What you should know about August soybeans

USDA's January crop report increased Mississippi's 2003 average yield from 36 to 39 bushels per acre. The crop exceeded our previous best-ever crop in 1992 by 5 bushels per acre.

Many changes have occurred over the last 10 years, and if we concentrate on the basics, we can continue to achieve above-average yields. Four criteria 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. Many are getting on board.

I am concerned that many growers who are going to plant Group 3s and early Group 4s have never planted beans of this maturity (4.5 or less) before.

Following is what we know about early planting and some dos and don'ts regarding August delivery.

First, this is predominantly a dryland system. You can make August delivery with Groups 3s and early Group 4s 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.

Maturity groups earlier than 4.6 planted prior to April 20 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 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 affected 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 very 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 4s (irrigated) 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.

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.

Larry Heatherly (Stoneville, Miss.) and I 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.

Heatherly compiled some maturity dates from all his early planting work that should serve as a guide (last column). The numbers are averages over several years, but I feel they may answer some questions.

Early delivery 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, for example). 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 in 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. To avoid these problems, stay on top of stink bugs; if you do not you may have a lot of beans that will be hard to sell in August.

Several options are available, but don't 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.

Alan Blaine is the Mississippi Extension soybean specialist. e-mail: [email protected].

Maturity date range for Maturity Group 3 soybeans grown at Stoneville, Miss., 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 Maturity Group 4 soybeans grown at Stoneville, Miss. (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 seven days earlier when planted on the same date. These dates are just guides. In addition, when comparing Group 3s and Group 4s, the Group 4s have consistently outyielded the Group 3s.

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