How often have you seen headlines like these: “Drainage improves timeliness of field work” and “Drainage improves crop yields”? Does research back these headlines?
Based on long-term research at the Southeast Purdue Agricultural Center near Butlerville, Ind., the answer is yes, notes Eileen Kladivko, Purdue University agronomist. However, she believes there are lessons to learn by digging deeper into SEPAC trials.
Tiling and timeliness
Tile was installed on 15 acres of poorly drained, Clermont soil in 1983. Four tile spacings were included: 16, 33, 66 and 132 feet. The 132-foot plots were considered an undrained control.
“The thinking then was that you couldn’t successfully tile-drain those soils,” Kladivko explains. “The initial goal was just proving tiling worked there.”
The entire field was in continuous corn for 10 years — chisel-plowed in the spring, and then field-cultivated when the soil was deemed “ready” and planted the next day.
Planting was later than May 10 only three of those first 10 years. There was a significant delay in planting due to wet soils on the control plot versus the 16-foot tiled plot only twice. However, there was only one year when both could be planted the same day.
“On actual farms with multiple fields, the timeliness benefit would be much greater,” Kladivko says. “Plus, looking at the most recent 10 years, including 2019, the site received more rainfall than it did during that first 10-year period.”
Tiling and yield
Corn yield for the tiled plots was higher some years during that first 10-year period, but not every year. There were years where the control wasn’t the lowest yielding. Yet lower grain moisture at harvest for tiled plots was consistent, averaging 1 to 2 points drier. “It can take time to see the effects of tile,” Kladivko notes.
However, long-term averages leave no doubt that tiling improves corn yield. Eventually, the plot was shifted to a corn-soybean rotation. Today, no-till and cover crops are part of the regimen.
If you look at 1984 through 2017, corn yield in the tiled plots is higher, averaging 24.5 bushels per acre more between the 16-foot tiled plot and the control. Zeroing in on ’07 through ’17, the yield difference is more dramatic. The 16-foot tiled plot averaged 58.9 bushels per acre more than the control. The 33-foot tile spacing averaged 46.6 more bushels per acre, and the 66-foot spacing averaged 41.7 more bushels per acre.
The advantage to tiling for soybean yields isn’t as clear-cut. “We haven’t seen a significant yield advantage for soybeans since they became part of the rotation,” Kladivko says.
Overall, based on average soybean yields from 1994 through 2018, the control plot yielded less, but only by a small amount. Some years within the past decade, it yielded more than the tiled plots.
“While most people consider Clermont soils flat, there is actually some slope on the plot field,” Kladivko says. “Surface drainage is important on these soils, and the slight slope may help.”
Kladivko notes that an area outside the test area that is lower and even wetter was planted three times in one year and drowned out all three times.