Whether it’s irrigated growers in Texas or the sometimes-water-logged Delta or other deep-South producers, southern farmers are likely sticking with traditional maturity groups after trying different ones to dodge one weather problem or another.

Four or five years ago saw some southern growers plant more Group 3 soybeans to gain earlier maturity and dodge fall weather problems that sometimes swamped 4s. But the yields haven’t been good enough for a permanent switch, says Ron Levy, Louisiana State University (LSU) Extension agronomist.

Some others have favored more Group 5s to boost yields. Wade Cowan was in that category the past few years, but he’s found that Group 4s are fine for his Brownfield, TX, operation.

Cowan’s diversified rotation includes soybeans, cotton, peanuts, wheat and sorghum, with an occasional guar crop thrown in the mix. “All of our crops are irrigated, except for a few dryland acres,” says Cowan.

Beans are normally grown in 40-in. rows before peanuts in the sandy-soil region.

His father traditionally grew Group 4 maturity varieties on the same land from the 1960s on.

“Our best yields have always been with mid-4s,” he says. “But I tried some Group 5.2s, thinking I could see some better yields when planting in early May. I haven’t seen it, so I’m sticking with 4.3s to 4.6s.”

Using an inoculant at 1 gal./acre along with a guar-based product that keeps microbes alive, he’s seeing yields in the 50-bu. range – 15% or more above regional averages.

Calvin Trostle, Texas AgriLife Extension agronomist in Lubbock, says growers may mistakenly feel they can shorten maturity with late-planted soybeans. In one AgriLife trial looking at June 16 and July 3 planting dates, he says the later-maturing Group 4s were significantly better yielding than Group 3s.

“Group 3 soybeans planted at the last two planting dates were 5-12 in.shorter than the group 4s,” he says. “This could lead to lower pod set and harvest inefficiencies.”

In the test, the greatest average yield was 42.5 bu./acre and was achieved with the early May 1 planting date. Mid-4 soybeans were highest in yield: 36 bu./acre. For every 14 days that planting was delayed from May 1 to June 16, he says yield was reduced an average of 4.6 bu./acre. 

In Mississippi State University (MSU) studies in the Delta region, Group 4s outyield 3s and 5s for beans planted in April. Group 3s outyielded 5s in mid-April, but not early April. Group 5s were yield leaders for beans planted in early May.

MSU research notes that when varieties best suited for mixed to heavy clay are planted in loamy soils, they should be planted in early April instead of mid- to late April or May to help reduce excessive growth and prevent lodging. In this case, growers may reduce the seeding rate 10-15% from the normal recommended rate and avoid planting in single 38-in. or 40-in. rows.

“Plant in a twin-row or narrow-row system,” says Trey Koger, former MSU soybean specialist, now with a private seed company. “In general, earlier-maturing varieties don’t produce as much vegetative growth as later-maturing varieties. Plant a variety better adapted for loam soils if possible.”

Levy notes that 65% or more of Louisiana soybeans will be Group 4s in 2011, followed by 5s and less amounts of 3s.

There was a demand for more 3s in the sugarcane area so they could harvest beans earlier and plant cane earlier, says Levy. “Even with that, the early 4s yielded better than the 3s.”

LSU has revised the planting dates for some maturity groups. “We’ve kept 3s and 4s (planting) at mid- to late April,” he says. “And we now know growers can plant Group 5s a little earlier in late March and through April.

“If they want to plant early, we encourage them to plant Group 5s because 3s and 4s have a short growing season and can’t stand adverse early conditions.”

Cowan says he is always eager to try something new to get the most production out of his farm – “but in our case, planting Group 5s in place of 4s just didn’t work. It was an unsuccessful experiment.”