Growth and physiological response of four shortleaf pine families to herbicidal control of herbaceous competition
Four open-pollinated families of short-leaf pine (Pinus echinata Mill.) seedlings were planted near Peryville, AR, in February 1988. Three herbaceous weed control were tested for each family along with an untreated check. A single treatment of 3 oz. ai/ac of Oust was applied in April 1988 for spot, band, and total control of herbs. Total control was maitained with directed applications of Roundup (3% product) as needed. Seedling survival averaged above 95% after two growing seasons for each treatment. Soil moisture, seedling growth, and seedling biomass were greatest and fascicle water potential of pines was least negative on plots recieving total control of herbs. Intermediate levels of fascicle water potentials occured in spot- and band-treated plots were seedlings realized 91% of the height and 83% of the diameter growth potential for the site. Lowest soil moisture and growth plus most negative fascicle water potentials occured on untreated check plots. Families differed in their physiological response when soil moisture increased. Needles and roots were the largest components of biomass. While improving pine growth, spot treatments for herbaceous weed control offer ecological and cost advantages over band treatments or total control.