Poster Number 532
Wednesday, 8 October 2008
George R. Brown Convention Center, Exhibit Hall E
Heavy metals in poultry litter (PL) can cause environmental problems despite the cost-effectiveness of PL as source of plant nutrients. We compared total Cu, Mn, and Zn levels in a Cecil soil near Watkinsville, GA, in a 5-yr each of cotton and corn study under conventional tillage (CT) and no-tillage (NT), with either PL or ammonium nitrate or sulfate fertilization (AN), depending on availability. For cotton, PL application rate was 4.5 Mg ha-1 yr-1. This increased 2 to 4 times for corn, partly because of corn’s greater nitrogen requirement and also due to inclusion of a water quality study component related to hormones. Poultry litter did not influence mean Cu, Mn, or Zn levels in the surface 15 cm of soil during the cotton phase (13-18,219-413, and 35-50 kg ha-1, respectively). During corn, however, Cu and Zn levels rose to 49 kg ha-1 and 70 kg ha-1, respectively, due to PL. Mn levels remained in the same range as before.
No PL influence was observed in the 15-30 cm depth with levels ranging 14-23, 187-289, and 35-56 kg ha-1 for Cu, Mn, and Zn, respectively. Copper and Zn levels showed stratification in the 0-2.5, 2.5-5.0, and 5.0-15.0 cm depths. Highest Cu levels were observed in the 0-2.5 cm depth (44, 72, 199 kg ha-1 for NTAN, CTPL, and NTPL, respectively), compared to levels in the 5.0-15.0 cm depth (19, 42, 37, respectively). Similarly, Zn levels in the 0-2.5 cm depth were 91, 98, 243 kg ha-1 for NTAN, CTPL and NTPL, respectively, compared to 32, 64, and 45,in the 5.0-15.0 cm depth, respectively. An alternative approach for PL use in Cecil soils for corn production needs to be developed to avoid build up Cu and Zn.