, “but we quickly found its bigger purpose was for seedbed preparation.”
Heavy rains shift N
In the short time he’s been farming, Armstrong quickly learned the weather can drastically alter N plans. “This past year, our plan for a 240-bushel yield of corn on one field called for very little N in June. But then we got 8 inches of rain in two weeks,” he says, “and all of a sudden we had yellow corn and we needed to fertigate to catch up.”
Armstrong and Arneal have achieved good corn yields with as little as 0.7 to 0.8 lbs. of nitrogen applied per bushel of corn harvested. But they've also seen much lower yields with as much as 1.5 lbs. of N applied. “How do you know what’s right?” Armstrong asks. “You don’t. You just have to trust the inputs, that they make sense to you, and manage accordingly.”
From 2015 through last year, Armstrong has applied N amounts varying from 0.94 lbs. of N per bushel harvested to as much as 1.17 lbs. of N per bushel of corn produced.
Learn each field
Armstrong continues to closely monitor yields and inputs across 1,900 acres of corn and soybeans, trying to learn what works best for each field. “It seems in the past few years, we’ve relied too much on fertigation,” Armstrong says.
“We’ve run into situations where we didn’t have enough N, but our soils were saturated so we didn’t want to put more water on the field with the nitrogen. And I like the idea of concentrating the nitrogen near the plant with Y drops. So, we’re planning to apply more nitrogen early in the season with Y drops, and in some cases go to fertigation late in the season on fields that have potential for top end yields," he says.
Other lessons Armstrong has learned and changes he’s making include:
- Some soils required N much sooner than expected—so they started to sidedress at V4 to V6 stage with homemade Y drops.
- They were under-applying N on highly productive ground because they were on a one-pass system, and pivots weren’t set up.
- They weren’t equipped to reapply lost N.
- They didn’t know how to determine how much N was lost. They plan to begin testing for nitrates in underground water.
- They’re now moving toward all variable-rate nitrogen application in-season, as opposed to pre-plant.
- They’ve dabbled in cover crops, with last year being their first, with mixed results.
- Their center pivot irrigation systems deliver nitrogen at a flat rate now, but Armstrong is considering a move to variable-rate application.
- He thinks the comparison of Y drops versus fertigation this year provided valuable data. He will continue to make comparisons, including some side-by-side comparisons--and test inputs against yields--while noting N losses.