Agronomy Notes

February, 2001

Contents

 

CORN

Dr. Erick Larson

Burndown herbicide timing: Moist soil conditions typically severely restrict planting time during the optimum corn planting period. Using a late winter burndown herbicide to control winter vegetation allows producers to manipulate soil moisture and encourage earlier planting. Killing winter weeds several weeks before planting time allows the soil to absorb much more solar energy than if soils are covered by a blanket of green vegetation. This warms and dries the soil, which widens planting time windows and promotes corn seedling vigor. Burndown herbicides should be applied four to six weeks before planting to gain these advantages.

Aerial burndown restriction: The Mississippi Dept. of Agriculture and Commerce will institute restrictions of burndown herbicides by aircraft to prevent off-target drift this spring. A tremendous number of off-target herbicide drift problems injured emerged corn plants in fields last spring. Aerial application of burndown herbicides containing the active ingredient glyphosate, sulfosate or paraquat will be restricted in Mississippi Delta counties from March 15 to April 30. Emergency exemptions may be granted if weather-related conditions exist which limit ground application, approval is granted by an authorized Bureau of Plant Industry employee, and atmospheric conditions are not conducive to drift.

Risk of ultra-early planting: Abnormally warm, dry conditions last spring allowed producers an opportunity to plant corn during a period when soils are normally too wet to plant. Although early planting is a critical component of successful corn production, there is such a thing as planting too early. Too, planting corn before recommended dates, even if soil temperatures are warm, provides little if any agronomic benefit, while causing considerable risk of stand failure. Extraordinarily early planting enhances maturity very little, because corn growth rate is correlated to temperature, and heat unit accumulation (GDD 50) is historically very low during early March.

Guidelines for corn planting date: The standard guideline for determining earliest planting date is this: plant when morning soil temperature is 55% F at a soil depth of two inches, or 50% F at six inches. Planting before the soil temperature is warm enough for germination greatly increases the potential for stand failure. Soil temperature may vary depending upon soil texture, slope, color and amount and type of crop residue. Randomly measuring soil temperature with a thermometer within a field should provide a reliable indicator of desirable conditions for stand establishment. Corn produces highest yields when planted within 4 - 5 weeks after soil temperature is warm enough for germination. Historically, this has corresponded with the following calendar dates:

Coastal region: February 25 - March 15

Southern region: March 5 - April 10

Central region: March 15 - April 20

Northern region: March 20 - April 25.

More on GMO's: Despite EPA and/or FDA approval of all commercially available GMO corn hybrids for both food and feed use in the U.S., numerous U.S. companies (Gerber, Heinz, Frito Lay, McDonald's, Burger King and Tyson Foods) continue to announce they will not buy GMO corn. These announcements are particularly disturbing to our industry and may lead to marketing difficulty at harvest, especially if another contamination problem, similar to StarLink, hits the press this fall. For comparison, aflatoxin contaminated corn is approved by the FDA for numerous specific feed uses at 100 ppb or above, but when a problem occurred in 1998, little or no grain exceeding 20 ppb was sold by producers at full market price.

SOIL TESTING

Dr. Keith Crouse

While knowing the residual nitrate nitrogen of the soil may be useful, the test is only good for the nitrate nitrogen that is present when the sample is collected and has very little value unless the following items are considered.

 

  • Since nitrate nitrogen is lost throughout the year in Mississippi, take samples before nitrogen fertilizer application.

 

  • Samples must be collected deeper than 6 inches and to depths of 36 inches, depending on the crop being grown.

 

  • Samples need to be taken in 6-inch increments and need to be representatively collected in the field with the appropriate number of subsamples in order to make up one soil sample.

Research in Mississippi has shown that nitrate nitrogen samples need air-drying immediately after being taken. This can be accomplished by spreading the samples out in metal or plastic trays.

The soil testing laboratory at Mississippi State University can provide the results of nitrate nitrogen analysis if the appropriate information sheet is filled out and accompanies the sample(s). The nitrate nitrogen sheet(s) and box(es) can be picked up at a local county Extension office or at the soil testing laboratory at Mississippi State. Cost of this service is $ 3.

WEED CONTROL

Dr. John Byrd

The Mississippi Department of Agriculture and Commerce Bureau of Plant Industry (BPI) has issued a statement and three section 24(C) labels to prohibit all aerial applications of sulfosate (Touchdown 5), glyphosate (Roundup Ultra and others), and paraquat (Gramoxone Extra and others) between March 14 and May 1 for preplant burndown in agricultural crops. The restriction is limited to Bolivar, Carroll, Coahoma, DeSoto, Grenada, Holmes, Humphreys, Issaquena, Leflore, Panola, Quitman, Sharkey, Sunflower, Tallahatchie, Tate, Tunica, Warren, Washington, and Yazoo counties. The Bureau has provided an exception to the restriction: if a weather-related emergency exists that prevents ground application, approval is granted by an authorized employee of BPI, and air movement and direction are monitored before application at the targeted site and avoided during conditions favoring inversions, or if velocity exceeds 5 mph.

The kudzu control data continues to look good for Escort at 4 oz/A, Tordon K at 64 oz/A, Tordon 101M at 2 gal/A, Roundup at 1 gal/A plus Escort at 2 oz/A, and Transline at 16 oz/A plus Escort at 3 oz/A. The Escort treatment looks good at Oxford and Holly Springs; the Tordon K and Roundup plus Escort looked good in Oxford after 1 year and the Transline plus Escort and Tordon 101 treatments looked good in Holly Springs after 2 years of applications. Escort is still the only treatment that can be used over pines or as a ground treatment under hardwoods, since Transline still has no forestry label.

Paul Baughmann, Extension Weed Specialist at Texas A&M, has indicated that EPA has approved their section 18 request for Oasis. It is highly unlikely that EPA will approve a section 18 request in one state and refuse it in another, so it is quite likely that our petition will also be approved. Use Oasis at a rate of 4 oz/A to control vaseygrass. Researchers will be evaluating the

effectiveness of this product on little barley in dormant bermudagrass and will continue to evaluate treatments on smutgrass, vaseygrass, johnson grass, and some broadleaf weeds, like horsenettle and sedges in bermudagrass.

PASTURE AND FORAGES

Dr. Malcolm L. Broome

3-S Grazing equals 4 -B Pastures - Now that your curiosity has been stirred up, what does it mean? If pastures are grazed simultaneously, severely, and short (the 3 S=s), you can expect over a period of time a pasture of mostly briars, bushes, broomsedge, and bitterweeds (the 4 B=s.) Why does this change occur? As grass leaves continue to be grazed shorter and shorter, the grass plant has little factory left to carry on carbohydrate (sugar, starch, and cellulose) production known as photosynthesis. This causes the plant to become very low in energy with no downward movement of carbohydrates to the roots, resulting in root die-back--which leads to a weak, poorly competitive grass plant with a shallow root system.

Research has shown that grazing has a very dramatic affect on root growth. When grazing removes only half of the grass leaves, root growth is only slightly impaired (2-4%). However when another 10 percent is removed, leaving only 40 percent, half (50%) of the root growth is stopped. Simply by grazing a six inch tall stand of grass down to 2 inches instead of 3 inches, half of the root growth ceases. If grass height is taken down to about 80% or just over 1 inch of leaf remaining, all root growth stops and does not start again for about 14 days. This cycle repeated over and over causes pastures to continually decline; this is one reason why so much emphasis is placed on rotating pastures to allow the grass time to recover.

By now, you are probably beginning to see how this leads to the 4 -B pasture. Grass plants become weak and die out; even if they survive, there is little competition from them for sunlight so weeds can establish easily. This decline of the pasture under these conditions ends when the desirable grasses are replaced by weeds or plants that are grazing resistant due to their low palatability or short growth form. Grazing without knowing how grass grows could be compared to baking a cake without knowing the recipe. The only free inputs into a livestock production system are sunlight and rainfall to produce pasture grass that can be eaten by livestock and then sold. Green, growing leaves carry out photosynthesis and to utilize this process efficiently means to capture all the sunlight on a green leaf on all the acres of your pasture every day of the year. Next, make sure the livestock use part of this green leaf before it is too mature and has lost quality, but without disrupting the factory by over grazing. Rotational grazing provides this needed rest period for grass plants so they can grow more leaves. When heavy grazing pressure is removed, the leaves will begin to grow back, root growth will resume, and pasture growth rate begins to increase.

The key to proper grazing management is adjusting the length of the grazing period and rest period to meet the needs of both plants and livestock. A basic understanding of how grasses grow and how animals graze will allow you to shift your pasture usage and avoid becoming a victim of the 4 -B pasture. Your pastures will also be less susceptible to environment factors such as drought or extreme cold. As a livestock producer, you must also check the pastures and correct any potential problems before they become apparent in livestock performance. If you would like to learn more about growing and managing grass, plan to attend the upcoming Cattlemen's College and Grazing School at Mississippi State University on April 27-28, 2001. To register, contact Charlotte Simmons at the Plant Soil Science Department at 662-325-2311, or by sending an e-mail to csimmons@pss.msstate.edu. There will be a registration fee of $15.

WHEAT

Dr. Erick Larson

Wheat nitrogen fertilization: In the mid-south, nitrogen application timing typically has a significant effect on wheat productivity. The initial topdress of a split application should be applied when dormancy breaks in late-winter during tillering stages (Feekes growth stage 3 or 4) and should not exceed 50% of the total seasonal amount. This normally occurs during early-February. The purpose of this application is to promote tillering and head size. The final topdress application should be applied by the time the first node appears at the beginning of stem elongation (jointing, Feekes growth stage 6). This application delivers the main nutritional needs of the crop, and generally occurs in early-March. Growers who choose to apply spring nitrogen in a single application should time it at Feekes growth stage 4 or 5. Recommended spring nitrogen rates vary from 90 - 140 lbs./a., with higher rates within this range recommended on clay soils and high yield potential wheat. Rates may often be reduced if the wheat's spring visual appearance is dark green, indicating considerable carryover nitrogen from the previous crop or fall nitrogen application. Urea-ammonium nitrate solution (N-sol 32%) topdress applic

NUTRIENT AND SOIL MANAGEMENT

Dr. Larry Oldham

According to fertilizer industry sources, natural gas accounts for 75 to 90 percent of the cash cost per ton of nitrogen fertilizer manufactured. Average daily natural gas prices increased from $2.30 per MMBtu to $8.80 between January and December, 2000. This has seriously impacted the fertilizer market and has serious implications for nutrient management in 2001.

Hydrogen from natural gas is combined with atmospheric nitrogen to synthesize ammonia that can be used as fertilizer or further processed into other fertilizer products. The products affected by the natural gas price increase include ammonium nitrate, urea, UAN solutions, APP solutions (10-34-0 and 11-37-0), MAP and DAP.

There is talk of a national shortage of nitrogen fertilizer; supplies may run from 85 to 90 percent of demand. It is too early to determine if this shortfall will occur. There may be a shift from nitrogen fertilized crops to soybeans, with resultant decreases in application rates.

Availability may be more of an issue than prices. Production was curtailed by many manufacturers as natural gas prices increased in the last quarter of 2000. In Mississippi, supply seems to be tight at the moment: farmers should find and lock in a reliable supply as soon as possible.

Late January quotes from dealers in the north Delta for UAN solutions have ranged from $170 to $185 per ton, or 26.5 to 29 cents per pound of nitrogen content. Anhydrous ammonia has been quoted at $400 per ton, or 24 cents per pound of nitrogen. Prices quoted on Monday, January 29, for bulk ammonium nitrate throughout the state were $250 to 260 per ton or about 38 cents per pound of nitrogen.

MSU-ES nitrogen recommendations are based on yield potential and soil type. Some soils are more efficient in utilizing nitrogen fertilizers than others.

Last year, to fertilize 1 acre of cotton at the rate of 100 pounds N per acre using 32% UAN solution cost about $14. At this writing, the same rate will cost $29/acre. For two bale cotton yields, this amounts to a $7/bale increase in production cost.

For a 100 bushel corn yield goal on non-heavy clay soils, 130 pounds of UAN cost $18.20/acre in 2000. The 130 pound rate currently would cost $37.70 for the 2001 crop--an increase of 19.5¢ per bushel at this yield goal.

While a greater than 100% increase in nitrogen fertilizer cost is dramatic, it is important to remember that nitrogen fertilization can have a tremendous effect on yields and production efficiency. Research performed in Lowndes County on Caledonia loam soil and published by Varco, Spurlock, and Sanabria-Garro in the Journal of Production Agriculture calculated that profit maximizing nitrogen rates ranged from 81 to 94 lb/acre across lint prices from $0.60 to 0.80/lb and nitrogen prices from $0.10 to 0.30/lb. At $0.60/lb lint and $0.30/lb N the profit maximizing nitrogen application rate was 81 lb/acre in this situation.

Research over two years in Leflore County, two years at Pontotoc, and over the past 3 years at Verona has shown that MSU-ES corn nitrogen recommendations are very reasonable for the range of soils in the state. The basic recommendation is 1.3 pounds of actual N per bushel of attainable, reasonable yield goal up to 100 bushels, then an additional 1.7 pounds of N for each reasonable, attainable bushel of yield goal over 100. On heavy clay soils, the final application rate should be increased by 10%.

However, if fertilizer supply is limited, the options are limited: 1) to allocate available fertilizer to all acres, or 2) change the rotation away from crops requiring nitrogen.

With a short, erratic supply, it is critical to get maximum fertilizer efficiency by following these Best Management Practices:

  • Calculate rates closely, depending on MSU-ES recommendations.
  • 'Tune up' and calibrate application equipment.
  • Use a balanced fertility program: soil test for P, K, and lime requirement and follow the recommendations.
  • Apply nitrogen fertilizers close to the time of actual crop need.
  • When possible, do not leave nitrogen fertilizers on the soil surface.
  • Use animal manures or by-products if available.
  • Give credit for nitrogen producing cover crops.

SOYBEANS

Dr. Alan Blaine

The 2001 growing season is rapidly approaching. The statewide trend is that soybean acreage

will once again decline. However, that is not the trend that is expected nationwide. Many circumstances are contributing to our state's acreage decrease, but doing everything we can to improve the bottom line is not one of them.

As a whole, producers are doing a much better job of growing soybeans; as in most endeavors, though, there is still room for improvement. Two major areas farmers may be overlooking are in-season scouting and marketing. While there are many factors over which growers have no control, once planting is completed, in-field scouting is essential. When commodity prices are low, we must continue to look for ways to cut costs.

One of the first places to start is with a good soil test. Spring is fast approaching, and a good soil sample can tell you a lot about your soil and where inputs need to be applied, versus a blanket application. Essentially, two extremes exist in the fertility arena, those who never fertilize and those that blanket apply some fertilizer every year. Needs will vary based on the crop, the previous cropping year, soil type and other factors. Take this into account as you formulate cropping plans. If you do not know your soil fertility status, find out, it will be some of the best money spent. Don't guess at soil fertility.

If you have not yet made varietal decisions, it is important that you do so now. Varietal differences exist and every producer in this state needs to plant varieties that performed in the top percentile. As you make your plans, center your program around a good seed treatment program. This is especially important if you are going to plant prior to mid-May.

Some major changes have just been implemented in the burndown area. Based on previous concerns, a restriction on aerial application of Roundup, Touchdown, and Gramoxone has been put in place. Unless an exemption is granted, these applications will not be allowed from March 14 through the end of April. Provisions are in place for exemptions; this is not a total ban. Supplemental labels and guidelines are available from the office of the Bureau of Plant Industry.

Can farmers overcome this obstacle (as many see it)? Yes. Think early. Early burndown is where farmers need to be moving anyway. Early burndowns cost less to apply, help conserve moisture, minimize tillage trips and eliminate some of the potential risks associated with later applications. The restricted time period for the use of aerial application may cause some growers to burndown earlier, but it can actually be beneficial, and opens up an opportunity to consider residual materials in combination with Roundup, Touchdown, or Gramoxone such as Delta Goal, Clarity, etc.

Last year, some producers planted soybeans in early March and saw good results. Most years, this will be far too early, but this early planting scenario gave us the opportunity to learn more about early planting.

Remember: you cannot control all inputs, but variety selection is one input you can control if you start early. Variety trials are available in your county Extension office. Give them a call and pick up a copy.

Department of Plant and Soil Sciences
Box 9555
Mississippi State, MS 39762

Will McCarty, Ph.D.
Extension Leader

RICE

Dr. Joe Street

The Command 3ME label has been approved by EPA for use in rice. Command 3ME may be applied up to 14 days prior to planting rice, or within 7 days after planting but prior to weed emergence. Command must be applied by ground sprayers in 10 to 40 gallons of spray solution per acre with nozzle types, sizes and pressure to minimize drift. Drift reducing additives are not recommended. There are no significant changes to the new label except that it contains a postemergence application timing that will fit several situations. However, the most effective use of Command is application to dry soil after planting. Rolling the field with a flat roller prior to application improves effectiveness of Command in most situations and improves seed to soil contact, which results in more even rice emergence. The use rate is from 0.4 pounds (1gal. to 7.5 acres) on medium textured soil to 0.6 pounds (1gal to 5 acres) on fine textured clay soils. The 0.5-pound rate (1 gal to 6 acres) is the most common on clay soils. Command will provide three to four weeks of residual control of barnyardgrass. Residual control of broadleaf signalgrass will be about two to three weeks. To get maximum benefits from Command, plant rice when soil temperature is conducive to rapid seed germination, to allow establishment of the permanent flood within four weeks after planting. Command should be activated by rainfall or flushing within five days after application. Even though there is enough moisture to germinate rice, the field should be flushed to activate Command and prevent weed emergence. If enough rainfall occurs to melt the clods, that should be sufficient to activate Command. If for some reason rice does not emerge to an acceptable stand, rice may be replanted into fields treated with Command. Do not apply additional Command.

Command is not a stand-alone herbicide and additional herbicides will be required for broadleaf weed control. Facet is an excellent tank-mix partner for preemergence residual broadleaf control. You can expect about one week of residual control per tenth of pound of Facet. Aim was registered late last season and is a good treatment for broadleaf weeds following Command. For grass and broadleaf control prior to flooding, application of Propanil or Arrosolo plus Grandstand has worked well. Bolero or Prowl may be tank-mixed with Propanil or Arrosolo to extend residual activity. Where nutsedge is a problem, Propanil or Arrosolo plus Permit or Duet plus Permit are excellent choices.

As a precaution, application of Command to fields that have been precision leveled with deep cuts may result in rice injury. Do not apply to sand, loamy sand, or sandy loams. Command should not be incorporated. Good agitation in spray tanks is required. If Command must be left in a spray tank for an extended time, a good compatibility agent should be added. Do not apply Command when weather conditions favor drift. Do not apply Command within 1200 feet of towns or commercial nurseries, vegetable production or greenhouses. We must be good stewards of this product and avoid any problems with off target movement to ensure that we will be able to continue its use in rice.

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