Agronomy Notes

February, 2004

CONTENTS:

CORN
WHEAT
RICE
SOYBEANS

 

 

CORN

Dr. Erick Larson

Managing Weather Limitations - Growing corn in Mississippi can be very profitable, but does have considerable risk which producers should address with management practices. The primary environmental risks include wet springs and hot, dry summers. Growers should utilize raised beds on fields with marginal drainage to relieve potential waterlogging and warm the soil for better seedling establishment and vegetative development. Early burndown herbicide application helps both these problems because it promotes warmer, drier seedbeds during the spring and encourages earlier planting. Early planting helps corn avoid stress associated with mid-summer drought. Irrigation can help alleviate water stress, but does not over-ride the importance of early planting (because of heat stress).

Burndown herbicide timing: Moist soil conditions often severely restrict planting time during the optimum corn planting period. Utilizing a late winter burndown herbicide to control winter vegetation allows producers to manipulate soil moisture and encourage earlier planting. Killing winter weeds several weeks before planting allows the soil to absorb much more solar energy, compared to soils covered by a blanket of lush weed vegetation. This warms and dries the soil, which allows earlier planting and promotes corn seedling vigor. Burndown herbicides utilizing glyphosate should be applied four to six weeks before planting (this month) to gain these advantages.

High Yield Key: Someone recently asked for a hybrid suggestion that had 250 bushel per acre yield potential. Actually, nearly all corn hybrids possess the potential to yield well more than 250 bushels per acre. In fact, a hybrid available in Mississippi produced a world record 408 bu/A a few years ago in east central Iowa. It is up to us to manage our corn crop so we may harvest as much grain that mother nature will support. Without downplaying the importance of hybrid selection - inadequate fertility may limit corn yields

statewide more any other management input. Everyone knows corn requires substantial nitrogen application; however, nitrogen does not normally the nutrient limiting yield. Corn requires nearly twice as much phosphorus and about 40-50% more potassium compared to cotton and soybeans. Additionally, low soil pH (below 6.0) substantially restricts nutrient availability and stunts crop growth drastically (resulting from increased availability of toxic elements) at pH below 5.5.

Risk of ultra-early planting: Abnormally warm, dry conditions sometimes allow an opportunity to plant corn during late February or early March. Although early planting is a critical component of successful corn production, planting corn extremely early (well before recommended dates), even if soil temperatures are warm, provides little if any agronomic benefit, while risking stand failure. Extraordinarily early planting enhances maturity very little, because corn growth rate is correlated to temperature, and heat unit accumulation (GDD 50) is historically very low during early March.

Guidelines for corn planting date: The standard guideline for determining earliest planting date is when morning soil temperature, at a two inch soil depth, is 55 degrees F or 50 degrees F at a 6 inch soil depth. Planting before the soil temperature is warm enough for germination greatly increases the potential for stand failure, because germination growth rate is dependent upon soil temperature. Soil temperature may vary depending upon soil texture, slope, or color and amount and type of crop residue. Thus, randomly measuring soil temperature with a thermometer within a field should provide a reliable indicator of desirable conditions for stand establishment. Corn produces highest yields when planted within 4 5 weeks after soil temperature is warm enough for germination. This has historically corresponded with the following calendar dates:

Geographical Region of Mississippi:

  • Southern : February 25 March 15
  • Central: March 5 April 10
  • North-Central: March 15 April 20
  • Northern: March 20 April 25

Aerial burndown restrictions: The Mississippi Department of Agriculture and Commerce will institute restrictions of burndown herbicides by aircraft to prevent off-target drift again this spring. This years restrictions will be the same as last year. Delta counties will be divided into two zones (north and south) divided by Highway 8. Aerial applications will be prohibited in the South zone from March

15TH through April 30TH, and the North zone from March 25TH through April 30TH, except by permit from an authorized Bureau of Plant Industry employee.

WHEAT

Wheat nitrogen fertilization: In the midsouth, nitrogen application timing typically has a significant effect on wheat productivity. The initial topdress of a split application should be applied when dormancy breaks in latewinter during tillering stages (Feekes growth stage 3 or 4 - normally early February) and not exceed 50% of the total seasonal amount. The purpose of this application is to promote tillering and head size. The final topdress application 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. This generally occurs in earlyMarch. Growers who choose to apply spring nitrogen in a single application should time it at Feekes growth stage 4 or 5. Recommended spring nitrogen rates vary from 90 140 lbs./a. with higher rates within this range recommended on clay soils and high yield potential wheat. Ureaammonium nitrate solution (Nsol 32%) topdress applications should be limited to a maximum of 50 pounds N per acre to prevent substantial leaf burn.

RICE

Dr. Tim Walker

It is nearly that time of year again. Last year, because of favorable spring weather, a considerable amount of rice acreage was planted from late March to early April. If that same weather pattern is present in 2004, you will want to be sure you use a good fungicide seed treatment. Speaking of seed treatments, if you intend to use Icon™, you should see your seed dealer immediately to check its availability. Bayer will not retain Icon™ beyond this growing season; however, other companies will have the opportunity to purchase it from Bayer. In small plot work, Icon™ has increased rice yields consistently where rice water weevil damage is a problem. In addition, when Icon™ treated seed is used on the levees, cattail billbug damage is reduced up to 50%.

Mark Kurtz and I have just completed writing support letters to BASF in their attempt to obtain a section 24-C for Beyond™ for use in Clearfield rice. Beyond™ is in the same herbicide family as Newpath™; however, if the label is approved, it can be applied to rice from tillering to panicle initiation in addition to the labeled rates of Newpath™. Let me stress that Beyond™ is not a replacement for Newpath™. If you plant Clearfield rice, you must apply two applications of Newpath™. Beyond™ should be strictly used as a treatment to kill escaped red rice. Remember the importance of moisture on Newpath™ activity. Depending on the weather that we have, flushing may be necessary to activate Newpath™. Beyond™ has little persistence in the soil; hence this application will not affect crop rotation in the same way that applying a late application of Newpath™ would.

Seeding rates should be considered before you go to the field to plant. If you are planting more than one variety on your farm, chances are you will need to adjust your planter before planting a different variety. Because of the number of varieties we are planting and the differences in seed sizes, planting in terms of seeds per square foot is more appropriate than planting an arbitrary number of pounds of seed per acre. For example, if you plant Cocodrie, Francis, and Priscilla at 90 lb/a, you are planting an average of 38, 43, and 34 seeds/ft2, respectively. The MSU-ES recommendations are to plant a target of 30 to 40 seeds/ft2. On well prepared seed beds, and where seed treatments are used, 30 seeds/ft should be sufficient. This target can be reached with 62 lb/a Francis, 70 lb/a Cocodrie, and 80 lb/a Priscilla. I would suggest lowering seeding rates only if seed beds are well prepared. For information regarding seeding rates for individual varieties and calibration, please contact me at the Delta Research and Extension Center.

The final production reminder for this article is soil sampling. I have had numerous producers approach me this winter stating that their yields are not where they want them. These are not producers stating that yields are 180 bu, and they want 200 bu; but many are cutting in the 120 to 130 bu range. The first question I ask is "Have you soil sampled lately". If your yields are still below average, I would check my fertility levels first. If your soil test levels are sufficient, then we can move on to other possible problems. On the other hand, if soil test levels are deficient, the proper rates and application times of nutrients can greatly improve yields. Phosphorus deficiency is one of the more common nutrient deficiencies that I have seen in the last several years; however, without a soil test, it is difficult to detect until after flood establishment. An application of P into the flood water will increase yields compared to where no P is added; however, if the P is applied between planting and 3 to 4 leaf rice, yield results will be more favorable. I would recommend sampling fields that were planted to soybeans in 2003. Sampling behind rice fields often leads to false results because the soil chemistry is greatly affected by the flooded conditions. If you have any questions, contact me at 662-822-2291.

SOYBEANS

Dr. Alan Blaine

The January crop report increased the Mississippi's state average yield from 36 to 39 bushels per acre. This crop exceeded our best ever crop in 1992 by 5 bushels per acre.

Many changes have occurred over the last 10 years, and if we will concentrate on the basics we can continue to achieve above average yields. Although many decisions go into producing a crop there are 4 criteria that have had the greatest impact on improving yields in recent years:

  • 1. New high yielding varieties/earlier maturity groups
  • 2. Earlier planting dates
  • 3. In season scouting
  • 4. Irrigation scheduling

With the shift to earliness another change is occurring that needs more thought than many have given. In late November, dollar plus premiums were being offered for August delivery; and based on the number of questions, I realize that many are getting on board.

The main thing that concerns me is that many are going to plant Group III's and early IV's that have never planted beans of this maturity (4.5 or less) ever before.

Based on the interest, I am going to attempt to tell you what we know about early planting and some do's and don'ts regarding AUGUST delivery. First, this is predominantly a dryland system. You can make August delivery with Groups III's and early IV's on irrigated ground, but it is not as absolute as dryland. In addition, soil type and planting date plays a major role, a factor I feel many have not considered.

On dryland acres, maturity groups earlier than 4.6 planted prior to April 20th should make August delivery but it will come right down to the wire. As you plant earlier, maturity will occur earlier. Under an early planting scenario (dryland) even a 4.8 or 4.9 maturity group could be planted in late March/early April and make August delivery.

As you plant earlier, plants are going to be shorter. To offset this, you could plant 4.8 or 4.9 maturity beans first (late March/early April) and they would get taller but they would mature the same time as an earlier maturity group (4.4) planted slightly later, April 10 for example.

Eighty percent of our acreage is planted on heavy ground. When beans are planted earlier they are shorter in height. If you experience some adverse weather conditions (prolonged wet weather) and drainage is not adequate growth will be reduced even more. On heavy soils even if drainage is adequate plant growth may be effected due to the poor internal drainage of the clay soils. A row or bed will help greatly and narrow rows are essential for all early plantings.

The best place for these real early maturity groups is sand to mixed ground. This is not to say it will not work on buckshot but you need to be aware of the possible impact regarding growth. Maturity group IV's (irrigated) if planted by mid April will be harvested the last few days of August. If you do not properly schedule irrigation the plant will stress and maturity will be delayed.

Keep in mind as you plant earlier things are going to happen earlier. Do not be surprised if early-planted soybeans need irrigation in early June. Provide inputs based on the stage of the crop not the calendar.

I spoke to Dr. Larry Heatherly (Stoneville, MS), and we both agree that early delivery should be considered first and foremost as a dryland system. However, when planted early and properly irrigated August delivery can be accomplished with irrigated beans. Following our conservation, Dr. Heatherly compiled some maturity dates from all his early planting work and I felt these would help serve as a guide. These numbers are averages over several years, but I feel they may answer some questions.

Maturity Date Range for MG III soybeans grown at Stoneville, MS in 2003
(from L.G. Heatherly)

Planting Date

Maturity Date (Range Depends on Variety)

April 1

Non-Irrigated/July 29-August 6
Irrigated/August 1-August 11

April 3

Non-Irrigated/July 25-August 1
Irrigated/August 1-August 8

May 6

Non-Irrigated/August 18-August 25
Irrigated/August 22-September 3

.

Predicted maturity dates for MG IV soybeans grown at Stoneville, MS (1991-2003)

Planting Date

Maturity Date

March 25

August 22

April 1

August 24

April 10

August 28

April 20

September 1

May 1

September 5

The above dates are for a properly irrigated crop. Nonirrigated soybeans will generally mature about 7 days earlier when planted on the same date.

Keep in mind these dates are just a guide. In addition, when comparing Group III's and IV's, the IV's have consistently out yielded the III's.

If you are pursuing early delivery it is going to require some in season/late season management. Soybeans maturing before night time temperatures cool off are much more susceptible to the elements (seed rot, etc..) It is almost a given that you will need to budget for at least one stink bug application. Some fields may not require any and other fields more than one. However, it will require field scouting at least twice a week during the peak of the growing season to stay on top of this potential problem.

Any problems we have this time of year (August) will increase exponentially in a very short period of time. If you recall the last couple of years many have had questions regarding damage estimates. Some elevators refused to accept soybeans over "x" percent damage. In order to avoid these problems you had better stay on top of stink bugs because if not you may have a lot of beans that will be hard to sell in August.

There are several options available, but we just do not need to wait too late to get concerned. We can deliver good quality beans early but it may require some additional inputs to get the job done.

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

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