Feature Story
Corn Gluten for Crabgrass Control By Jeffrey Derr, Ph.D., Professor of Weed Science, and Adam Nichols, Research Assistant, Virginia Tech Hampton Roads Ag. Research and Extension Center, Virginia Beach
T
here is interest in organic approaches to weed management in turf. Building on the research conducted by Dr. Shawn Askew and other researchers, we conducted a trial to evaluate corn gluten for crabgrass control. A byproduct of corn milling, corn gluten contains approximately 60% protein and 5% to 10% nitrogen. Reported preemergence control of crabgrass appears to be due to a combination of the nitrogen component enhancing turf growth and the presence of allelopathic chemicals that inhibit seed germination.
Our research
We conducted our trial in an established stand of ‘Justice’ tall fescue. We compared a single and split application of corn gluten to single and split applications of a conventional fertilizer, Pendulum 2G (pendimethalin), and to a combination of a conventional fertilizer plus Pendulum 2G. The first application (A) was made on March 21, 2014, under 57°F air temperature, 29% relative humidity, 0% cloud cover and wind 3 MPH N. The second application (B) for the split treatments was made May 21, 2014, under 77°F air temperature, 69% relative humidity, 40% cloud cover and wind 3 MPH W. Rates for WOW corn gluten and fertilizer are in pounds N/1,000 ft2. Application rates for
the corn gluten were 10 and 20 lb./1,000 ft2, as WOW contains 8% nitrogen.
Research results
Treatments containing fertilizer or corn gluten caused an increase in turf color at 61 and 125 DAT compared to the treatments that did not receive fertilizer (Treatments 1, 6 and 7) (see Table 1). There was essentially no difference in color among treatments at 137 and 175 DAT. Apparently the N effect from the fertilizer or the corn gluten had run out by these time periods. Treatments that did not contain Pendulum (pendimethalin) had lower quality at 137 and 175 DAT due to brown patch disease and smooth crabgrass infestations (Table 2). Corn gluten did not control crabgrass in this study, while Pendulum gave excellent control (Table 3). Plots that were fertilized with corn gluten or a conventional fertilizer without application of Pendulum had higher infestations of brown patch; perhaps the higher density of crabgrass in these plots resulted in greater canopy moisture, resulting in greater amounts of Rhizoctonia, or perhaps the crabgrass served as a source of inoculum for the disease. Crabgrass does show symptoms of Rhizoctonia infection, although it is not controlled by the disease. c
Research Sponsors: The Virginia Turfgrass Council and The Virginia Turfgrass Foundation 22 | Virginia Turfgrass Journal September/October 2015 www.vaturf.org