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2-Plants: Yield problems with RR soybeans under dry conditions

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TITLE:  Soybeans
SOURCE: Agronomy Notes, Mississippi State University Extension Service
        by Alan Blaine,
DATE:   November 8, 2000

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This year turned out to be the worst year ever for many soybean growers, as 
drought conditions caused problems statewide. Since much of the soybean 
crop is grown in a dryland setting, growers must continue to carefully 
consider variety selection, the use of early maturing varieties, and 
planting dates.

Variety selection.
This year has proven how unpredictable a growing season can be. Varietal 
differences are observed every year, but quite a few varieties showed their 
ability to withstand adverse conditions this year. Many varieties that 
looked good last year proved failures this season. This emphasizes the need 
for a yield history, preferably at least two years of yield data, before 
planting a large acreage in new varieties.

Early maturing varieties.
Due to the earliness of the past couple of growing seasons, we will see an 
increase in early maturing varieties. Some interest is being expressed in 
Group III's, but the bulk of the plantings to early maturing varieties 
should be in IV's. From a dryland standpoint, Group IV's offer a greater 
potential to increase yields than any of the later maturity groups.

If we could predict the weather, we would know exactly what and when to 
plant. Since this cannot be accomplished, Group IV's allow us the 
opportunity to increase yields by setting pods during a time frame more 
conducive for fruit set. For the 2000 soybean crop, pod set was as good as 
farmers have experienced. However, there was not enough moisture to fill 
them out after pod set.

Another consideration is the use of Roundup Ready varieties. As a whole, 
when growing conditions become extreme, the Roundup Ready varieties seem to 
be more greatly affected. While the Roundup Ready option is an excellent 
technology, especially dryland, growers need to do their homework regarding 
varietal performance prior to planting.

Many producers would be better off planting a proven variety like Hutcheson 
rather than take chances with a new variety. If you do plant new varieties, 
do not plant more than 5 to 10 percent of your acreage in any variety with 
less than two years of state yield data. This may seem slightly extreme, 
but your entire crop depends on the variety you plant. This is a decision 
you will live with all year and one that should not be made lightly. 
Roundup Ready varieties are getting better, but few of them have the yield 
history needed to put all your acreage in them.

With more than 250 varieties available for sale, variety selection is a 
monumental task. The 2000 growing season was quite extreme, but several 
varieties consistently performed in the top 10 to15 percent. These are the 
varieties growers should plant on the bulk of their soybean acreage.

Planting dates.
One input over which growers have less control is planting dates. Early 
planting should be a goal of every soybean producer in this state. Although 
farmers grow other crops, in order to make soybeans profitable, they must 
plant soybeans as early as possible. Unless you are double cropping or 
planting behind flood waters, soybeans growers should have a goal of 
planting soybeans before you start planting cotton. While growers need to 
spread their risks with maturity groups, not enough growers are taking 
advantage of the option of early planting.

After this past season, we can look for three things to take place: Roundup 
Ready acreage, Group IV plantings, and the percentage of acreage planted 
early will all increase. All of these options are good, but we will still 
need to do some advance planning regarding how to make these things work. 
Preliminary yield information (Group IV's and V's) are currently available. 
If you would like a copy, please contact your county extension office.

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