Agronomy Notes

March, 2004

CONTENTS:

RICE
SOYBEANS
SOIL & NUTRIENT MANAGEMENT
FORAGE
CORN
WHEAT

 

 

 

RICE
by Dr. Mark Kurtz

Rice planting in Mississippi is fast approaching. Many farmers will be putting down Command (1.125- 1.6 pt/A depending on soil type) for preemergence grass control, however, some may choose not to. Mississippi has applied for a 24 (c) registration for the aerial application of Command and it should be ready for the 2004 use season. For those choosing not to use Command, Facet (0.33-0.67 lb/A)+ pendimethalin [(Prowl or Pendimax) at 1.8-2.4 pt/A] delayed preemergence is a very good choice. In either case you will more than likely need a postemergence treatment prior to permanent flood to control emerging broadleaf and grass weeds.

We have many options available for this preflood timing. Propanil (Stam, Riceshot, SuperWham, and Arrosolo) is one of our most versatile herbicides and although it has been around a very long time, still offers a good choice for control of both grass and broadleaf weeds at 3-4 lb/A. These propanil containing products can be applied in split applications up to a total of 8 lb/A total per season. If annual grasses are your only problem, Clincher (13.5-15 fl oz/A) or Ricestar (13-17 fl oz/A) can be used. Remember that soil moisture is very important at this timing. Regiment (0.4-0.67 oz/A) will control barnyardgrass, hemp sesbania, and some aquatic weeds. Aim (1.6-3.2 fl oz/A), Grandstand (0.67-1.0 pt/A) and Permit (0.666-1.33 oz/A) can be used when broadleaf weeds or sedges are a problem. If grasses are also present and you want to tank-mix these products, check the label of the companion herbicide for use.

Clincher is a good choice for salvage control of annual grasses in the flood and Regiment will also give control of barnyardgrass, hemp sesbania, and will suppress smartweed at this timing. Do not make applications after panicle initiation.

Red rice, when present, has been and continues to be a very serious weed. With the advent of the Clearfield system we now have a viable option for control.

Newpath can be applied preplant incorporated or preemergence at 4 fl oz/A and must be followed by Newpath 4 fl oz/A postemergence on Clearfield rice only. Newpath can also be applied as two postemergence applications at 4 fl oz/A each. The first application, to enhanced Clearfield varieties, is at spike - 1 leaf rice followed by a second application at 10 to no more than 14 days later when rice is at the 3-5 leaf stage. Mississippi has also requested a 24(c) registration of Beyond for control of escaped red rice and it must be applied from tillering until panicle initiation of Clearfield rice, following 2, 4 oz/A applications of Newpath. It is not sure at the time of this printing that either 24 (c) registration mentioned above will be available for the 2004 production season. Check with your Extension specialist prior to use of either Command by air or Beyond for red rice control.

SOYBEANS
by Dr. Alan Blaine

Hopefully by now varietal decisions have been made. If not this decision should be made as soon as possible. Variety information is available on the internet and has been for several months. If you have not made your selection, I advise you to do so. We had an excellent harvest season so seed quality should not be a major issue. Keep in mind varieties with the best performance history will go first.

In order to meet your needs, companies must look into their crystal ball and plan a year in advance of what varieties will be needed. Although, this is difficult it is frustrating that we do not plan better than we do. In addition, to offering many different varieties, companies would be better off to grow larger quantities of 2-4 of their best lines and if their competitors could not meet market demand, they could.

Every year the most sought after varieties are never available in sufficient quantities. In my opinion this is the major point where I disagree with patented varieties. If you want to hold a patent, you need to supply the market. I can not think of another example where the free enterprise system fails except in this regard. If you go to Walmart and want "x" item you can get it, if they are out they will have some more next week. It is based on this situation that I question our current seed supply scenario.

After you have made varietal decisions attempt to find out as much as you can about the quality of your planting seed. As a result of the favorable growing and harvest season last year, I expect two things to happen: 1.) seed as a whole should be of fairly high quality, and 2.) seed size should be larger than average.

Regardless, there are two things you should do every year to allow you to better know the varieties you have purchased.

First, ask for the actual germination. If it was not conducted within the last three months run a new germination test. Ask for any additional vigor tests. These tests can help you determine the quality of your planting seed. If no additional tests were conducted you should have additionals test run. Seed vigor is very important especially, when planting under less than optimum conditions. Also, additional tests will help you verify which materials such as Thiram, Vitavax, etc., are needed as a seed treatment.

If you have some seed lots that are of less quality than others they should be planted last or under more optimum conditions. Take delivery of seed early or obtain as much information as possible prior to planting. Lower quality seed will translate into poor quality, slow growing plants; a condition you will live with all season long.

Under adverse harvest conditions materials such as Thiram, Vitavax, and Maxim (examples) can improve germination. With the early planting system a full spectrum seed treatment is a must. I will admit I am shocked that producers still attempt to plant a crop with little or no seed protection.

All seed treatments are not created equal. Do not take a chance. Utilize a broad spectrum treatment that includes Apron plus a product such as Vitavax or Maxim. Most of the broad spectrum mixes also include Thiram, a seed protectant.

Use of a broad spectrum seed treatment can help avoid replanting. A combination of high quality seed, proper seed placement, a broad spectrum seed treatment, and in some cases a bed plays a major role in getting a stand the first time. Keep in mind using the proper seed treatment is nothing more than insurance. If a seed treatment saves you a replant just one year you will have paid for 10-12 years of seed treatments. Replanting will cost you yield not to mention additional time and expense.

In order to reduce seed treatment costs, many are using only Apron and Thiram. This is fine (at times), but if seed possess seed borne fungi this is not broad spectrum enough.

If you are planting early, or have to do a lot of replanting every year, make plans to protect your crop at the start. Seed treatments may not result in an increase in yield, but failure to use the proper seed treatment may result in replanting and this delay will cost you yield.

SOIL & NUTRIENT MANAGEMENT
by Dr. Larry Oldham

There is concern about increased nitrogen (N) fertilizer cost for the 2004 production year by producers and consultants. Nitrogen is essential for plant growth, but soils typically do not supply sufficient quantities for maximum and economic production of non-legume crops. In Mississippi, N fertilizer normally is used in cotton, corn, rice, grain sorghum, pasture, and forage production.

Natural gas accounts for 75 to 90 percent of the cash cost per ton of N fertilizer manufactured. Hydrogen from natural gas is combined with atmospheric nitrogen to synthesize anhydrous ammonia that can be used as fertilizer or further processed into other fertilizer products. Nitrogen fertilizer supplies and prices have been an issue since a 400% increase in natural gas prices in the winter of 2000-01. Natural gas prices decreased after that spike, but have recently climbed due to a variety of factors.

MSU-Extension Service N application rates are calibrated to provide sufficient nutrient for the current crop, and not have a detrimental effect on the environment. Producers these recommendations should concentrate on more effective and efficient fertilizer management strategies rather than cutting N applications from the recommended levels.

Nutrient Management Planning principles provide a framework for economical and environmentally friendly use of plant nutrients.

1) Soil test for P, K, pH, and lime requirement. The results will include a N recommendation based on the crop identified with the sample submission. The N recommendation is not based on a lab analysis of the soil sample at MSU.

2) If manures or sewage sludges are used, obtain nutrient analysis for that material.

3) With the above information, use the Best Management Practices listed below to plan and implement a soil fertility program.

Best Management Practices are cost-efficient operation methods that ensure that fertilizers are used effectively with minimal impact on the environment.

  • Use realistic yield goals. Use average crop yields from the past 3 to 5 years, then add 10% for a realistic projection of the production potential on your soils, using your production management, in your climate area.
  • Use the most suitable nitrogen fertilizer source, depending upon the crop, application method, and climatic conditions. Some fertilizers work better in certain situations due to climate and soil conditions. For example, anhydrous ammonia is lost due to incomplete soil sealing when soils are wet.
  • Price fertilizers on the cost per pound of nutrient. This is the best way to compare cost of nitrogen among equivalent sources. (Price per ton of fertilizer)/(2000 x material N content as decimal value)

    Example 1: UAN at $185 per ton with 32% N content ($185/ton) / (2000 lbs/ton x 0.32 N) = $0.289/lb N or $0.29 cents per pound of N

    Example 2: Ammonium nitrate at $250/ton with 33% N content ($250/ton) / (2000 lbs/ton x 0.33 N) = $0.379/lb N or $0.38 cents per pound of N

  • Use proper application techniques. Use the correct technique for the particular situation. Refer to the specific commodity pages for more particular information.
  • Maintain and calibrate application equipment. Improperly maintained and poorly set equipment 'steal' crop input dollars. Make sure owned equipment is properly working and calibrated. Confirm with custom applicators that they have calibrated the equipment.
  • Avoid application to surface waters. Care must be taken to avoid direct application to any surface streams.
  • Time application properly for the crop. Nitrogen use efficiency is best when applied close to the time of crop uptake. We hear reports every year of N application to fields for cotton several weeks prior to planting. These increases the probability of N loss from the field, and may necessitate supplemental N fertilizer later in the growing season.
  • Control soil erosion. Nutrients move when soil particles move. Using soil conservation keeps soil and nutrients where they can be utilized by growing crops.
  • Properly control water flow. Nitrogen movement in the landscape is closely linked to water movement. Slow water down when appropriate by conservation practices.
  • Use cover crops, and maintain crop residue on the soil surface. Cover crops reduce the likelihood of N movement in the landscape by 'scavenging' N left in the soil profile after the previous crop. Using the residual N increases cover crop dry matter production, thus enhancing soil quality attributes such as soil organic matter levels and tilth.

For more information on optimizing nitrogen fertilizer management, visit the recently updated Fertilizer Management page at: http://msucares.com/crops/fertilizer/.

FORAGE
by Dr. Richard Watson

Managing the transition from cool-season to warm-season forage production.

To achieve year-round grazing (or close to it) in Mississippi we need to utilize a combination of cool season and warm season forage species. Most commonly, we rely on annual ryegrass, and tall fescue on the heavier soils, to provide the bulk of our cool season forage supply, and then bermudagrass and bahiagrass to take care of our summer forage needs. While this is a great system for providing forage for most of the year, the transition from cool-season to warm-season production is not always a matter of one type of grass picking up where the other left off. For instance, annual ryegrass, which provides us with large quantities of high quality forage during the late fall, winter, and spring, will often shut down and die before the warm season grasses have had a chance to accumulate enough forage to meet our needs.

How we manage this transition from cool to warm-season production depends on the forage species we are using, and whether we have monocultures (a single grass species in each pasture), or mixtures of warm and cool-season species in the same pasture (e.g. a tall fescue/bermudagrass mix).

In general, monocultures are easer to manage as we can apply management strategies that suit the individual species, without needing to consider the differing needs of any other species present. However, due to the seasonal production of forage grass species, a single species pasture will be unproductive for at least some of the year, requiring us to have alternative species in other pasture to produce our forage needs.

On the other hand, a mixture of cool and warm-season forage species in the same paddock provides us with a pasture that is productive for more of the year but requires more careful management.

Transitioning from cool to warm-season production with single species pastures.

Cool-season forage species, such as tall fescue and annual ryegrass, should be managed to extend their production as far as possible into the summer so that the warm-season grasses, such as bermudagrass and bahiagrass, have more chance to get going before you need to graze them. The key to doing this is careful timing of nitrogen (N) applications and grazing the pastures to reduce the production of seed heads. Most of the annual ryegrass varieties used in the south are early-flowering so there is only so much grazing management and fertilizer applications can do to prevent these varieties from going reproductive and dying. However, we can often accumulate enough forage in April to help carry us through May, and into June when the warm season grasses are able to take over. Nitrogen applications of 50-60 lb/acre (actual N) in early February will help the annual ryegrass pastures remain vegetative and produce enough forage for use in May.

Tall fescue is much easier to keep growing into the summer and will even continue to grow throughout the summer if moisture is not limiting. In cases where you want to promote fescue growth into the summer, it is advisable to use one of the later-flowering, summer-active fescue varieties. Ideally, we would like to have at least some acreage of tall fescue to help bridge the gap between annual ryegrass and bermudagrass production. Unfortunately, the use of tall fescue is generally restricted to the heavier clay-based soils of northern Mississippi, so further south we are more likely to be using annual ryegrass for our cool season production. Tall fescue will also respond well to 50-60lb of N/acre in early February. Further application in late spring will also help continue growth into the summer so long as there is still moisture around.

Transitioning from cool to warm-season production in mixed pastures where annual ryegrass has been interseeded into bermudagrass sod, we need ensure that the ryegrass forage is removed by May so it does not hinder the new bermudagrass growth. This can be done by close grazing and/or making hay from any excess growth. While an early N application is still recommended for the annual ryegrass in early February, any later applications in late February or early March may promote annual ryegrass to grow too aggressively for the new bermudagrass growth to take off. Over time this can lead to sever thinning of the bermudagrass stand. An application of at least 100 lb N/acre in late April should be too late for the annual ryegrass to use and will help give the bermudagrass a much needed boost.

More care will need to be taken where tall fescue is mixed with bermudagrass as there is a longer period of time that both species are actively growing. Applications of N (at similar rates to the ARG/BG mix) in February for the fescue, and late April/early May applications for the bermudagrass should ensure that you favor each species at the appropriate time. Make sure the tall fescue stand is grazed down tight during May to allow the bermudagrass to reestablish itself. Keeping a close eye on your pastures will give you an idea for when the pasture is either fescue or bermudagrass-dominant, and be able to respond accordingly with fertilizer and grazing pressure. It is possible that early flowering, summer-dormant tall fescue types may be more compatible with bermudagrass in a mix, particularly where fescue has a tougher time surviving the hot summer on more sandier soils. In the future, I will be evaluating fescues with different flowering dates to see how well they complement bermudagrass in a pasture mix.

CORN
by Dr. Erick Larson

Plant density - Growers should strive for 24,000 to 32,000 plants/acre depending upon mainly upon a field's yield potential, planter row width and planting date. If a corn yield goal of 200 bu./a. (50 bu./a. soybeans or 2 bale cotton) is realistic, particularly under irrigation, then strive for 28,000-32,000 plants/acre. If this goal is unrealistic, then lower the seeding rate accordingly - do not generally exceed 28,000 plants/acre in dryland culture! Also, row width changes optimum plant population because it ultimately affects plant spacing. Seeds spaced closer than six inches apart increase competition for light, water and nutrients which weakens stalk quality without increasing yield potential, particularly under stress. Thus, optimum plant population in wide rows is generally around 2,000 - 4,000 plants/acre less than narrow rows. Remember to over plant desired plant population about 5 to 10% depending upon seed germination and planting conditions. Early planted corn (soil temperature 50-55 degrees F) should be seeded slightly thicker than normal because cool spring conditions promote higher seedling mortality and cause shorter plants at tassel, meaning more plants are needed to intercept light. Conversely, growers should lower seeding rate with later planting dates since warm soils enhance seedling establishment, taller plants are produced and yield potential decreases.

Plant uniformity - Francis Childs, 5-time NCGA corn yield contest winner and world record holder (442 bu./a.) year, says "Root systems and uniform stands are the foundation of high corn yields." Poor corn plant spacing and seeding depth are common problems that can affect yield potential as much, or more than your actual plant population. Planter meter system tune-up and calibration can certainly improve planter performance, but performance also depends upon planter operation in the field. One common cause of seed distribution problems is excessive planter speed. The standard maximum performance speed for plate and finger-pickup planters is 4.0-4.5 mph and vacuum-type planters is 4.5-5.0 mph. Speeds exceeding these values can also contribute to much poorer seed spacing and less seed depth uniformity because seeds may roll and/or bounce in the seed furrow. Corn plants are extremely sensitive to plant spacing because they do not tiller or produce branches to alter their plant size. Crowded or late-emerging plants produce small ears and spindly stalks due to intense competition for light, water and nutrients with their neighbor. Corn seed is available in numerous combinations of size and shape which may further aggravate planting problems. Growers with plate-type planters should match planter plates with their seed size. Likewise, growers with vacuum-type planter should match disc size with seed size and match air pressure with their seed. Excessive wear to planter plates or finger pick-ups often also cause major problems - just because something worked last year, doesn't necessarily mean it will this year.

Planting depth - Many producers unfamiliar with corn seedling development plant corn too shallow. Corn seed should be planted 1 ? - 2 inches deep. Planting depth should be set in the field during planting. This is important because soil type, seedbed condition and moisture may influence actual depth. Corn seed's inherent energy and germination process ensure emergence from depths as great as 3 inches. The origination point of the nodal root system is moved upward when corn seed is not planted deep enough. Corn seed placed less than 1 inch deep will develop nodal roots at or above the soil surface. This exposes these roots to factors such as hot, dry soil, herbicide injury, and insect predation which can significant impede root development. This often leads to standability problems, nutrient deficiencies and even drought stress throughout the year. Birds may also cause stand loss by extracting shallow planted corn seeds.

Starter fertilizer - Many corn growers utilize starter fertilizer to supplement their corn fertility program. Starter fertilizer enhances vigor, promotes earlier maturity and often improves grain yield, particularly in minimum or no-tillage systems. Starter fertilizer enhances growth primarily by providing a concentrated phosphorus supply in the root zone of young plants. Phosphorus placement is very important too young plants with small root systems because phosphorus is not mobile in the soil. Growers applying starter fertilizer in the seed furrow should apply a maximum of 4 gallons per acre in 38 - 40" width rows or 5 gallons per acre in 30" width rows, or salting injury may occur to seedlings. The most commonly used source of starter fertilizer is ammonium polyphosphate (10-34-0 or 11-37-0). Orthophosphate fertilizers are also available, but are much more expensive and have seldom shown any superior response to supply phosphorus in field trials.

Bt refuge - Growers can plant no more than 50% of their corn acreage in Bt hybrids trademarked YieldGard which contain the MON-810 insertion event. Growers will be required to plant an equal acreage of non-Bt corn as a refuge within a half mile of their Bt corn. Neighbors' conventional corn does not count as refuge. The non-Bt refuge may be treated with insecticides (excluding sprayable Bt products) as needed. Thus, growers should plant their refuge as a separate block, so they may manage it separately, if infestation warrants insecticide treatment.

Roundup Ready / Johnsongrass: Although glyphosate should offer excellent Johnsongrass control, growers should carefully analyze hybrids for resistance to Maize Dwarf Mosaic Virus (MDMV) before positioning a specific Roundup Ready hybrid in a field heavily infested with Johnsongrass. Aphids vector MDMV from Johnsongrass to corn plants. When the Johnsongrass host is controlled during the season with glyphosate, mass aphid migration to corn may promote considerable MDMV infection on susceptible hybrids.

Prevent stand loss - Growers who wait to apply a burndown herbicide near planting greatly increase their likelihood of experiencing stand loss from cutworms. Cutworms feed on green winter weed vegetation present in fields during the early spring. If a burndown herbicide is applied near planting, cutworms will still be present and will be forced to feed on freshly emerging corn. Thus, growers should use a labeled pyrethroid before corn emergence or with the burndown herbicide to control cutworms, unless a granular insecticide or labeled seed treatment is used at planting.

WHEAT
by Dr. Erick Larson

Late nitrogen application - Frequent February rainfall likely prohibited or delayed nitrogen application on many wheat acres. Wheat growers still have ample time to apply nitrogen without reducing yield potential, particularly if a first split application was applied during February. Cool February temperatures slowed wheat growth more than normal, slightly prolonging the optimum timing for nitrogen fertilization. However, the final nitrogen topdress should be applied by the time the first node appears at the beginning of stem elongation (jointing, Feekes growth stage 6). This application delivers the main nutritional needs of the crop. Growers should never apply nitrogen fertilizer to wet, saturated soil.

 

Dr. Frank Matta, Interim Department Head
Department of Plant and Soil Sciences
Box 9555
Mississippi State, MS 39762
(662) 325-2701

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