Average yields this year of 76 bushels per acre for irrigated soybeans grown in south Georgia sound pretty darn good. But they probably should have been even better.
That’s the assessment of retired University of Georgia Extension Soybean Specialist and Professor Emeritus John Woodruff, who spearheaded a project this year to help establish guidelines for 70-plus bushels per-acre soybeans when including irrigation with production.
“It wasn’t quite as good as we thought it would be,” says Woodruff of plots located at the Sunbelt Ag Expo site in Moultrie, Ga., and the Stripling Irrigation Research Park in Camilla. “Overall, we had yields of 68 to 86 bushels per acre with an average of 76 bushels per acre.”
Although the high-yielding soybeans show promise, Woodruff says he wants to warn producers about the risks involved in growing the earlier varieties. “These risks include market grades and test weights not being on par if you don’t harvest in a very timely manner. Because of late-season tropical storms, we had to make some adjustments in our harvest dates this year, and that had an effect,” he says.
Consistently high yields are required, says the agronomist, to make soybeans more competitive with other crop options in Georgia.
“Currently, farmers occasionally will make 70-plus bushels per-acre yields, but typically average 50 to 60 bushels when irrigating soybeans. We explored high-yield possibilities at Camilla and Moultrie with both traditional determinate varieties and early-system indeterminate varieties.”
Throughout the season, all management went as planned on the soybeans, says Woodruff, with irrigation being applied on schedule and all pest management treatments made effectively.
Yields might have been hindered by very hot days in late July and early August and an extended cloudy period resulting from Tropical Storm Fay, he says. “Canopy photosynthesis has certainly been restricted because of these weather events and likely impacted seed weight, he adds.
“At Camilla, four irrigation regimes were imposed. These ranged from dryland to full-season applications. Summer rainfall there was so good and consistent that even the dryland plots yielded well,” says Woodruff.
Maturity Groups IV, V and VII were planted on April 25 and May12, he says.
In planting the soybeans, Woodruff used The 10 Steps to High Yield Soybeans (see details at the UGA Soybean Web Site: www.caes.uga.edu./commodities/fieldcrops/soybeans/productionguide).
In addition, the plot area received 2 tons of chicken litter per acre, and plots were planted in 18-inch rows. In addition to the standard recommended determinate varieties, early maturing indeterminate varieties also were included.
“In-row subsoiling is used for most south Georgia soybeans,” he says. “Row spacing for such is 36 to 38 inches. We used special equipment to accomplish this with 18-inch rows.”
The chicken litter, says Woodruff, was $25 per ton and was actually cheaper than regular fertilizer. “The seeding rate was the same as for wide-row planting, but the equipment for close-row planting would be a bit more expensive than what is commonly used for wide rows, and the high-yield plots probably received one to three more irrigations than normal. We plan to do a detailed cost analysis to determine all the expenses that were incurred,” he says.
According to the National Agricultural Statistics Service, Georgia farmers planted 420,000 acres of soybeans in 2008, with about 75 percent of that double-cropped. Much of the crop was planted late because of a very dry late May and early June. July was dry for much of the state, but consistent rains during August had the crop in generally good condition.
Soybean yields in Georgia this year are forecast at 30 bushels per harvested acre, and production is forecast at 12.2 million bushels, up significantly from the 8.3 million bushels last year. Harvested acres are estimated at 405,000, up 130,000 acres from last year’s 275,000 acres.
The 2008 Georgia soybean plantings were up by about 40 percent from 2007. If current market prices are maintained, 2009 acreage will probably climb another 10 to 20 percent, says Woodruff.
In addition to following Georgia Extension’s 10 step soybean management program, Woodruff also recommends the following for high-yielding, irrigated soybeans”
• Plant early (before May 25).
Indeterminate varieties: April 25-May 10.
Determinate varieties: May 10-May 25.
• Plant a high-yielding, early maturing variety (use nematicide in Coastal Plain if variety lacks RK nematode resistance).
• Plant in close rows (15 to 30 inches).
• Use deep tillage equipment that will provide for deep rooting with close rows.
• Irrigate as needed:
During vegetative growth — irrigate if soybeans wilt by mid-day.
During reproductive growth (R2-R5) — irrigate to keep soybeans from wilting.
During reproductive growth (R6) —I rrigate to keep soybeans from wilting by mid-day.
• Scout fields: Apply PO herbicides, insecticides and fungicides as needed on a timely basis.
• Harvest soybeans soon after maturing soybeans dry to 13-percent moisture. Use harvest aid, if needed, to get timely harvest.
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