Loblolly Pine Stand Fertilization at Mid-rotation to Increase Small and Large Sawtimber Volume

There are over 500,000 family forest landowners in Georgia who own approximately 67% (24.3 million acres) of the state’s 36 million acres of forested land. The family forest landowners in the southeastern United States own from 49% to 67% of the forestland. Real Estate Investment Trusts and Timber Investment Management Organizations, which currently own mostly former forest industry lands, have been fertilizing between 600,000 and 1 million of primarily loblolly pine stand acres annually in the southeastern U.S. over the last decade. Fertilization on family forest landowners’ acreage is well below that of larger landowners. Yet numerous loblolly pine family forest landowners’ stands are candidates for fertilization based on diagnostic tool use (leaf area index estimates or LAI, soil test-P, crown visual symptoms, and foliar nutrient concentrations). Financial returns ranging from 5 to 12% over an eight-year period can be realized with proper fertilizer applications.

Twenty-one 1/6 A permanent measurement plots were located and established in September and October 2013 in a 1988 planted loblolly pine stand that was thinned approximately 5 years ago on former Weyerhaeuser lands, now part of Charlane Plantation in Georgia. The gross treated plots are ¼-acre and there are 30 feet on untreated buffer between each plot. Herbicide plots were treated with 3 quarts of Razor Pro/A at 25 gallons per acre (gpa) on September 9 to October 2. All living loblolly pine trees greater than 4.5” diameter at breast height (dbh) in each plot were aluminum tree tagged, numbered, measured for dbh, total height and height to base of live crown on February 3 to 5, 2014. Soil and foliage sampling will be done on February 13, 2014. Randomly assigned to each plot will be the following treatments: (1) control (no herbicide, no fertilizer), (2) herbicide only, (3) herbicide + a full dose of NP (342 urea +125 DAP/A), (4) herbicide + NPK (342 urea + 125 DAP + 100 KCl), (5) herbicide and a ½ + ½ dose of NP (171 urea + 63 DAP), (6) herbicide and a ½ + ½ dose of NPK (171 urea + 63 DAP + 50 MOP) to be applied in February 2014 and again in February 2017, and (7) no herbicide + full NPK. Cumulative fertilizer application rates are 180 lb N/A + 25 lb elemental-P for the NP treatments and the same for NP+ 50 lb elemental-K for the NPK treatments and are planned for first application in later part of February 2014.