Agronomy Notes

March 8, 2000

Contents

WEED CONTROL

Dr. John Byrd

Pesticide calibration -Three critical steps are necessary to control pests with pesticides: identify the pest, select an effective pesticide and rate, and apply the pesticide at a time the pest is susceptible. Calibration is a critical component to making sure the correct rate is applied. Calibration is not a difficult task and does not require a lot of time. In fact, the time spent making sure the equipment is properly calibrated could prevent the need for additional time to correct a pest -control failure a few weeks later.

The first step toward calibration is a thorough inspection of the application equipment. Make sure all hoses are in good, usable condition, without visible signs of wear or cracking and all connections are tight. Check the pressure gauge. The indicator needle of a usable pressure gauge should point to zero (0) if the sprayer is not operating. If the needle is pointing to a number other than zero while the sprayer is not operating, take the hint the gauge needs replacing. Do not waste time trying to repair a pressure gauge by tapping on it with a hammer; replace it. Check the strainer and control assembly to make sure all is functional. If the sprayer has been in winter storage, check for dead birds, snakes, or rats (or nests of either) in the tank or pump. Check the tank for cracks. Repair or replace parts that need repairing or replacing.

After you are convinced the equipment is functional, it is time to clean. If you're not CERTAIN the sprayer was stored clean, take time to wash inside the tank, hoses, and lines with a 2-percent ammonia solution (2 gallons ammonia plus 98 gallons water) or an approved tank cleaner. Flush the ammonia solution through the hoses and tips before emptying the tank. After flushing the boom and tips and draining the 2-percent ammonia solution from the tank, thoroughly rinse the tank, lines, and tips with clean water.

After you are convinced the equipment is clean, it is time to check output uniformity. Partially fill the tank with clean water. Collect, measure, and record the output from each tip for a given time, that is, 15 seconds. After the output from each tip has been recorded, calculate the average by adding the value for all tips and divide the sum by the number of tips. Replace any tip that applies 5 percent more or less than the average. Do not assume new tips conform to this standard without checking.

After you are convinced the output uniformity is good, it is time to calibrate. Measure the nozzle spacing on the boom. Refer to Table 1 to determine the distance to drive to calibrate the sprayer. Measure and mark a driving distance for calibration. Use the same speed, gear, engine rpm, etc. , that will be used for pesticide applications during the calibration. Record the amount of time required to drive that distance. Collect the output from one spray tip, and measure the volume in ounces to determine gallons per acre.

The distances in Table 1 are calculated by dividing 43,560 (square feet in an acre) by 128. The result is 340.31, the drive distance corresponding to a 12-inch tip spacing. Divide 340.31 by the nozzle spacing (measured in feet) to determine the correct distance to drive. Example: Nozzle spacing is 20 inches. 20 ˜ 12 =1.67 feet nozzle spacing 43,560 ˜ 128 = 340.31 340.31 ˜ 1.67 = 203.77 203.77 rounds off to 204 feet to drive to calibrate.

Please refer to Publication 1006, "Calibration of Ground Spray Equipment".

SOIL TESTING

Dr. Keith Crouse

The Soil Testing Lab at Mississippi State can provide soil sample test results via the Internet. This will enable you and your clientele to receive soil sample recommendations in a more timely manner. All results completed during the day will be on the web after 6 p.m. The address for clientele is http://www.ext.msstate.edu/special/soiltest.cgi ; however, your office can access recent test results for all customers in your county through Extension's Intranet.

For the clientele to access soil test results, they need to know their AAA number, customer account number, county and report type such as soil (field crops, pastures, commercial crops) or horticulture (gardens, flowers, lawn grasses, etc.). Computer Services will continue to update this web page. Research reports will be included in the near future. We will also continue to mail customers a hard copy of test results. If you have problems accessing soil results, please let us know.

RICE

Dr. Joe Street

Rivers and streams are at record lows in Mississippi, and rice growers who irrigate with surface water may face some challenges unless there is an unusually wet spring. At this point, the groundwater supply is expected to be adequate for this growing season. According to the latest survey, average water use for rice production is about 29 acre-inches per year for straight-leveed fields and 31 inches for contour-leveed fields. The range was a low of 10 inches to a high of 60 inches, thus, there is room for improvement on some farms. At an average cost of about $1.50 per acre-inch, water conservation is important, especially at current rice prices.

Several methods are used to conserve water, including land forming, constructing permanent levees or roads around the field perimeter, tailwater-recovery systems, and multiple-inlet irrigation. The use of multiple-inlet (or side-inlet irrigation as it is sometimes called) has the potential to reduce water usage and to reduce the cold water area around the well. Although installing polypipe is not appealing to many, water management throughout the season is much easier once polypipe is in place. By simultaneously running water into each cut, you increase fertilizer efficiency and herbicide efficacy, especially if you use a preemergence herbicide. A shallow flood may be maintained and overflow gates may be set one to two inches above the normal flood depth to capture rainfall during the growing season. One of the problems with multiple-inlet irrigation in our area is a coyote making extra holes in the polypipe. There is some indication that this problem can be reduced by using blue pipe, which appears to be less attractive to coyotes than white pipe.

Multiple-inlet irrigation may not be for everyone, but it is worth trying, especially with the implications associated with the Clean Water Act. Non-point-source pollution and total maximum daily load (TMDL) will become common terms as we move forward with the Clean Water Act. Pesticide and nutrient runoff from rice fields is much less than many expected, but it is an area that will receive increased monitoring in the near future. Any technique to reduce runoff from a rice field will be beneficial to the rice grower and the environment.

SOIL AND NUTRIENT MANAGEMENT

Dr. Larry Oldham

Changes in the Natural Resources Conservation Service Standard 590 for Nutrient Management has raised levels of interest never seen before by that agency. Farms that participate in cost-share programs with part of the program dedicated to nutrient management are the only farms required by NRCS to use the 590 guidelines.

Mississippi poultry producers who have initiated or expanded production since 1993 have been required by the Department of Environmental Quality to develop waste management plans as part of a site permit. To meet this requirement operationally, DEQ accepts plans prepared according to the NRCS standards. NRCS works with the Extension Service in developing the standards, but neither agency has any regulatory capacity.

Mississippi was probably the first state to adapt a phosphorus- based nutrient management planning system (1993). In May 1999, each state NRCS conservationist was ordered to update their 590's within two years. Guidelines to them gave three options for phosphorus management: soil test P levels, soil P thresholds, or a site-specific P index.

Strict adherence to an agronomic soil test P based philosophy would eliminate poultry litter applications almost all forage and pasture lands in south-central Mississippi. Current Mississippi research database cannot justify setting a threshold level; therefore, development of a P index for Mississippi is the only viable management alternative. The standard is still undergoing comment, but given the facts, I am confident P indices will be the format used in Mississippi.

Phosphorus indices are site-specific. Factors in the index (as currently envisioned) include: 1) potential erosion as calculated by the Revised Universal Soil Loss Equation for a particular soil, site, and slope; 2) runoff class/permeability; 3) distance to significant water stream; 4) soil test P levels/index; 5) inorganic P application rate and method; and/or 6) organic P application rate and method. Sites with low or medium P indexes (important: index, not soil test p alone) will have nitrogen-based nutrient management plans. High P indexes will have P-based plans. Very high P indexes will have P-based plans at a 50-percent application rate. Most sites in south-central Mississippi likely will have N-based plans.

Remember. If it is not a livestock farm meeting a permit requirement, use of the 590 guidelines is purely voluntary unless there is a nutrient -management component in a government cost-share program.

Large Mississippi livestock operations are permitted under different, much more stringent guidelines in the NPDES program. Some confusion surrounds the two different programs.

SUSTAINABLE GRAZING SYSTEMS

Dr. Malcolm L. Broome

In the last few years, a lot of attention has been given to various types of grazing systems. While each grazing system has its place, use of the same grazing system on all forage systems will not always be environmentally sound or profitable.

Beef producers are really "grass farmers" in the business of converting plant material into an animal product and harvesting sunlight in dollar form. Commonly, continuous grazing is practiced by most cattle producers, but the most palatable plants are often overgrazed, and less desirable plants are undergrazed, leading to their increase over the pasture.

Rotational grazing has the advantage of promoting more efficient use of pasture grasses. Bermudagrass and bahiagrass, common forage grasses in Mississippi, do not require periods of rest for maintenance and vigor; thus, the rotation schedules are used to control use and quality. Rotating bermudagrass pastures hardly ever increases average daily gain. The goal of rotating such pastures is better use of forage to increase gain per acre or to allow for other management practices. When rotating summer pastures, remember the effect of maturity on quality. Pastures should be grazed within 21 to 28 days of growth. Hay should be harvested from excess growth.

Increasing stocking rates on pastures decreases quantity available for each grazing animal. This will decrease the opportunity of selectivity by the animal, and in stocker animals, decreases the average daily gain (ADG). Gain per acre, however, is increased by heavier stocking as long as some forage quantity is present.

Increasing stocking rates on cow-calf systems decreases the level of forage available to the animal. This restricted forage is more drastic on the performance of the cow as compared to the calf. Milk provides a "buffer mechanism" for the suckling calf, which allows for acceptable gains, usually at the expense of cow performance under high stocking rates. The effect of cow weight loss, of body condition, and hence rebreeding, must be considered.

Higher stocking rates increase gain per acre but not ADG. Pasture cost per pound of calf gain, however, is lower for higher stocked pastures. Extending the forage season is important in sustainable pasture management. Feeding hay or silage is expensive compared to grazing due to the labor and machinery costs. In rotational grazing systems, however, it is not always possible to graze all the growth, especially in the spring, so the forage should be harvested as hay to ensure good quality and proper storage for use when needed. Contact your county Extension agent for information on developing or improving your grazing system.

CORN

Dr. Erick Larson

Risk of ultra-early planting: Abnormally warm, dry conditions this spring are allowing producers an opportunity to plant corn during a period which is normally too wet to plant. Although early planting is a critical component of successful corn production, there are certain parameters which constitute when is too early. However, planting corn extremely early (before recommended dates), even if soil temperatures are currently warm, provides little if any agronomic benefit, while causing considerable risk of stand failure.

Guidelines for corn planting date: The standard guideline for determining earliest planting date is when morning soil temperature at a two inch soil depth is 55 F or 50 F at a 6 inch soil depth. 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. Thus, 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. This has historically corresponded with the following calendar dates:

Geographical Region of Mississippi: Coastal : February 25 - March 15 Southern: March 5 - April 10 Central: March 15 - April 20 Northern: March 20 - April 25

Abnormally warm, dry weather during February and early March may necessitate delaying planting until the risk of sub-freezing temperatures is slight and increasing soil temperature is assured. Although the growing point of a corn plant remains underground until about the V6 growth stage (12" tall), temperatures cold enough to freeze the soil can kill seedlings. Falling soil temperature also substantially increases the likelihood of stand failure, since seedling vigor is closely correlated to soil temperature. 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. Thus, extremely early planting greatly provides little, if any agronomic benefit, while significantly increasing the risk of stand failure.

Plant density - Growers should strive for 18,000 to 30,000 plants/acre depending upon mainly upon a field's yield potential and planter row width. If a corn yield goal of 150 bu./a. (45 bu./a. soybeans or 2 bale cotton) is realistic, particularly under irrigation, then strive for 26,000-30,000 plants/acre. If this goal is unrealistic, then lower the seeding rate accordingly. Row width changes optimum plant population because it ultimately affects plant spacing. Optimum plant population in wide rows is generally around 2,000 - 4,000 plants/acre less than narrow rows. Remember to over plant desired plant population about 5 to 10% depending upon seed germination and planting conditions. Early planted corn (soil temperature 50-55 degrees F) should be seeded slightly thicker than normal because cool spring conditions cause higher seedling mortality and shorter plants at tassel, meaning more plants are needed to intercept light.

Plant density - Growers should strive for 18,000 to 30,000 plants per acre, depending mainly on a field's yield potential and planter row width. If a corn yield goal of 150 bushels per acre. (45 bushels per acre soybeans or 2-bale cotton) is realistic, particularly under irrigation, then strive for 26,000 to 30,000 plants per acre. If this goal is unrealistic, then lower the seeding rate accordingly. Row width changes optimum plant population because it ultimately affects plant spacing. Optimum plant population in wide rows is generally around 2,000 to 4,000 plants per acre less than narrow rows. Remember to overplant desired plant population about 5 to 10 percent, depending on seed germination and planting conditions. Early planted corn (soil temperature 50 to 55 degrees Fahrenheit) should be seeded slightly thicker than normal because cool spring conditions cause higher seedling mortality and shorter plants at tassel, meaning more plants are needed to intercept light.

Plant uniformity - Poor corn-plant spacing is a common problem that significantly reduces yield potential. Research indicates that most growers could improve yields 5 to 10 bushels per acre by just improving plant spacing. Best of all --- it will not cost you a dime to gain this improvement. One common cause of stand problems, particularly poor plant spacing, is excessive planter speed. The optimum speed for plate-type planters is 4.0 to 4.5 mph, and for vacuum-type planters speed is 4.5-5.0 mph. Speeds exceeding these values will usually cause increased double-drops, much poorer seed spacing, and less seed depth uniformity. Corn plants are extremely sensitive to plant spacing because they do not tiller or produce branches to alter their plant size. Crowded plants produce small ears and spindly stalks due to the excessive competition for light, water, and nutrients. Corn seed is available in numerous combinations of sizes and shapes that may cause compatibility problems. Growers with plate-type planters should match planter plates with seed size. Likewise, growers with vacuum-type planter should match disc size with seed size and match air pressure with seed weight. Excessive wear to planter plates or finger pick-ups often also causes major problems --- just because something worked last year, doesn't necessarily mean it will this year.

Planting depth - Many producers unfamiliar with corn seedling development plant corn too shallow. You should plant corn seed 1 ½ to 2 inches deep. Planting depth should be set in the field during planting. This is important because soil type, seedbed condition, and moisture may influence actual depth. Corn seed's inherent energy and germination process ensure emergence from depths as great as 3 inches. The origination point of the nodal root system is moved upward when corn seed is not planted deep enough. Corn seed placed less than 1 inch deep will develop nodal roots at or above the soil surface. This exposes these roots to factors such as hot, dry soil, herbicide injury, and insect predation that can significantly impede root development, which will likely lead to early season problems with standability and nutrient deficiencies. Birds may also cause stand loss by extracting shallow-planted corn seeds.

Bt Refuge - The refuge requirements for YieldGard Bt corn in Mississippi are the same as last year's requirements. Growers may plant up to 50 percent of their acreage in Bt corn hybrids trademarked YieldGard, which contain the MON-810 insertion event. Growers will be required to sign an agreement requiring them to plant non-Bt corn as a refuge within a half mile of the Bt corn. The non-Bt refuge may be treated with insecticides (excluding sprayable Bt products) as needed.

Should I plant Bt corn? - Bt corn effectively controls Southwestern and European corn borers and has moderate control on corn earworms and fall armyworms. Bt corn during stand establishment, however, does not control the primary insect pests such as chinch bugs, cutworms, rootworms, wireworms, etc. Using a Bt hybrid will not serve as a substitute for the use of a soil-applied insecticide at planting. Preliminary research data and industry yield trials suggest the inclusion of a Bt event does not increase hybrid yield potential, as compared a closely related conventional isoline in the absence of corn borers . You would not likely recover the higher seed cost of the Bt technology (about $10 per acre) unless significant corn borer infestation is likely. Unfortunately, seasonal corn borer populations are not predictable; therefore, local historical infestation levels should be used to justify Bt hybrid use.

COTTON

Dr. Will McCarty

Many cotton growers are putting the final touches on plans for the 2000 cotton crop. Acreage looks to be up from last year. In 1999 growers harvested some 1, 180,000 acres. The 2000, NCC planting estimate for Mississippi was 1,280,000. I think the actual plantings may exceed 1,300,000 before it is over - especially if growers are financed and seed are available.

Extension information sheets for 1999 weed control information and recommendations will soon be available through the local county Extension agent offices. Cotton variety publications are also available.

Tips for a good yearóPerhaps the overall objective for 2000 should be "earliness," which is a production objective where a grower designs the cotton program to focus on things necessary to result in a uniformly fruited, early maturing crop. Earliness is not just planting early. Your objectives are to get a healthy, uniform stand, set a high percentage of the first 4 weeks of squares, retain a high percentage of these as bolls, let the crop cut-out, and pick it in a timely manner. Here are a few briefs for growers as planting season approaches:

Variety selectionóPlant an adapted, high-yielding variety. This is easy to say, but at this stage of the game, if varieties have not been secured you will have not plant what seed are available. Now, this may not be all bad because demand for many of these may have been reduced because they are conventional varieties. However, there are plenty of tools available to manage conventional varieties in a successful manner. Do not be afraid of a high yielding conventional variety. Seed supply of some varieties have gotten in short supply. Retain the flexibility to regroup in variety selection and make the best of opportunities given you. Several new varieties with high-yield potential are available. For the bulk of your acreage, plant proven and tested varieties. Consider planting the earlier maturity types on your strongest land or under irrigation. Plant the more mid-season types on thinner land as they can tolerate mid-season stress better than early types.

Seed testing informationóThe precision planters that growers use allow for accurate placement of seed (depth and number of seeds per row). Ask for and use the actual germination values and cool-test germination values of each seed lot being you plant. These data can help set seeding rates óIf you are not going to use it, don't ask for it! Where transgenic varieties are planted, seed cost per acre is quite expensive. There is a tendency for growers to shave seeding rated to save money. If you are considering cutting seeding rate to save money on technology fees, you must know the actual gemination and cool test data for the lots of seed in question. There is nothing wrong with reducing seeding rates as long as you are planting high quality seed, planting into decent soil and weather conditions, using a recommended fungicide program and are still shooting for three to four plants per row foot in 38-40 inch rows, or 1.8 tp 2.0 plants per row foot in 30 inch rows.

Planting datesóYou must use common sense when it comes to planting dates. Ideally the soil temperature at a 2-inch depth needs to be a minimum of 68 degrees Fahrenheit for 2 to 3 consecutive days, measured at approximately 8 a.m., and with a favorable 5-day weather forecast. Weather reports just before planting can be important, since a front can bring rains that will lower the soil temperature and reduce stands. The first 36 hours after planting have tremendous impact on the resulting seedlings. If the seed imbibes cool water during that period, the resulting seedlings will have weak root systems and will be stunted.

Plant protectionóA sound fungicide program at planting is recommended for seedling survival and for root protection. Root development occurs early in the crop's life; therefore, proper protection is essential. This especially critical this season. We are starting the season dry and we will need to develop as strong a root system as possible early in the season. Match fungicide program to planting conditions. Fungicides will not compensate for cold, wet soil conditions. An at-planting systemic insecticide is also recommended. This helps ensure a head start in protecting the plant from early damage and should result in a potentially earlier crop.

NitrogenóAvoid excessive rates of nitrogen. As a general recommendation, about 50 pounds of supplemental nitrogen per acre per bale are recommended for sandy loam soils and about 65 pounds per acre per bale on heavier soils. Another general recommendation is to apply 80 to l00 pounds per acre in the Hills and 100 to 120 pounds per acre in the Delta; refine as necessary. Excessive nitrogen delays maturity, increases rank growth potential, and complicates insect control.

Avoid late applicationsóNitrogen may be applied pre-plant or split into a pre-plant and side-dress application. Where timing may be a problem, or on soils with problems of late-growth history, an all-pre-plant application method is recommended. Nitrogen management is especially important on mid-season to full-season varieties. High rates may tend to cause excessive vegetation growth and delay maturity. A lush, green plant and a dense plant are attractive to insect pests. A dense canopy is more difficult to penetrate with pesticides and defoliants.

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