Nitrous Oxide Emission from Two Soils under Commercial N Fertilizer and Swine Slurry Application in a Rhizotron Experiment.
Marek K. Jarecki1, Timothy B. Parkin2, Alvarus S.K. Chan1, Jerry L. Hatfield3, David W. Meek4, and Raymond A. Jones5. (1) AgCert Services, Inc., 2150 Pammel Drive, Ames, IA 50011, (2) USDA-ARS, National Soil Tilth Lab, 2150 Pammel Dr., Ames, IA 50011, (3) National Soil Tilth Lab, 2150 Pammel Dr., Ames, IA 50011, (4) National Soil Tilth Laboratory, 2150 Pammel Dr., Ames, IA 50011, (5) AgCert Canada Co., Manulife Place, 10180 101 Street, Suite 100, Edmonton, AB T5J 3S4, Canada
Direct nitrous oxide (N2O) emission from agricultural soils depends on several factors including the application of slurries and manures, commercial N fertilizers, availability of soil organic carbon, soil structure and pH. The purpose of the study was to compare N2O and carbon dioxide (CO2) fluxes from soils amended with swine slurry and fertilized with commercial N. Two soils from central Iowa, were selected for the experiment. The first soil was a loamy sand with a surface layer texture of 79.0 % sand, 13.8 % clay and 7.2 % silt containing about 1.8% of organic carbon (C) and is classified as a Storden fine-loamy, mixed, mesic Typic Udorthents, and the second, a clay loam with a texture of 25.6% sand, 37.5% clay and 36.9% silt containing 4.4% of organic C is classified as a Webster fine-loamy, mixed, mesic Typic Haplaquolls. The pots were prepared containing 12 kg of soil without vegetation and were kept at field moisture capacity and 180C temperature for 8 weeks. The following treatments were applied to both soils: control (no N), commercial N fertilization as a Urea-Ammonium Nitrate solution (UAN), and swine slurry, both injected at the 5 cm depth. UAN and slurry were applied at the rate of 200 kg N/ha. Measurements were performed every day over the first two weeks and every second day over the remaining period. The cumulative emission of N2O was 3 times higher from sandy than from clayey soil. Sandy soil N2O emission from slurry and N fertilizer treatments were about 8 to 9 times higher than from control. For the clayey soil, N2O emission from the N fertilizer treatment was over 2 times higher than from control and 13 times higher than control from the slurry treatment. In sandy soil there was no significant difference in cumulative N2O emission between commercial N and slurry but in clayey soil more N2O was emitted from slurry than from commercial N treatment. Carbon dioxide emission, similar to N2O, was higher from sandy than from clayey soil. In both soils higher emission of CO2 was observed from slurry treatments with no difference between control and commercial N treatment. The nitrogen losses through N2O emission from the commercial N treatment amounted to 3.3 and 0.2 % of applied N for sandy and clayey soils, respectively. From soils treated by slurry, N losses through N2O emission amounted to 2.7 and 1.8 % of applied N for sandy and clayey soils, respectively. Results for N2O emissions from this trial obtained for manure on both soils and for commercial N treatment on sandy soil are higher than the present IPCC value of 1.25% N2O-N/kg N.