Comparison of the Effects of Ammonium Nonanoate and an Essential Oil Herbicide on Weed Control Efficacy and Water Use Efficiency of Pumpkin

Abstract

Abstract Weed management is one of the major challenges responsible for growers’ reluctance to switch from conventional to organic vegetable production. Competition from uncontrolled weeds can significantly reduce the yield and water use efficiency (WUE) of vegetable crops. A field study was conducted during the summers of 2019 and 2020 at the Quaker Research Farm of Texas Tech University, Lubbock, TX to determine physiology, plant growth, yield, soil water depletion pattern, and WUE of pumpkin as affected by the weed control treatments: 1) ammonium nonanoate 5% (active ingredient; a.i.), 2) ammonium nonanoate 6% ai, 3) clove oil + cinnamon oil 4.5% ai, 4) clove oil + cinnamon oil 9% ai, and 5) an untreated control. Each plot received the same herbicide treatment at 20 and 30 days after planting (DAP). The experiment was conducted in a randomized complete block design with 4 replications of each treatment. Both herbicides resulted in significant weed suppression compared to untreated control and weed control was 88 to 98% with ammonium nonanoate and 39 to 69% with clove oil + cinnamon oil. Photosynthesis rate, stomatal conductance, shoot dry biomass, average fruit weight, total fruit yield, and WUE of pumpkin were significantly higher in ammonium nonanoate treatments compared to the untreated control. All the aforementioned parameters were not significantly different between clove oil + cinnamon oil and untreated control. Use of higher ai concentration did not improve the performance of either herbicide. Soil water depletion and evapotranspiration were comparable among all the treatments. Based on the results, ammonium nonanoate at its lower concentration could be an option for effective weed control, and for improving fruit yield and WUE of pumpkin.