Vol. 17, No. 10 May 25, 2007 ********************************************************************** Preemergence Herbicides in Roundup Ready Soybean? By Kevin Bradley Even as recent as a year or two ago even the mention of a preemergence herbicide application in Roundup Ready soybeans at a grower meeting or field day would have brought a few laughs from the audience. This past season, however, I noticed a little more acceptance of this practice and from what I can tell, applying residual herbicides in soybean, even Roundup Ready soybeans, appears to be gaining a little ground in Missouri. Don’t misunderstand me, the efficacy and economics of a properly timed two-pass glyphosate program in Roundup Ready soybeans is hard to beat. However, there are still some reasons you may want to consider the use of a residual herbicide in your soybean weed management program. First, residual herbicides may be a good option for you simply from an “insurance” or yield protection standpoint. Often, a properly timed early postemergence glyphosate application to weeds that are 4- to 6-inches tall somehow mysteriously turns into an application where the weeds have reached 10- or 12-inches tall and the soybeans are barely noticeable. Without fail, I see this in some Missouri fields each year. Last year it seemed to be particularly bad. The reasons are many; it may have been too wet and you couldn’t get in the field to spray, there is just too much to do and too many acres to cover, etc., etc. Regardless of the reason, when this type of situation occurs some yield has already been lost. To see the effects of increasing weed sizes and weed competition on soybean yield loss for yourself, go to http://weedsoft.unl.edu/weedsoftApps.htm and use the WeedSOFT yield loss calculator. This is a tool developed by a number of university weed scientists that enables you to estimate the season-long yield loss, as well as the yield loss that has already occurred, for soybeans that are at a particular stage of growth and infested with specific weed species. It will also estimate the additional yield loss that may occur if you delay treatment. Another reason you might want to consider the use of a residual herbicide in Roundup Ready soybeans is due to the increasing number of glyphosate-resistant weeds that are being identified in Missouri and throughout the U.S. Almost exclusively, these weeds have been discovered in continuous Roundup Ready cropping systems where glyphosate has been used as the sole active ingredient for weed control. In Missouri, perhaps the most concerning development is the confirmation of glyphosate-resistant common waterhemp that occurred in northwest Missouri in 2006. Since this initial confirmation, we have conducted greenhouse research on waterhemp populations sent in last year from other locations around the state and have found glyphosate-resistant waterhemp in at least 5 other counties. One of the best ways to prevent these kinds of situations from developing is to rotate to herbicides other than glyphosate that act at an alternate site of action, such as with preemergence residual herbicides. In our research, some of the more effective residual herbicides used in soybean for common waterhemp include S-metolachlor (Dual II Magnum, Cinch, etc.) and premixes containing S-metolachlor (Boundary, Prefix CP), sulfentrazone (Spartan) or premixes containing sulfentrazone (Sonic, Authority First), flumioxazin (Valor) or flumioxazin premixes (Gangster, Valor XLT), and alachlor (Intrro). Kevin Bradley 882-4039 BradleyKe@missouri.edu ********************************************************************** Some Early Planted Soybean Fields Sprayed for Bean Leaf Beetle Control By Wayne Bailey High numbers of bean leaf beetle adults have required insecticide applications to reduce numbers below economic threshold levels in some early planted soybean fields. Adult bean leaf beetles migrating from overwintering sites to early planted soybean fields have resulted in heavy leaf feeding and some plant mortality. In many areas wet weather has limited soybean planting and accumulated high numbers of beetles in seedling soybean fields that are available. The bean leaf beetle produces two generation annually in Missouri with larvae feeding on soybean roots. The economic threshold for bean leaf beetle adult feeding on seedling soybean is five or more beetles present per row foot or 1 or more plants destroyed per row foot. In most years control of beetles causing early season defoliation of soybean seedling is not needed. However the limited number of soybean available early season has forced high numbers of beetles into fields with seedling soybeans. Economic damage from bean leaf beetle is more common later in the season when beetles of the second generation feed on soybean pods. Recommended Insecticides for Management of Adult Bean Leaf Beetles in Soybean ----------------------------------------------------------------------------------------------------- | Chemical name | Common name | Rate of Formulated | Rate of Active | | | | Material | Ingredient (a.i.) | |--------------------|--------------------|------------------------|--------------------------------| |Esfenvalerate | *Asana XL | 5.8 to 9.6 fl oz/acre | 0.03 to 0.05 lb a.i./acre | |--------------------|--------------------|------------------------|--------------------------------| |Beta-cyfluthrin | *Baythroid XL | 1.0 to1.6 fl oz/acre | 0.0078 to 0.0125 lbs a.i./acre | |--------------------|--------------------|------------------------|--------------------------------| |Dimethoate | Dimethoate | see specific label | 0.5 lb a.i./acre | |--------------------|--------------------|------------------------|--------------------------------| |Chlorpyrifos 4E | *Lorsban 4E | 1 to 2 pts/acre | 0.5 to 1 lb a.i./acre | | | *numerous products | see specific labels | see specific labels | |--------------------|--------------------|------------------------|--------------------------------| |Thiodicarb | *Larvin 3.2 EC | see specific label | 0.45 to 0.75 lb a.i./acre | |--------------------|--------------------|------------------------|--------------------------------| |Zeta-cypermethrin | *Mustang Max | 2.0 to 2.8 fl oz/acre | 0.0125 to 0.0175 lbs a.i./acre | |--------------------|--------------------|------------------------|--------------------------------| |Encapsualted Methyl | *Penncap-M | 2 to 3 pts/acre | 0.5 to 0.75 lb a.i./acre | | Parathion | | | | |--------------------|--------------------|------------------------|--------------------------------| |Permethrin | *numerous products | see specific label | 0.05 to 0.10 lbs a.i./acre | |--------------------|--------------------|------------------------|--------------------------------| |Gamma-cyhalothrin | *Proaxis | 1.92 to 3.2 fl oz/acre | 0.0075 to 0.0125 lb a.i./acre | |--------------------|--------------------|------------------------|--------------------------------| |Acephate | Orthene | see specific label | see specific label | |--------------------|--------------------|------------------------|--------------------------------| |Permethrin | *numerous products | see specific label | 0.05 to 0.10 lbs a.i./acre | |--------------------|--------------------|------------------------|--------------------------------| |Carbaryl | Sevin 4F | 1 to 2 pts/acre | 0.5 to1.0 lb a.i./acre | |--------------------|--------------------|------------------------|--------------------------------| |Carbaryl | Sevin XLR Plus | 1 to 2 pts/acre | 0.5 to 1.0 lb a.i./acre | |--------------------|--------------------|------------------------|--------------------------------| |Lambda-cyhalothrin | *Warrior | 1.92 to 3.2 fl oz/acre | 0.015 to 0.025 lb a.i./acre | |--------------------|--------------------|------------------------|--------------------------------| |Lambda-cyhalothrin | *Numerous products | see speciic labels | see specific labels | |---------------------------------------------------------------------------------------------------| |* Designated a restricted use product. Read and follow all label directions, | | precautions, and restrictions | ----------------------------------------------------------------------------------------------------- Wayne Bailey BaileyW@missouri.edu ********************************************************************** Diagnosing Nitrogen Status of Wet or Flooded Fields By Peter Scharf Much of northwestern and western Missouri received excessive precipitation in early May. The Missouri and other rivers topped numerous levees, flooding tens of thousands of acres of cropland. Many fields that did not go under water may still have received enough rainfall to cause nitrogen loss. For corn fields that were kept, replanted to corn, or replanted to another N-demanding crop such as milo, producers need to make decisions about whether to apply additional N, and, if so, how much. Unfortunately, there is no way to make this decision that is simple, reliable, and convenient. However, the difference between a good decision and a bad decision can be quite a bit of money. I would suspect that there will be quite a few fields where applying additional N will be profitable. I have, in another article in this issue (see ‘Nitrogen Loss Scoresheet’), proposed a decision aid that is simple and convenient, but not necessarily very reliable. This is because the factors and processes that lead to nitrogen loss are complex. I do not put a lot of stock in any calculation- or score-based method of diagnosing N loss. However, they can be better than a seat-of-the-pants guess. And some broad principles in these systems are pretty solid, such as that spring-applied anhydrous ammonia is less vulnerable to N loss than other N source/timing combinations. Using soil or plant measurements to diagnose the N status of a field is more reliable than any scoresheet method, but is either difficult or inconvenient or both. Given the heavy loads already on producers and service providers, it’s going to be difficult to use diagnostic tests on very many acres. However, they may pay off for those who can find the time. Just sampling a few fields representing different scenarios may provide useful guidance for other similar fields. Interpretation can also be tricky, because producers should expect to find not only their fertilizer N but also N that was contributed by the soil, typically around 50 lb N/acre. A more detailed description of how to use soil tests to assess N availability can be found in University of Missouri Extension Guide G9177 (http://extension.missouri.edu/explore/agguides/soils/g09177.htm). Another option is to use the color of the crop to diagnose how much N remains. This option is simple and reliable, but is inconvenient in that the diagnosis can’t be made until the corn is at least a foot high. That means sidedress or possibly high-clearance N application equipment, or application through pivot irrigation. To use the color of the crop as a guide requires knowing the color with sufficient N. I would recommend adding at least 100 pounds of additional N in a small area of the field. This can be done when replanting for fields that were flooded, or by hand or with sidedress equipment for fields where the crop was not lost. The high-N area should be marked with flags or using a GPS. Then, if you can see that the crop is darker in the area where extra N was applied, you know that the field will need additional fertilizer. The bigger the color difference, the more N is needed. The fastest and most convenient way to assess corn color over many fields is with aerial photographs. Nitrogen loss is usually patchy, so it’s hard to evaluate color in all parts of a field from the ground. However, it’s also hard to do a good job of diagnosis with aerial photos unless the soil is mostly covered by the canopy. With corn this doesn’t happen until it’s about waist high. Waiting until the corn is waist high to make a decision is unlikely to cause yield loss in our current situation, but applying N at that stage is practical for only a small minority of producers or service providers. But for those who have the high-clearance equipment or pivots with injection pumps, it’s a great option. For people who use other methods to make their decisions about nitrogen, there may still be a need to evaluate whether enough N was applied. Aerial photographs can be a good way to accomplish this. I will be hiring a plane to take aerial photos of corn fields over the next four to six weeks. Anyone who’s interested in getting aerial photos is welcome to contact me. I can probably provide a fairly large (but not unlimited) number of free aerial photos to interested producers or service providers. Those who are interested in using the photos as their main decision tool will get top priority. I can also arrange for an even more limited number of photos to be translated into maps of potential yield loss and recommended N rate. Aerial photos can also be obtained from Tom McMurren, John Deere Agri Services, 815-970-4897, McMurrenTom@JohnDeere.com, and from InTime (Derek Emerine, 573 670 2667). These companies will also provide maps defining nitrogen stress zones based on their aerial photos. Peter Scharf 573-882-0777 scharfp@missouri.edu ********************************************************************** Potato Leafhopper Numbers High in Some Alfalfa Fields By Wayne Bailey Potato leafhoppers are about 1/8-inch in length, wedge shaped and greenish-yellow in color. They are very mobile and quickly move sideways, jump or fly when disturbed. This is a native insect that migrates into Missouri each spring from more southern states and Mexico. The potato leafhopper is often transported into the state by early spring storms that move in a northeast direction. The leafhoppers are thought to fly into the storms and be carried great distances by low level winds which approach 100 mph. After a storm containing hail passes, high numbers of leafhoppers can often be found in their wake. In Missouri, the potato leafhopper adults generally arrive about May 5 of each year. The arriving adults may first feed on several tree species before moving to alfalfa to feed and reproduce. Two to three generations of potato leafhopper are often produced, and economic damage generally occurs on alfalfa following removal of first harvest. Damage is caused when both adult and nymphal (immature) leafhoppers use their piercing-sucking mouthparts to penetrate alfalfa leaflets and stems. They remove plant juices and often cause yellowing of established plants, stunted plant growth and mortality of seedling alfalfa. Both forage quality and quantity are reduced by this pest. This year, potato leafhopper adults were found in alfalfa very early with adults arriving sometime during mid-April. Similarly, Arkansas entomologists are reporting very high numbers of this leafhopper in the state. Elevated numbers of leafhoppers in Missouri and Arkansas along with early arrival in Missouri suggest potato leafhoppers may be a moderate to severe threat to alfalfa this year. Scouting is best accomplished using a 15-inch diameter sweep net. Take 10 pendulum sweeps at five random locations in the field. If the average number of potato leafhopper adult and nymphs per sweep reach or exceed the threshold numbers listed below, treatment is justified. The economic threshold for potato leafhopper in alfalfa depends on the height of the alfalfa and whether the alfalfa is a potato leafhopper resistant variety or a traditional alfalfa variety. Economic Threshold for Potato Leafhopper in Alfalfa --------------------------------------------------------------------- | Alfalfa Stem | Ave # PLH/Sweep | Ave # PLH/Sweep | | Length (inches) | (traditional variety) | (PLH Resistant Variety) | |-----------------|-----------------------|-------------------------| | <3 | 0.2 | 0.6 | | 6 | 0.5 | 1.5 | | 8-10 | 1.0 | 3.0 | | 12-14 | 2.0 | 6.0 | --------------------------------------------------------------------- Recommended Insecticides for Management for Potato Leafhopper Adult and Nymphs in Alfalfa ---------------------------------------------------------------------------------------------------------- | Chemical name | Common name | Rate of Formulated | Rate of Active | Preharvest | | | | Material | Ingredient (a.i.) | Interval | |------------------|------------------|----------------------|------------------------------|------------| |Beta-cyfluthrin |*Baythroid XL |0.8 to 1.6 fl oz/acre |0.0065 to 0.0125 a.i./acre |7 days | |------------------|------------------|----------------------|------------------------------|------------| |Dimethoate |Dimethoate |see specific label |0.25 to 0.5 lb a.i./acre |10 days | |------------------|------------------|----------------------|------------------------------|------------| |Carbofuran |*Furadan 4F |1 to 2 pts/acre |0.5 to 1 lb a.i./acre |14 - 28 days| |------------------|------------------|----------------------|------------------------------|------------| |Chlorpyrifos 4E |*Lorsban 4E |1 to 2 pts/acre |0.5 to 1 lb a.i./acre |7 - 14 days | | |*numerous products|see specific labels |see specific labels |7 - 14 days | |------------------|------------------|----------------------|------------------------------|------------| |Malathion |numerous products |see specific labels |1 to 1.25 lbs a.i./acre |0 - 7 days | |------------------|------------------|----------------------|------------------------------|------------| |Methyl Parathion |*numerous products|see specific labels |0.5 to 1 lb a.i./acre |15 days | |------------------|------------------|----------------------|------------------------------|------------| |Zeta-cypermethrin |*Mustang Max |2.0 to 2.8 fl oz/acre |0.0125 to 0.0175 lbs a.i./acre|3 days | |------------------|------------------|----------------------|------------------------------|------------| |Permethrin |*numerous products|see specific label |0.1 to 0.2 lbs a.i./acre |7 - 14 days | |------------------|------------------|----------------------|------------------------------|------------| |Gamma-cyhalothrin |*Proaxis |1.92 to 3.2 fl oz/acre|0.0075 to 0.0125 lb a.i./acre |1 day forage| | | | | |7 day hay | |------------------|------------------|----------------------|------------------------------|------------| |Carbaryl |Sevin 4F |1 qt/acre |1.0 lb a.i./acre |7 days | |------------------|------------------|----------------------|------------------------------|------------| |Carbaryl |Sevin XLR Plus |1 qt/acre |1.0 lb a.i./acre |7 days | |------------------|------------------|----------------------|------------------------------|------------| |Lambda-cyhalothrin|*Warrior |1.92 to 3.2 fl oz/acre|0.015 to 0.025 lb a.i./acre |1 day forage| | | | | |7 day hay | |------------------|------------------|----------------------|------------------------------|------------| |Lambda-cyhalothrin|*Numerous products|see specific labels |see specific labels |1 day forage| | | | | |7 days hay | ---------------------------------------------------------------------------------------------------------| | Read and follow all label direction, precautions, and restrictions. | | * Designated a restricted use product. | ---------------------------------------------------------------------------------------------------------- Wayne Bailey BaileyW@missouri.edu ********************************************************************** Crop Insurance and the Flooding of 2007 By Ray Massey Flooding in northwest Missouri has farmers asking questions about crop insurance again. The first important point is that farmers should contact their crop insurance agent before making any decisions. Notify your crop insurance agent if flooding has occurred on your fields, even if the crop was not yet planted. Some of the insurance issues you are likely to encounter, and can plan for, are below. If the field was not already planted, you have until the final planting date before you officially have a claim. The final 2007 planting date for corn is June 5; for soybeans, June 20. If planting is prevented in the flooded field past either date for the intended crop, you are eligible for a prevented planting claim. Prevented planting claims have several provisions that must be noted. First, the indemnity for prevented planting would only be 60 percent of your guarantee compared to if you had actually planted a crop and suffered a loss. Second, what you decide to do with the field on which you were unable to plant has an impact on your proven yield history. If you claimed prevented planting and decided to plant another crop on the field, the yield from the prevented planting acreage will be equal to 60 percent of your approved yield for the first insured crop to calculate your average yield for subsequent crop years. So, your proven yield will be adversely affected. But if you let the land lie without crops for this season or you do not claim prevented planting on corn, the prevented planted acreage is not considered when computing your production history. You need to weigh the potential for profit from a second crop against the cost of adversely affecting your yield history should you claim prevented planting and then plant a second crop. If an already planted field is damaged or destroyed due to flooding, the first question is whether or not you will be able to replant. If able to replant, you can do so and receive from your crop insurance company a replanting payment to defer some of the costs. If you are unable to replant the intended crop before the final planting date (due to continued wet fields), you have two choices. You can let the land lie idle or plant a second crop. If you take the loss and let the land lie idle, your indemnity will be computed based on your expected yield for that field. If you plant a second crop (e.g. plant soybeans on land originally planted to corn or on land which you were prevented from planting corn), your indemnity payment on the first crop will be 35 percent of what the indemnity would have been had you let the land lie idle. The remaining 65 percent of the indemnity will be held until the harvest of the second crop. If the second crop has no problems requiring an indemnity, you will receive the 65 percent of indemnity that was held back. If the second crop does earn an indemnity, you will need to choose whether to receive the indemnity on the second crop or the remaining 65 percent of the corn indemnity. You will not be able to get both indemnities. Some other factors that will affect your decisions include: * Should you decide to plant a second crop, you must have purchased crop insurance for that crop in 2007. For example, if you only insure corn acres and not soybean acres, you can’t plant soybeans this year and have them insured. The deadline for purchasing crop insurance on soybeans is past. * Should you decide to plant a second crop you will have premiums due on the first crop and the second crop. The first crop premiums will be adjusted downward to reflect the reduced indemnity associated with insuring a second crop. * Should you decide to plant late (after June 5 for corn, after June 20 for soybeans in northern MO), there is a 1 percent drop in coverage for each day for 25 days past the final planting date. * You must report your acreage in each crop to your crop insurance agent by July 15. Any changes from expectations when the crop insurance was originally purchased need to be recorded with your crop insurance agent. Ray Massey MasseyR@missouri.edu ********************************************************************** Egg Mortality Overwinter Reduces Soybean Aphid Threat By Wayne Bailey Surveys conducted this past fall by researchers at the University of Illinois and Purdue University found very high numbers of soybean aphid eggs on Buckthorn in several states. They predicted the possibility of high spring and summer populations of aphids if these eggs successfully survived the winter. In a survey two weeks ago, they found egg mortality was very high due to winter weather conditions. Although some areas of the Midwest may still experience damaging soybean aphid populations, the threat of problems from this pest are reduced for the 2007 season. Problems in Missouri could still occur during June and July if high numbers of aphids migrate into the state from more northern states with soybean aphid infestations. We have two aphid suction traps operating in Missouri (Columbia, Portageville) to assist in the detection of migrating aphids. Wayne Bailey BaileyW@missouri.edu ********************************************************************** Replant Options Following Preemergence Corn Herbicides By Kevin Bradley Some of the corn acreage in Missouri has recently been devastated by the heavy rains and flooding that occurred last week, and in some of these fields preemergence corn herbicides had already been applied. This has raised many questions about the replant restrictions of preemergence corn herbicides, as many producers now wish to plant soybeans into fields that had corn and have now been flooded. Table 1 provides a list of some of our most common preemergence corn herbicides and the replant restrictions of these herbicides for corn, grain sorghum, and soybeans. As you can see from this table, soybeans SHOULD NOT be planted into fields where applications of atrazine or an atrazine premix have already been made this season. The label clearly states that soybeans should not be planted until the following year due to the likelihood of soybean injury from residues of atrazine that may still be present in the soil. The average field half-life of atrazine will vary dramatically depending on the soil and environmental conditions experienced, but the Herbicide Handbook published by the Weed Science Society of America lists the average field half-life of atrazine as 60 days. High soil pH’s (>7.5) will also slow the degradation of atrazine, along with cool soil conditions. Fortunately, replanting corn or planting grain sorghum into these damaged areas will still be an option where atrazine or most of these atrazine premixes have been applied. Table 1. Replanting restrictions for some common preemergence corn herbicides ------------------------------------------------------------- | |Interval Between Application and Planting| | | Field Corn | Grain Sorghum | Soybeans | | |----------------- Months ----------------| |Atrazine | 0 | 0 | NYa | |Balance Pro | 0 | 6 | 6 | |Basis | 0 | 10 | 0.5-10d | |Bicep II Magnum | 0 | 0b | NYa | |Callisto | 0 | 10 | 10 | |Camix | 0 | NYa | NYa | |Cinch | 0 | 0b | 0 | |Cinch ATZ | 0 | 0b | NYa | |Define | 0 | 12 | 0 | |Degree | 0 | NYa | NYa | |Degree Xtra | 0 | NYa | NYa | |Dual II Magnum | 0 | 0b | 0 | |Epic | 0 | 12 | 6 | |Expert | 0 | 0b | NYa | |Frontier | 0 | 0b | 0 | |Guardsman Max | 0 | 0b | NYa | |Harness | 0 | NYa | NYa | |Harness Xtra | 0 | NYa | NYa | |Hornet | 0 | 12 | 10.5 | |Keystone | 0 | NYa | NYa | |Lexar | 0 | NYa | NYa | |Linex/Lorox | 0c | 0c | 0c | |Lumax | 0 | NYa | NYa | |Marksman | 0 | 0 | NYa | |Outlook | 0 | 0b | 0 | |Princep | 0 | NYa | NYa | |Python | 0 | 12 | 0 | |Radius | 0 | 12 | 6 | |Resolve | 0 | 10 | 10 | |-----------------------------------------------------------| | a NY=next year. | | b Replant interval only applies if safener-treated seed | | is used. | | c Thoroughly rework soil before replanting. | | d If 1/3 oz Basis applied, rotation interval is 15 days. | | If >1/3 oz Basis applied, rotation interval is 10 | | months. | ------------------------------------------------------------- Kevin Bradley BradleyKe@missouri.edu ********************************************************************** Scientists Find Crop-Threatening Levels of Root-Knot Nematodes in Southeast Missouri and Northeast Arkansas Cotton Fields By Allen Wrather Crop-threatening levels of root-knot nematodes (RKN) are present in some cotton fields in southeast Missouri and northeast Arkansas. During a recent survey, University of Missouri scientists found root-knot nematodes in 20 percent of the New Madrid County cotton fields, 27 percent of Pemiscot County cotton fields, and 43 percent of Dunklin County cotton fields. Reniform nematodes were very rare in Missouri. University of Arkansas scientists found root-knot nematodes in 70 percent of samples from Clay County, 32 percent of samples from Craighead County, 45 percent of samples from Green County, and 56 percent of samples from Mississippi County. Reniform was only in a few Mississippi County samples. Root-knot nematodes can cause severe injury to cotton. The symptoms of RKN injury will initially be visible 6-8 weeks after cotton emergence. The symptoms of root-knot nematode injury are stunted cotton plants, and these plants may wilt more quickly than healthy plants during a hot afternoon. Plants injured by these nematodes will also have swollen areas, galls, visible on infected roots. Be cautious about diagnosing the cause of stunted cotton because other factors such as low soil pH and drought may cause plants to be stunted. Ask your scout to tell you about areas in your fields where they observe this symptom and then determine the cause of the stunting. Growers suspicious of RKN problems in their cotton should dig up roots of stunted plants 6-8 weeks after emergence or soon after harvest and look for galls on the roots. Some but not all research results from southern states show that a side dress application of Temik and/or foliar application of Vydate from the first to seventh true leaf stage of growth will result in a cotton yield increase in fields with RKN. We do not have results from research in Missouri to support this. Cotton farmers can take precautions to avoid this problem next year. They should consider using a nematicide next year such as Avicta Complete Pak, Temik, or Telone in fields where RKN reduced yield. There are advantages and disadvantages to the use of each of these products. No cotton varieties are resistant to RKN, but Stoneville 5599 is tolerant. These nematodes will reduce yield of 5599 but not as much as they reduce yield of other varieties. Following these suggested procedures will give cotton farmers a better chance of producing higher yields and greater profits. For more information contact Allen Wrather at the University of Missouri Delta Center or check the Delta Center Web Page (aes.missouri.edu/delta). Allen Wrather, Professor 573-379-5431 WratherJ@missouri.edu ********************************************************************** Nitrogen Loss Scoresheet By Peter Scharf I’ve had a lot of questions coming in about nitrogen loss from corn fields that either went under water or just received excessive rainfall during the first half of May. These questions are difficult to answer because the N loss process is complicated. However, producers need to be able to make decisions about applying additional N that are at least in the ballpark. And they need to be able to correctly prioritize which of their fields need the largest additional applications of N fertilizer. Need for additional N is probably the same regardless of whether a field was replanted or not. Ideally, producers would be able to conduct a diagnostic test to determine whether to apply additional N and how much. However, most producers who may be dealing with N loss are also so pressed for time that this may not be a realistic option. Wet conditions have delayed planting and other field operations and people are running as hard as they can to get back on top of things. A lot is known about the effects of N fertilizer source and date, soil type, and degree of wetness on nitrogen loss. I have put my knowledge and opinions about these factors into a simple scoring tool. My goal is to give producers and service providers an easy-to-use way to identify those fields that are likely to respond to additional N, and to identify the fields that need the largest additional N applications. I’ve put this scoring system together quickly and have not been bounced it off of many people yet. Consider this a first stab at creating a useful tool, but do not take the results as gospel. Use your own knowledge and opinions to modify what may be suggested by this scoring tool. The scoring system consists of three factors: a fertilizer management factor, a soil factor, and a wetness factor. The fertilizer management factor mainly aims at ranking how much of the fertilizer N is likely to be in either the nitrate form or the urea form. Both of these forms are vulnerable to loss by leaching or being carried away in flood waters. Nitrate can also be lost due to denitrification, which is temperature-sensitive and probably has been important in some fields since soil temperatures have mostly been 65 or higher during and since the wet period. The soil factor recognizes that sandy soils are especially vulnerable to N loss by leaching, and that clayey soils are more prone to denitrification than are loamy soils. To quickly assess potential N loss and response to additional N for a field, score each factor using the following three tables, then multiply the three numbers together to get a nitrogen loss score. Nitrogen loss score = fertilizer management factor x soil factor x wetness factor Fertilizer management factor ---------------------------------------------------- | Nitrogen source | Date applied | Score | |----------------------|-------------------|-------| | Anhydrous ammonia | before November 1 | 5 | | Anhydrous ammonia | Nov. 1 - Dec. 31 | 4 | | Anhydrous ammonia | Jan. 1 - Feb. 28 | 3 | | Anhydrous ammonia | March 1 - 31 | 2 | | Anhydrous ammonia | April 1 - 30 | 1 | | Anhydrous ammonia | May 1 or later | 0 | | Urea or UAN solution | before April 10 | 5 | | Urea or UAN solution | April 10 - 30 | 3 | | Urea or UAN solution | May 1 or later | 4 | | Ammonium nitrate | before April 20 | 5 | | Ammonium nitrate | April 20 - 30 | 4 | | Ammonium nitrate | May 1 or later | 3 | ---------------------------------------------------- Soil factor -------------------------------- | Surface soil texture | Score | |----------------------|-------| | Loamy | 2 | | Clayey | 3 | | Sandy | 5 | -------------------------------- Wetness factor --------------------------------------------------------- | Water situation | Score | |-----------------------------------------------|-------| | Flooded 6 or more days | 5 | | Flooded 3 to 5 days | 4 | | Flooded 1 to 2 days | 3 | | Never flooded but saturated 3 or more days | 2 | | Never flooded but saturated 1 to 2 days | 1 | | Never saturated but sandy and excess rainfall | 1 | | Never saturated and not sandy | 0 | --------------------------------------------------------- My suggestions for application of additional nitrogen are: * Nitrogen loss score 0 - 10: No additional N needed. * Nitrogen loss score 11-24: Don’t apply additional N now but watch for possible development of N deficiency symptoms. * Nitrogen loss score 25-49: Apply 40 to 60 lb N now. * Nitrogen loss score 50 or more: Apply 60 to 120 lb N now. No matter what decision is made, the most important measure of whether enough nitrogen was applied is the response of the crop. Keeping an eye on the corn (or milo) as it develops will pay dividends. For fields with additional N applied, I would recommend having one double-applied strip in each field. Then if you can see the doubled strip, it probably means that the crop does not have enough N and more should be applied. Putting a small high-N area in fields where no N is applied now would also be good insurance. That way, if it was the wrong decision, it can be seen and corrected. Peter Scharf 573-882-0777 scharfp@missouri.edu ********************************************************************** Weather Data for the Week Ending May 20, 2007 By Pat Guinan Weather Data for the Weekly Period May 14, 2007 - May 20, 2007 -------------------------------------------------------------------------------- | Monthly | Growing Weekly Temperature (deg. F) |Precip (in.)|Degree Days^ -----------------------------|------------|------------ Ext- Ext- Depart| Depart|Accum Depart Avg.Avg. reme reme from |May 1 from |since from Station County Max.Min. High Low Mean avg. |May 20 avg |Apr 1 avg. ------------------------------------------------------|------------|------------ Corning Atchison 79 53 89 42 66 2 | 5.19 2.38 | 572 257 St. Joseph Buchanan 75 53 85 46 64 0 | 6.71 3.58 | 539 181 Brunswick Chariton * * * * * * | * * | * * Albany Gentry 77 50 88 40 64 0 | 8 5.02 | 499 173 Auxvasse Audrain 75 50 87 43 63 -1 | 1.76 -1.83 | 553 185 Columbia Boone 75 50 86 43 63 -2 | 2.5 -1.11 | 558 150 Sanborn Field Boone 76 52 88 43 65 0 | 2.21 -1.43 | 606 181 Williamsburg Callaway 77 49 89 41 64 1 | 1.32 -2.34 | 568 210 Novelty Knox 73 48 85 40 62 -2 | 3.63 0.4 | 464 116 Linneus Linn 75 48 85 41 63 0 | 3.33 -0.04 | 502 171 Monroe City Monroe 75 49 87 40 63 -1 | 1.57 -1.73 | 501 126 Versailles Morgan 76 50 87 44 64 -1 | 4.58 0.85 | 604 150 Green Ridge Pettis 74 50 85 45 63 -1 | 2.12 -1.68 | 551 207 Lamar Barton 75 52 85 48 64 -2 | 2.76 -1.19 | 565 99 Cook Station Crawford 77 44 87 35 60 -6 | 1.74 -1.66 | 543 64 Alley Spring Shannon 78 43 88 37 59 -5 | 3.21 -0.25 | 520 89 Round Spring Shannon 79 43 88 36 60 -4 | 3.02 -0.41 | 532 100 Delta Cape 76 50 87 44 63 -5 | 3.44 0.14 | 615 57 Girardeau | | Cardwell Dunklin 81 52 91 46 66 -4 | 1.09 -2.25 | 710 55 Clarkton Dunklin 79 51 90 45 65 -4 | 2.71 0.19 | 667 32 Glennonville Dunklin 78 51 88 45 65 -4 | 4.11 1.74 | 671 35 Charleston Mississippi 77 52 87 46 64 -4 | 2.61 -0.46 | 661 116 Portageville- 78 54 90 48 66 -4 | 1.89 -1.17 | 718 81 Delta Center Pemiscot | | Portageville- 79 54 90 48 66 -3 | 2.44 -0.67 | 721 93 Lee Farm Pemiscot | | Steele Pemiscot 81 54 92 48 67 -3 | 0.68 -2.69 | 753 114 * Complete data not available for report ‡Growing degree days are calculated by subtracting a 50 degree (Fahrenheit) base temperature from the average daily temperature. Thus, if the average temperature for the day is 75 degrees, then 25 growing degree days will have been accumulated. Pat Guinan Commercial Agriculture Program 573.882.5908 GuinanP@missouri.edu