Planted Loblolly Pine Survival and Growth Responses to Herbaceous Vegetation Control
Abstract Plots in 13 loblolly pine (Pinus taeda L.) plantations established on sandy or sandy-loam soils in SE Oklahoma and SW Arkansas received herbaceous vegetation control using hexazinone and sulfometuron methyl. Treatments consisted of a one-time herbicide application over-the-top of loblolly pine seedlings by one of three methods: spot, band, or broadcast. At the end of 1 and 5 growing seasons, data were collected for survival, height, and diameter growth and compared for seedlings in areas untreated and treated for herbaceous vegetation control. Only data corresponding to herbicide rates and application methods labeled for use today are included in data analysis. When compared with untreated checks, seedlings treated for herbaceous vegetation control exhibited significant increases in first-year survival at 11 sites and in height and groundline diameter (GLD) at 12 of the 13 test sites. At the end of 1 growing season, herbaceous vegetation control provided mean seedling increases of 16.7%, 0.4 ft, and 0.1 in. for survival, height, and GLD, respectively. After 5 growing seasons, advantages from herbaceous vegetation control had increased with significant differences existing in survival, height, and diameter at breast height (dbh) on 10 of 11 test sites, as 2 sites were lost to wildfire. Numerically, treatment differences had increased to 18.4%, 2.4 ft, and 0.6 in. for survival, height, and dbh, respectively. South. J. Appl. For. 20(1):53-57.