Forest Nutrient Cycling after Biosolids Application in the Virginia Piedmont.
Eduardo Arellano and Thomas Fox. Virginia Polythecnic Institure and State Univ, Dept of Forestry, 228 Cheatham Hal, Blacksburg, VA 24060
Forestland in the Piedmont and Upper Coastal Plain of Virginia provides a good alternative location for land application of biosolids. Effective specific design criteria are required for successful forestland surface application systems. Issues such as loading rate, nutrient assimilation rates in the ecosystem, nutrient losses, and growth response for various types of biosolids must be addressed. It may not be possible to simply extrapolate agricultural land application practices to forest settings.The objectives of this field study are to quantify nutrient availability changes on a Loblolly pine (Pinus taeda L.) plantation following the application of a fall and a spring application of biosolids types, under different rates, and determine the impact of biosolids application on nutrient cycling in forest ecosystems. The study has been conducted since September 2005, in a thinned Loblolly pine plantation, located in Amelia Country in the Piedmont or Upper Coastal Plain of Virginia. The study was established as a random complete block design with nine treatments, determined from different biosolids type (lime stabilized, anaerobic digested, and pelletized), conventional fertilizer (Urea+DAP), and seasonal timing (fall and winter). In this work, we report the effect of the treatments on forest floor and mineral soil properties for a period of one year after the first application, and six months for the last one. Soil moisture content and temperature have been measured at 15 cm depth. Soil solution samples collected in the tension lysimeters have been analyzed for total N, total P, NO3-N, NH4-N, PO4-P, K, Ca, Mg, Na, pH and conductivity. Ion exchange membrane (Ionic) extractable total N, total P, NO3-N, NH4-N, PO4-P, K, Ca, Mg, Na have been determined. Organic forms of N and P have been determined by differences between direct measures of the total and inorganic forms.