Switchgrass Fertilized with Poultry Litter or Urea on a Coastal Plain Soil: Response, Nutrient Dynamics, and Phosphorus Runoff

Alternative use of poultry litter (PL; bedding material, spilt feed, and excreta) as a fertilizer for switchgrass ( Panicum virgatum L.; SG) on low P soil rather than P-enriched pasture would improve local surface water quality. Effects of PL or urea on Alamo SG yield and nutrient removal were determined in a randomized complete block experiment with three replicates over 4 years. Treatments were (1) no fertilizer, PL at (2) 80, or (3) 160 kg N ha −1 , and urea at (4) 80, or (5) 160 kg N ha −1 . Treatment effects on soil fertility and P movement were also examined. The average yield without fertilization was high (25.5 Mg ha −1 y −1 ), and neither N nor additional nutrients in PL significantly increased yield. Total N in the 0–15 cm soil decreased ~20% over time, probably due to increased mineralization upon conversion of the long-term grassland fallow, harvest removal, and drainage/volatilization. Inasmuch as N uptake was similar with and without fertilization, much of the applied N was apparently lost. Despite high K removal, soil test values did not decrease. Little (1.6%) of the P in PL applied at the higher rate was removed in runoff. Thus, periodic use of PL in a fertilization program for SG to offset nutrient removals would entail limited P loss.