Soybeans are marching westward into what once was mostly wheat and cattle country. And they're doing quite well, thank you.

That westward movement is happening in several states, but nowhere like in South Dakota. It's happening all up and down the east side of the Missouri River in the central part of the state, where rainfall dwindles to 15-17" per year.

The vehicle that's made it possible is no-till, with its moisture-saving advantage. Most of these new soybean acres are grown without irrigation.

"We really gained a lot of new soybean growers in our county last year," notes Ralph Holzwarth at Gettysburg, less than 20 miles from the Missouri River. "I was recently talking to a seed dealer, and he said his soybean sales were up 300%. I don't think the area will be up 300%, but I'd guess we'll double our acreage."

Farther north at Selby, Mark Stiegelmeier, who also raises and sells seed beans, agrees.

"This area is seemingly exploding now with soybean production," Stiegelmeier says. "It increased dramatically last year. And if seed sales are any indication, it's going to increase again this coming season - no question about that."

Marv Schlomer at Glenham, in sight of the river at some points, adds: "No-till, or at least some form of conservation tillage, is probably the only reason soybeans are working quite well around here under dryland conditions. They work great in a long rotation under no-till."

Dwayne Beck, manager of South Dakota State University's Dakota Lakes Research Center at Pierre, managed a research farm at Redfield, about 100 miles east, in the 1980s.

"When I went to Redfield in 1983 there were about 1,900 acres of soybeans in Spink and Brown counties combined. Now they grow about a quarter million acres of soybeans in these two counties.

"It was kind of a step process in soybeans moving out to the Missouri River, and to a large extent, it follows no-till adoption in this drier country," Beck says. "The two go together like hand and glove."

What are the big attractions moving soybeans westward?

* Decent to very good yields, considering the low rainfall.

* Virtually no soybean disease on this new ground for the crop.

* Lower land costs than in the main Corn Belt.

* Lower machinery and fuel costs with no-till.

* Low wheat prices in recent years.

Until soybean prices headed south in '98, these growers were reaping some nice profits from their new or relatively new crop - hence the explosion in new soybean acres.

"Our cost per unit of production here at the research farm - long-term average on dryland, no-tilled soybeans, depending on the rotation - is somewhere in the high $3- to low $4/bu range," Beck says. "We're making good money here growing soybeans as part of a long-rotation system."

If you're chafing under much higher land costs, higher taxes and increased disease challenges in the heart of the Corn Belt, don't let the old "the-grass-is-greener syndrome" bite you without doing some sober consideration. No area is Camelot, caution Stiegelmeier, Holzwarth and Schlomer.

"Soybeans are not as big a gravy train as farmers from farther east might think," cautions Stiegelmeier. "We are in a typical 16-17" total-moisture-for-the-year area. We typically go dry from mid-July through August, which is a critical time for soybeans.

"I have seen many times where it looked like we had a 50-bu/acre yield coming along, and when it was all over, it made around 30 bu. It's pretty rare when we hit those really big yields without irrigation."

Schlomer, who now raises no-till soybeans only under irrigation, notched a 72-bu yield with one variety one year. He got a 66-bu average for all beans under that center pivot. For crop insurance purposes, he's got a 50-bu proven yield under irrigation.

By no-tilling, Schlomer can often hold off on irrigating soybeans until mid-July or Aug. 1.

Beck, whose main success formula in dryland no-till soybeans is a long rotation, has notched irrigated no-till yields of 90-plus bushels. But '98 was fairly typical, even drier than normal in July and August. At least seven days above 100 degrees, and 20 days over 95 degrees, were also recorded.

"In that warmer-than-normal period, we had only a quarter inch of rain from July 3 to Sept. 1. And we still harvested an average of 35 bu/acre on dryland, long-rotation, no-tilled beans," Beck says.

When nature cooperates, Stiegelmeier harvests field-average yields in the mid- to upper 40-bu range. In one field that got a lot of moisture the previous fall, Holzwarth had a yield pushing 50 bu, but with more average moisture, 40 is about tops without irrigation. And the mid-30s range is more typical for both growers.

These growers are all following the long-rotation formula. Typically, a five-year rotation might include: spring wheat, then winter wheat the second year, followed by chick peas (a drought-resistant edible bean) or sunflowers, then corn and finally soybeans.

Actually, the biggest reason to grow soybeans was that it allowed growers to include a warm-season, broadleaf crop in their long rotations. Soybeans are a medium-water-requirement crop, offering more herbicide alternatives and more residue ground cover with no-till than sunflowers. Also, soybeans provide nitrogen for the following wheat crop.

According to Beck and these growers, the formula for good yields and profits in that arid country includes these key points:

* Adopt no-till as the starting- point requirement.

* Use a long rotation - at least three years, preferably longer.

* Double-inoculate using a liquid or dry seed treatment, or use the newer in-furrow dry or liquid inoculant, because there are no nitrogen-fixing bacteria in soils where soybeans have never been grown.

* Plant early for that area - early to mid-May.

* Use narrow rows - drilled or no wider than 15", to provide a quick canopy and higher yields.

* Make certain you get a good stand, a little more difficult under no-till.