Minnesota farmer Ron Prahl is what you might call an “accidental” no-tiller. He planted soybeans into corn stalks a decade ago because it was too wet for tillage, “so we were forced into it.” To his surprise, soybean yields were great. “That made us take a closer look at no-till. I don't know if we would have otherwise.”

Plenty of Midwest farmers found themselves in the same boat this season. A wet fall in 2008 followed by a wet spring prevented many tillage operations. “People who normally wouldn't consider no-till were forced to plant soybeans into standing corn stalks,” says Dave Franzen, North Dakota State University (NDSU) Extension agronomist.

He hopes that some of this season's accidental no-tillers will become converts, concluding that there's no need to spend time and money tilling corn residue before planting soybeans. Long-term tillage studies show that even in the Upper Midwest, no-till is almost always the best choice for soybeans after corn, Franzen says. “Going into standing stalks the first time without tillage may seem crazy, but the results have been overwhelmingly positive through the years.”

RESEARCH THROUGHOUT the north shows that tillage has little effect on soybean yields, says Mahdi Al-Kaisi, Iowa State University Extension agronomist. Any no-till yield penalties are offset by fuel and labor savings, and soil and water quality benefits.

In Iowa, for instance, conventional tillage for soybeans costs $18-25/acre more than no-till. Yet, “soybean yields are not significantly different for all tillage systems,” Al-Kaisi says. He led a six-year Iowa-wide study that compared soybean yields for five tillage systems: no-till, strip-till, chisel plow, deep-rip and moldboard plow in corn-soybean and corn-corn-soybean rotations. Regardless of the soil type or rotation, he says, tillage did not improve soybean yields.

Research from other northern states confirms that. In 10 years of Wisconsin tillage trials, no-till soybean yields matched intensive tillage yields, averaging 54 bu./acre for both systems, says Shawn Conley, University of Wisconsin Extension soybean agronomist.

Likewise, a six-year study on clay loam soils in south-central Minnesota found no advantage for chisel plow, spring field cultivation or zone tillage for soybeans after corn, says University of Minnesota soil scientist Gyles Randall.

EVEN ON THE heavy clay soils of eastern North Dakota, Franzen says, no-till soybean yields usually equal intensive tillage yields. In 2008 — a record wet year in the Red River Valley — no-till soybean yields actually beat conventional yields by about 5 bu./acre, he says. This was probably because of better soil aggregation in the no-till plots, which enabled the soil to shed excess water and maintain larger soil pores.

A 2006 literature review by Pioneer Hi-Bred International summarized 43 soybean tillage trials, representing 455 site-years of data. Overall, soybean yield differences between no tillage and conventional tillage were negligible, the review found, although no-till yields were slightly lower in the northern U.S. and Canada. “Even in the northern region the yield penalty to no-till soybeans is often more than outweighed by the labor and fuel reductions and improvements in soil quality and conservation,” Pioneer reported.

Skipping tillage for soybeans frees up extra work days, too, says Hans Kandel, NDSU soybean agronomist. “That's a huge benefit, especially in our region, where the number of days for planting is limited.”

About 40% of U.S. soybeans are no-till, according to a 2007 survey by the Conservation Technology Information Center (CTIC). In some states, such as Indiana and Illinois, growers have embraced no-till soybean production, raising more than half the crop without tillage.

Northern growers have been more reluctant to farm with a lot of surface residue, fearing yield loss from slow emergence in cold, wet soils and a short growing season, says Minnesota's Randall. For example, fewer than 10% of Minnesota crop acres are no-till, according to the CTIC. Although no-till corn production is a challenge in the central and northern Corn Belt, soybeans are “more tolerant of no-till,” able to compensate for uneven emergence and slower early season growth, Randall says.

No-till soybeans also benefit from later planting dates, compared to corn, Al-Kaisi adds. Iowa State University research shows that by May 1, temperatures in the critical top two in. of soil are about the same for all tillage systems.

“I've never had any emergence problems with no-till beans,” says Ron Prahl, who raises soybeans, corn and wheat with his father Jim on 1,000 acres of rolling, erosion-prone clay loam soils near Hoffman, MN.

He seeds Roundup Ready soybeans in 10-in. rows using a John Deere no-till drill, and sprays two postemergence glyphosate applications. He selects tall soybean varieties with a strong emergence rating.

Prahl is one of the few no-tillers in his part of Minnesota. His bean crop often looks tough for the first six weeks, coming up in heavy residue, he says. “A lot of people have trouble getting past that.”

Although he doesn't disclose yields, Prahl says he definitely comes out ahead on no-till soybeans. “You can't evaluate it strictly on yield. You have to look at returns.” Prahl figures no-till saves him 3-4 gal./acre in fuel, plus labor and machinery expense for stalk chopping, fall primary tillage and spring field cultivation.

The University of Wisconsin (UW) estimates that each field pass costs $7-10/acre in fuel, depreciation and labor. In 2007, no-till soybean production returned 26¢/bu. more than conventional tillage, UW calculates.

Just as important, Prahl says, when heavy rains last March caused severe washouts in the region, his soil stayed put. “Our landlords really like it.”

Prahl does tillage every other year for the corn crop, deep ripping in the fall after soybean harvest, followed by spring field cultivation. He still does limited tillage for the soybean crop on his flat, poorly drained ground. No-till works best on soils with good internal drainage, he says. However, he says “it's not meant for every situation.”

Good drainage is important for successful no-till, agrees North Dakota's Kandel, especially in regions with a lot of rainfall. In the gumbo soils of the Red River Valley where there's little subsurface tiling, he expects no-till acres to increase as growers install tile. “They go hand in hand,” he says.

Prahl does a lot of custom planting in west-central Minnesota. Working around the region, he sees plenty of ground that is ideal for no-till soybeans. “Yet, people go through all the work and expense of tillage,” he says.

NO-TILL TIPS

If you're a northern grower who is thinking about reducing tillage for next year's soybean crop, here are some tips from Upper Midwest Extension agronomists.

Understand your soil. When you choose a tillage system, you should think about your soil's characteristics, including erosion potential, internal drainage, compaction and fertility, says Gyles Randall, University of Minnesota. For example, soils with high erosion potential need minimum tillage to maintain productivity. No-till is a challenge in poorly drained soils, so it's best to solve any drainage problems first, says Mahdi Al-Kaisi, Iowa State University. The same is true of compaction, weed and fertility problems. “Tillage is not just metal and soil,” Al-Kaisi says. “It's a whole system.”

Intensify management. Switching to a no-till system is “like going from being right-handed to being left-handed,” Randall says. You can cover up some management mistakes with tillage, but with no-till, “all the cards have to be in the deck.”

Find out what works in your neighborhood. “Talk to farmers in your area who are longtime no-tillers,” suggests Shawn Conley, University of Wisconsin. “Attend a no-till conference, and go to local field days.”

Invest in the right tools. No-till equipment has improved a lot in the last few years, says Dave Franzen, North Dakota State University (NDSU). “Work with a machinery dealer who knows your soils and has the experience to help you select the right machinery.” Use residue managers on the planter, adds Al-Kaisi, and make sure your combine is properly calibrated to evenly distribute residue.

Consider seed treatments. Seed treatments might pay off for no-till soybeans, especially if you plant early or use lower seeding rates, says Hans Kandel, NDSU.

Avoid planting on corn rows. Kandel is seeing more no-till soybeans planted at a slight angle to last year's corn rows. This may be especially useful in narrower corn rows, “but it depends on your corn and soybean row spacings.”

Don't plant too deeply. Conley recently surveyed Wisconsin growers and found that many are planting soybeans too deeply. The optimum seeding depth is ¾-1¼ in., he says.

Rotate tillage. Periodic tillage in a corn and soybean rotation may be beneficial for some northern no-tillers, Randall says. In high-yielding environments with a lot of residue, a little shallow tillage every fourth year or so incorporates some of the residue and breaks up surface consolidation, he says. Minnesota research suggests that periodic tillage could raise corn yields by as much as 15 bu./acre, and soybean yields by 3-4 bu./acre. However, economic returns for rotational tillage depend on local conditions and are highly site-specific, Randall says.

Give it a fair trial. “No-till is a constant learning process,” Conley says. “Don't just try it one year and give up. It takes a few years to get it down.”