Poultry Litter Fertilizer with Switchgrass: Environmental Parameters for Northern Louisiana.

Yields, nutrient uptake, surface soil chemical and runoff water quality parameters were measured for Alamo switchgrass transplanted to a hillside meadow in northern Louisiana and annually fertilized with N at two rates (80 and 160 kg/ha) using urea or poultry litter, compared to companion planting of crimson clover, no fertilization and native vegetation (grass and herbaceous).  Despite consistent numerical differences in yields, a significant effect due to fertilization did not appear until the third year after establishment (e.g., 25 compared with 18 Mg/ha for 160 kg N/ ha, urea and no fertilization).  Volume-weighted concentrations of TP and DRP in natural runoff reflected loss of P in poultry litter, with concentrations for the 160 kg N/ha treatment being an order of magnitude greater than from the no fertilization control.  Concentrations in runoff for native vegetation  were intermediate, reflecting the smaller volume of runoff from these plots.