Agronomy Notes

October 5, 1999

Contents

COTTON

Dr. Will McCarty

This is a busy fall for Mississippi cotton growers. Harvest of the 1999 crop is not over, and it is past time to make plans and begin preparation for the 2000 crop. The Mississippi crop did not live up to its midseason potential. When the crop hit the first of July, it was showing great potential and driving forward at remarkable speed. As mid-July came and went, heat and drought began to take a toll. While yields will be variable from near average to below, profits will not be strong.

Variety Selection: I think cotton acreage will be slightly down next year, but it is still too early to tell. To be assured of adequate supplies of necessary materials and seed for the 2000 crop, you must make your production decisions as soon as practical. I know it is difficult to do, but you must decide on your acreage soon so you can develop a production plan (acreage, varieties, fertility, row patterns, tillage, etc.), secure financing, and to get the varieties you want to plant.

Variety selection is one of the most important decisions you will make. During the season you may get to make fertility decisions two or three times, insect control decisions are made almost every day, and weed control decisions are made several times. Variety selection decisions are made once or maybe twice. Once you plant and get a stand, you live with it the rest of the season. Generally speaking, there will be little difference in seed cost among varieties, excluding technology fees if applicable; therefore, it cost about the same, or less, to plant an adapted, high-yielding variety as it does one that is not suited to your farm or area. Study variety trial information and your personal experiences; select varieties you feel comfortable planting and feel certain will be top performers on your farm. If you wish to plant new varieties, try only limited acreage. Before you plant transgenic varieties, be sure you need the value-added trait. Also evaluate the yields of varieties with the transgenic trait you desire, and study the risk and benefit ratio, if any. In other words, if you feel you need to plant Bt and the variety does not or has not yielded well for you or in your area, consider the risk of not using it and the potential cost of additional insect control versus potential yield loss to planting it. The same can be said for a transgenic variety for herbicide tolerance. Before you pay extra for the convenience of using a particular herbicide over-the-top, be sure the variety fits your farm and will yield well. Also, consider if you really need that particular program. Is your farm growing up each year? If not, maybe what you are doing is not working, and if the transgenic program cost more, you need to be sure it will yield more. If your fields are growing up, is the problem weed pressure? Management? Weed resistance? What I am saying is that what you are doing may not be all bad and you need an economic incentive to change. If you have a field with MSMA resistant cockleburs, or a similar problem, one of the transgenic programs could be of great help. Remember. Plant the bulk of your acreage in proven performers and try limited acreage of new varieties. Also, transgenic varieties may not preform as well as did their parents. Just because you have had good experience with a particular variety does not mean you will have the same results with a transgenic version. Variety selection is critical. Make good decisions and make them early. More on variety selection as variety trial information comes in.

Other points to consider: 1) Skip row cottonóSkip row production is a means by which the per land acre cost of cotton production can be reduced. With technology fees based on the pounds of seed planted, coupled with reduced cotton prices, this system merits review by many growers. 2) Reduced -till/ no-tillóWith increased labor and machinery cost and reduced cotton prices, a production system using less trips across the field is highly advisable. 3) UNR cottonóThis system may indeed have a place, especially on some of the Hill area soils. These three points are mentioned for your consideration; get as much information as possible.

SOYBEANS

Dr. Alan Blaine

As of September 23, 1999, the Mississippi soybean crop was approximately 50 percent harvested. Yields are extremely variable, with reports ranging from the high teens to some irrigated fields averaging in the high 60s. Yields are much better than expected in some areas.

Some parts of Mississippi have gone almost 3 months without any appreciable amount of rainfall with the northeast corner the hardest hit area. As you look at the state average yield prediction, (25 bushels per acre), there is little doubt this is not an accurate reflection of many farms.

Although the 1999 growing season has dealt a serious blow to the state soybean crop, several scenarios warrant attention.

Over the last few weeks, I have received numerous phone calls regarding deep tillage. Like any practice, deep tillage is a tool. Much of the state's crop was just one rain away from making above-average yields; however, that one rain never materialized. Although deep tillage can and will help, it could only hold this crop up for so long.

Expecting a response to deep tillage every year on all soil types is not possible. The only reason growers have been able to observe a response to deep tillage is the fact they are growing some early maturing varieties (Group IVs, corn, etc.) and planting early. If not for these two options, the window of opportunity for deep tillage would never have presented itself. The fact that deep tillage has entered the picture is not to say that reduced tillage is not a viable option. The response to deep tillage will be variable, by soil type and by year. Regardless of the growing season, the greatest response will be observed on mixed soils. As soils get heavier, the yield responses decrease. Researchers have found that deep tillage has a carryover effect. On heavy soils, a response has been observed to every other year but we may go to every third year. Response on mixed soil will be much more consistent and should be considered more frequently.

I spoke to a producer who did some deep tillage last fall in areas of a field he could not irrigate. He told me that one dry corner where he did not deep till cut 13 bu/A and another corner where he ran a Ripper cut almost 30 bu/A. He is currently leveling this field and said where he ran the ripper the ground was wet or sticky compared to the nonsubsoiled area. Subsoiling is a viable option; unfortunately over the last 2 years, yield responses have been less than expected.

Concentrate on using deep tillage as part of a tillage rotation program much like crop rotation. There will be springs when fall tillage will have a negative impact on early planting. Consider tilling your dryland acreage every other year or on heavy soils every third year. This would put you in a situation where not all of your acreage would have to be tilled in the fall, and in the likelihood of a wet spring, only a portion might be subject to planting delays. Remember. This is currently a practice recommended for dryland fields only.

In addition to questions regarding deep tillage, we are seeing a tremendous break in yields from later planting. This growing season, it appears that soybeans planted after mid-May are taking a pretty good hit yieldwise.

Numerous disease problems cropped up throughout the growing season, but the one most widespread is charcoal root rot, which is induced by stress because of wet or dry conditions. Charcoal is extremely widespread and most noticeable before harvest. Charcoal attacks a plant's root system causing plants to shut down prematurely. It is usually observed in sandy areas first following an extended drought. Currently there is no known resistance to charcoal root rot. Deep tillage, varieties, maturity groups, crop rotation, and early planting are practices that can help minimize this problem.

It will be early December before complete variety trial information is available. Variety selection continues to be the most important input, with the exception of water. Take some time in making this decision. Base the bulk of your decisions on past experiences. If you want to try some new varieties, do so on a limited acreage. This year we entered more than 200 varieties in the state yield trials; over half of these were Roundup ready lines. Order early, if possible, and make your choices based on your needs and consistent performance. Although 1999 was a difficult year, some obvious choices should still stand out.

CORN

Dr. Erick Larson

Fertility ProblemsóFall is the best time of year to address many fertility problems. Soil acidity is a perennial problem due to Mississippi's 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 many fertility problems. For example, it is common to see corn phosphorus deficiency following a cotton crop. This is because corn's phosphorus requirement is much greater than cotton's requirement. Soil testing for corn provides a phosphorus recommendation that will prevent this problem. Thus, take soil samples this fall so incorporation and neutralization of lime and broadcast fertilizer can occur before next spring. Delay application of potassium on low CEC soils until spring because of leaching problems.

Fall Johnsongrass ControlóFall 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 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. Successive tillage after chemical application should preferably be delayed 4 to 6 weeks.

WHEAT

Dr. Erick Larson

Wheat VarietiesóThe 1999 MSU Wheat Variety Trials are available at your county Extension office. Base your variety evaluation primarily upon your area of the state, variety yield history, expected planting date, soil type, and variety disease resistance. My list of recommended varieties for north Mississippi and the Delta include AgriPro Shiloh, Mallard and Patton, FFR 522W, Northrup King Coker 9663, Pioneer 2684, Roane, and Terral TV 8555. In south Mississippi, variety choices become more limited due to the warmer winter climate. This eliminates use of many Ohio Valley-adapted varieties that need substantial cool temperatures to trigger seed head development (vernalization). The highest yielding varieties that meet these vernalization requirements for south Mississippi are AgriPro Shelby and Mason, NK Coker 9663 and 9835, and Pioneer 2684 and Terral LA422. Characteristic profiles of these recommended varieties are listed on the MSU Extension Service grain crops web site, or contact your county Extension agent for a copy.

Planting datesóMany producers plant wheat too early to maximize yield potential. Planting wheat early increases stress (fall drought stress, spring freeze injury) and promotes pest problems (Barley yellow dwarf and Hessian fly damage) with little advantage. The optimum wheat planting date should be within 2 weeks of the first fall frost date. This normally corresponds to: 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 RatesóProducers 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 then calculate how many pounds of seed per acre you need. For example, 1.35 million seed 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.

SOIL AND NUTRIENT MANAGEMENT

Dr. Larry Oldham

Get your soil samples pulled now! It's a lot easier to get out in front of the fall and winter rains than to sit around and wait for it to dry up next spring. October is probably the optimum time to apply lime. Soils are usually pretty dry, and it will have the maximum time to neutralize soil acidity before next year's crop.

I would prefer lime be applied before any fall tillage; however, if it is needed, do not hesitate to leave it on top of the ground. The weather will help you get it reacted with the soil. Fall is also a good time to apply phosphate and/or potash fertilizers on soils with CEC's greater than 8. Lower CEC soils will not have the capacity to hold the potash against leaching through the winter.

FERTILIZERS INCREASE THE SUSTAINABILITY OF CROPS

Dr. Malcolm L. Broome

Until fertilizers became widely used, farmers were constantly searching for new land on which to grow crops. The increase in use of fertilizers has enabled farmers to grow crops continuously on land that otherwise would have been abandoned. During the period of seeking new land, crop yields were maintained or increased by animal manures, green manures, crop rotations, and lime.

On large acreages these practices did not supply sufficient plant nutrients to sustain crop yields. Commercial fertilizers have supplied sufficient nutrients to maintain or increase crop yield. As a result, the search for new land is mostly a relic of history.

Plant nutrients provided by fertilizer promote a more vigorous, healthy, and productive crop. This is apparent by the plant's developing a greater root system, more above-ground residue, quicker ground cover, greater water use efficiency, and higher resistance to crop stresses produced by the environment. However, if farmers don't adopt management plans to achieve production and environmental goals, sustainable crop production will be limited.

Goals that should be a part of a fertility best management practice(BMP) or plan: 1. Yield goals should be optimistic, yet realistic for each crop but also for each field. Nutrient requirements increase with yield, and it is a BMP to be sure that adequate but not excessive nutrients are readily available to the growing crop from seeding through to maturity. 2. Soil testing and even plant analysis, if needed, are the best tools available to determine the amount and availability of soil nutrients and the amounts of nutrients that should be applied to achieve the yield goal. 3. Soil and water conservationóBMPs for soil and water are site-specific, and a good plan for each farm can be the single most important factor in decreasing soil erosion and the potential loss of nutrients, especially phosphorus attached to sediment and organic particles. Some form of conservation tillage can be practiced in virtually all types of farming systems. 4. Adopt BMP's of all controllable inputsóHigher yields, with their associated increases in crop residues, have positive impacts in reducing water runoff and erosion losses. Research shows that as crop residue was increased from one-quarter ton per acre to one ton per acre, soil loss decreased ten-fold. 5. Using an application timing plan is especially important for nitrogen efficiency and yield potential. Consider making applications as close to the time of greatest crop uptake. Not only will this BMP increase yield potential but environmental protection is enhanced. 6. Fertilizer placement plans are keys to higher yields in rates, timing, and placement. New fertilizer equipment technology makes it possible to place nutrients correctly with increased accuracy and with a minimum of delay.

The use of adequate amounts of plant nutrients for optimum crop yields and profitability is essential for sustainability. BMPs developed through research, modified and adopted for site-specific conditions, are a key to efficient use of nutrients and protection of Mississippi's soil and water resources.

SOIL TESTING

Dr. Keith Crouse

A question that the MSU Soil Testing Lab has received more than once over the past few days is will 500 pounds of pelletized lime equal to 2,000 pounds of aglime per acre? If a soil test lime recommendation calls for 1 ton per acre, that means 2,000 pounds per acre.

Pelletized lime is a fine-ground limestone material pelletized with an aid of clay or synthetic binders to typically provide pellets in the 5- to 14-mesh range. Pelletized lime is made up of the fine-ground limestone material (finer than 100-mesh), which means it is a relatively fast acting material; however, research shows some synthetic binder used may inhabit disbursement of the pellets, thus increase the amount of time it takes to neutralize an acid soil. An advantage of pelletized lime is that it is easier to spread as compared to pulverized aglime.

One ton of a typical aglime contains about 500 pounds of particles finer than 100-mesh, which brings about the rapid soil pH change. The rest of the other particles provide medium and long-term acidity neutralization, which prevents the need to relime each year.

These particles of aglime finer than 100-mesh are used to make up pelletized lime. Even though each ton of aglime has about 500 pounds of fine material (finer than 100-mesh), that doesn't mean that 500 pounds of pelletized lime have the same neutralization value of 1 ton of aglime. Using pelletized lime at a rate of 500 per acre requires more and frequent applications to meet a ton of aglime per-acre recommendation to adjust the soil acidity.

WEED CONTROL

Dr. John Byrd

The last two agronomy notes articles have been focused on preharvest weed control and postharvest perennial weed control. Last month, I referred to Banvel SGF for postharvest weed control in corn, cotton, and soybeans. One of the difficulties of using a postharvest treatment in soybean for perennial weed control is the combine header removes the weed foliage that should be treated. Time for weed regrowth must occur for treatments to be successful. Frost often occurs before sufficient regrowth develops. However, Clarity has been labeled for preharvest applications in soybeans for perennial weed management. Clarity contains 4 lbs. acid equivalent dicamba and is essentially the same as the old formulation of Banvel, except Clarity contains a diglycolamine formulation of dicamba which is supposed to be less volatile. Clarity can be applied at 8 to 64 oz per acre either as a broadcast or spot treatment after soybean pods are mature brown color and at least 75% of leaves have dropped. An interval of 14 days between application and harvest should be followed. Soybean treated with Clarity as a preharvest treatment should not be used for seed unless acceptable results are obtained from a germination test. In cotton, postharvest applications of 8 to 64 oz per acre can be used for perennial weed management. Clarity can also be used for spring preplant weed burndown, but combined postharvest plus preplant applications should not exceed 64 oz. per acre.

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