7 steps to better soybean yields

7 steps to better soybean yields

By: Gil Gullickson 10/01/2012 @ 10:08am

Soybean yields have been knocked in recent years for not keeping pace with corn yields.

“Two years ago, I would have agreed with that,” says Ron Moore, Roseville, Illinois.

In 2010 and 2011, though, Moore's soybean yields bounced back, with bushel-per-acre yields ranging from the upper 50s to the low 80s. The bounceback was a relief during a difficult 2011, as summertime moisture was scant.

Then came the drought of 2012. The year started out fine, with 4 inches of rain falling at the start of May in Moore's area. After that, though, drought relentlessly set in, sending soybean yields south.

What 2013 brings is anyone's guess. Moore plans to maintain practices like no-tilling lighter soils to conserve moisture. That helps soybeans withstand hot and dry conditions like those in 2011 and 2012. Genetics, preemergence herbicides, and fungicides all play a part, too.

“With higher land costs, you have to have higher management,” he says.

Here's a look at some steps to take to snap up future soybean yields.

1. Maximize fertility

Successful soybean production starts the year before. “You need to manage the previous corn crop for maximum yield potential,” says Seth Naeve, University of Minnesota Extension agronomist.

Excellent fertility is key, says Naeve. Soybeans respond well to previous phosphorus, potassium, and sulfur.

2. Pick the best varieties

Select the best-yielding, full-season varieties coupled with appropriate defensive characteristics that you can plant, says Naeve.

“You have to figure out how to get the right variety in the right field,” he adds.

In Moore's case, he tailors varieties to soil types. He plants early to late Group 3 soybeans. Moore sets the bar high for yield; they have to yield in the top one half of varietal tests.

Picking defensive characteristics is key. Moore picks varieties resistant to soybean cyst nematode (SCN), Phytophthora root rot, and brown stem rot. Planting SCN-resistant varieties can help you minimize yield losses on SCN-infested soils.

“You can literally have 40% yield loss with no symptoms,” says Greg Tylka, Iowa State University (ISU) Extension nematologist. A root dig can indicate the telltale SCN sign of little white SCN females on roots.

There have been cases where SCN has clipped yields of SCN-resistant varieties. Reliance on the main genetic source of SCN resistance (PI 88788)may be helping SCN to overcome SCN-resistant varieties. Out of 807 resistant varieties listed by ISU this year, just 18 had a genetic background outside of PI 88788.

“We have lots of varieties to pick from, but the genetic background is not as diverse as we would like it to be,” says Tylka.

For now, Tylka advises farmers to continue planting SCN-resistant varieties on infested soils. In most cases, they still work.

“Cyst-resistant varieties pay dividends twice – with decreases in egg population and yield increases,” he says.

3. Tile wet spots

Drought has eased concerns about wet soils. Prior to 2012, though, wet soils were often the norm. Moore has gradually stepped up tiling to give crops a good start on well-drained soils.

“Soybeans don't like wet feet,” says Erich Hasler, chemical and fertilizer manager for Beck's Hybrids. “Look at ways to control surface water, and tile to move water away. If soybeans are underwater for 48 hours, it will kill nodules (where bacteria fix nitrogen). It takes 72 hours for those nodules to reform. So that puts you behind during the growing season.”

4. Start clean

After corn harvest, Moore applies Valor XLT on fields going into soybeans the next year. This takes care of any annual weeds that have been problems in no-till, such as henbit and purple deadnettle. He also follows up in spring with Warrant, an encapsulated formulation of acetachlor that curbs weed growth when applied preemergence. Besides adding another action mode, its residual nixes weeds for 35 to 40 days before he makes a postemergence glyphosate application.

Weather can throw a twist in these plans. In 2011, a wet spring delayed preemergence herbicide applications. For the most part, though, this strategy mixes up modes of action that help forestall herbicide-resistant weeds.

“We don't have any glyphsoate-resistant weeds yet, but we want to head them off by applying two or three modes of action,” says Moore.

5. Seed correctly

Moore normally seeds 150,000 plants per acre in 30-inch rows.

Economic optimal seeding rates are lower than they were years ago. They may be as low as 125,000 live seeds per acre, says Naeve. Still, a soybean research project ranging from the Delta to the northern Plains and upper Midwest shows slight yield increases occur with higher seeding rates. Higher seeding rates – such as 150,000 seeds per acre – give slightly greater yield stability across environments.

“This indicates to me that farmers have some flexibility in seeding rates,” he says. “Slight yield increases across increased seeding rates may not cover all of the cost of the extra seed, but it will likely cover a portion of it.”

6. No-till on the right fields

Of all the changes Moore has seen in his farming career, one change stands out. “It's the equipment and technology that have allowed us to do no-till,” he says.

Moore's no-till stint started in the 1990s with a John Deere 750 no-till drill. Replacement costs for the bearings and wheels soon dashed its appeal. “Another thing that killed the drilled beans was when Roundup Ready technology came along,” he says. “You couldn't afford planting soybeans at 225,000 plants per acre in 7.5-inch rows.”

Now he uses a Case International 1200 12-row planter to plant soybeans in 30-inch rows.“The double-disk openers do a good job of slicing through trash,” he adds. During dry summers, the extra moisture that no-till conserved helped maintain yield potential.

Soil type limits no-tilling 30% to 40% of his acres. “I tried to no-till heavy soils with the 750 drill, but it didn't work,” he says. He chisel-plows the remaining fields.

7. Use fungicides

Moore started using fungicide on his soybeans two years ago. A nearby soybean field farmed by his brother yielded 9 to 10 bushels per acre more.

The difference was his brother treated soybeans with a fungicide; Moore did not.

“Ever since, I've used fungicide,” he says. “I am a believer in them.”