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Specialists Speaking - February 2008

Attack Weed Problems Early

MISSOURI
Mike Milam
milammr@missouri.edu

With the volatility in the grain markets and the increase in acreage for corn, soybeans and wheat, an opportunity exists for cotton producers. With the decrease in acreage, the cotton prices are far better than most would have predicted. If you can’t plant more acreage, then manage for the highest yields possible.

The key for cotton production this year will be management. Producers who had irrigation last year during the drought had yields well above the Missouri projected yield of 962 pounds per acre. In fact, some producers had personal yield records due to the high number of heat units. So, producers who increased their irrigation capacity during the off-season can at least have more yield stability.

Final plant populations should be in the 1-2 plants-per-foot range, and the crop should be managed for early maturity in some of the fields by either planting earlier maturing varieties for managing growth regulators and fertilizer inputs to keep the internodes shorter and the total plant height more manageable.

Producers should look at all of their inputs and see what they can change to stay in production. With the high cost of fuel and labor, reduced tillage systems will benefit producers, yet we still have holdouts that use conventional tillage. Fertilizer inputs should be managed to increase earliness. Split applications are very beneficial on the sandy soils.

Missouri producers should take advantage of the increased yield potential created by removing the boll weevil as an economic pest.


LOUISIANA
Sandy Stewart
sstewart@agctr.lsu.edu

The time to begin farming the 2008 cotton crop is right after harvesting the 2007 crop. That is when land preparation takes place, and it begins with shredding stalks, reforming beds, fixing drains, etc. Most of those things have already taken place, so preparations for 2008 now become more intense in February and March. The time for burndown is quickly approaching.

In recent years, the trend for burndown sometimes appears to center around the question of ’How close to planting can I go?’ Through research, labels are generally revised to lower the re-plant interval on common burndown herbicides. In the First Forty Days Best Management Practices, a weed-free interval of three weeks is recommended prior to planting.

The benefits of having a clean start are obvious from a weed competition standpoint, but also extend into early season insect management by removing potential hosts for many pests. Three weeks weed free is a rule of thumb, but producers should strongly consider going much earlier.

Burndown applications in February and early March have many benefits that should not be overlooked. It is a fact that weeds are easier to control when they are smaller as opposed to larger. In Louisiana, troublesome weeds at burndown such as cutleaf evening primrose and curly dock are more responsive to our burndown tankmixes when small.

Henbit is another weed that has begun to drive some burndown decisions. Henbit larger than just a few inches can quickly become almost impossible to control adequately. In 2007 in Louisiana, the number of fields with significant populations of henbit that survived through planting increased across the state.

Burndown applications in February and early March, therefore, can be very beneficial and help control these more troublesome weeds when they are small. If a second application needs to be made closer to planting, then it will be more efficacious when following an early burndown treatment, especially in fields where henbit is a problem.

Louisiana producers have done an excellent job over the years of tankmixing multiple products at burndown, recognizing that there is not one herbicide that controls all weeds. Consider an earlier burndown to start the 2008 season.


FLORIDA
David Wright
dlwright@ifas.ufl.edu

With the price of cotton headed up along with the other commodities, producers have a much better option of choosing rotation schemes than at any time that I can remember in the recent past.

In a perfect world, with high crop prices for all commodities, most producers, consultants and Extension specialists could recommend a rotation for best yields and long- term suppression of pests. However, a year like this one is rarely the case, so now may be the time to look at other crops in certain fields – especially ones that have had nematode and other pests build up, limiting yields and resulting in high pesticide use and costs.

With the price upswing, producers have the option of choosing corn, soybeans, cotton, peanuts and the best crop to grow behind wheat in late May and early June. Cotton can be planted after wheat but has little chance for a replant if the first stand fails. Soybeans may be a better fit in that scheme, but consideration of past cropping history is recommended.

Use the best fields for the crop from past history in 2008. However, weather and pests can often take the potential for a good year away in a matter of weeks. Most producers need to consider weed control options in February for horseweed, evening primrose, wild radish and henbit if they are using conservation tillage for any of the row crops.

This will prevent high costs of trying to control these weeds at planting or in the crops when options are more limited. Early weed control will also help in preventing loss of soil moisture, which is still very short in much of the Southeast.


NORTH CAROLINA
Keith Edmisten
keith_edmisten@ncsu.edu

We used to have a lot of experience with the varieties we planted to substantial cotton acreage. Now we have less experience as the ‘lifetime’ of a variety is much shorter than it was 15 or 20 years ago. Because we don’t have these standard ‘go to’ varieties to rely on, I think it is important that we try to spread our risk by planting several varieties in North Carolina.

There has been some talk of a ‘yield drag’ with Bollgard II/Roundup Ready Flex varieties as compared to Bollgard/Roundup Ready. Many Bollgard II/Roundup Ready Flex varieties have tended to yield less than Bollgard/Roundup Ready varieties in some variety trials. Remember that these are usually small trials where Roundup is carefully applied if it is applied at all.

Producers may not see this same yield drag as they often have a more difficult time being precise with Roundup applications in non-Flex varieties. Less precise applications to Roundup Ready cotton may result in pollination problems.

Producers who have a difficult time controlling weeds without post-directing higher on the plant than would be desired with Roundup Ready cotton may not see this ‘yield drag’ at all. In fact, in situations like this, Flex varieties may outperform Roundup Ready varieties.

Weed resistance in Roundup Ready cotton is here, and it is scary. There is not enough space here to thoroughly cover the subject, but keep in mind that to reduce the effects of weed resistance, producers need to rethink their weed control programs with Roundup Ready and Roundup Ready Flex.

The use of alternate chemistries and particularly the use of preplant or preplant incorporated herbicides will help with weed resistance management. Roundup is too important of a tool in today’s cotton production systems not to take this seriously.


MISSISSIPPI
Darrin Dodds
darrind@ext.msstate.edu

Let me start by offering my congratulations to Dr. Robert Lemon of the Texas AgriLife Extension Service on being named Extension Cotton Specialist of the Year at the 2008 Beltwide Cotton Conferences. Dr. Lemon is truly deserving of this honor and serves as an outstanding role model for young specialists.

Probably to no one’s surprise, soybeans are a very hot topic right now. With soybeans going for around $13 per bushel, many producers are making plans to plant soybeans. However, in speaking with seed company representatives, it appears that seed demand will exceed seed supply. As a result, some producers will plant cotton instead.

For those who were planning on going with soybeans but are thinking of planting cotton, it is important to begin making preparations for your cotton crop now. Fertilizer prices are increasing as we speak. Sitting on the fence and deciding to go with cotton at the last minute could be an expensive proposition if fertilizer prices continue to increase.

Regardless of the crop you decide to plant this season, begin thinking about your burndown program now. Glypho-sate-resistant weeds are a reality in Mississippi. Adding additional herbicides to your glyphosate burndown program (i.e. 2,4-D, etc.) may help control glyphosate-resistant weeds; however, they will not control weeds that have exceeded size limits indicated on herbicide labels.


ARIZONA
Randy Norton
rnorton@ag.arizona.edu

As you are painfully aware, we have seen dramatic increases in costs associated with many inputs into our production systems. The cost of fuel has continued to rise, which has a direct impact on the cost of fertilizer.

Some forms of fertilizer, particularly phosphorus-based fertilizers, are approaching $600 per ton. In visiting with those involved in the fertilizer industry, it is clear that we will not see prices back off anytime in the near future. Unfort-unately, attempting to grow a crop of cotton with no fertilizer is not a realistic option; however, it is quite possible that a reduced rate of fertilizer would be adequate to produce a good crop of cotton.

It is important to evaluate thoroughly your fertility management plan to identify areas that may be trimmed and reduced.

For example, research has indicated that soil test critical levels for phosphorus (P) are 5 part per million (ppm). Soil test levels below 5 ppm will have a 90 percent probability of positive yield response to applied P fertilizer. If soil tests reveal levels above this critical value, the probability of a positive yield response is greatly reduced (approximately 60 percent).

Managing nitrogen (N) is a different story. The most efficient method for managing N is through a yield goal approach. Approximately 60-70 pounds of N are required to produce one bale of cotton lint. So, if expected yield is three bales per acre, approximately 180-210 pounds of N will be removed from the soil system by the crop.

This N may come from several different sources, including the following three major sources: irrigation water, residual soil N and fertilizer N. Soil testing for N is tricky because soil N is extremely mobile and subject to various transformations.

Performing a soil test as close as possible to the beginning of the season will improve the accuracy of the test with respect to predicting the amount of N available to the crop.

For more information on this and other soil fertility related topics, go to http://cals.arizona.edu/crops or visit www.extension.org/cottonindustry.


ALABAMA
Charles Burmester
cburmest@acesag.auburn.edu

Growing cotton in a conservation tillage system requires a good burndown treatment for weeds and cover before planting. This is becoming more complicated because of glyphosate-resistant horseweed in many areas.

Some areas are finding this resistant horseweed continuing to emerge after the cotton has been planted. This is causing many farmers to consider residual herbicides in their burndown.

Another weed that emerged suddenly in northern Alabama last year is common groundsel. This weed was difficult to control and served as a host for false chinchbugs. The chinchbugs moved to cotton and killed cotton plants in several fields last season. Determining what weeds are present in the fields before burndown will be critical in determining herbicide combinations to use.


TEXAS
Robert Lemon
r-lemon@tamu.edu

I think we would all agree that variety selection is the most important decision affecting the bottom line. And the variety/technology portfolio of all the seed companies changes with regularity these days. At the Beltwide Cotton Conference last month there were plenty of new varieties unveiled for 2008, and many new varieties introduced in 2007 will now be available on a commercial scale this year.

In 2007, Texas acreage was about 87 percent transgenic and 34 percent of the acres were planted to Roundup Ready Flex technology. Considering that the Bollgard registration runs through 2009, it’s probably a wise choice to start evaluating the new varieties/technologies on your farm so that you can identify replacements for your favorite Bollgard varieties.
Our variety trial data is at http://varietytesting.tamu.edu./cotton/index.htm.


TENNESSEE
Chris Main
cmain@utk.edu

Tennessee producers are still trying to figure out how many acres of cotton to plant. Markets are favorable for grain, and there are already 620,000 acres of wheat planted. Our producers are mostly trying to gain financial footing after last year’s April freeze and extreme summer drought.

Mother Nature has blessed us with some relief in the form of rainfall this winter, but the pattern needs to continue to be beneficial this summer. Most producers have not booked cotton seed as of mid-January, waiting to see what the market does in the next few weeks (and how many group 4 and 5 soybeans are available). Acreage estimates range from 375,000 to 500,000 acres.

Management wise, producers should be planning on a February to early March burndown for no-till acres. This early burndown, including dicamba, provides the best and most consistent control of glyphosate-resistant horseweed. Also this early burndown has the potential to help with some early-season insect management by removing the ‘green bridge’ between winter weeds and an emerging cotton crop.


ARKANSAS
Tom Barber
tbarber@uaex.edu

It’s hard to believe we are approaching the new crop season because it seems like it was just yesterday that we were harvesting the ’07 cotton crop. But, after attending the Beltwide Cotton Conferences last month in Nashville, there is no doubt that we are getting closer to planting the ‘08 crop.

One of the things we heard a lot at the Beltwide was the importance of starting the season with clean fields. And that means an effective pre-plant burndown strategy. Besides the need for clean fields, we have to continue to be vigilant as we deal with the glyphosate horseweed resistance problem.

We need to have our producers put out 2-4,D or dicamba as soon as possible. If we use these type approaches, we can get some residual benefit on the horseweed, and get some help on the palmer pigweed problem early in the season.

We want to do this early in the season, so that we don’t have any residual carryover that might injure the cotton after it’s planted.


CALIFORNIA
Bob Hutmacher
rbhutmacher@ucdavis.edu

Some badly-needed rain in December and January hopefully will help renew prospects for more cotton plantings in the San Joaquin Valley. Decisions on variety choice, seed treatments and basic needs for soil amendments to build or at least maintain adequate soil structure and fertility are right around the corner.

If specific difficulties are still on your mind, think about which fields had the most severe problems, and use that information to help decide where alternative varieties might be needed or where management changes need to be considered. Yield results from University of California and SJV Cotton Board trials are at http://cottoninfo.ucdavis.edu, or you can contact your UCCE Farm Advisor.

Basic fiber quality tables, when available, will be posted on that same site. Price differentials in favor of Pima will likely continue to drive additional Pima plantings in 2008, but there remain some important considerations.

Available Pima varieties represent a range of relative maturities, but generally range only from those that can be managed to mature at close to Acala timing all the way to some very long-season varieties. Pima cotton requires an effective growing season 7-10 days to 20 days longer than for Acalas most years.

Varieties differ in their tendencies, so it is worthwhile for producers to gain their own experience through strip plantings where varieties and management options can be evaluated in something other than full fields.

 

 
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