Double-crop beans offer challenges

The high price of wheat and nitrogen, loss of thousands of acres of cotton and the high cost of re-planting corn damaged in an Easter freeze may all add up to a significantly higher number of double-crop or late-planted beans in the upper Southeast.

While most row crop farmers in the upper Southeast have grown soybeans over the past few years, most have not grown them as a primary cash crop.

Evaluating the inputs of growing high yielding soybeans versus the continued good prices is a balancing act many farmers have had to perform over the past few years.

Virginia, gained 25,000-30,000 acres of soybeans when peanut acreage dropped dramatically in 2004. In 2007 a big drop in cotton acreage will likely add several more thousand acres of soybeans — in all probably more than 50,000 acres since 2004.

Ten years ago, Virginia produced nearly two-thirds double-crop beans and now has a little more full-season beans.

This past year, people were planting wheat up until Christmas to try and fill out forward contracts. All these factors add up to some significant management challenges, especially for large acreage farmers who are now producing more soybeans.

One of the ways growers may look at to offset production costs is to reduce seeding rates — a big mistake according to Virginia Tech Soybean Specialist David Holshouser. He says the popularity and high cost of Roundup Ready soybean seed has already resulted in some farmers cutting back on seeding rates.

“In Virginia, long-term, multi-site studies show cutting seeding rates on double-crop beans is a losing proposition. My recommendation is to have about 180,000 plants per acre in a double-crop system. So, a grower will have to plant 200,000-220,000 seed to get a final stand of 180,000 plants,” Holshouser says. That works out to be 70-75 pounds of seed per acre.

Full season beans are another story. “If a grower can get 80,000 plants in a May planting, I am confident he won’t lose yield. It has to be a uniform stand of 80,000 plants per acre, which can be a problem with growers using a drill to plant beans,” he adds. Using comparable seeding rates in double-crop versus full-season beans will result in less foliage and reduced yields, he stresses.

“Most growers use a drill to plant soybeans in Virginia to get more narrow rows. Going to the narrower (20-24 inches or less) rows will increase canopy cover, which is critical for double-crop beans. In a multi-year study on double-crop beans, we showed significant yield increases using a 7.5 inch precision drill versus a 15-inch planter. Unfortunately, most growers are using older drills that do not uniformly distribute the seed along the row. The result can be non-uniform stands,” Holshouser cautions.

Many southeastern Virginia growers have taken no-tillage and minimum-tillage practices common to growers north of the James River and are applying these to soybeans. “Now, soybeans are becoming more of a cash crop than in previous years when cotton and peanuts were so profitable. While growers know how to grow soybeans, some may not fully understand the risks of cutting seeding rates in double-crop beans,” Holshouser says.

If a grower can make 70-80 bushels of wheat per acre and follow that with 30-40 bushel per acre double-crop beans, he can do well because of the combination of good wheat and bean prices. Key to producing 30-40 bushels of double-crop beans usually gets down to selecting the right variety, Holshouser says.

“We don’t grow many Maturity Group VI varieties because of the risk on the back end of the season. If an early frost comes, Group VI will be hurt. In southern Virginia Group V is the primary group of varieties, though farther north in the State Group III and IV work well.

“In our cotton growing areas, where soils tend to be sandier and lower in organic materials, some growers may look at how profitable early maturing varieties have been in the Delta and think this is the way to go. In these type soils, early maturing varieties are a tremendous risk. In the darker, heavier soils, Maturity Group III and Group IV may be a good alternative,” Holshouser says.

Another problem for soybeans on sandier, lighter soils previously planted to cotton and corn is nematodes. To combat this problem, Virginia Cooperative Extension will conduct a broad scale statewide nematode survey — the first in the past 15-20 years. Growers should look for nematode defensive characteristics before looking at yield potential.

New races of cyst nematodes are now popping up around the state, and most soybean varieties have primarily Race 3 and 14 resistance. Race 1 and Race 4 have been identified and most varieties with nematode resistance just won’t work. New varieties with a broader range of nematode resistance and different types of resistance are coming onto the market.

New growers, especially those switching acreage from cotton need to identify nematodes and adapt a variety of soybeans to the problem, Holshouser warns.

Whether to use fungicides on soybeans is a big question, because of the $7.50 or so value of a bushel. “Over the past 10 years of observing soybeans in Virginia, it appears the yield gap between full-season beans and double-crop beans seems to be getting wider. I can’t prove that scientifically, but it appears to me to be getting wider,” Holshouser says.

One way to offset the yield loss is to use fungicides, but that’s a tricky question on a crop that may be less valuable than full-season beans. “In multi-year testing, we get a cost-effective response from the strobilurin fungicides in one year out of three. By cost effective, I mean a 3 to 4 bushel per acre increase. With today’s prices that is an economically beneficial input, but on $5 per bushel beans, it may not be beneficial to the bottom line.”

However, he points out that application on narrow rows will cost 1 percent to 4 percent of yield by running over the rows.

“In some fields, we see a 6-10 bushel per acre increase. Most of these large yield increases come from soybean varieties with poor disease packages. So, most of the routine yield increase from fungicides may be achieved by choosing varieties with good disease resistance. In high disease situation, like we had with frogeye virus three years back, fungicides can be a life saver.”

With more double-crop beans, and many going in later in the year, the risk to soybean rust becomes greater. Though soybean rust hasn’t caused yield loss the past two years, it is a risk. The sentinel plots, additional scouting in grower fields, plus plot testing in Virginia will give growers ample time to treat for soybean rust, according to Holshouser.

Making the right management decisions on double-crop beans can add significant profit to an already profitable wheat crop. Making the wrong decision on late planted beans can also take the profit out of wheat.

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