Farm Progress

Answers in box mapping: D&PL addresses cotton quality issues

David Bennett, Associate Editor

October 26, 2001

7 Min Read

As Mid-South farmers look over their cotton grade sheets, questions about cotton quality are again being asked. Many of those queries have been directed at seed companies.

This year, fiber distribution in cotton plants hasn't functioned as it typically has in the past, says Tom Kerby, Delta and Pine Land's vice president for technical services. Kerby thinks the real surprise is the micronaire counts.

“In looking at Paymaster1218, where we've had an average of a 4.8 mike, we'd probably have about a 4.7 on the first week of flowering, a 5.3 in the second week and a 5.0 in the third week. That leaves a 4.2 or 4.3 mike for the top bolls.

“What we have this year with the way distribution broke out is the first week the mike was 4.4. The second week was 4.8 and the third week was 5.4 — when it should have been dropping. The top bolls, which historically are the lowest mike, averaged 5.6.”

Why was the mike so high? That will vary, says Kerby, but many fields had a big “buggy whip” in the top. The upper bolls were affected because there was a strong cutout and heavy stinkbug pressure and, most importantly, because the Delta had late rains and warm nights leading to fields with green leaves late into the season.

What normally causes mike to decrease is heavy competition from new bolls and overnight temperatures below 60 degrees. This is the same thing that causes leaves to turn color in the fall.

“I believe temperatures remained high into late September. That, coupled with sustained rains, meant the top bolls went ahead and matured. So the answer to why mike counts are so high is that we finished out the top crop very well. That also explains why people are happy with yield.”

Short fiber is still a bit of a mystery, says Kerby.

“I have the trends of a few varieties and how they did side-by-side in a field. They all vary in fiber quality in both length and mike, but they all follow the same trends. So it isn't that one variety did something different than another.”

In reality, the fiber qualities have ended up being very close to what D&PL publishes those qualities as being, says Kerby. “In our product guide for 2001 we show 1218 has an average mike of 4.8, average staple of 33.4 and an average strength of 26.3. I'm a week out of date with classing office info, but I think when it's all said and done, 1218's fiber quality performance will be at least equal to the above averages. Now, individual farms will see higher mikes. But averaged out, those numbers will be close.”

In many areas, Delta cotton set a good bottom crop. But with all the rain, farmers lost some of that bottom crop to boll rot and hard-locking.

“I'm wondering if some of the shorter staple numbers are due to that fact. But as I look at the box map data, it doesn't show that the bottom crop was any longer than the rest of the crop. That isn't typical.”

A box map is a way to measure a cotton plant's progress through the season. The map takes advantage of the fact that the cotton plant produces first-, second- and third-position bolls about a week apart. All positions are related to each other by date of flowering. So what researchers do with a box map is assign a main stem node number.

“We take 40 plants and harvest each boll off a plant one at a time and place it into a compartment according to where it grew on the plant.”

By doing that, Kerby and colleagues can take all yield and put it in appropriate positions according to age. Then he can check those bolls and break the season into what's expected in terms of yield components, boll size, and fiber qualities. Researchers can line up past numbers for reference and to see how the current crop is doing.

“I've compared four varieties grown in Scott, Miss. (D&PL's headquarters), along with plants a farmer pulled in his Mississippi Delta field. The varieties I mapped include DPL 215 BGRR, Paymaster 1218 BGRR, DPL 451 B/RR, and a new DPL conventional variety, 491. We're introducing 491 next year.”

In doing a box map on these varieties, there were several things that Kerby wanted to look at, including staple length and micronaire by week of flowering.

With micronaire, the expectation is the mike of the first week's flowers is higher than average for the crop, but will still be lower than the highest mike count the plant will produce. The second week of flowering is usually where plants see the highest mike count. By the fourth week of flowering, the mike count typically declines dramatically.

Kerby says the thing that stands out in this year's data is that the highest mike count in the plant occurred in the last set of bolls — week four flowering and up. That makes no sense when viewed beside historical patterns, he says.

“That shows me that the first couple of weeks of flowering, the bolls didn't develop as they normally do. The third week of flowering was excellent. But by the fourth week, the mike tanked. And this is the case in all four varieties.”

The crop didn't have long fiber during the first two weeks of flowering. That gives Kerby pause because “I didn't remember those weeks as being tough on the crop. In talking to others, though, I found that there was some stress and that pumps had to be turned on several times before mid-July.”

The third week of flowering shows typical fiber length. The fourth week, however, shows fiber longer than that in the bottom bolls — an odd reversal of normal growth patterns.

“The net result, however, is we're seeing about the same fiber length as we expect. If a farmer has short fiber, he likely planted a short fiber variety.”

Boll size follows the same pattern as mike. By week four, bolls are as large as any other segment in the plant. The crop finished off very well and is yet another reason why yields are good and mike is high, says Kerby.

Kerby says he doesn't want to appear to downplay concerns by harkening back to what happened in the previous three years. What happened this year was completely different, he says.

“The last three years, we had high mike and short staple because of drought in July and August. This year, the high mike is associated with very favorable late weather and the capacity to produce and develop the top crop.

“I believe staple length is coming in around average for what varieties are supposed to be doing. For PM 1218, we're getting a staple for week one or two flowering of 32.5. At week three, staple is hitting around 34. That's a very unusual trend as the longer fibers are in the top. However, the staple average will likely be around 33.7 or 33.8. That's right where our crop guide has the staple set.”

There have been many comments from farmers about a perceived indifference by seed companies regarding quality concerns. Part of that concern, however, must be tempered with the pressure on seed companies to produce high-yielding varieties no matter what. Kerby admits there is pressure.

“As a seed company, do we have a responsibility to not put a high-yielding variety on the market that farmers want to plant? Well, we're supposed to provide options and information to customers that help farmers make decisions. We've built a staff of high-quality agronomists to assist with that.

“I've seen many growers who have given us their classing numbers and gin sheets. We looked at those numbers and realized the farmers made more money with 1218. Even though they didn't get the same price per pound, because of the high yield they made more.

“So what is the producer expected to do? The producer is expected to grow whatever will give him the most revenue at the end of the day. It's true that he'd love to have high yields without fiber quality questions, but the bottom line is actually healthier by planting 1218.”

e-mail: [email protected]

About the Author(s)

David Bennett

Associate Editor, Delta Farm Press

David Bennett, associate editor for Delta Farm Press, is an Arkansan. He worked with a daily newspaper before joining Farm Press in 1994. Bennett writes about legislative and crop related issues in the Mid-South states.

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