Issue No. 17, Article 4/July 17, 2009
Soybean Growth and Development: Mid-July Update
As I write this, it is another rainy July morning in Urbana. On June 1 the Illinois State Climatologist Office reported that 2009 was the fifth wettest spring on record, with 15.9 inches. That was good for 4.5 inches above normal; some areas of the state around Peoria had their wettest spring on record, with 27.7 inches. June added 5.25 inches average, for another 1.2 inches above the statewide normal precipitation. Now it's mid-July, and, well, through the 14th the statewide average is nearly 3/4 inch above normal, with only the northeast and west districts receiving slightly below average rainfall. June temperatures, interestingly, averaged 72.6°F which is only 0.7 degrees above normal; however, the first half was 2.6 below and the last half 4.1 above normal. The first half of July has been cool again, averaging 75.7°F, which is 5.4 below normal.
What does all this mean? For one, it has been a tough year to get field work accomplished--that's a given. Two, soybean acres established in decent field conditions have been given excellent conditions for vegetative development. Adequate moisture and the relatively cool temperatures in late June and early July, may perhaps have early June–planted soybeans behaving as if they were planted in mid-May.
The July 13 USDA NASS Weather and Crops report indicated soybean conditions were 31% fair, 49% good, and 11% excellent. And while soybean planting progress was slightly behind that of 2008, only 11% of the soybeans have begun reproductive development (flowering). This is half the amount of acres in bloom at this date in 2008 and 1/5 of the 5-year average. If rainfall remains adequate in amount and periodicity throughout the later reproductive stages and as temperatures increase, the extra time devoted to vegetative development before beginning reproduction (flowering) could prove to be a good sign for the availability of nodes for potential flower and pod set. In Urbana my soybeans planted in late May are in the first reproductive stage (R1), which signifies that 50% of the plants are flowering, and some experiments are approaching R2. The soybeans planted in mid-May are at the R2 growth stage, or "full bloom," signified by flowers on one of the upper two nodes of the main stem with a fully developed leaf.
For some more good news, I have heard of few isolated instances of soybean lodging or defoliation due to storm damage. I have also not heard of any major insect or disease outbreaks, but I know Drs. Mike Gray and Carl Bradley will continue to monitor and keep all of us updated for official scouting concerns. In general, the value of scouting can never be stressed enough, and applications of insecticides and fungicides in the reproductive stages should be made to protect from yield losses due to pests. They do not generally increase yield in the absence of pests, so scouting should always come before planning an application. Let's hope for the favorable weather and conditions to continue.--Vince M. Davis