Roy Roberson 2

November 20, 2012

5 Min Read
SOUTH CAROLINA RESEARCHER Pawel Wiatrak says management decisions made prior to planting can make and save growers money on soybeans.

High soybean prices and record wheat plantings across the Southeast indicate more soybeans will be planted in the region this coming spring. Making good decisions at planting time may be the best way to insure profit at harvest time.

Soybeans have often been the ‘me too’ crop to cotton, peanuts and, of late, corn in the Southeast. However, long-term price stability and improvements in production technology have motivated many growers to elevate beans to the No. 1 slot in their rotation.

Clemson University researcher Pawel Wiatrak says timing, variety selection and seeding rate of soybeans can make a big difference in final production and in final profit.

In South Carolina, based on research across the state over the past three years, Wiatrak says, Group V and VI varieties offer top yield performance when full-season planting occurs from early May until May 20.

Often, when a grower plants soybeans, how many seed per acre, what maturity group, and when he plants the crop — all decisions made before he actually puts seed in the ground — can have as big an impact on final profitability as what the producer does with his crop during the growing season, Wiatrak says.

When planting Maturity Group V beans in early May, for example, there is typically about 118 days between planting and full seed stage. If you plant Maturity Group V in mid-June, you have only 88 days from planting until full seed.

In general, this later planting date means not only shorter intervals between growth stages, but also less leaf area, fewer and shorter fruiting branches, and fewer pods set — all of which contribute to less yield.

Some growers in South Carolina like to plant Maturity Group VII beans in May, because they like to get higher vegetative growth. And for May planting, that is true — more vegetative growth and higher yields.

At the same time, there are more branches and more pods per branch, which contribute to higher yields, he says.

“My research over the past few years indicates reducing seeding rates from about 140,000 to 82,500 per acre, if you plant soybeans by June 5, will not significantly reduce yields,” Wiatrak says.

“The recommended seeding rate would be about 110,000 per acre for planting from June 6 to June 15, and 140,000 to 150,000 per acre for planting from June 16 through July 1. Lower seeding rates for early-planted soybeans means a grower can just about double the amount of acres planted per bag of seed.”

However, if growers can’t plant in the ideal window for the Carolinas, Group VII and VIII varieties are recommended for later planting dates to allow adequate vegetative growth prior to flowering. But, research has shown about 0.4 bushel per acre reduction for each day of delayed planting between May 20 and June 3; 0.3 bushel per acre for each day of delayed planting between June 3 and June 16; and 0.6 bushel per acre for each day of delayed planting between June 16 and July 2.

This past year, most growers got wheat out early or on time and were able to get soybeans planted by early June,” Wiatrak says. “However, in some years, weather and other factors cause a delay in soybean planting, which will have a detrimental effect on soybean yields. Regardless of row width, planting after July 1 will not allow adequate growth prior to flowering, and yields will be greatly suppressed.”

He stresses the importance of precision when planting soybeans. “Farmers should use plants per row foot as a seeding rate guide rather than pounds per acre, because there can be significant differences in seed size among varieties.”

Along with the high value of soybeans this coming year, will come the high cost of seed and other production items. A simple thing like using foot of row versus pounds per acre can make or lose a lot of money for soybean growers in this high stakes game.

Wiatrak reminds growers that seeding rates based on pounds per acre can cause an inadequate or excessive plant population. Either way, planting the wrong number of seed will cost growers money.

In today’s world, the cost of a bag of soybean seed can vary from about $30 for conventional seed to $48 for Roundup Ready to $60 for drought-resistant varieties. From an economic standpoint, getting the seed population right is critical to the financial success of a soybean crop, regardless of yield.

By planting Maturity Group V or VI in South Carolina by June 5, Wiatrak contends, growers can cut seeding rates enough to reduce the total cost of seed by $18 per acre.

With soybeans pushing $20 per bushel, most growers are concerned about getting as many beans in the bin as possible in order to maximize  profit. In reality, Wiatrak says, as much or more money can be made at the front end by getting seeding rate and planting date right.

Planting seed at the right depth also contributes to the  success of a soybean crop. He says soybean seed should be planted at about three-fourths to 1 inch deep in soil moisture adequate for both germination and emergence.

The first, and likely the most critical, pre-plant management decision is to select the correct soybean variety to plant, he says. In South Carolina, an often repeated mistake is to plant high-yielding varieties without regard to their genetic resistance to nematodes.

In fields with high nematode populations, don’t expect to get the same yields that are obtained in variety tests.

Maximum yield potential can better be achieved, Wiatrak says, if farmers choose nematode-resistant, disease resistant, and top-yielding varieties that match the soil, pest, and production practices like date of planting and seeding rate.

The following steps should be referenced when selecting varieties:

  • Select nematode-resistant varieties for fields where parasitic nematodes (soybean cyst, southern and peanut root-knot, Columbia lance, or reniform) have been identified as a problem.

  • Choose varieties that are high yielding over multiple years, environments and locations.

  • Consider varieties with good tolerance to diseases, lodging and shattering.

  • Select varieties in the maturity group appropriate for the time of planting.

Wheat planting this fall is expected to increase in most Southeastern states. Combined with high soybean prices, there is ample reason to believe soybean acreage also will be up significantly across the Southeast.

Getting everything right on the front end of either conventional or double crop beans will go a long way toward determining profitability of the upcoming soybean crop.

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