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Implications of a cool, wet growing season

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Column by Matt Adams

The 2013 growing season certainly has been an unusual one. Following record drought in 2012, rain has been plentiful all spring and summer in Hardin County — sometimes too plentiful. While the wet conditions have boosted potential for crop yields, it has come with some unwanted circumstances.

Recently, two University of Kentucky grain crops specialists touched on two of these implications by posting in the UK Grain Crops Blog.

Dr. Chad Lee shared his thoughts on what could be a later grain harvest, and Dr. Don Hershman shared an update on the probability of Asian soybean rust affecting Kentucky.  Here are their comments”

“Farmers can expect a later and wetter harvest this fall.  Corn was planted late and the cool and cloudy days are slowing development. Most corn hybrids in Kentucky need about 2,700 to about 3,300 GDD’s or heat units to reach black layer (physiological maturity). Looking at the GDD calculator on the UK Ag Weather Center, corn planted April 15, 2013 in Mayfield won’t get to 3,000 GDD’s until Sept. 1.  Corn planted April 15 in Henderson will get to 3,000 on Sept. 3. Corn planted May 15 in Lexington will get to 3,000 GDD’s about Sept. 27.

“Once the corn reaches black layer, it then relies on simple physics to dry down to a harvestable moisture. Corn this season will reach black layer and try to dry down in September and early October, when the day length is shorter and temperatures historically are cooler. Those shorter days and cooler temperatures will slow dry down of the corn kernels. Barring a sudden and dramatic shift in the current weather, corn harvest in Kentucky will be late.

“If September ends up being one of the hottest and driest on record, then disregard the previous comments. However, if September is ‘normal’ or follows the current weather patterns, producers need to look at what should be a good harvest, but a late and wet harvest, and prepare their bins and driers now.

“With the wet weather, soybean diseases have become a concern in Kentucky, with Asian soybean rust being one of those possible concerns, however, Dr. Hershman says Kentucky producers shouldn’t be too worried about this disease at this point. Soybean rust has really picked up in Alabama, Florida and Georgia and has recently been detected in South Carolina and southeast Arkansas. There is no question that SBR is on the move, but more so in the southeast U.S. compared to the mid-South.

“Let me put all of this into the proper perspective. Based on limited SBR activity in the mid-South to date, and we are monitoring five sentinel plots on a regualr basis, it is very unlikley that SBR is here and we are missing it. SBR in Kentucky is dependent on spores of the SBR fungus blowing in from the south. Since most of our spores come from places like Texas, Lousiana, Arkansas and Mississippi, it is clear to me the volume of spores available to infect soybean in Kentucky is very limited at this time. I am sure this will change over the next month as SBR ramps up in the mid-South. But for now I feel like we are free and clear of SBR. Once spores do make it here, even if it is today, it will take three weeks for us to find the disease. Then it will take another three weeks for the disease to increase. This means that even if SBR spores arrive today it would be the end of September before yield loss is possible. By then, the vast majority of fields will be at the R6 stage or later and will be safe. Some later-planted fields still will be at risk, but frost probably is the greater risk for those fields. This is all based on SBR spores blowing into the state and infecting crops today, which is highly unlikely. More realistically, we will not begin to be showered with SBR spores until early/mid-September because the disease still has to build up in the mid-South. So, under this more realistic timeframe, SBR would not ramp up here until sometime in mid-October, which is just too late to do much damage.”

Bottom line:  I am fairly sure Kentucky again will escape damage caused by SBR this season. Know that we are closely monitoring the developing situation and will make it know immediately if the SBR risk status here changes. But for now, the SBR risk remains very low.

Next On-Line Grain Production Series Meeting: The next meeting of the online Grain Production Series is 9:30-10:30 a.m. Wednesday and can be viewed at the Hardin County Extension Service.  This month, Dr. Jim Martin discusses herbicide resistant weeds and management strategies.  Even though this is a web-based meeting, producers participating by viewing at the office still have a chance to interact with specialists as in a face-to-face meeting. If you plan to attend, please call the Hardin County Extension Service at 270-765-4121.

Matt Adams is a Hardin County Extension Service agent for horticulture and natural resources.