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What Field Tiling Can and Can't Do

Don't expect tell-tale coloring of subsoil to change.

This may not seem like the year to invest in more tiling, after a hot, dry summer across much of Indiana, except in those portions lucky enough to catch timely rains, often through thunderstorms. But farmers with an eye on the future know that every season in Indiana isn't like '83, '88 or now '07. Tile pays more years than not if you're on wetter soils that benefit from improved drainage.

Now here's a brainteaser for you: if a soil is wet, and you drain it, will the soil below the surface change back to colors indicating good drainage? Before you answer, understand that poorly and somewhat poorly drained soils typically have characteristic gray coloring, or a pattern of gray and brown mottles. Soils started out brown due to iron in the soil. But as water sat in the soil through high water tables, a conversion took place. That's where the characteristic colors come from that soil judgers take as a sign of damage problems.

If you said, yes, the colors will change back, you're not alone. Many would think so. But you're also not right, says Gary Steinhardt, the Purdue University soils specialist who teaches this principle to his college students, and hopefully to hundreds of FFA and 4-H soil judgers who will take to the soil pits shortly this fall.

The reaction that affects the iron that occurs in waterlogged soils is oxidation. But the misconception is that iron content is reduced. "It's depleted," Steinhardt says. "And once it's gone, you can't put it back by reversing the drainage process. So no, you're not going to affect coloring of subsoils by adding tile drainage."

A naturally poorly drained soil once tiled will still appear as a poorly drained soil to a scientist suing the rules of this trade, Steinhardt notes. All this doesn't mean that drainage isn't a big help, however.

"Drainage is a tremendous help if you need it," Steinhardt stresses. "And we're not saying drainage doesn't improve workability of the soil. We're just clarifying the point that the coloring of the soil that many people use to determine if a soil is well-drained or has drainage problems doesn't change. Once again, the iron that provided the brown color is gone. Preventing water from setting there in the future by tiling and getting the water out faster doesn't bring the iron, or the brown color, back."

In reality, there are often indications a soil has drainage problems in the natural state before gray mottles appear, Steinhardt says. Two tones of brown in some cases may indicate iron is affected. "That's why those who analyze where to put septic symptoms may seem to determine a soil isn't suitable for septic because of drainage problems before a soil judger determines there is a problem," he says. "Determining drainage at that level can become complicated."

Knowing the basics is a good start, Steinhardt says. Basics include that well-drained soils are typically brown without gray colors, and that gray colors indicate signs of drainage problems. Add to that now that tiling will make a tremendous difference in removing water from the field and determining how quick you can work the soil, but won't change the appearance of the soil beneath the surface.

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