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Corn+Soybean Digest

No-Till Needs At Least Five Years

The long-term benefits of no-till - five years or longer - will knock your socks off. So if you tried the practice and quit sooner than that, you probably got misleading results.

Consider these results, gleaned by Lloyd Murdock, University of Kentucky soil scientist, from 25-year and longer no-till studies:

* Soil loss on highly erosive land can be reduced 50-100 times by no-tilling rather than using conventional tillage.

* Soil organic matter can be at least doubled with long-term no-till, greatly increasing water-holding capacity.

* Plant-available water is increased 20% in long-term no-till compared to conventional tillage.

* Long-term no-tilled soil shows a higher load-bearing capacity than conventional tillage because of improved soil structure.

* Long-term no-till isn't likely to cause compaction problems. That's contrary to what many farmers fear.

* No-till always handles dry years or more arid climates better than conventional tillage. Short-term no-till doesn't always do better in wet years, but that changes in long-term no-till.

* No-till yields and profits will be equal to or higher in long-term no-till.

Those conclusions by Murdock are based mostly on research by himself and colleagues at the University of Kentucky, the state in which no-till was born. Some are gleaned from studies in other states. And they might not apply on all soils in all states. But Murdock is confident they'll apply at least in the southern Corn Belt, plus states like Kentucky and Tennessee - and very likely many others.

"Many experiments with no-till have been set up for the short term, a year or two or three or five at the maximum," Murdock says. "There are a lot of things, such as soil changes, that are not going to happen in five years. I want to show you what will happen if you stick with no-till a long time."

The one overwhelming fact you can't ignore if you farm highly erosive ground is the soil-loss difference no-till can make, Murdock points out.

"It can be up to 100 times, if you look at different experiments across the U.S. where no-till and conventional tillage have been compared side by side. It's certainly not always that high, but it's always significant."

In a University of Kentucky long-term experiment, for example, 8 tons/acre of soil were lost on a 7% slope in 1985 with conventional tillage. With no-till, it was 0.16 ton - a 50 times difference.

In 10 years, the conventional-till loss would be 80 tons; in 20 years, 160 tons - about 1" of topsoil. In 100 years, that would be 5" of topsoil. With no-till, the loss is negligible, Murdock notes.

Scientists have probed soil in fields that have never been eroded and fields cropped for 100-150 years using conventional tillage in Indiana, southern Illinois and Kentucky.

"These scientists say there is an 8-12" difference in the amount of topsoil left in those two situations," Murdock explains.

Water movement off sloping fields and infiltration into the soil is changed a lot in long-term no-till, too, compared to conventional tillage, the scientist explains. Residue on the surface forms minidams to slow water movement in no-till. Root channels and worm tunnels aren't destroyed in tillage and carry water rapidly into the soil.

In no-till, the system of soil pores - ideally half of them should be large and half small - is greatly improved because they aren't disrupted by tillage. A few days after a rain, the large pores are empty again and contain only air.

"The small pores are the ones that hold plant-available water for the weeks to come. If you stay with no-till, you will change the porosity of the soil for the good," says Murdock.

Kentucky scientists examined the amount of water that went through plants in research plots that compared no-till and conventional tillage after 20 years.

They tracked evaporation from the surface and transpiration. The results? "There was 20% more plant-available water where it had been no-tilled as opposed to conventional tillage," says Murdock. "That's really important on those side slopes in the middle of the summer in Kentucky."

One of the real barometers on how well you're doing with no-till is the percentage of organic matter in the top 2" of soil, Murdock insists. That's where most everything that counts happens with no-till.

"In our studies over 20 years, we have twice as much organic matter in the top 2" of soil as with conventional tillage," Murdock says. "We have a good bluegrass sod area that hasn't been disturbed for at least 60 years. And we found you can build as much organic matter with no-till corn over 20 years as you can with a good bluegrass sod. I think that's pretty remarkable - it's as good as nature."

In both the laboratory and the fields in southern Kentucky, scientists found a strong relationship between organic content of the soil and density. In other words, they found a higher resistance to compaction.

In another long-term study, begun after no-till was well-established, conventional tillage looked best in wet years; no-till, in drier years. After about 10 years, the flip-flop melted away and no-till always looked best. It didn't translate into higher yields every year, but almost. And it looked better every year.

The bottom line for farmers, of course, is long-term yield and profit. Murdock points to the MAX Program in Indiana, where more than 250 farmer fields were compared. Fields no-tilled five years or more had higher yields and profits than those no-tilled two years or less.

"Our research shows that it takes four or five years in our situation to make no-till come out on top. So don't give up on no-till after a year or two or even three," Murdock concludes.

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