Effects of fertilizer and herbicide application on the growth and yield of older loblolly pine plantations-two-year results

摘要

Three treatments of fertilizer, herbicide, and a combination of fertilizer and herbicide were applied to loblolly pine (Pinus teada L.) plantations of age 25 and 30 years. Two year results show significant diameter and volume growth increases per tree and per acre with the application of fertilizer and the combination of fertilizer+herbicide as compared to the herbicide treatment alone and the control. Diameter increment of fertilized only trees was 29.6 percent greater than the control during thesecond year, averaging 24.5 percent over the two years since treatment. Trees receiving the fertilizer+herbicide treatment were 33.3 and 26.4 percent greater than the control during the second year and in the two year average, respectively. The volume increment for the fertilizer treatments over the same time period on a per tree and per acre basis displayed similar percentage gains over the control. A difference in growth response was noted between the two age classes, with the 25-year-old plantationsdisplaying greater gains in diameter growth (28.6 percent) than the 30-year-old plantations (17.6 percent) over the two-year period as compared to the control. Similar growth gains in volume growth per tree and per acre were also realized.