Agronomy Notes

April 3, 2000

Contents

COTTON

Dr. Will McCarty

Cotton acreage is expected to be up from 1999. Early estimates of this year's crop fell around the 1,280,000-acre range. All winter, however, I felt acreage would go over 1,300,000 and it may well exceed 1,400,000 when all is said and done. This acreage increase will bring some "marginal" land into cotton production.

Regardless of acreage planted, timeliness is critical. Producers must do everything possible to reduce costs, reduce trips across the field, and increase profitability in 2000. 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: (1) If you aren't sure you can side-dress on time, put all nitrogen out preplant 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. (2) With the soil moisture a premium this year, deep tillage or tillage in general just before planting may not be effective and will waste moisture. Save the trip. A timely application of a burn-down herbicide may save several trips over the field and allow you to plant on time.

Timing is criticalóIf 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 RestrictionsóMany 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 2000 Weed Control Guidelines for Mississippi, Extension/MAFES Publication 1532.

At Planting FungicidesóReplanting is costly. Seedling diseases can contribute to replanting, and nonlethal effects may contribute to reduced yields. Seed supplies of popular varieties are short this year. With the probability of not being able to replant to the same variety, cost of seed, cost of replanting, potential yield reductions because of delays and nonlethal effects of seedling diseasesóthe 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.

Surface DrainageóCotton 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 afer 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 If no-till farming is used, you 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.

Soil TemperatureóMany growers will begin planting cotton in April. You can plant high-vigor cottonseed when the soil is a minimum of 68 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 ½ to æ 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 60 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 seedsman's responsibility 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 PopulationsóFinal 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 uniformed plant shape and uniformed 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 1363, Understanding and Using Results of Cottonseed Germinations Tests.

Preplant and Preemergence Weed ControlóBase your selection of preplant and preemergence 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 Information Sheet 1619, Preplant and Preemergence Weed ControlóCotton.

RICE

Dr. Joe Street

The Command 3ME Section 18 request was approved by EPA for control of Propanil-resistant barnyardgrass in rice. Command 3ME may be applied up to 14 days before planting rice of within 7 days after planting but before 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.

For the most effective use, apply Command after planting. Rolling the field with a flat roller before 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 (1 gallon to 7.5 acres) on medium- textured soil to 0.6 pounds (1 gallon to 5 acres) on fine-textured clay soils. The 0.5-pound rate (1 gallon to 6 acres) is the most common on clay soils. Command provides a maximum of 3 to 4 weeks of residual control of barnyardgrass. Residual control of broadleaf signalgrass will be about 2 to 3 weeks; thus, to get maximum benefits from Command, plant rice when soil temperature and moisture are conducive to rapid seed germination that allows establishment of the permanent flood within 4 weeks after planting.

Command should be activated by rainfall or flushing within 5 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, you may replant rice into fields treated with Command. Do not apply additional Command.

Command is not a stand-alone herbicide. About 40 percent of the growers who used Command in 1999 were able to make it to permanent flood without additional grass control measures, except on the levees. Most of the growers planted after April 15 and flooded 3 weeks after emergence. 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 1 week of residual control per 1/10 of a pound of Facet. If you expect to have to apply a herbicide for grass control before flooding, then a postemergence 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, applying 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; do not incorporate Command. Good agitation in spray tanks is required. If Command must be left in a spray tank for an extended time, add a good compatibility agent. Do not apply Command when weather conditions favor drift. Do not apply Command within 1,200 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 we will be able to continue its use in rice.

CORN

Dr. Erick Larson

Be cautious about herbicide driftóOff-target drift of nonselective burn-down herbicides was the most prevalent corn production problem in 1999. Use extreme caution when applying herbicides near emerged susceptible crops, which likely are wheat or corn. 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.

Planting recommendationsóLatest 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 it is appropriate to decrease seeding rates to allow for near-perfect emergence.

Don't speedóDon't try to make up time lost to wet conditions by planting corn fast. Research indicates many growers could improve yields 5 to10 bushels per acre by improving seed spacing. The optimum speed for plate-type planters is 4.0 to 4.5 mph and with vacuum-type planters it is 4.5 to 5.0 mph. Speeds exceeding these values will usually cause increased double-dropped seeds, poorer seed spacing, and less seed depth uniformity.

Planting date effect on maturityóPlanting dates within the suggested range will not have a large influence on crop maturity because 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 greater the effect on crop maturity. This is why planting late (after recommended planting dates) considerably increases the likelihood of severe yield reduction by subjecting corn to drought stress during pollination and grain fill and increasing the likelihood of insect and disease problems.

Scout fieldsóScout 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. Insect or weed pests 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 timingóSplit application of nitrogen fertilizer may substantially improve corn nitrogen use efficiency. Corn extracts less than 15 percent of its seasonal nitrogen uptake before rapid vegetative growth begins. The maximum nitrogen use rate occurs just before pollination. During early growth stages, considerable nitrogen may be lost because of denitrification and leaching. Therefore, delay the bulk of a split nitrogen application until just before 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.

GRAIN SORGHUM

Dr. Erick Larson

Don't plant sorghum too earlyóGrain sorghum will not germinate at soil temperatures less than 65 F. Thus, the optimum planting dates for sorghum are similar to those for cotton: April 20 to May 15. Optimum seeding depth is 1 º to 1½ inches, rather than a more shallow depth at which cotton and soybeans are planted.

Seeding rateóA final plant population ranging from 40,000 to 70,000 plants per acre should produce optimum grain sorghum yields grown in dryland culture. Grain sorghum has tremendous ability to compensate for low stands, especially if plants are spaced fairly uniform. Sorghum seeding rate should exceed the population goal by 10 to 20 percent, depending on seedbed conditions and planting date. This over-planting rate is relatively high because sorghum usually has poorer establishment success than corn.

GRAZING MANAGEMENT

Dr. Malcolm Broome

Animal performance is improved when pastures are grazed closely. The forage in closely grazed pastures is younger, has a higher leaf content, higher protein level, and is more digestible than forage in undergrazed pastures when excess forage accumulates and matures.

A difference exists between a closely grazed pasture and an overgrazed one. When pastures are overgrazed, forage availability is limited and animal performance declines because of reduced intake. When growing conditions change and forage growth slows, it is easy to overgraze unless stocking rate is reduced. Perennial pastures such as bermudagrass, bahiagrass, and endophyte-infected tall fescue will tolerate close grazing (2- to 4-inch stubble height) and maintain good stands.

Pastures can be continuously or rotationally grazed. There are advantages and disadvantages to each system. A continuous system requires less fencing to subdivide pastures and less labor to handle the cattle. The major disadvantage of the continuous system is the difficulty in matching stocking rate to the forage growth rate to prevent accumulation of excess forage. Some areas of the pasture will be heavily grazed or "spot grazed," yet forage in the ungrazed areas grows and matures.

In the rotational system, a large pasture is fenced into smaller pastures. Cattle are confined to the smaller pasture until the forage is grazed to the desired stubble height. The cattle are then moved to another pasture and the process repeated. Depending on the number of pastures and growing conditions, each pasture should get 21 to 28 days of rest between grazing. Pastures not grazed during this time should be harvested for hay for use during the winter. The disadvantage is the cost of extra fencing, even when temporary electric is used, and more labor and management are needed. Water supply is also a problem.

Most Mississippi cattle producers use a continuous system or a modified rotational system, which is profitable in an intensively managed operation. Weeds can also be a problem in either system by competing with the forage for light, water, and nutrients, but a vigorous grass sod provides good weed competition; use herbicides also to control weeds. Contact your county Extension agent for help in this area.

SOYBEANS

Dr. Alan Blaine

Planting time has arrived and you should have made your varietal decisions by now. Although it has taken the University a while to make available a bound copy of the variety trials, this information is available earlier through your county Extension office or on the Internet. Keep this in mind next year, and access this information as soon as possible to capitalize on the top choices.

This year there are adequate supplies of seed, just not adequate supplies of the better varieties. Eighty percent of the varieties on the market have nothing to offer, so to obtain the top performers, it is imperative you start early.

The approach to take in variety selection is to get aggressive. Select varieties based on yield potential and consistent performance. Do not settle for second best. Variety selection is a difficult task and one that should not be taken lightly.

Seed TreatmentsóIf you are not using the Early Soybean Production System, you owe it to yourself to give it a try. An integral part of this system is the use of the proper seed treatment. Based on comments, I feel the need to clear some major misconceptions regarding seed treatments. The best way to do this is to set the stage as to why growers need a seed treatment. Use a seed treatment to ensure a stand; it is a form of insurance. Several criteria were published in the early 1970's regarding when a grower needs to use seed treatments, including the following: 1) if planting into a lot of residue (no-till /reduced till); 2) if you have a history of seedling disease; 3) planting when it is cool/wet or hot/dry; and if 4) seed germination is less than 80 percent.

An additional criterion to add is if planting flat on poorly drained soils. When you look at these criteria and consider the ESPS system, what has come into play that normally was not a factor 20 years ago? In the case of early planting, one for certain is cool, wet conditions.

If you plant after May 15, you probably do not need to use a seed treatment. As planting dates get later, weather fronts spread out and become slightly more predictable. By using the ESPS system, producers expose themselves to more adverse weather conditions. Also, on a large percentage of acreage in Mississippi, growers are planting reduced till; therefore, these two points need to be considered.

Do you need to use a seed treatment early? The answer is yes, unless you can predict when it is going to rain. In that case, we can do a much better job determining when and what you need to do.

I have had questions regarding yield increase. In most cases, the only way to get a yield increase is if it saves a stand. Where comparisons have been made, yield increases have been minimal. The big question should be to focus on where tests are conducted and under what conditions. In the case of seed treatments, I feel growers have more exposure to numerous variables such as poor drainage, higher inoculum potential, etc., than in small plots.

As I stated earlier, seed treatments are a form of insurance. The in-field results experienced on many acres have solidified our decisions on when and why to use the proper material. Eighty percent of the state's acreage is planted on poorly drained clay soils. Even if surface drainage is adequate, they are still poorly drained. .

Consider the following points about seed treatments. First, if you do not get a stand the first time, you will in all likelihood replant with a secondary choice, not what you used originally. Secondly, lost growing time is irreplaceable. There is no comparison in yield for an early stand versus one 2 to 3 weeks later. Third, the extra expense of replanting: seed costs, trips across the field, additional seed treatment cost, etc.

Consider cost should you have to replant. With some varieties costing $26 per bag, if you save a stand 1 year out of 12, you have paid for approximately 10 years of seed treatments. If you decide to use the bare minimum treatment, one saved stand would pay for 26 years of seed treatments.

In all honesty, I am not concerned about a 3- out of 4-year response to a seed treatment. I want a stand. We need to get a stand every year, the first time. In 1999, I saw five days' difference in planting dates translate into 10 bushels per acre yield difference on several fields. Given this scenario, it is easy to see why lost yield is irreplaceable.

The number one problem seen on early planting of soybeans is pythium, which thrives under cool, wet conditions; soybeans are much more effected by pythium than cotton. Your base seed treatment program should include a material active against pythium (for example, Apron XL, Allegiance). If you want to broaden the spectrum of your program, you can add materials such as Vitavax, Thiram, Captan, etc. This year there will be several available premixes that should make application on the turn row easier; however, whatever you decide to use, remember what the significance of getting a stand means.

Burn-downsóA lot of burn-down materials have gone out over the last few weeks and, looking at the current situation, more growers should have taken advantage of this option. I realize the use of burn downs may not be considered as a savings to many. But, they can be, especially if spring weather puts growers in a position where they cannot perform desired field operations when they want. It appears that after the state's excellent fall, this year will be one where more burn downs should have been applied, particularly from a moisture-conservation standpoint.

The lack of early burn downs will be obvious this year if the state stays in this dry cycle. Fields already burned down are going to have a definite advantage over grown-up fields. In the future, use burn-downs to avoid planting delays in the spring. Grown-up fields require more field preparation, which contributes to planting delays.

Plant PopulationsóCurrent recommendations for plant populations are 75,000 to 125,000 plants per acre for row plantings, and 125,000 to 175,000 plants per acre for drills. These are final plant populations.

The soybean plant has a tremendous capability to compensate. Plant populations mentioned have a 50,000-plant per acre spread. Research shows that variations 25 percent above or below these ranges will have no impact on yield if weeds are controlled.

Higher plant populations are recommended for drill plantings because of two major factors: (1) less than optimum seed placement and (2) inaccurate metering of seed. A drill is not as easy as a planter to regulate. Vast improvements have been made in regards to seed placement; however, the accuracy from a seed metering standpoint still has room for improvement.

I point out the opportunity surrounding plant populations because growers have a tendency to overplant. With seed costs escalating to the point they have in recent months, growers are going to start paying closer attention to seeding rates.

Keep several points in mind as you prepare to plant: Attempt to plant early. Use the proper seed treatment. Regulate seeding rates based on variety, row spacing, seed quality, time of seeding, and future weather.

SOIL AND NUTRIENT MANAGEMENT

Dr. Larry Oldham

There's conventional wisdom, and there are myths; some things we "know" are subject to change. Phosphorus movement through the landscape has become a concern because some basic "facts" have become open to challenge. Following are some observations from "Agricultural Phosphorus and Eutrophication," published by the USDA Agricultural Research Service.

Soils are not infinite storage houses for P. When growers continue to apply amounts of P beyond crop requirements, as often happens when organic by-products are used, soils become saturated with P and are unable to fix more.

Meeting crop nitrogen requirements with organic by-products can lead to soil P saturation because of the unfavorable N to P ratios of most manures with respect to crop nutrient needs.

Phosphorus can move through soils with low P-fixing capacity, high percolation potential, or extremely high P saturation. Erosion control is not the sole answer for minimizing P movement in the landscape. You must use practices that minimize P loss at the source and that reduces total P in the runoff. All fields and water bodies are not created equal. Management plans should be tailored to the unique situation at each location. Using the P Index risk assessment tool is one way to do this.

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