Impacts of Rate of Hexazinone Application on Survival and Growth of the Loblolly Pine
Hexazinone [3-cyc1ohexyl-6-(dimethylamino)-1-methyl-1,3,5-triazine-2,4(1H, 3H)-dionel in 2-cc pellets (10% active ingredient) was applied at rates of 0,2,4, and 8 pounds of active ingredient per acre for site preparation on clay soil in a randomized experiment in May 1980. Loblolly pine seedlings planted to the site in January 1981 were measured for diameter 3 inches above the ground, height, and survival in January 1981, December 1981 and 1982, and November 1983. Four and 8 pounds of active ingredient per acre resulted in significant growth of the treated seedlings over that of the untreated seedlings for each of the 3 years of this study.Growth responses for seedlings treated with 4 and 8 pounds of hexazinone were not significantly different. Diameter growth of the seedlings responded to the treatments to a greater degree than did height growth, although both were significant at the p=0.05 level by analysis of variance (ANOVA) and Duncan's multiple range test. Seedlings in the 2-pound treatment failed to grow significantly more than the untreated plants during the 3 years of study. Survival was not significantly affected by any of the treatments. Results of this study suggest that 2 pounds of hexazinone per acre is too low a rate for significant growth benefits to accrue from site preparation with the grid application method on clay soil.