Agronomy Notes

November, 2002

Contents:
COTTON
FORAGE AND PASTURES
CORN
WHEAT
SOIL and NUTRIENT MANAGEMENT
WEED CONTROL
SOYBEANS

 

 

COTTON

Dr. Will McCarty

The 2002 cotton production season has been one to remember and is not over yet. As of October 20 or so, our crop was only about half harvested. This has been the worst harvest season since 1984. Perhaps the 1990's made us a little complacent as we had near perfect harvest conditions most ever year. The 2002 harvest season has re-taught us the importance of timeliness in management, and the importance of harvest capacity and drainage.

When growers began harvest operations, it looked like we had a chance of picking the highest yielding crop in recorded history. The record yield for Mississippi is 901 pounds per acre, and our chances of exceeding that disappeared as weather conditions deteriorated and remained unfavorable for harvest. As it stands now, we may have a difficult time picking a five year average crop statewide, and some growers are struggling to harvest any cotton at all as localized flooding has taken it's toll on numerous fields.

The overall result of this may be a reduction in acreage in 2003. I encourage growers to closely evaluate their leverage and make crop acreage decisions very cautiously. While our acreage certainly does not need to go up, our cotton infrastructure is in danger if acreage goes down much.

Getting Ready for 2003

Variety Selection: Variety selection is one of the most important business decisions cotton growers make. The longstanding and ongoing position of the MSU Extension Service is to extend variety trial research results, coupled with direct professional experience, to allow cotton producers to make their own informed variety selection decisions.

General guidelines for variety-related recommendations by MSU-ES scientists are these:

  • 1) to recommend that crop producers combine MAFES variety trial information with on-farm personal experience to select varieties that will perform well on their farms
  • 2) to recommend that crop producers try new varieties only on a very limited acreage
  • 3) to recommend that crop producers plant the bulk of their commercial acreage in proven performers
  • 4) to recommend that growers evaluate fiber quality as well as yield
  • 5) to recommend that crop producers critically evaluate the need for value-added traits in transgenic varieties.

Variety selection for 2003 will need to be done very soon. Weather conditions this fall have had significant impacts on seed production in the Midsouth. Seed companies generally spread their production across a wide area in case of years like this one. However, to avoid getting shut out of varieties you really weant - lock them is as soon as you can.

Other Fall Jobs - Cut stalks as soon after harvest as is possible. This will help in boll weevil control efforts. Sandy soils should be subsoiled when compaction problems are shallow enough to shatter and soils are dry enough. Avoid tillage operations on wet soils. Leave subsoiled fields rough until spring.

NOTE - Due to rutting of many fields more winter/spring tillage will be required in more fields than in past several years. If tillage will be done anyway, take advantage of the situation and apply needed fertilizer nutrients, especially lime. While placing nutrients on the surface may work, incorporation into the soil is much better. Have your soils sampled and take advantage of this tillage, especially for lime applications. When it come to LIME and POTASH (and sometimes PHOSPHATE) just remember this saying - "When in doubt, put it out".

Monitor Soil Fertility Levels - Fall is an excellent time to test soil. Cotton is an intensely managed crop and requires high levels of fertility to produce acceptable yields. While cotton farmers generally practice good soil fertility programs, there is still a lag in soil fertility levels. If pH levels are low and soil test recommends lime, it is critical that it be applied. If pH levels are low, applied nutrients such as nitrogen, potassium-especially phosphorous-will not be as effective.

Low Soil pH = Low Yields - Fall is the preferred time to apply lime; fall is also an acceptable time to apply mixed fertilizers to soils with a CEC of greater than 7. On soils with a CEC of less than 7, leaching of fall-applied fertilizer may be a concern.

Growing cotton in low pH soils can lead to root growth problems, nutrient deficiencies, and/or toxicities. Liming acid soils will improve plant growth and significantly increase the efficiency of applied fertilizer nutrients. In fact, if pH levels are in the low 5's or high 4's, applying fertilizer nutrients may be almost a waste of money. If lime is required, it should take precedence in a fertility program.

Selecting lime material is also important. When selecting lime materials, be sure they meet the requirements for Grade A as set by the state's lime law; this law, which is for your protection, regulates the quality of material that can be sold as agricultural lime. Particle size and calcium carbonate equivalent (CCE) are the major considerations, and of these two, particle size is perhaps the more important. The larger the particle size, the slower the material will react and the poorer the quality of the material.

Be careful as you select materials. Pelletized lime and/or liquid lime materials can be good sources, but consider the CCE and quantity of application. If the recommendations call for l ton per acre of a 90-percent CCE material, applying 500 pounds per acre of a 95-percent CCE material will not meet the requirements. Always consider the CCE of the material you select.

Nematodes - Populations of nematodes, especially Reniform, have been going up each year. If you have not had your soil sampled for nematodes, you should-especially if growth and yields have been erratic in fields or parts of fields. Using nematicides and/or rotating with corn/grain sorghum have proven to provide significant yield increases in Reniform infested fields. However, infestations must first be detected before any control strategies can be implemented.

FORAGE AND PASTURES

Dr. David Lang

Late Fall Pasture Problems -It's been a wet and warm fall! While conditions have been poor for harvesting cotton and soybeans, growth in pastures has been superb. Any winter annuals planted by September are well on their way to providing early fall and winter grazing. It's not too late to broadcast wheat or even ryegrass seed, but you generally won't be able to prepare a seedbed. A late broadcast seeding will work best into a permanent summer grass. Once the summer grass is killed by a frost, it will provide some insulation to the winter annual and help it survive later frosts. A late planted winter annual can suffer freeze damage, however, if we encounter temperatures in the mid-teens before the end of December. You'll need to weigh your winter forage needs with this risk. Late planted winter annuals will not provide substantial forage until February or March.

Frosts in the fall can also cause Prussic Acid Poisoning in Sorghum species. These include Sudangrass, Johnsongrass, and grain or silage Sorghum which has regrown after harvest. The regrowth of these particular grasses accumulate prussic acid after a frost. It can also accumulate during drought periods in the summer. Prussic acid releases cyanide gas and can kill an adult animal. Grain or silage sorghum harvested over the past month has had considerable regrowth due to our moist and warm conditions. This growth is VERY DANGEROUS to graze once we encounter temperatures in the low 30's and below. It is NOT SAFE to allow animals access to these fields. Pastures with Johnsongrass or Sudangrass are also not safe to graze once there has been a frost. The danger continues for up to a month following the first frost and for a couple of weeks after we get a good hard freeze. Do not take a chance with this. It will kill your animals.

Johnsongrass and Sudangrass can also contain Prussic Acid if made into hay in the fall. You need to let the stems dry out completely before baling. Although fall conditions are usually dry enough to safely make a fall hay cutting from these species, it has been too wet this year. Hopefully, you've already made enough hay from your summer grasses, because it's too wet make hay of any kind!

Regrowth of Pearl Millet is generally safe to graze as it produces only very low levels of Prussic Acid. Other millet such as Browntop or Foxtail are also safe to graze after a frost. A lot of corn has volunteered following harvest this fall. Corn is not known to produce Prussic Acid and this growth can be safely grazed. Corn stalks are also safe to graze.

The new Forage Variety test results are now available. Copies can be obtained through your local county extension office. It will soon be posted on the Internet at: http://msucares.com/pubs/infobulletins/ib391.pdf

CORN

Dr. Erick Larson

Addressing Fertility Problems - Fall is the best time of year to address many fertility problems. Soil acidity is a perennial problem due to our warm, rainy climate. Applying and incorporating lime during the fall allows pH neutralization before crop growth begins. This will also improve nutrient availability. The increasing use of corn in crop rotations has also contributed to phosphorus and potassium deficiencies. Phosphorus deficiency is especially prevalent when corn is grown following a rice crop, because the absence of a flood reverts soluble ferrous phosphates to unavailable ferric phosphates. Thus, considerable phosphorus application is required to overcome this phenomenon. Phosphorus deficiency also often occurs following cotton or soybeans, because corn requires double the amount needed for cotton or soybeans. Potassium deficiency often occurs following a high-yielding soybean crop, since 70 bu./a. soybeans remove about 100 pounds of potassium from the soil. Yearly soil testing generating recommendations for corn will prevent these problems. Thus, take soil samples this fall, so that incorporation and neutralization of lime and broadcast fertilizer may occur before next spring. However, delay application of potassium on low CEC soils until spring because of leaching problems.

Fall Corn Borer Control - Southwestern corn borers overwinter as larvae underground inside the extreme base of the corn stalk. Disruption of this site using various tillage practices will theoretically reduce the survivability of larvae during the winter. Thus, producers with corn borer infested fields should consider this opportunity to alleviate next year's problem. Discing is considered the most effective (disruptive) treatment, due to its cutting, shredding and turning activity. Stalk shredding is ineffective, since the Southwestern corn borer larvae are underground, inside the base of the corn stalk.

Fall Weed Control - Fall is the best time to reduce populations of some tough perennial weeds, including Johnsongrass and Bermudagrass. These perennial weeds are most susceptible to chemical application at this time of year, because they are storing energy in their rhizomes in preparation for winter. A translocated herbicide, such as Roundup or Touchdown, will be drawn into the rhizomes and have a higher likelihood of killing these reproductive organs. Chemical applications should be made when weeds are actively growing and at least two weeks before the normal first frost date. Tillage or stalk shredding should not be done after harvest, unless Johnsongrass has time to regrow to the boot stage. Successive tillage after chemical application should preferably be delayed 4-6 weeks.

WHEAT

Dr. Erick Larson

Keys to High Yields: Drainage and fertility are two extremely important factors governing wheat yields which should be addressed in the fall. Wheat is grown during the rainy season, potentially exposing it to saturated conditions at any time. Thus, field selection and physical improvements, such as multiple surveyed water furrows and clean ditches, capable of improving drainage should enhance wheat yield potential tremendously. Because wheat is a relatively inexpensive crop, growers often overlook fertility needs with the exception of nitrogen. Wheat is a very shallow rooted crop grown during the wet season, making it nearly impossible to mine nutrients from the soil profile, particularly if substantial amounts of mixed fertilizer have not been recently applied. Thus, growers will likely need to supply enough phosphorus and potassium to meet crop uptake and apply lime to correct soil pH, if needed, or yields will suffer.

Don't Plant Wheat Early: Early planting unnecessarily exposes wheat to potential development, fertility, weed and numerous pest problems which ultimately reduce yield potential. Early-planted wheat may proceed past the tillering stages (when it is most tolerant of sub freezing temperatures) before winter induces dormancy, particularly during a warm winter. This substantially increases the likelihood of winter or spring freeze damage and nitrogen deficiency related to excessive fall development. Early planting also promotes infestation of insects and disease infection by increasing exposure. Lush vegetative development encourages fall infestation of aphids, Hessian fly and Fall armyworm. Aphids vector Barley yellow dwarf, a disease which stunts wheat development and may cause substantial yield reduction, particularly from fall infection. Fall infestations of both Hessian fly and Fall armyworms may destroy stands. Hessian fly also cause broken stems and lodging in the spring. The development of Take-all, a fungus which prematurely kills plants by rotting the lower stem and root system, is also encouraging by early planting. Early planting promotes winter weed problems by allowing the entire winter weed seed bank to potentially emerge and compete with the wheat crop. Delayed planting allows a flush or two of winter weeds to germinate before planting commences. Thus, producers may control these weed flushes with fall tillage or burndown herbicide application to reduce the potential weed population. This is particularly important for hard to control winter annual grass species, such as ryegrass and cheat.

Optimum Planting Dates: The suggested wheat planting dates (within 10-14 days of the average first frost date in the fall) should provide warm enough temperatures and long enough days for seedling emergence and tillering to begin before dormancy occurs. This normally corresponds to:

North and Central Mississippi: October 15 - November 10

Delta Region: October 20 - November 15

South Mississippi: November 1 - November 25

Coastal Region: November 15 - December 10

Seeding Rates: Wheat growers should strive to establish 1.0 to 1.3 million plants per acre or 23 to 30 plants per square foot. Assuming 85% successful emergence planting with a grain drill, you will need a seeding rate of 1.2 to 1.5 million seeds per acre. Using the number of seeds per pound listed on the seed tag, you can then calculate how many pounds of seed per acre are needed. For example, 1.35 million seeds per acre divided by 13,500 seeds per pound is 100 pounds of seed per acre. This seeding rate is equivalent to 18 seeds per foot with a seven inch drill spacing. If planting with a drill is not feasible, assume about 70% emergence with broadcast seeding, combined with mechanical incorporation, or 55% emergence with aerial/broadcast seeding.

SOIL and NUTRIENT MANAGEMENT

Dr. Larry Oldham

Travel through the state during the last week of October found activities to be in a state of 'suspended animation'. By this I mean the cotton pickers, boll buggies, module builders, and other equipment sitting in fields throughout the state.We are dealing with the aftermath of three named systems, as well as some unnamed prolonged rain events. According to the Delta Research and Extension Center Weather/GIS Data Center, they have dropped 12 to 17 inches on the state between September 15 and October 31.From a soils perspective, implications will occur far into the future. These include drainage problems, rutted field issues, soil compaction, lost fall phosphorus and potassium application opportunity, potential loss of potassium on sandier soils, potential nitrogen loss through denitrification, and possible decreased phosphorus availability after the flooding subsides.I will start with the best case soil management scenario given the situation as it is safe to say there will be no opportunity for subsoiling for several weeks or months. Based on what I saw in the field this week and conversations throughout the state, I do not foresee any subsoiling on heavy clay soils between now and next fall.If you have harvested but not yet subsoiled silt loam or lighter soils, when we dry out, use a soil compaction tester (also called a penetratometer) to determine whether or where you should do it.These devices measure resistance, or soil strength in the field. They are available for about $215 from Forestry Suppliers in Jackson, as well as other suppliers. Some area agronomy agents have them, as well as local NRCS offices.According to the preliminary enterprise budgets from the MSU Agricultural Economics Department, subsoiling costs $9.74 per acre. Excluding fixed equipment costs, it still costs about $5.50 per acre for the operation.An additional consideration in late or spring subsoiling is it may delay planting, depending on how the weather conditions turn out, thus potentially lowering yield potential due to the change in soil condition.Between the out of pocket costs and potential yield limitations, determining whether subsoiling is needed rather than doing it indiscriminately has a tremendous potential effect on your bottom line.Use the meter to determine whether there is resistance greater than 300 pounds in a zone six to 20 inches below the surface. If the resistance is not this great, the economic return for subsoiling likely will be marginal at best.As the winter progresses, we will address other soils issues arising from our very unique late September to October weather period.

WEED CONTROL

Dr. John Byrd

Vegetable Weed Control for 2003

I'm planning to discuss some of the proposed changes in the vegetable section of the weed control guidelines. Keep in mind these recommendations have not been approved by the Mississippi Weed Science Committee, but hopefully by early November, when the Committee meets, they will be approved to appear in the 2003 Guidelines.

Select has been labeled for application to cantaloupe, cole crops (broccoli, cabbage, cauliflower), cucumber, greens (leafy, such as collard, kale, mustard, turnip), peppers, Irish potatoes, pumpkin, squash, sweetpotato, and watermelon. Application rate in most instances is 6 to 8 fluid oz per acre, with low rate used for emerged annual grass control and the high rate used for emerged perennial grass control. Harvest intervals vary among crops, but for greens is 14 days for harvesting greens and 30 days for harvesting roots.

Perhaps one of the most important additions will be Strategy, which is a premix of Command and Sonalan. Strategy has been labeled for preemergence application to cantaloupes, cucumbers, pumpkins, squash and watermelons. The application rate ranges from 2 to 6 pints per acre with the lower rate used on coarse textured soils, the middle rate on medium textured soils and the high rate on fine textured soils. Strategy controls a number of annual grasses and small seeded broadleaf weeds and can be used broadcast preemergence after seeding or as a banded spray to row middles after crops emerge or after transplanting.

Several questions have been asked about purple nutsedge control in vegetable crops. I am happy to say it looks like an answer is partly here. Monsanto has Sempra (active ingredient halosulfuron) labeled for sweet corn. This recommendation should be added to the '03 Guidelines. Application rate is 0.67 oz per acre applied with 1 quart nonionic surfactant per 100 gallons spray. Sempra is not recommended for application to 'Jubilee' sweet corn and should not be applied to sweet corn previously treated with a soil applied organophosphate insecticide. There are several other restrictions on the label. For purple nutsedge control in cantaloupe, cucumber, peppers, pumpkins, squash, tomato, and watermelon Gowan has sent a draft label for Sandea to EPA for approval. Hopefully, by time the '03 Guidelines goes to the printer, that label will be approved by EPA and we can add these recommendations. Most importantly, by the '03 planting season, Sandea will be available for our vegetable producers to control purple nutsedge, pigweed, ragweed, smartweed, and the other broadleaf weeds on the Sandea label.

SOYBEANS

Dr. Alan Blaine

Many growers this year had soybeans remain green at harvest. We experience some degree of this problem every year, but this year we observed more than ever before. Stinkbugs, aerial blight, three cornered alfalfa hoppers, the use of foliar fungicides, late season cercospora and anything that might alter seed set have the potential to cause this problem. What we observed in Mississippi were plants that stayed green, but pods matured. Ironically even with this problem, all of the fields we have looked at had an excellent yield potential, even though harvest may have been slowed.

The problem did not occur in every field, nor did it occur 100 percent on any one variety. In the 65 fields in our SMART program the last two years we have seen this problem in only one field (on Oct. 10, 2002), and it was a late-planted field behind wheat. Still, it had an excellent yield potential.

Several varieties have exhibited the problem&emdash;some more than others. Some of the varieties many have expressed concern about have cut beans from the mid 70s to the low 80s.

I believe stinkbugs contributed significantly to the problem. We have seen stinkbugs contribute to a stay green appearance around field borders in years past.

This is the third year we have dealt with high numbers, and it will probably be no different next year. Please get prepared and scout fields at least once a week from bloom through the end of pod-fill.

Even with high numbers, stinkbugs have been quite variable. They occurred in some early planted fields early and not others. Later in the season they became more widespread as corn, rice, and grain sorghum began to dry down. As plants mature, you can tolerate higher numbers, but you have to scout for them to accurately determine what and when to spray.

Subthreshold populations over an extended period of time make me question current threshold recommendations. For example, from mid-pod fill through when pods have become golden in color, the threshold is nine per 25 sweeps. In my opinion, if I have watched a sub-threshold population of 4 stinkbugs per 25 sweeps for two weeks, I am most likely going to spray.

Current guidelines do not address resident sub-threshold populations; this is where you have to apply some sound reasoning. Experience has shown us what they are doing, and I think we need to get them under control before they begin reproducing in the field. Allowing sub threshold numbers to feed for an extended time has proven to be a mistake.

I know many will disagree with this comment. But if you spend as much time in the same fields week after week as we do, I think you can understand the confidence we place behind this strategy. The number one objective is to scout your fields. Many growers do not want to look because they do not want to find stinkbugs, worms, or whatever else is in a field. This strategy has cost us yield.

In our SMART program, we scout fields weekly in an attempt to head off potential problems. Once we start picking up insects, diseases, or during peak irrigation, we try to scout twice a week. This year it was obvious that with aerial blight and stink bugs once a week scouting was not enough. We had several fields that were pest free one week, and the next week thresholds were exceeded and needed spraying as soon as possible.

Louisiana often experiences a condition known as "Green Bean Syndrome". This was not what occurred in Mississippi this year. Fields that remained green had some leaves and green stems but pods matured. Most fields had an excellent yield potential but due to the green appearance many went unharvested for an extended period of time. Fields that are affected by "Green Bean Syndrome" remain green and have little fruit on the plant. Anything that effects fruit set: aerial blight, stink bugs, anthracnose, pod and stem blight, and three cornered alfalfa hoppers can contribute to this problem.

There are numerous variables which can not be controlled, but with timely scouting many can be controlled.

High yields can be obtained on your farm but it may require different management strategies from year to year. Focus on those things you can control, such as, scouting your fields regularly and making timely management discussions.

Upcoming Events:

  • Cotton Production Short Course-Dec.4-6, Mississippi State University
  • Agronomic Professional Continuing Educational Workshop - Feb. 10-12, 2003, Mississippi State University
  • Agri-Day (Corn/Soybean Day) - Feb. 20, 2003, Leflore Civic Center, Greenwood, MS

 

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

Will McCarty, Ph.D.
Extension Leader

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