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Issue No. 13, Article 8/July 2, 2010

Midseason Soybean Growth Update

As I have driven around the upper three-quarters of Illinois recently, it has been clear that this is a year for most growers either to appreciate or to desire good fields. Rainfall in most areas has continued to be abundant in both amount and frequency. Since April 1, most of Illinois is at least 4 to 14 inches above normal for rainfall, with the amounts highest above normal in the west and northwest. Temperatures are also an average of 3 to 5°F above normal over the same period.

Due to adequate moisture and warm temperatures, early-planted soybeans have been well into flowering (R1) for the last week, and some are approaching R2. The R2 growth stage, or "full bloom," is achieved when flowers are developing on one of the upper two nodes of the main stem with a fully developed leaf.

Earlier-planted soybean fields are approaching full canopy closure, and the biggest challenge for many growers has been finding a window to apply postemergence herbicides. Fields that received preemergence herbicides had a tremendous advantage this year in most areas. As you work to finish postemergence herbicide applications, make sure they fall within the label's specified growth stages.

Soybean fields planted in the latter half of May and June have struggled in many areas with saturated soils; entire fields, or large portions, have remained yellow and struggled. The recent round of drier conditions should improve the appearance of these yellow beans. If yellow portions don't green up, scout these areas by digging roots and looking for proper nodulation and root rots.

There are still growers looking to replant some wet areas, and in some cases to plant fields for the first time. It is generally unclear if dramatically switching maturity groups will make a significant difference in achieving a decent yield at the end of the season. Heat and sunlight available in September and October , as well as a 7- to 10-day swing in the first killing frost, will make all the difference. However, if you are planting on the later edge of making a crop, reducing row widths and increasing seeding rates to 160,000 for planter units and 200,000 for drills will help achieve a canopy as quickly as possible to capture much needed sunlight.

Continue to scout in the coming weeks for insects and foliar diseases before determining whether to apply foliar fungicides or insecticides.--Vince M. Davis

Author:
Vince Davis

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