Missouri Cotton News
April 2003

We are in the war, whether you not like it or not, so support it and back the troops. I don’t mean a war in the Middle East but the war against the boll weevil. We have to work together to make it a success and cost the least possible.

Leave an area around the field so the eradication trucks and trappers can cover the areas that cannot be reached by a spray plane. It may mean fewer applications will need to be applied to the field thus cutting the cost. It would be nice at the end of the eradication program to have money left. The military would call it preparing the battlefield.

Help prevent the destruction of the traps and better decisions can be made regarding the application of the necessary insecticides. The traps are part of our surveillance. You are also part of surveillance team. If you observe a problem, call the command headquarters at 573-276-4553 and speak to Dewey King or Pat McCrate.

For this program to be a success and for us to win the battle against the weevil we must be a team just like in the military forces. The Boll Weevil Eradication Program is our army. Lets help them win the weevil war.

Visit us on the web at www.aes.missouri.edu/delta

It will not be long before cotton seeds start going into the ground; therefore, NOW is the time to consider how best to manage thrips in your fields. Unlike other pest populations that fluctuate from year to year, thrips infestations remain fairly constant and can always be a substantial threat to Missouri’s cotton crop. For example, Missouri cotton producers lost an estimated 13,000 bales and spent approximately $3.2 million on insecticide treatments (foliar, in-furrow, and seed) to control thrips in 2002. Over the last ten years, thrips have caused an annual yield loss of over 5,000 bales in Missouri.

Because of a combination of factors (low cotton prices, higher fuel costs, and tight budgets), you may be tempted to forego an at-planting insecticide treatment (in-furrow or seed) in favor of a foliar application. This approach can be a very ‘risky’ when managing your cotton for thrips infestations. Despite the chance this winter’s cold and wet conditions will help reduce insect pest populations, the current mild weather will favor rapid growth of weed hosts and allow thrips populations to quickly rebound. Since large thrips infestations can easily migrate into neighboring cotton fields and damage seedling plants as they emerge from the soil, a seed or in-furrow insecticide treatment is your best option of ‘insuring’ the seedling plants are protected from thrips damage. This will help plants grow more rapidly, set fruit earlier in the season, and help generate higher yields.

Waiting to apply an insecticide with your over-the-top herbicide application would greatly increase the risk that plants will be damaged by thrips. This feeding damage can delay maturity and thus increase the risk of additional yield losses to other cotton pests. A less risky approach to managing thrips and ‘insuring’ your crop isn’t damage is to utilize an in-furrow (ex. Temik) or seed (ex. Cruiser, Gaucho) treatment. A foliar insecticide treatment should only be considered your second line of defense should weather conditions slow the plant’s growth and uptake of an at-planting treatment.

In a couple of trials I conducted at MU Delta Center Lee Research Farm in 2001, we observed a significant increase in yield where an in-furrow (aldicarb or Temik) or seed treatment (thiamethoxam or Cruiser) was used versus plots strictly protected with a foliar treatment. Thrips populations in the untreated and foliar-treated plots were substantially higher than the recommended MU action threshold (1 thrips / plant).

For the latest information on insecticidal control recommendations for thrips and other cotton pests in Missouri, logon to the following MU Delta Center webpage: http://aes .missouri.edu/delta/muguide/ctnmgtgs.stm

Good crop yields together with an efficient production system can lead to high farm returns. High yielding crops require large amounts of plant nutrients to achieve their full potential. This past harvest was good for many producers with many yields being above target. This means that more plant nutrients than expected have been removed from the soil. It is a good idea to soil sample to find out the nutrient status of your soil before the next growing season. Soil testing is the best guide for the efficient use of your lime and fertilizer dollars.

When compared to machinery, labor, seed, and fertilizer the cost soil testing is minor. Correcting a soil fertility problem before planting is much easier and often cheaper than after your crop has been planted. If the ground is not frozen winter can be a good time to collect soil samples. Soil testing now will put you ahead of your neighbors during the last minute spring rush. This would also give you more time to make plans before planting.

Collecting a good soil sample is the key to using fetilizers profitably. First divide your fields into sampling areas that are uniform with respect to erosion, slope, and past management. Do not mix high and low yielding areas together. Ideally these areas should be 20 acres or less in size. Next use a soil probe or auger to collect a composite samples from each area. This composite should be made up of 15 to 20 individual soil cores collected from random locations with in each sampling area. These cores should be taken to a depth of 6 inches. These cores are then composited in a plastic bucket, the soil should be mixed thoroughly crushing all clods and removing plant residue. Finally a representative portion (about 2 coffee cups worth will do) of the composit sample is shipped to the lab for analysis. Make sure that you draw a field map and label your samples appropriately.

When your soil test results come back follow the recommendations. This should ensure that soil fertility is not limiting your profits.

The price of nitrogen fertilizer has taken several large increases since the first of the year. Nitrogen fertilizer prices are closely linked to oil prices which have jumped because of the colder than normal winter weather and prospect of war with Iraq. Currently, the lowest price per pound of N is from anhydrous ammonia followed by 32% UAN. Urea is selling locally for around $265 per ton, ammonium nitrate for $200 per ton, anhydrous ammonia for $410 per ton, UAN 32% solution for $170 per ton, and ammonium sulfate is at $190 per ton. To see the true difference in price convert the costs to per pound of N based on % N in each fertilizer. This calculates to 29 cents per pound of N for urea, 30 cents per pound of N for ammonium nitrate, 25 per pound of N for anhydrous ammonia , 27 cents per pound of N for UAN 32% solution, and 45 cents per pound of N for ammonium sulfate.

In the past, ammonium nitrate is usually a little more expensive per pound than urea. But not this year. Many fertilizer dealers are opting to stop handling ammonium nitrate due to tighter regulations from the danger that terrorists might steal it for making bombs. This has resulted in a short-term glut in ammonium nitrate reserves which has made it more competitive with urea in price. In years to come, manufacturing of ammonium nitrate will probably decline to the point where farmers have a difficult time getting any other dry N fertilizer other than urea.

What are the pros and cons of urea and ammonium nitrate? Ammonium nitrate can be broadcast on the soil surface without incorporation. If urea fertilizer sits on a warm, moist soil surface for several days, urease enzymes produced by bacteria in the soil can react with some of the urea producing a N gas that will be lost to the atmosphere by volatilization. Since bacteria multiply faster in warm soil, the problem becomes potentially worse as the Spring progresses. In a wheat experiment that I conducted in Mississippi, wheat with ammonium nitrate applied on April 15 averaged more yield than wheat with urea. In plots with urea applications made in February or March, wheat made the same yields as plots with ammonium nitrate.

One advantage that urea has over ammonium nitrate is that it is a more concentrated N source. In other words, you will not have to haul as much urea fertilizer to the field. For crops such as corn, cotton, and grain sorghum try to get broadcast urea below the soil surface as soon as possible. This can be done by cultivation, a light irrigation with a center pivot, or rainfall. Paying careful attention to the weather forecast can help. Farmers planning to broadcast urea on no-till fields should consider having the urea treated with a urea inhibitor such as Agrotain. If treated correctly, Agrotain does a good job of stopping volatilization for about 2 cents per pound of N. Urease inhibitor technology is listed as a Best Management Practice in the 2002 Farm Bill’s EQIP options.

As the price of N goes up and commodity prices go down, the most profitable N decreases (or vice versa). There is not as much difference between optimum N rates between fertilizer sources as you might think. I used current corn and fertilizer prices and yield response curves from irrigated field tests at Charleston, Hayti, and Caruthersville (1999-2001) to calculate the most profitable N rates for urea, ammonium nitrate, UAN solution and anhydrous ammonia. Using these tests with current prices, the most profitable corn N rate is 184 lb N/acre for urea, 183 lb N/acre for ammonium nitrate, 186 lb N/acre for UAN 32%, 188 lb N/acre for anhydrous ammonia. For irrigated cotton, the most profitable N rate is 86 lb N/acre for urea, 85 lb N/acre for ammonium nitrate, 87 lb N/acre for UAN 32%, 88 lb N/acre for anhydrous ammonia. To calculate the most profitable N using your own fertilizer prices and prices for corn, cotton, rice, or grain sorghum , contact me at stevensw@missouri.edu for a copy of the University of Missouri program called NITROMAX.

Each spring I get several calls about wheat that won’t green up. The first thing that comes to mind is Nitrogen (N). In recent years more and more “yella” wheat can not be explained by N. What you are seeing might be Sulfur (S) deficiency.

Sulfur deficiency in wheat looks similar to N deficiency, a closer look however shows some differences. Both S and N deficiencies produce stunted, light yellow green plants. Unlike N, S is not highly mobile in plants. Accordingly S deficiency is first expressed in the younger leaves while N deficiency first appears in older leaves. Other symptoms of S deficiency in wheat include shorter, thinner and woody stems, delayed maturity, and reduced grain fill. Commonly S deficiency will occur in a spotty pattern in the field. Proper identification of the problem is critical as excessive N fertilization can induce S deficiency. Adding more N will not help your wheat if S is the problem. Plant tissue testing offers a method for diagnosing S and N deficiency. For best results collect 15 to 20 plants each from both a good and bad area of your field. It is a good idea to also collect soil samples from the same areas of the field.

In previous years Sulfur was delivered free to the farm by rain. Volcanoes and fossil fuel burning power plants release millions of tons of S annually. This Sulfur was then brought to earth with rain and snow. While the government can not regulate volcanoes the EPA has restricted Sulfur emissions from fossil fuels. S deficiencies in crops have increased each year.

Most of the Sulfur in soil is contained in soil organic matter. This sulfur is made available to plants by bacterial action. Soil bacteria increase in numbers and activity as the temperature goes up. As wheat grows in the spring before the soil warms up it is particularly susceptible to S deficiency. The lighter-sandy or silt-loam soils of Southeast Missouri are also prone to low Sulfur conditions. Regular soil testing is a good way to head off potential Sulfur problems. These problems are easily corrected by adding Sulfur fertilizers.

Ammonium sulfate is a commonly available Sulfur fertilizer. It is 24%S and 21%N. When applying green up Nitrogen consider including 30 to 40 lbs. ammonium sulfate per acre. This will give you 7.5 to 10 lbs./acre of S. Ammonium Sulfate (NH₄SO₄) is more expensive in terms of N than urea or ammonium nitrate (NH₄NO₃), but when you consider the Sulfur the cost is more reasonable. When I compared a mix of NH₄SO₄ and NH₄NO₃ to NH₄NO₃ alone, adding the 10 lbs. of S cost an additional $1.50/acre. This is inexpensive insurance against Sulfur deficiency.

Pesticide applicators test at the Delta Center April 22 and May 22, 2003.

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