Agronomy Notes

October 3, 2000

Contents

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 because of Mississippi's warm, rainy climate. Applying and incorporating lime during the fall allows pH neutralization before crop growth begins; this also improves nutrient availability. The increasing use of corn in crop rotations has also contributed to many fertility problems. For example, it is common to see corn phosphorus deficiency following a cotton crop, because corn's phosphorus requirement greater than cotton. Soil testing for corn provides a phosphorus recommendation that will prevent this problem. Take soil your samples this fall, so incorporation and neutralization of lime and broadcast fertilizer can occur before next spring; however, delay application of potassium on low CEC soils until spring because of leaching problems.

Fall Weed Control Fall is also 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, providing a higher likelihood of killing these reproductive organs. Make your chemical applications when weeds are actively growing and at least 2 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. Delay successive tillage after chemical application 4 to 6 weeks.

WHEAT

Dr. Erick Larson

Updated Variety List Several varieties have been added to the suggested wheat varieties list. Two varieties are recent releases: AGSouth Genetics AGS2000 and Genesis 9939. The other two varieties have above-average multiple-year yield records: Delta King 1551W and 9027. Characteristic profiles of these varieties and the complete list are posted on the MSU Extension Service Grain Crop web site; or contact your county Extension agent for a copy of the list. Two varieties suggested for south Mississippi were not submitted to this year's Variety Trials; AgriPro Mason and NK Brand 9835 were omitted.

Don't Plant Wheat Early Planting too early unnecessarily exposes wheat to potential development, fertility, and pest problems that ultimately reduce yield. Winter wheat cultivars are developed to proceed through winter dormancy in the tillering growth stages. During these growth stages, the wheat plants can tolerate of freezing temperatures. Thus, early planted wheat that proceeds past tillering in the fall substantially increases the likelihood of subfreezing temperatures damaging plants. Early planting may also cause nitrogen-timing problems that reduce yield potential. The warm, rainy winter climate in the Midsouth necessitates the majority of nitrogen application be delayed until the spring to avoid nitrogen loss during the winter. However, wheat nitrogen needs increase substantially beginning at stem elongation. If stem elongation begins in the fall, the wheat plants will suffer from nitrogen deficiency until the spring, causing reduced head number and size and significantly reducing yield potential. Early planting also promotes infestation of insects and disease infection. Lush vegetative development encourages fall infestation of aphids, Hessian flies, and fall armyworms. Aphids vector Barley yellow dwarf is a disease that stunts wheat development and may cause substantial yield reduction, particularly from fall infection. Fall infestations of both the Hessian fly and Fall armyworm may destroy stands; Hessian fly also causes broken stems and lodging in the spring.

Optimum Planting Dates The suggested wheat planting dates (within 10 to14 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 the following dates: North and Central Mississippi: October 15 to November 10 Delta Region: October 20 to November 15 South Mississippi: November 1 to November 25 Coastal Region: November 15 to December 10

Seeding Rates Producers should strive to establish 1.0 to 1.3 million plants per acre, or 23 to 30 plants per square foot. Assuming 85 percent 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 seed per pound listed on the seed tag, you can calculate how many pounds of seed per acre are needed. For example, 1.35 million seeds per acre divided by 13,500 seed per pound is 100 pounds of seed per acre. This seeding rate is equivalent to 18 seed per foot with a 7- inch drill spacing. If planting with a drill is not feasible, assume about 70 percent emergence with broadcast seeding combined with mechanical incorporation or 55 percent emergence with aerial or broadcast seeding.

SOYBEANS

Dr. Alan Blaine

This year will turn out to be a disappointment to many soybean producers. If you look at the total weather picture, 2000 was a worse year than 1980, a year many are using for comparison. In 1980 Mississippi's average soybean yield was 16 bushels per acre. Although yields this year will not be that low, end results will be worse because of the moisture deficiency before planting, the lack of rain in July and August, and low prices. In some areas of the state, this is the third consecutive year yields have come in short. I realize this is no consolation, but yields of early planted soybeans have been respectable. At Stoneville, a 7-day difference in planting dates translated into a 50-percent reduction in yield (dryland). On dryland fields, it appears anything planted after April 23 was late. Late April to early May is considered early but not this year with the kind of rainfall most growers received.

For the second year in a row (statewide), producers had one of the best looking crop on July 1st I have ever seen. With no appreciable rainfall from that point on, soybeans could not hold on, with a large percentage dying in the field. Pod set was tremendous but there was no moisture to fill out seed. The low moisture seed most are harvesting is an example of just how fast things dried down. Overnight in many fields, beans went from virtually unable to cut, to 7 percent moisture (high temperatures/low humidity). Calls regarding damage have been variable. Several factors contributed to the degree of damage: variety, planting dates, and rainfall. In many fields where plants just died, seed exhibited a green color, which is a sign of immaturity.

We had an early crop this year, but plantings from late April through mid-May were not early enough. The bulk of this crop shut down prematurity, and the only way this could have been avoided is by planting earlier or irrigating. No one is at fault for this crop; every grower I have spoken with did all they could from a dryland perspective. It is just too much to go 10 to12 weeks with no rainfall. I still feel Group IVs are a viable solution. Early planting remains an integral part of this. Who would have believed that the crop could deteriorate so fast?

I have had several growers tell me they wish they had planted Group V soybeans, which I promise you this is not the answer. If you were disappointed in some dryland IVs, you may have been disappointed even more in some Vs. We need to grow Vs also, but the best option this year to have avoided these concerns was to have planted prior to April 20. The main inputs to focus on again this coming year include throwing out a few varieties (but this happens every year), plant earlier, and in the case of irrigation, irrigate on a better schedule.

As this crop comes in, consider minimizing field trips, especially where fields are in good shape. If you pursue some type of minimum tillage, concentrate on a early burndown next spring. Do not delay this application.

Producers have expressed concern about damaged seed. We are in the process of collecting seed samples from several variety trial locations. Hopefully, getting a quality analysis will help with varietal decisions.

The projected state average soybean yield is forecast at 23 bushels per acre. Nineteen-eighty was the year with weather conditions most similar to 2000's conditions, and producers harvested 16 bushels per acre. We will not drop to those levels, but things are much worse given input costs and commodity prices. Many changes are taking place, but producers must stay focused on what production practices are working and which ones are not.

FORAGES AND PASTURES

Dr. Malcolm Broome

Productivity and desirable forages that make up a pasture can be quickly altered by grazing. Repeated severe defoliation of desirable species in pastures can change the composition to one of limited availability of quality forages. Ideally, grazing management provides a recovery period for a forage to optimize plant growth and animal production (gain per acre).

The grazing beef animal will clip or tear off selected plant parts (such as leaves) with large bites. This gives the common defoliation pattern seen in pastures of having large mature patches of growth mostly ungrazed. This repeated pattern of overgrazing has been found to result in complete cessation of root growth and in poor plant development. Often this allows annual and perennial weeds to become established and compete with the forage for water and nutrients. With plants at less than an optimum height and with few leaves, sunlight is not used efficiently and growth of less desirable forage is encouraged.

Pastures are also damaged by the trampling of plants from the hooves of animals. This can lead to soil erosion (paths or barren areas), altered grazing patterns, and soil compaction. As stocking rates increase on a pasture, so does reduction in forage yield over time. The damage or lost production will depend on soil type and fertility, plant species, and soil moisture. The number of plants and tiller density are reduced immediately upon treading by the animal. Research has shown as much as a 20-percent reduction in forage yield where excess trampling occurred to forages.

Lastly, the grazing animal overtime brings about a redistribution of nutrients in the pasture. Most of the nutrients from the forage are excreted by the animal but not uniformly over the pasture. Usually large amounts are concentrated under shade areas and around mineral feeders, and watering sites. This causes these areas to become enriched and the more distant pasture areas decline in fertility. Potassium levels 10 times greater and phosphorous levels 4 to 5 times greater in these areas than in the pasture as a whole were noted in a 1993 Missouri study. Ways to help reduce these impacts are better location of water sources within pastures, more uniform layout of pastures, and scattering of concentrated manure areas by harrowing in some way.

Animals can cause changes in the productivity of a pasture, which, in turn, will affect animal performance and profitability of the operation. Economic returns depend on forage quantity, quality, and grazing efficiency; therefore, grazing distribution, duration of grazing, and degree of use must all get equal emphasis in the grazing program.

WEED CONTROL

Dr. John Byrd

Smutgrass is an increasing problem for many cattle producers in Mississippi. This year, several experiments were established around the state to evaluate a new herbicide, Oasis, for control of smutgrass and other "weedy" grasses such as vaseygrass and dallisgrass in bermudagrass pastures. Oasis is a mixture of imazapic (active ingredient in Plateau and Cadre herbicides) and 2,4-D. Rates evaluated were 4 to 12 ounces per acre with nonionic surfactant and 1.5 pints per acre Velpar. These treatments were applied before and after seed head emergence. What a disappointment! Oasis is NOT going to be the saving treatment for smutgrass control based on the performance of the product this season; however, the activity of Oasis on vaseygrass and dallisgrass was excellent. So good, in fact, a Section 18 label will be petitioned for 2001, and additional evaluations will be done on smutgrass. Sites treated this season will be evaluated next spring to determine if control increases over winter, if application timing can be modified to improve control, if the addition of liquid nitrogen fertilizer to Oasis will enhance activity on smutgrass, or if lack of rainfall and active growth influenced control. By comparison, Velpar treatments looked good for smutgrass control although still expensive (roughly $18 per acre).

Work has also started toward reapplying for the Section 18 for Zorial in bermudagrass pastures for 2001. EPA reminded us this year that little progress had been made by Novartis to get the Section 3 label, so there may be resistance to granting this request in 2001. Agents will be informed via e-mail if these labels are granted.

In soybean, Dr. Al Rankins, Assistant Specialist, Weed Science and I, along with two MSU Weed Science graduate students, conducted a soybean weed survey across the state; 192 samples were taken from 38 counties. Survey sites were randomly selected before the field was in sight. All weeds in a 10-foot square area were identified and counted. The 10 most common weeds in Mississippi soybean were (in order of occurrence) prickly sida, pitted morningglory, entireleaf morningglory, broadleaf signalgrass, nodding spurge, barnyardgrass, yellow nutsedge, hemp sesbania, johnsongrass, and prostrate spurge.

NUTRIENT AND SOIL MANAGEMENT

Dr. Larry Oldham

Someday it will rain again, and there will be another crop. This is the time to start preparing for it. Fall tillage should be done now, while it is dry. I think we eventually will see spring tillage go the way of the dinosaur in the row crop areas of Mississippi. Deep tillage, if it is needed, must be done on dry soils to get the best shattering of the hardpans.

If cash or acceptable dealer terms are available, phosphorus and potassium can be applied, according to soil test recommendations, to soils this fall for the next crop. If you have not developed a regular, planned soil testing program, now is the time to do it. Developing a plan and following it greatly increases the power of the nutrient management process.

More and more Mississippi farmers are adopting conservation tillage as a way to reduce costs as well as being good environmental stewardship. The proper setting of planters is critical to the success of any conservation tillage program. We are in the process of developing a series of planter clinics. These sessions will show and tell growers how to set planters, as well as proper repair or replacement maintenance procedures, to get the best stand in both conventional and limited till systems in a variety of soils, moisture conditions and killed vegetation

We are working with a number of industry partners to provide three clinics in mid-January in Verona, Yazoo City, and Clarksdale.

Upcoming Meetings:

December 6 and 7 - Cotton Short Course, Mississippi State University

January 5 - Tri-State Soybean Forum and Agri-Day, Tunica, MS

February 13-16 - Agronomic Professional Continuing Education Workshop, Mississippi State University

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