Mother Nature likes to have her way, but farmers can have more say over how much water stays in or out of their fields, thanks to controlled drainage technology.
The basic concept with controlled drainage is a water-control structure attached to traditional tile can be used like a dam in farmers’ fields, says Isaac Ferrie, who works with the Farm Journal Test Plots. When gated with stacked baffles, the structures allow you to release water when you don’t want it in the field, such as during planting or harvest, or to hold it back for a crop when rainfall is scarce.
Farm Journal Test Plots research on two, 80-acre fields in central Illinois for the past 17 years has evaluated the effect of tile spacing and depth on yield as well as the number of days the field is fit for planting, nutrient applications and harvest. The study was expanded in 2013 to include controlled drainage.
Ferrie says their research shows controlled drainage technology contributes to corn yield increases.
University of Missouri Extension studies at the Greenly Research Center near Novelty, Mo., found controlled drainage paired with subirrigation boosts corn yields by 45% and soybean yields by 20% in claypan soils, reports Kelly Nelson, Extension agronomist, in a press release.
Beyond yield increases, one of the most significant benefits from water-control structures is they can help farmers stem the tide of nutrient runoff. University of Missouri Extension found its drainage water management system reduced nitrate losses by 70% and phosphorus losses by 80%.
Natural Resources Conservation Service funded demonstrations in several states in 2016 showed controlled drainage decreased nitrate losses by about 45% and the amount of water drained from fields by about 40%.
Ferrie also measured runoff reductions in 2016. “In our gated field, with tile spaced 120' wide we saw close to a 40% reduction in the amount of nitrogen lost through a single large rain event,” he notes.
During heavy rainfall, Farm Journal Test Plots research has shown roughly 70% of the nutrient loss happens within the first 48 hours. “Though the gates allow water to flow over top in times of high flow to avoid saturating active root zones, the gates still significantly reduced the amount of water that left the field,” he says.
Ferrie says one of the biggest challenges is determining if your tile system should be gated and where to install the gates. “For every 1' to 2' change in elevation you need a water level control structure,” Ferrie says. “If you have a bunch of parallel runs all with a 4' drop, you may need a drainage control structure in every run, which could be cost prohibitive.”
On new tile installs, Ferrie recommends getting a professional involved to help design a plan that is tile-gate compatible, making it more practical to install gates later if warranted.
Prices can vary significantly for the gated structures and installation, as little as $500 and upward to several thousand dollars. Ferrie says conservation services could be available to help you cost-share the installation because of the environmental benefits. He also says to put a value on moisture availability.
“If you could hold back water that fell on your field in the winter, keep it through spring and then use it in July, that could provide a yield benefit, reduce nutrient losses and help cover the cost of the purchase and installment,” Ferrie says.