|Sauer, Thomas - Tom|
Submitted to: World Agroforestry Congress
Publication Type: Abstract Only
Publication Acceptance Date: 7/2/2004
Publication Date: 7/2/2004
Citation: Sauer, T.J., Defauw, S.L., Brye, K.R., Brahana, J.V., Skinner, J.V., Coblentz, W.K., Thomas, A.L., Hays, P.D., Moffitt, D.C., Robinson, J.L. 2004. N and p assimilation in a silvopastoral system receiving poultry litter or inorganic fertilizer [abstract]. World Agroforestry Congress. p. 207.
Technical Abstract: A silvopastoral demonstration/research site was established to quantify differences in nitrogen and phosphorus cycling due to nutrient source (poultry litter or commercial fertilizer). Northern red oak (Quercus rubra), eastern black walnut (Juglans nigra) and pecan (Carya illinoensis) were planted at 15 m row spacings on a 4.25 ha site near Fayetteville, AR in 1999-2000 and alleys were seeded to orchard grass. Beginning in 2001, ½ of the site received a single 4.5 Mg/ha poultry litter application each spring and the other ½ received 56 kg/ha nitrogen as commercial fertilizer each spring and fall. Monitoring results indicate consistently greater concentrations of NO3-N in both soil water and ground water samples collected from the area receiving commercial fertilizer. Average NO3-N concentrations for the soil water samples were 7.9 and 5.2 mg/L for the fertilizer and litter-treated areas. Ground water samples displayed the same trends, as average NO3-N concentrations in ground water samples were 9.4 and 7.0 mg/L for the fertilized and litter-treated areas. Nitrate nitrogen concentrations were greater in the spring with maximum concentrations exceeding 20 mg/L in both soil water and ground water. Very little change in soil phosphorus concentrations were observed as both litter-treated and fertilized areas averaged ~35 mg/kg phosphorus as measured by the Mehlich 3 extract. However, phosphorus concentration in forage harvested from the litter-treated area had consistently greater (~0.05%) total phosphorus. Tree, forage, and environmental monitoring to quantify nutrient and carbon cycling components will continue and intensify as the trees mature.