Estimating the availability of nutrients from processed swine lagoon solids through incubation studies

Potential environmental hazards from the excess accumulation of swine (Sus scrofa domesticus) manure in eastern North Carolina and new state guideline s on treatment alternatives have necessitated the reevaluation of best mana gement practices for disposal of swine waste (manure and effluent) as a fer tilizer source on local crop land. Creation of a value-added product is one viable means of utilizing and economically redistributing the nutrients in swine manure. Incubation studies using four agricultural soils from easter n North Carolina were conducted with pelletized processed swine lagoon soli ds (PSLS) (1.7% N, 2.5% P, 0.12% Cu and 0.18% Zn) composed of dewatered swi ne lagoon sludge plus rock flour. The PSLS was added at three application r ates (0, 200, 400 mg N kg-l soil) and incubated for 16 weeks at 25 degrees C. The soil was sampled at 0, 1, 2, 4, 8, 12, and 16 weeks and analyzed for NO3-N, NH4-N and Mehlich III-extractable P, Zn, and Cu. High concentration s of NH4-N and low concentrations of NO3-N were present in the soils shortl y after addition of PSLS. After the second week, extractable NH4-N dropped to <4 mg kg(-1), while the soil concentration of NO3-N increased rapidly. T he amount of NO3-N generated reached 90% of its final value after the fourt h week. Across the four soils, 24-35% of the added N, 15-50% of the added P , 20-50% of the added Zn and 15-20% of the added Cu was extractable after 8 weeks. The PSLS is an excellent source of P, but may require additional N if used as a fertilizer source for most row crops. (C) 1999 Elsevier Scienc e Ltd. All rights reserved.