Because these water-quality control measures ultimately play out on the farm, Corn & Soybean Digest asked growers from the Coldwater/Palmer Creek watershed group what’s worked for them to reduce farm-nutrient loss.

The most effective practice for Ted Pitzenberger to reduce nitrate loss was shifting fall N application timing to spring. The watershed group secretary abandoned fall N application 35 years ago, but still harvests 200-bu. corn yields.

“It’s a management issue,” says the Dougherty, IA, grower. “We buy liquid fertilizer in the fall, apply it in the spring, then sidedress through the growing season. On my continuous corn I use 135 lbs. of liquid N/acre preplant, then sidedress the heavier, more productive soils with 45 units. On the bean ground we use 135-145 units of total N, some of it sidedressed.

“Maybe it costs more, but we save 45 units/acre by waiting till spring, so that’s a financial cushion. And I save that extra trip across the field,” Dougherty says.

He and grower Dennis Cassmann each installed woodchip dentrification bioreactors to retain nitrates from tile-drainage flows.

Cassmann’s bioreactor reduced drainage water nitrates by 35% in one year, from 11 to 7.2 ppm.

The Bristow, IA, grower spreads his N applications through the growing season. “We see economic and environmental returns from splitting our applications,” he says. The first is anhydrous with a nitrification inhibitor injected deeply in the fall to place it below the roots, says the grower/cattleman/hog producer and treasurer of the watershed group. When he plants, he adds 32% N “over the row to nourish the microorganisms that decompose the crop residue.” And in June he sidedresses anhydrous “because it always gives me a yield boost.

“ISU research shows similar nitrate loss between spring and fall application when the fall application occurs at soil temperatures below 50° F,” Cassmann says.

Sidedressing is high on Jon Giselson’s list. The 20-year conservation-tillage veteran from Floyd, IA, says, “There isn’t a farmer in Iowa who would apply anhydrous ammonia in the fall if he was limited in the amount of total N he had. Fall application’s advantages are more logistical than agronomic.

“Getting it all done in the spring is not a problem. I cover 200 acres/day at 7 mph,” says the Iowa Learning Farm conservationist and chair of the Floyd County Soil and Water Conservation District.

Strip-tilling in the fall allows Giselson to place nutrients “where the plants use it.” In the spring, he sprays for weeds and sidedresses with 32% N solution after the corn’s up. “I save fuel, reduce my time in the field and save on input costs. I find my yields are the same, costs are less and profits higher than if I tilled the soil black,” he says.

 It’s all about risk, says grower and swine producer Dave Muth, Dougherty, IA. “We know what we should do, but we still have to profit.” As a member of the watershed group, his favorite tools were the cornstalk nitrate test (CNT), N stabilizers and phytase to reduce his hogs’ manure P content.

“The CNT gave us the scientific proof that we could trim our N rates and not affect yields,” he says. His initial CNT results dropped from over 3,000 ppm into the ideal 700-2,000-ppm range as he cut back on N rates and used N stabilizer.

Fear of yield hits from compaction prevents him from shifting his manure application to spring, so he uses N stabilizers.

“It’s interesting that focus has shifted back to water quality from carbon, which was the big focus last year,” says the Iowa Corn Growers environmental committee member.

“Spring N application is very viable but I think it will cost at least $10-15/acre more, between increased prices and labor,” says Scott Bruns, Allison, IA, grower and watershed project chair.

The bottom-up approach used producer experiences to make the most beneficial and profitable management changes, says watershed Bruns, grower-leader of the voluntary watershed group. “We worked harder to make the program work because it was our design.”