A Comparison of Herbicide and Mulch Mat Treatments for Reducing Grass, Herb, and Shrub Competition in the BC Interior Douglas-Fir Zone—Ten-Year Results

Abstract

Abstract We present results from a study established in 1993 in the Interior Douglas-fir biogeoclimatic zone of southwestern British Columbia to test the effectiveness of several herbicide and mulch mat treatments for reducing grass, herbaceous, and shrub competition. The effectiveness of the preplant herbicide applications of hexazinone (Velpar L) at 2.1 kg ai/ha, glyphosate (Vision) at 2.1 and 1.0 kg ai/ha, and the installation of plastic mulch mats (Tredegar 90 × 90-cm mats) for controlling competing vegetation, improving seedling growth and survival of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings and improving soil moisture availability was evaluated. Ten-year results indicate that application of hexazinone and glyphosate enhanced the survival, diameter, and height growth of planted Douglas-fir seedlings. These herbicide treatments provided effective control of grass and herbaceous vegetation for three to four growing seasons. Plastic mulch mats did result in improvements in growth and survival, but these were not statistically different from untreated seedlings. The results of soil moisture monitoring from within the various treatments indicated delay in the onset of soil drought as a key determinant of the seedling growth improvement noted. West. J. Appl. For. 20(3):167–176.