Planting date and variety selection studies indicate that early planting of early maturing soybeans can increase yield and reduce stress for many Mississippi producers, says Tom Eubank, assistant Extension and research professor at the Delta Research and Extension Center at Stoneville.

Also, he says, studies using the PHAUCET computer program to assist with polypipe irrigation have shown reductions in water and energy use of as much as 20 percent. “We feel this program can not only help reduce demand on the aquifer, but can potentially reduce farmer inputs as well.”

Eubank, who discussed the studies at the annual meeting of the Mississippi Agricultural Consultants Association, says many later planted soybean varieties put a lot of energy into nodes and vegetative growth and less energy into pod production, resulting in lower yields for those varieties compared to early-maturing varieties planted early season.

“We’re reaffirming that the early planting system pioneered by Larry Heatherly, Alan Blaine, and others is definitely beneficial to producers,” he says.

“We’re evaluating some of newer germplasms, particularly some of the earlier Group 3s, to see if we can move that planting window up even more.

“If we plant some of these varieties early enough to get ahead of late season drought stress, it could possibly eliminate one or two irrigations toward the end of the season that we would likely need for later, full season varieties.”

One of the studies Eubank cited, sponsored by Pioneer, had seeding rates of 100,000 and 150,000 plants per acre, with mid-April and mid-May planting dates.

“We looked at several different maturity groups, all indeterminate varieties in Maturity Groups 3, 4, and 5. While I would have liked to have had additional planting dates, we still saw some pretty marked differences in this particular study.

“Early May was pretty wet in the Stoneville area, followed by dry conditions into late June. All treatments, once we got past planting, were exactly the same — irrigation, chemical applications, etc.”

There was no benefit to the 150,000 seeding rate versus 100,000, Eubank says, but there were significant differences for planting dates.

“Typically, we expect that many of the Group 3 varieties planted early won’t get a lot of height and won’t set a lot of nodes. And we did see a significant reduction in the number of nodes produced on these varieties versus the longer season varieties. Also, the earlier we planted these varieties, the less plant height we saw.

“The later-maturing varieties planted later had more modes and the plants were taller, but there was no significant yield difference compared to the early varieties planted early.

“Harvest dates were fairly similar: the Group 3s planted at mid-April were harvested in early September — surprisingly, only about 7 days different from those planted 30 days later.”

The later planted varieties put on more pods, nodes, and height, but had no significant yield advantage over the early planted varieties, Eubank says.

“The later planted beans averaged around 65 bushels, which was comparable to those planted April 15. Despite planting early and despite lower plant height and fewer nodes, the early planted beans still yielded comparably to the fuller season varieties planted later.”

With the later season, late planted varieties, he says, “We see sort of a downward progression in yield by planting them later. They form many more nodes and additional plant height that does not necessarily correspond with yield — which tells me they’re putting a lot of energy into producing vegetation and not as much energy putting on pods.”

The study reaffirms that the Heatherly/Blaine Early Season Planting System  “still is our best opportunity to maximize soybean yield,” Eubank says. “One of the next stages in this study will be to evaluate some additional planting dates. I think we probably aren’t pushing the early planting window early enough. Some Asian soybean rust sentinel plots planted by Dan Poston and Brewer Blessitt in February a couple of years ago yielded over 60 bushels.

“I’m not saying we need to start planting a lot of beans in February, but soybeans are very tough plants — while they can’t take a heavy freeze, they can tolerate a light frost. We’ve all seen volunteer beans come through some pretty cold weather.

“What we want to evaluate is how early can we push this planting window with some of these newer germplasms.”

Eubank says additional work would be useful also to “look at how we might possibly fit these really early-maturing varieties into irrigation efficiency studies. If we could possibly eliminate an irrigation later in the season by planting these early Group 3s, that might help growers to reduce pumping costs.”