The wet spring of 2008 was a dramatic reminder—as if you needed one—of how much drainage impacts crop yield. The yield map for a field belonging to Keith Morgan of LeRoy, Ill., tells a typical story: The field averaged 196 bu. per acre, but six acres of it yielded zero.
"As the area that actually produced a crop got smaller, my per-acre costs went up,” Morgan says. Here's how Farm Journal Field Agronomist Ken Ferrie views the impact of poor drainage on production cost: Say you're renting a 100-acre field for $200 per acre. If you lose 30 acres because of standing water, you actually farmed 70 acres. That means you paid $286 per acre to rent the land that produced a crop (100 acres x $200 = $20,000 rent; $20,000 ÷ 70 acres = $286 per acre)
If you applied $150 per acre in
inputs on that field and got nothing in return on the 30 acres, that's a $4,500 loss. The phosphorus and potassium that you applied may still be there for next year, but the herbicide, insecticide and nitrogen—well, let's not even speculate where your nitrogen went.
The solution, of course, is to improve the field's drainage. But drainage is more than simply "tiling a field,” points out Dave Williamson. Along with his brothers Dale and Dennis, Dave operates Williamson Farm Drainage Inc., in Bloomington, Ill.
Size up the field. "Effective drainage may include either surface or subsurface measures or, frequently, both,” Dale says. Surface drainage simply requires cutting channels to an outlet.
"It's a misconception that tile can solve all water problems,” he says. "If water is ponding, the size of tile needed to remove water in 30 hours, before it harms the crop, may be prohibitively expensive.
"If you have both surface and subsurface drainage problems, you have to fix the surface drainage problem first or you won't be satisfied with your tile system,” Dale continues. "If you can fix the surface drainage, it will make the tile system cheaper and improve its performance.”
There are a surprising number of such areas, Dave adds. "We sometimes think that if drainage could have been improved, Dad would already have done it,” he says. "But just recently, I saw a field where water was standing because a ridge remained from an old fence row that had been removed a long time ago.
"On another farm, which was bisected by a county drainage ditch, the spoil that formed the ditch bank created a ridge that prevented water from running off the field. All it needs is an inlet pipe running 30' from the pond to the drainage ditch,” Dave says.
Where will water go? If you have a stream or county drainage ditch running through your farm, you're lucky. "We can put in multiple outlets and use smaller mains in the field,” Dave says. Outlets, which may require running tile to a distant drainage ditch, are the biggest factor in the cost of most drainage projects.
- December 2008