Earlier this season UGA Extension Weed Scientist Dr. Stanley Culpepper and I did a herbicide injury trial here in the county. With some of our sandy soils, we often wonder about injury in different field situations. Much injury from at-plant herbicides have been observed for many years through 2013. We put out a this trial to observe different rates and combinations. Though much of our crop in the county is not under pivot, we observed the difference under irrigation to make sure we had proper water timing. This is one of many plots Dr. Culpepper will have this year, but it still provided good information as we are continuing to learn about injury with preemergence.
We set up plots behind planting of DP 1252 on May 23rd. Each plot was treated with equivalent of 15 gallons of water per acre at rates and herbicides listed below. Irrigation ran 0.5 inch two days following planting. Cotton was not irrigated again until it was completely emerged. We then rated three times: 5, 11, and 21 days after treatment.
Injury was only observed once on the 2nd rating. The injury was just 8% with our Direx + Warrant mixture. Once we got to the third rating, no difference in injury was observed. Looking at the results below, note each column under “% injury.” Where the letters change is where difference in injury was observed. This gives us more confidence in our preemergents that we may be safer than we originally thought. Lack of injury is likely due to well-timed irrigation program and better understanding of how and when to irrigate. We’re going to share this info at our cotton meeting this year, along with other data Dr. Culpepper has from other trials. If you want to read more, I have a screen shot of a poster at the bottom.