Initial response of loblolly pine and competition to mid rotation fertilization and herbicide application in the gulf coastal plainThis article is part of a larger document. View the larger document here.
Application of N and P to mid-rotation loblolly pines (Pinus taeda L.) stands is a common silvicultural practice used to increase crop tree production in the Gulf Coastal Plain. Mid-rotation applications of herbicides or combined applications of herbicide and fertilizer are a less common practice. We applied herbicide (1.17 l imazapyr and 0.23 l surfactant/ha) and fertilizer (409 kg-urea and 196 kg-diammonium phosphate/ha) to four mid-rotation stands (17- to 22-years-old) in southern AR and northern LA to evaluate the response of pine and woody competition to each of these treatments as well as a combination of these two treatments. Three years after initial herbicide application 50 to 83 percent of the initial woody competition had died. Mortality of the woody competition from the herbicide application was significantly greater with the addition of fertilizer than without. Net pine basal area and merchantable volume growth was increased. Net basal area growth 2 to 3 years after initial treatment application was 10 to15 percent greater with fertilization than without. Net volume growth was greatest with the combined herbicide and fertilization treatment.