By Marcus Gay, NM WRRI Student Program Coordinator
Jackson Powers is a graduate student in the Department of Plant and Environmental Sciences at New Mexico State University (NMSU). In FY2020, Powers was awarded an NM WRRI Student Water Research Grant for project entitled, Herbicide Phytotoxicity Under Drought Conditions in Warm and Cool Season Turfgrass. Under the guidance of his faculty advisor, Dr. Ryan Goss, the objectives of the project are to (1) determine the severity of herbicide turfgrass phytotoxicity at differing water statuses, and (2) investigate whether these differing turfgrass water statuses effect herbicide efficacy.
In the southwest, drought is a pressing issue for turfgrass managers. Local and state governments often restrict water for non-essential uses like golf courses and athletic fields. This can result in drought stressed turfgrass on golf courses, home lawns, and other public turfgrass systems. Drought stressed turfgrass is not able to provide the common benefits of turfgrass such as increased oxygen production, ambient temperature reduction, and providing low-cost surfaces for activities that greatly improve quality of life in the southwest. Also, under drought conditions, herbicide efficacy can be reduced in turfgrass stands because the plants are not able to perform normal physiological functions. Herbicides are the primary management practice to reduce difficult weeds in turfgrass stands. As a result, it is important to determine the interaction between decreasing water applications, severity of herbicide turfgrass phytotoxicity, and identify the effect of decreasing water applications on herbicide efficacy.
Providing a decision-making tool that turfgrass managers can use when deciding on an herbicide application during periods of drought will benefit New Mexico and regions that experience periodic drought conditions. The information from this tool can be used in determining if herbicide applications will be effective in preserving turfgrass quality by controlling weeds during periods of drought. Local governments, athletic field managers, golf course superintendents, and other landscape managers can use this decision-making tool to effectively manage their turfgrass sites like parks and athletic fields under reduced water conditions. In addition, water use for turfgrass reestablishment or turfgrass recovery can be avoided if the turfgrass stand does not receive damage due to a poor herbicide application decision.
Two experiments were conducted in order to determine the results of the project, both at the NMSU Fabian Garcia Research Science Center in Las Cruces, New Mexico. One experiment was conducted outdoors in the research fields, and the other experiment conducted in the research greenhouses.
One of the experiments conducted in the research field used a Linear Gradient Irrigation System (LGIS) to determine the interaction of precise water use and herbicide application responses. Two warm season experimental areas were established with Bermudagrass. Three unique cool-season experimental areas were established with perennial ryegrass, Kentucky bluegrass, and a mixture of perennial ryegrass with Kentucky bluegrass and tall fescue. Four weed species were inter-seeded into each experimental area after establishment, including Green foxtail, annual bluegrass, dandelion, and white clover. Each plot was irrigated on a gradient of applied water through LGIS for two weeks and received a combination of herbicide applications. Plots were then visually rated for turfgrass and weed phytotoxicity, turfgrass and weed quality, and percent turfgrass green cover.
In the greenhouse experiment, Bermudagrass and Kentucky bluegrass were grown in pots with uniform irrigation. After maturity, plants were exposed to four decreasing water contents for two weeks and then sprayed with a combination of herbicide applications. Each pot was then visually rated for turfgrass phytotoxicity, quality, and density.
Initial results show that some herbicides like fluazifop-p require different irrigation amounts in order to maintain acceptable turfgrass quality after application. The results also revealed that one herbicide could require different irrigation amounts depending on what species of turfgrass it is applied to. As Powers explains, “Initial findings from our research have shown that certain herbicides require turfgrass be well-watered in order to maintain turfgrass quality. Ultimately this research will ensure that the environmental benefits turfgrass provides will not diminish under the drought conditions seen in New Mexico.”
Powers plans to graduate in May 2020 with a Master of Science in Horticulture focusing on Turfgrass Science and Management with a minor in Applied Statistics. After graduating, Powers plans on moving to Kansas City, Kansas, to work for a major lawn care company. Powers, originally from Portales, New Mexico, also received his Bachelor of Science in Agriculture from NMSU, focusing on Turfgrass Science and Management with a minor in Business Management.