Agronomy Notes

October, 2003

CONTENTS:

 

 

 

SOIL TESTING

Dr. Keith Crouse

Maintaining soil levels for crops and pastures requires a regular soil-testing program. An acceptable soil pH level promotes better overall availability of essential nutrient for healthy crop growth; good pH levels increase the efficiency of fertilizers applied. The availability of various plant nutrients is affected somewhat differently by changes in the soil pH. A fertility recommendation is only as good as the soil sample submitted.

Generally, this is about 15 to 20 cores per soil sample. Take your soil cores from the surface to plow layer. Mix your soil cores thoroughly. Send a full soil box or a pint of soil for analysis. If soil results indicated low soil pHs and fertility, you can make corrections this fall by following recommendations of your soil analysis. For most crops, lime should be incorporated into the top 5 to 6 inches of the soil, preferably at least 3 months in advance of planting.

We are still receiving samples without proper payment or MSU customer identification number. These samples are placed on hold thus effecting the sample turn around. To avoid such delay make sure that the MSU-ES Soil Testing receive the proper payment or customer identification number with the sample.

SOYBEANS

Dr. Alan Blaine

USDA's September crop report projects Mississippi to harvest a record soybean crop this year. Projected yield is 34 bushels per acre, which ties the highest yield ever produced (in 1992). It is my opinion this estimate is too low, and recent rains insured that -- the late portion of the crop benefited greatly from the rains in late September.

If you compare 1992 to this year, rainfall was more frequent, but we also experienced Midwest temperatures virtually season-long -- something we did not observe in 1992.

Although Mississippi's soybean crop is going to be above average, it has not been void of problems. I realize this is probably not the time of year to discuss plans for next year, but I wanted to highlight several items for consideration this fall. I am only going to mention these briefly; I will attempt to discuss these in detail over the next few weeks.

1. Seed treatments. This option may not contribute to an increase in yield versus non-treated seed, but the year it does you will know it. Getting a stand the first time is the key to increased yields. There is no substitution for planting date, and if it takes using a seed treatment to achieve a stand in April versus May, this is your yield increase.

The impact of early planting is real, and we must continue to do everything in our power to capitalize on it.

In addition, the use of the proper seed treatment must be addressed. Many are using Apron + Thiram. This is not as broad spectrum as was needed this year. A broad spectrum seed treatment utilizing a higher rate of Apron on clay soils should be considered if you are having problems.

Many observed that anything less than an Apron Max/ Apron Vitavax combination was not adequate after the type of conditions in which we harvested seed beans last fall. Harvest conditions last fall contributed to lower germination and lower vigor in some varieties, which was obvious following planting.

2. Variety selection. It all begins here. There are many things we cannot control, but the easiest approach to minimizing some major yield-robbers is variety selection. This is particularly true with stem canker. I have continued to try new varieties in an attempt to achieve top yields, but I feel my approach has not been justified on some fields.

In the future, new varieties will occupy very small acreages where I am involved, and we will use race horse varieties in high yield environments, not all environments. This coming year, I doubt I will need 10 fingers to count the varieties we will plant in our verification program.

Updated variety information is not yet available, so I may be premature with this comment, but I seriously doubt it.

3. No-till plantings. Continuous no-till fields continue to cause us concerns every year. Many soils in our state will respond to tillage and we need to attempt to identify those soils. A stale seedbed system is probably all that is needed to avoid some of the problems we have observed over the last five years.

4. Drainage. This is an age old problem, but if we did nothing but open up our tail ditches we would solve a lot of problems. Many fields are too flat so they need some help from time to time. Water on/water off, both are very important.

We observed far too much charcoal rot in irrigated soybeans this year. Charcoal rot lets us know that some stress occurred -- either too wet or too dry.

5. Timing of fungicide and insecticide applications. To continually produce high yields will require some degree of late season management. Whether that requires the use of a fungicide, insecticide, or a combination of the two, timing is the key to achieving benefits.

We used Dimilin on all our dryland fields and a Dimilin/Quadris combination on our irrigated fields. I realize that all do not feel these treatments are justified, but if you recognize what these products can do, and properly time your application, they can provide benefits.

I have two gentlemen that work with me, that have observed the benefits of Dimilin under numerous scenarios since the early 1980s. This is over a 20-year period under various environments. Is this, or other treatments, justified to make a blanket application on every field every year? No, but you need to know what they can and cannot do for you, so you can make a better informed decision on when to use them.

I spoke to a friend from Arkansas the other day and he told me that he has tried Dimilin in test plots several times and has not gotten a yield increase. That may be true possibly due to the maturity group, time of year applied, cropping system, planting date, etc.

However, in the same breath he asked me what we were doing for salt marsh caterpillars in Mississippi. We have not sprayed any salt marsh caterpillars in our verification fields, and you know why, because we used Dimilin. Dimilin will smoke salt marsh caterpillars, providing a three to three and a half week residual.

It is so effective on several worm species (velvetbean caterpillars, green cloverworms, and cabbage loopers) that populations fail to develop following an application. Realize that nothing is absolute. It is often difficult to observe benefits from small plot research when it comes to diseases and insects. My research counterparts will cringe at this comment, but growers have a greater potential for problems due to increased variability/inoculum. Working in the precision ag arena has made me rethink my approach on large fields.

6. Late applications of Roundup. For the second year in a row we have observed fields that stay green from applications of Roundup made to blooming/early podding soybeans. The stems stay green and the plant retains its leaves and petioles. The pods will dry down, but not the plant itself.

Yields have still been pretty decent, but if you scout beans by looking from the turn row you will fail to see that pods are dried and ready to harvest. The best way to avoid this is do not push the label. If a field gets a little wooly we can make a preharvest shot after plants approach maturity. Until we learn more about this problem, do not push an application too late.

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

Wheat Short List: A list of the wheat varieties which have had superior yields over the past several yields is now available on the MSUcares website (listed in Frequently Asked Questions as "What are some good wheat varieties?") or at your county extension office. Plant characteristics, maturity, straw strength, disease resistance and other helpful information are noted for each variety.

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.

No-Till Production: Wheat can be successfully grown using no-tillage production by making some minor adjustments to compensate for leftover plant residue from the previous crop, compared to conventional seedbed preparation:

1. Adjust combine to spread residue evenly during harvest of the previous crop to allow subsequent planter operation and evenly distribute recycled nutrients.

2. Adjust drill to ensure proper penetration, seed placement, and furrow closure. Producers will likely need to reduce drill operating ground speed, compared to a conventionally prepared seedbed. Planting depth should be 1 to 1.5 inches below the soil surface. Planting success is highly dependent upon moderate soil and residue moisture content. Planting at an angle different than the previous crop row pattern may improve drill performance by reducing residue accumulation in specific locations on the equipment. Narrow drill row spacing (less than 7 inches) may compound equipment operation in heavy residue.

3. Growers may need to increase seeding rate 10-15% or to about 1.5 million seeds per acre for difficult planting conditions, particularly for heavy corn or sorghum residue. This may not be necessary when planting into well distributed soybean or cotton residue.

4. Use a burndown herbicide to kill existing weed vegetation before planting or wheat emergence. This weed control is particularly important for minimizing competition from winter annual weed species, such as ryegrass, Bromus species, and chickweed.

5. Phosphorus, potassium and lime should be applied in the fall before planting. These fertilizer applications should be based upon soil test analysis recommendations. If wheat will be subsequently double-cropped, phosphorus fertility should be based upon wheat uptake needs and potassium fertility upon soybean or grain sorghum uptake requirements. Nitrogen needs will primarily depend upon amount of crop residue present and the previous crop/N fertility program.

PLANT AND MAINTAIN CLOVERS

Dr. David Lang

Clovers and other legumes are able to provide 50 to 200 lbs of nitrogen per acre depending upon species. Most of this nitrogen is not available to grasses until clovers have been established for 6 months or more. Perennial species such as white clover can provide up to 200 lbs of nitrogen per acre year after year, if the pasture is managed to maintain it with the grass.

There are many reasons why more clovers are not present in Mississippi's pastures. These include under grazing, use of broadleaf herbicides, and excessive use of nitrogen fertilizer. With the cost of nitrogen fertilizer increasing, excessive application rates are not much of a problem, and the value of adding clovers is enhanced. Another reason clovers are not present is because seed have not been purchased and planted. The seeding rate for whiter clover is 3 to 5 lbs per acre; red clover is 8 to 10 lbs per acre. The cost is generally $2 to $4 per lb so it's very economical to invest in clovers.

Red clover is a short-lived perennial that is well adapted to heavy soils and it makes a good companion with tall fescue, johnsongrass, and dallisgrass. Improved varieties developed for the south include Cherokee, Cinnamon Plus, Redland, and Redlandgraze II. These come from Florida and Georgia and are adapted to Mississippi. Red clover is adapted for hay and it can also tolerate moderate grazing pressure.

White clover is a longer-lived perennial with great potential for improving perennial grass pastures in Mississippi. It needs to be managed properly to persist. White clover is short and likes to grow close to the ground. It is shade tolerant so it will do well under the canopy of dallisgrass and bermudagrass, but it needs to be grazed short to persist. It does not make a good companion plant if your objective is to grow hay. The smaller dutch or common varieties of white clover are more persistent than the larger ladino types. Osceola is a tall ladino white clover that won't persist more a couple of years. Researchers have found that flower and seed production are critical for white clover to persist. The ladino types are much less seed produced than the smaller common type. Allow clovers to go to seed in June to insure persistence.

White clover varieties such as La-S1, Will, Durana, and Patriot have been selected and developed in the south and are well adapted to Mississippi. Grasslands Huia and Pitua are from New Zealand and may have difficulty surviving our hot and drought prone summers. Tripoli will persist, but Alice and Barbian are more adapted to cooler climates. Read the advertisements carefully to see where they were developed. If it wasn't in the deep south, then they probably will not do well.

Clovers can be planted throughout the fall and early winter. The main requirement is to graze closely. Seed can be broadcast on the surface; the wet winter conditions are ideal for clover establishment. Successful stands have been achieved with plantings from October through February. Inoculate all clover with the proper Rhizobium bacteria if the seed is not already precoated.

Weed control in a clover/grass pasture is more complicated than spraying broadleaf herbicides. Close, rotational grazing will control many broadleaf weeds as will timely clipping. If you have a broadleaf weed problem before you plant clovers, you will still have a broadleaf weed problem after you've introduced clovers. Your pasture management will need to change. Check you soil fertility and add lime, potash, and phosphorus as called for by the soil test. Apply broadleaf herbicides such as Weedmaster or Grazon to kill broadleaf weeds not controlled by changes in clipping and grazing management the summer before you plant clovers; you won't be able to use either of these herbicides once clovers are established. Butyrac or 2-4DB is a modified 2,4D type of herbicide that can be used once clovers are established, but it is a rather weak herbicide that won't control difficult to kill broadleaf plants such as horsenettle.

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

Will McCarty, Ph.D.
Extension Leader

A black line that separates the body text from footer information