Double-cropping cotton?

Louisiana wheat acres are sure to jump this year and LSU AgCenter researchers are trying to stay ahead of the cropping game.

“We’ll be looking at double-cropping systems with cotton and wheat,” says Rob Ferguson, AgCenter Extension associate. “What led us to this was the big increase in wheat acres in 2007 and what’s expected in 2008.”

Last year, Louisiana harvested about 250,000 acres of wheat. This year, Steve Harrison, LSU AgCenter wheat breeder, believes the state could double that acreage.

“Prices continue to rise and a lot will depend on how the planting season goes,” said Ferguson, who explained recent plot work at the Dean Lee Research and Extension Station in Alexandria, La. “In this study, we went into the field last fall, lightly rolled it and broadcast 90 pounds of wheat to the acre. We harvested that wheat last May 21 and planted back on May 23.”

In an adjacent plot, “we have an April planting — the normal type. Also, there’s a planting into 9-inch stubble and into a stale seedbed. You can see differences — something we’ve noticed the whole way through.”

In stand counts, with stale seedbed planted in April, there were 2.7 plants per foot. In the stale seedbed planted on May 23, there were 2.4 plants per foot. The stubble had 2.2 plants per foot.

“We’re also checking plant height. You’ll notice in the first plot there’s a difference between the stale bed and the stubble. At the 10- to 12-node stages, there was a 6-inch plant height difference. It was at 22.4 on the stale and 16.5 on the stubble.”

Stubble management

In a second test, Ferguson and colleagues are looking at different stubble management techniques. There’s a burn treatment, a stale seedbed, a 12-inch stubble test and a 6-inch stubble test. The burnt test has a plant height of 22.1 inches, the stale seedbed is at 26 inches, and the 12-inch test is at 21.1 inches with the 6-inch stubble at 19.9 inches.

“When we were planting the plots, we knew we’d have to change the normal process with the planter when (approaching plots) not in stale seedbed. We ran into some difficulties.

“The first thing we had to deal with were rows that were so tall that we had to drop the drive wheels down about as far as they go. Initially, we thought we’d have to set the planter on no-till settings. But because the rows were so tall we kind of adjusted that on the pressure spring.

“We had Yetter trash sweeps on our planter. Because we had adequate moisture at the time of planting, we were able to set them low, cleaned out a lot of debris, and made a nice, clean strip down the center of the stubble. That meant good seed-to-soil contact.”

One of the things Sandy Stewart, LSU AgCenter cotton specialist, has noticed in past double-crop research is in dry years “you really need to set sweeps where they’ll just part and dust the stubble away to get the best stand.

“We know we can get a quality stand — that’s proven here. But there are differences along the way. We’re still trying to figure out varieties and how they work in these systems.

In the first test, we planted 10 varieties: five Roundup Ready varieties and five Roundup Ready Flex varieties. Both short- and long-season varieties are in the mix.

“We’ll take the plots to yield and see what happens. We’ll replicate the tests again next year.”

The cotton

Stewart says a stand can be brought out in many ways. “High rows, short rows — there are many ways to do it. But once we get the stand, what we’re dealing with is late-planted cotton.”

Having just walked some of the April-planted test cotton, he said, “It’s about two to three nodes above cracked boll. Is it time to defoliate? Yes, it’s close and I’d be tempted to defoliate.”

As for the May-planted cotton, whether in stubble or stale seedbed, there are no open bolls. Prior to the success of the boll weevil eradication program, “we wouldn’t have even considered this as an option. Of course, Bollgard and Bollgard II can also take out some late-season Lepidoptera pests. Those have made double-crop cotton possible.”

But there are some kinks to work out. “As Rob pointed out, the differences in height could bring on some weed control issues. Some of these varieties still haven’t reached canopy closure and probably won’t, this year.”

What about early-season insect issues between stubble and no stubble? “I think that’s yet to be worked out.”

That’s also true of some fertility concerns following wheat. Is there enough residual nitrogen left in the soil? If so, how much? “Those are questions that must be addressed because with $6.50 soybeans, something will be double-cropped behind. Personally, I’d like it to be cotton.

“I don’t think double-crop cotton will ever be at 1,300-pound yields. But we don’t have to have that when there’s $6 wheat. I don’t know what the magic number is for cotton. But realistically, we should be able to end up with consistent 800- or 900-pound cotton.”

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