Agronomy Notes

April, 2001

Contents

CORN

Dr. Erick Larson

Expect slow emergence of early plantings - Corn seedling growth rate is dependent upon soil temperature. Seedling growth rate is slower when soil temperature is close to the minimum requirement of 50º F. Corn seedlings normally take three weeks or more to emerge when soil temperature is slightly above 50º F. When soil temperatures warm above 55 degrees F, emergence will occur in two weeks or less.

Be cautious about herbicide drift - Off-target drift of non-selective burn-down herbicides was the most prevalent corn production problem the last two years . Use extreme caution when applying herbicides near emerged susceptible crops. Herbicide drift injury often results in catastrophic crop loss. Increasing acreage of herbicide tolerant crops may also raise potential for injury from off-target herbicide drift as well.

Planting recommendations - Latest suggested corn planting dates range between April 10 and April 25 from central to northern Mississippi. Planting into a warm, moist seedbed should improve stand emergence considerably, so decreasing seeding rates to allow for near-perfect emergence would be appropriate.

Don't speed - Don=t try to make up time lost to wet conditions by planting corn fast. Research studies indicate that many growers could improve yields 5-10 bu./a. by just improving seed spacing. The optimum speed for plate-type planters is 4.0-4.5 mph and vacuum-type planters is 4.5-5.0 mph. Speeds exceeding these values will usually cause increased double-dropped seeds, much poorer seed spacing and less seed depth uniformity.

Planting date effect on maturity - Planting dates within the suggested range will not have a large affect on crop maturity, since it is determined by heat unit accumulation. The number of heat units accumulated during March is relatively low. Therefore, corn planted in early April will have little difference in maturity than corn planted in early March, especially in northern Mississippi. However, the longer planting is delayed past mid- to late-April, the more maturity will be delayed. This is why late planting (after the recommended planting dates) considerably increases the likelihood of severe yield reduction by subjecting corn to drought stress during pollination and grain fill, and increases the likelihood of insect and disease problems.

Scout fields - Scout corn for stand, insect and weed problems every 2 to 3 days until corn is about 12 inches tall, and be prepared to take control measures. Insects or weeds may quickly ruin a good stand or become too developed to control. Timely problem identification allows specific treatment selection and application timing, which likely will improve control and lower expenses.

Nitrogen application timing - Split application of nitrogen fertilizer may substantially improve corn nitrogen use efficiency. Corn extracts less than 15% of its seasonal nitrogen uptake before rapid vegetative growth begins. Maximum nitrogen use rate occurs just prior to pollination. During early growth stages, considerable nitrogen may be lost due to denitrification and leaching. Therefore, the bulk of a split nitrogen application should be delayed until just prior to rapid vegetative growth. This growth period begins at the V10 growth stage (10th leaf stage) which occurs about 40 days after plant emergence or when plants are about 30 inches tall. The normal nitrogen recommendation specifies applying 1/3 of the total N at planting and applying the remaining N about 30 days later.

PASTURE AND FORAGES

Dr. Malcolm Broome

Warm Season Annual Grasses

Warm season annual grasses can be grown from seed and are used during the spring and summer months. Quite often these are used as temporary forage for stockers and mature cows. These annuals provide excellent grazing for dairy cows, especially in the warmer months when perennial grasses often decline in quality. Horses may also be grazed on these annuals except the sorghum x sudan hybrids.

Despite their high establishment cost and grazing management when compared to establishing perennial warm season grasses, there are several advantages to planting warm season annuals: fast growth, high yields and a high quality forage. All summer annuals need a pH of 5.8 or higher. Weeds are generally not a problem with these forages. If weed control is needed, contact your county extension agent for the current recommendations. A description of several summer annual grasses follows.

Pearl Millet (Pennisetum glaucum)

Pearl millet is a tall-growing, erect grass that produces several stems from a central plant. It tolerates well-drained acid soils better than sorghums but does best with a pH of 5.8 or higher. When planted in late April it should be ready for grazing in 30 to 40 days after planting and provide grazing for about 90 days. Its greatest growth will occur during the first 60 days. Pearl millet will use approximately 150 to 200 pounds of nitrogen (N) per acre. Use a soil test to determine pH, phosphorus and potassium needs. Apply 60 pounds of N per acre at or shortly after seeding with another 40 to 60 pounds per month for a total of three applications. As growth slows, N rates should be reduced accordingly especially if moisture is limited. Nitrate accumulation can cause toxicity problems under periods of low moisture and high rates of nitrogen fertilizer. A laboratory analysis should be used if this condition is suspected.

If productive stands are to be maintained, grazing should not begin until the plants are 18 to 24 inches tall. Graze to a stubble height of 6 to 8 inches, then remove animals and allow the millet to regrow before grazing again. Properly fertilized pearl millet should have a stocking rate of three to four stocker calves or two mature cows per acre during the first 60 days. As the season progresses, the stocking rate should be reduced. Based on these stocking rates, additional (May and June) plantings could be used to provide more uniform, quality grazing. As the April planting is declining, these May or June plantings will be in peak production. Seeding rates are 12 to 15 pounds per acre drilled about 2 inches deep or 25 pounds per acre if broadcast. Several hybrid millets are sold in Mississippi.

Browntop Millet (Panicum ramosum)

Browntop millet produces lower forage yields than pearl millet resulting in less forage and can be used for hay or grazing. Browntop can become a weed if planted on row crop land due to its reseeding ability and long period of seed viability in the soil. Browntop millet is best seeded broadcast at 20 to 25 pounds per acre on a prepared seedbed in late April or early May.

Sorghum x Sudangrass Hybrids

Sorghum x Sudangrass hybrids are tall-growing annuals similar to pearl millet in growth habit, yield and stocking rate. They tend to grow best on fertile soils and are more productive than millet in late summer. These hybrids can cause prussic acid poisoning of cattle when young forage is grazed after severely dry weather or when cold temperatures limit growth. As with the pearl millets, nitrate accumulation can also occur. Prussic acid poisoning requires producers to use grazing management, which is a disadvantage for the sorghum x sudangrass hybrids.

Seed sorghum x sudangrass hybrids into a prepared seedbed at the rate of 20 to 25 pounds per acre drilled or 30 to 35 pounds broadcast. These hybrids respond to high rates of fertilizer, so apply a complete fertilizer according to soil test recommendations before planting. As with millets, apply 60 pounds of nitrogen about every 30 days during the growing season. With good grazing management, plants should remain leafy, however if plants become stemmy, clip them to a 10- to 12-inch height. There are several thin-stemmed commercial varieties available; this is advantageous when cutting for hay.

Sudangrass (Sorghum bicolor)

This is another warm season annual grass that produces lower yields than millet or the sorghum x sudan hybrids. Newer varieties have been developed that produce satisfactory yields with quality that is comparable to the millets. Sudangrass is not planted on many acres in Mississippi, but can be used for either hay, grazing or silage.

Sudangrass also performs best on a well-drained fertile soil and should be fertilized as the sorghum x sudan hybrids. This grass needs a minimum of 65 degrees F soil temperatures before planting. Two different plantings about four to six weeks apart should provide forage throughout the summer. Sudangrass is seeded at 20 to 25 pounds per acre drilled and 30 to 35 pounds per acre broadcast.

Crabgrass (Digitaria sanguinalis)

This low-growing reseeding annual grass is present in most cultivated fields and pastures in the state. It is most often used to furnish summer grazing following winter annuals like ryegrass or small grains. Crabgrass is highly dependent on good soil moisture conditions for best growth. The forage has excellent digestibility and is also very palatable. Generally, it will provide grazing from May until early fall. Red River is the only commercially available variety.

Harvesting for Hay

All these annuals, except browntop millet and crabgrass, should provide two or three cuttings of hay. Browntop and crabgrass generally don't produce enough forage to justify their use for hay except in special cases such as excess forage or shortage of hay. Harvest these other annual grasses when they are at 30 to 40 inches tall, but do not cut any closer than 6 inches. This stubble height will aid in holding the cut forage off the ground, thus improving air circulation and speeding drying. In addition, this height allows for faster regrowth of the plant.

Weather is often a problem in getting enough time without rain for these annuals to be used for hay. A cutter-conditioner is recommended for these annuals since they have large stems that are high in moisture. Crushing the stems helps shorten the drying time. Moisture content should be 18 percent or lower before baling. Without a conditioner, these plants may require 5 or 6 days from cutting until baling.

SOYBEANS

Dr. Alan Blaine

March saw a large amount of soybean planting--the most ever for Mississippi--with some going in the ground on March 8th! As of April 1, nearly 100,000 acres had been planted. Several producers have actually finished planting.

Many producers question the early planting concept, and some areas have yet to dry up enough to even get in the field. While early planting is not the total solution to the problems soybean producers face, it is certainly an important option.

The temperature at which soybeans will begin the germination process is slightly lower than for corn. However, due to the greater vulnerability of soybeans to emergence problems, soil temperatures should be approaching or above 50º F before planting is considered. Soybean seedlings have a surprising ability to withstand freezing temperatures for relatively short periods. Research in growth chambers at the University of Minnesota showed that soybean seedlings in the two-leaf stage exposed to temperatures ranging from 25-30º F for 2 hours experienced no major leaf injury. Longer periods at these temperatures killed leaves but not all axillary buds, and regrowth occurred.

Axillary buds are found from the terminal all the way down the plant to the cotyledons. If the uppermost branches are injured (by cold weather), they serve as protection to the lower nodes. The uppermost node not affected will become the new dominant branch. A good illustration of this is to consider Adeer feeding." If a deer breaks the top out of a soybean plant, the next node down (all the way down to the cotyledons) has the potential to establish a new terminal. However, if the plant is broken off below the cotyledons, no new growth will take place. By this you can see how resilient the soybean plant is, even though it is not often thought of in this way.

Early planting should be the goal of all soybean producers if they desire to increase yields. Producers can reduce the risks associated with early planting by following these steps:

  • 1) Plant shallow. Because of low soil temperatures at this time of year, seeds can lie in the soil a long time before emerging. Soil temperatures warm faster at shallower depths, so shallow planting encourages more rapid emergence.
    •
    • 2) Prior to May 1, plant for a rain. Many will disagree with this suggestion but it is one way to minimize stand problems. It is going to rain in late March and April (most of the time). Moisture loss is not very great this time of the year and the intensity of rains during this time can wreak havoc on emerging soybeans.
    • 3) Everything you do from harvest to planting should be centered on "earliness." Think early. Stale seedbeds, no-till, and early burndowns all are options that should be used to the fullest.
    • 4) Use the proper seed treatment.
    • 5) Calibrate planters each year. Check seeding rates when changing varieties. Base seeding rates on seeds per foot of row, not pounds per acre. Do not over plant. Since the 2000 growing season was extremely dry, seed size may be quite small this year. It is imperative that you properly calibrate planters.

    The need for burndowns has varied tremendously this year. Use has ranged from a full-blown program to a "plant and wait" approach. In many fields where Roundup Ready soybeans were going to be planted, producers added Goal to the mixture hoping for some residual control. The tank mix looks great (several other options are also available) and has offered broader spectrum control and faster activity than a Roundup program alone. The objective is to maybe get enough residual activity to need only one post-emergence application.

    If you are planting early, watch for weed emergence. Watch weed pressure, keep track of when emergence occurs and control weeds for the first 4-5 weeks after emergence of the crop. Time your post-emergence spraying to avoid competition but coincide with the crop canopying. It will not happen in all fields but many may only require 1 over-the-top application.

    Remember that drilled plantings will need spraying sooner than row plantings because of faster canopy closure.

    COTTON

    Dr. Will McCarty

    If planting conditions are favorable and the weather cooperates, Mississippi cotton acreage will increase in 2001. According to the National Agricultural Statistics Service (NASS), in 2000 Mississippi cotton growers planted some 1,360,000 acres and harvested 1,280,000 acres of that. The yield for 2000 was 649 pounds of lint per acre. The 2001 Planting Intention Grower Survey, conducted by the National Cotton Council (NCC), estimated that MS would plant 1,470,000 acres in 2001. The NASS Planting Intentions Report, released March 30, 2001, estimated that Missippi would plant 1,500,000 acres in 2001. If the weather cooperates, Mississippi will probably plant the 1,500,000 acres--and then some. However, a lot of the expected acreage increase will come on heavy textured soils with poor internal drainage.

    Regardless of acreage planted, timeliness is critical. Producers must do everything possible to reduce costs, reduce trips across the field, and try to survive 2001. Take a hard look at every operation; if you aren't sure it is necessary, eliminate it.

    A couple of areas where trips can be reduced and money saved include the following.

    • If you aren't sure you can side-dress on time, put all nitrogen out pre-plant or at planting. Late side-dress applications, approaching first bloom, can delay maturity and increase insect control and harvesting cost, especially in dry-land cotton.
    • After three years of drought farmers should have learned to take care of soil moisture. If you did not subsoil in the fall, the soil may be too wet this spring to give desired results. In this case, perhaps you should not run your sub-soiler, but opt to rip the non-traffic middles instead. Ripping the non-traffic middles with a chisel shank will increase water infiltration and may boost efficiency of sprinkler irrigation systems.

    Surface Drainage

    Cotton cannot tolerate wet field conditions. Regardless of soil type, drainage is critical and must be managed. With acreage expanding onto mixed-textured fields to clay fields historically planted to soybeans or rice, you must address drainage. Establish tall beds in fields that have been formed to flat grades; drains must be opened to allow rapid drainage of water away from the field. Fields not land-formed should have water furrows properly placed for rapid field drainage and drains opened to allow rapid movement of water away from the field.

    Establish water furrows and field drains before planting, and clean out after planting. The "ditcher" should keep up with the planter each day. Do not let the day end and catch you behind on water furrow placement. Adequate surface drainage is absolutely critical in cotton production. No-till farming may eliminate in-season cleaning of the drains.

    Adjust planters to consistently close the seed slot and to shape the row where water will drain into the middles and not into the seed slot. Regulate planters to a planting depth of 0.5 to 1.25 inches, depending on moisture. Seed-soil contact is critical, since the seed will not draw water from farther away than about 10 millimeters. Remember: the three most important things in cotton production are drainage, drainage and drainage.

    Timing is critical. If you look around, you will realize that most cotton farmers do the same types of things, but it is timing that makes the difference.

    Rotational Crop Restrictions

    Many herbicides used in soybeans, rice, or corn have planting restrictions for cotton. Before planting cotton in fields where other crops may have been planted last year, determine the herbicide program used and evaluate the risk of planting cotton this year. Rotational-crop restrictions may be found on product labels, or for your convenience, this information is included within each crop section of the 2001 Weed Control Guidelines for Mississippi, Extension/MAFES Publication 1532.

    "At Planting" Fungicides

    Replanting is costly. Seedling diseases can contribute to the need for replanting, and non-lethal effects may contribute to reduced yields. Seed supplies of popular varieties are short this year. With cost of seed, cost of replanting, potential yield reductions because of delays and non-lethal effects of seedling diseases, and the probability of being unable to replant to the same variety, the use of an at-planting fungicide program is recommended. Several options are available to fit every planting situation. For more complete information, refer to Cotton Seedling Disease Control, Extension Publication 802.

    Soil Temperature

    You can plant high-vigor cottonseed when the soil is a minimum of 68º F in the top 2 inches, measured at 8 a.m., for 2 to 3 consecutive days. Also, a good 5-day weather forecast is important. Cotton is planted about 1/2 to 3/4 of an inch deep. At that depth, the soil is not well buffered against daily changes in temperature. By daylight, the seed-zone temperature will be within one degree of ambient temperature. The absorption of water that occurs in the first 24 to 36 hours after planting is critical. Unfavorable soil temperature (especially less than 60º F) during this period can result in root and seedling injury. Use standard germination and cool-test results to determine the planting order of seed lots or varieties and to determine seeding rates. Ask your dealer for the actual germination and cool-test values of your seed. It should be the responsibility of the seed company to supply this information to your dealer. You want a warm germ above 80 percent, with a cool test of 60 percent or better. In some years, 50 percent in the cool test may be acceptable, but plant those seeds with a cool test below 60 percent only in very favorable conditions.

    The cool test information is especially important. In most cases, the cool test data will more closely approximate the actual field emergence of a lot of seed than will the warm test. The conventional warm test is not a good indicator of the strength of a seed lot, only its viability.

    Common sense must apply at planting time. Some varieties are apparently in short supply this year. It is possible that if we get into a real replant situation, there will not be enough seed of some varieties to resupply the market. "Read the weather" and take the necessary time to set the planter properly.

    Plant Populations

    Final plant population should be 3 to 4 plants per foot of row in 38- to 40-inch rows, or 2.8 to 3 plants per foot of row in a 30-inch row. Long-term research indicates cotton is tolerant to a plant population range between 30,000 and 70,000 plants per acre with significant impacts on yield. A population in the 45,000 plants per acre range (row cotton), however, will produce a more uniform plant shape and fruiting pattern.

    Set planters to deliver a desired number of seeds per foot of row, based on desired stand and seed quality, rather than a specified "pounds per acre" of seed. Refer to Extension Information Sheet 1364, Understanding and Using Results of Cottonseed Germination Tests.

    Pre-plant and Pre-emergence Weed Control

    Base your selection of pre-plant and pre-emergence herbicides on expected weed species and pressure. Rate selection should approximate the recommended rates for soil type. Calibration is critical. For help in selecting herbicides and rates, refer to Extension Publication 1619, Preplant and Preemergence Weed Control-Cotton.

    Additional information can be found on summer annual grasses in newly released MSU-ES Information Sheet 1616, Forage-Warm Season Annual Grasses.

    SOIL AND NUTRIENT MANAGEMENT

    Dr. Larry Oldham

    This is the year to use soil testing. Retail nitrogen prices have eased some, but not to the levels of yesteryear. On the other side of production there has not been a huge increase in commodity prices to offset all the production cost increases.

    One of the oldest illustrations of the benefits of soil testing is the barrel rule. An old-fashioned wooden barrel will hold water only to the height of the shortest stave or slat, no matter the height of the tallest stave. The same is true for soil fertility. It makes no difference how much nitrogen is applied if some other nutrient is limiting production. The best way to determine this is to use a recent soil test.

    If the soil tests are medium or higher for phosphate and/or potash, it may not be necessary to apply them. However, if the test shows either is low or very low, this could limit crop use of the nitrogen fertilizer.

    Another very important factor governing soil nutrient availability is the lime requirement. This is different from the pH value, and is reported on MSU-ES forms as tons/acre needed. Applying lime to raise pH will allow more efficient utilization of native phosphate and potash, and (perhaps more importantly) micronutrients in the soil.

    Therefore, as you wind down corn planting, get started on soybeans, think about forage fertility programs, and make final plans for the cotton crop, look at your soil test results for any short barrel staves that may limit your income potential this year.

    RICE

    Dr. Joe E. Street

    Planting

    Because of the different seed sizes of the new varieties, plant rice seed based on the desired rate of 40 seed per square foot rather than the standard 90 pounds per acre. The following table provides the guidelines for planting rate.

    Row Spacing (inches)

    6

    8

    10

    Seed per foot of drill row

    20

    27

    33

    If possible, locate rice fields away from Roundup Ready soybeans and cotton. As much as possible, minimize the potential for Roundup/Touchdown drift. Document any Roundup/Touchdown applications around the rice field. Drift onto young rice will be readily evident and rice that survives the original drift will generally recover and produce a crop although it may be delayed. Symptoms from Roundup drift onto rice at later growth stages (such as midseason to booting) may or may not be manifested until harvest.

    If you plant your levees, the levee ditch should be filled in as much as possible to reduce the depth of the flood in the ditch. Levee ditch rice yields better quality and quantity than rice on the levee.

    Seed Treatment

    Fungicide seed treatments should be used if you plant early in cool weather. Fungicides may not improve emergence if rice is planted in May when temperatures are favorable for rapid germination. Seed-borne diseases such as Brown Spot can be controlled with Dithane or Thiram. Pythium can be controlled with Apron XL or Aliegence. Maxim or Vitavax controls rhizoctonia but that is generally not a problem. Vitavax also has some activity on pythium.

    Zinc seed treatment may help on soils with a pH greater than 7.5, a light silt loam soil or newly land-formed fields. Rice in clay soils has generally shown little response to zinc.

    Icon seed treatment is very effective in controlling rice water weevil. It offers partial control of chinch bug but will not control a heavy infestation. Icon also offers control of some stem borers.

    DD50:

    Record the emergence date and use the DD50 program as a management tool. The program is on the Internet at www.deltaweather.msstate.edu. This program is an excellent tool to use as a reminder for several input decisions.

    DD50: Record the emergence date and use the DD50 program as a management tool. The program is on the Internet at www.deltaweather.msstate.edu. This program is an excellent tool to use as a reminder for several input decisions.

    Weed Control

    Command was applied to over 70 percent of the rice acreage last year. Performance was good with few complaints. Rolling the field prior to Command application minimizes crop injury and improves weed control. Although Command may not require much water to remain active, flush the field as needed to maintain weed control. Expect about 3 to 4 weeks of residual grass control from Command. Because of delayed germination in cold weather, Command may not hold very long after emergence. Consider the cost of the total weed control program. Prices of other herbicides have been reduced and are becoming more competitive. The new Command label allows it to be tank-mixed with a post-emergence herbicide such as propanil, Facet or others and applied by ground only. If used in this manner, it must be activated by rain or flushing to get residual benefits. Good agitation is required if mixing Command with propanil. The RiceStar (Whip + Safener) Section 18 was approved for control of small grasses (1-4 leaf). The NewPath 24C label was approved but Clearfield rice will be grown only for seed in 2001 so acreage will be limited. EPA is still reviewing the Regiment Section 18.

    Weed Control: Command was applied to over 70 percent of the rice acreage last year. Performance was good with few complaints. Rolling the field prior to Command application minimizes crop injury and improves weed control. Although Command may not require as much water to remain active, flush the field as needed to maintain weed control. Expect about 3 to 4 weeks of residual grass control from Command. Because of delayed germination in cold weather, Command may not hold very long after emergence.

    Fertilizer Application

    With the cost of nitrogen, efficient management is a must. With the newer varieties such as Cocodrie and Priscilla, apply two thirds of the fertilizer prior to flooding and one-third at midseason. With Lemont and Wells (to reduce potential for lodging), apply half the nitrogen prior to flooding and half at mid season. Research is continuing to fine tune fertilizer rates; at this point, we are recommending 150 to 180 pounds of nitrogen per acre on each of the new varieties. Soil moisture, temperature, and soil pH (>7.5) influence volatilization of urea fertilizer so flood as soon as possible after fertilizer application.

    GRAIN SORGHAM

    Dr Erick Larson

    Don't plant too early - Grain sorghum will not germinate at soil temperatures less than 65 degrees F, which will greatly increase likelihood of stand failure. Thus, the optimum planting dates for sorghum are similar to those for cotton: April 20 to May 15. Optimum seeding depth is 1 3 - 12", rather than a shallower depth at which cotton and soybeans are planted.

    Don't plant too much seed - A final plant population ranging from 40,000 to 70,000 plants per acre should produce optimum grain sorghum grain yields grown in dryland culture. Grain sorghum has tremendous ability to increase yield potential if given favorable environmental conditions, especially if plants are spaced uniform. However, excessive stands compound drought stress, lower stalk quality and increase disease likelihood. Sorghum seeding rate should exceed the population goal by 10 to 20% depending upon seedbed conditions and planting date. This over-planting rate is relatively high because sorghum=s seedling vigor is low, compared to corn.

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

    Dr. Will McCarty
    Extension Leader

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