Yield maps and aerial images, such as normalized difference vegetation index (NDVI) maps, make spotting problem areas in a field easier. "Inevitably, hybrid differences are the first thing that show up. Drainage is second,” says Farm Journal Field Agronomist Ken Ferrie.
In other words, to make the biggest yield difference fastest, improve water management. Apparently, a number of farmers are acting on that advice.
"All the drainage contractors I've spoken with recently are quite busy,” says University of Illinois ag engineer Richard Cooke. "There was a little lull a couple years ago, but drainage has picked up a lot because of the [wet] weather and the increase in the price of corn and soybeans. Higher commodity prices make drainage projects pay for themselves much faster.”
The advent of do-it-yourself drainage, in the form of tile plows, has made drainage management easier for farmers. "Our sales are on track to be about triple last year—and that already was our best year ever,” says Denny Bell, who manufactures Gold Digger tile plows.
"For what land sells for, a lot of farmers say it makes more sense to improve the productivity of land they already have, instead of buying more,” Bell says.
Another factor contributing to drainage growth is yield monitors, Cooke says. By revealing the impact of wet soil on crop yield, "monitors have launched a trend toward more systemic tile systems, instead of random drainage or just running a line to a wet spot,” he says.
Why drainage matters. The effects of wet soil in fields extend beyond the poor-yielding spots.
"Yield maps don't show the impact of poorly drained areas on an entire field,” Ferrie says. "The field may average 140 bu. per acre. But when you look closely, you see that some areas averaged 200 bu., but others made from zero to 90.”
Wet areas also determine the timing of every operation, from tillage through harvest. "That can be crucial in a wet year like 2009,” Ferrie says. "Say you have 70% or 80% of a field ready to plant but the remainder is too wet. You save the field for later. If you had planted on time, maybe the best parts would have yielded 240 bu. per acre. But you sacrificed that opportunity, waiting for 20% of the field to dry.”
Yield maps show the difference in yield between well-drained and poorly drained areas, but they can't tell you how much better yield would have been if you had planted four or five days earlier. "In 2009, waiting a few days for wet spots to dry out sometimes made the difference between planning in April or June,” Ferrie says. "In the end, the field was still planted wet, but it was also planted late.”
"If a field dries uniformly, it's easier to make the decision whether to plant or not,” says Mike McLaughlin, who farms near Leroy, Ill. "It also makes it easier to set your tillage tools. A variation in moisture is just one more variable to deal with. The fewer variables there are, the easier it is to farm.”
- December 2009