Greenhouse gas emissions from two soils receiving nitrogen fertilizer and swine manure slurry

The interactive effects of soil texture and type of N fertility (i.e., manure vs. commercial N fertilizer) on N2O and CH4 emissions have not been well established. This study was conducted to assess the impact of soil type and N fertility on greenhouse gas fluxes (N2O, CH4, and CO2) from the soil surface. The soils used were a sandy loam (789 g kg(-1) sand and 138 g kg(-1) clay) and a clay soil (216 g kg(-1) sand, and 415 g kg(-1) clay). Chamber experiments were conducted using plastic buckets as the experimental units. The treatments applied to each soil type were: (i) control (no added N), (ii) urea-ammonium nitrate (UAN), and (iii) liquid swine manure slurry Greenhouse gas fluxes were measured over 8 weeks. Within the UAN and swine manure treatments both N2O and CH4 emissions were greater in the sandy loam than in the clay soil. In the sandy loam soil N2O emissions were significantly different among all N treatments, but in the clay soil only the manure treatment had significantly higher N2O emissions. It is thought that the major differences between the two soils controlling both N2O and CH4 emissions were cation exchange capacity (CEC) and percent water-filled pore space (%WFPS). We speculate that the higher CEC in the clay soil reduced N availability through increased adsorption of NH4+. compared to the sandy loam soil. In addition the higher average %WFPS in the sandy loam may have favored higher denitrification and CH4 production than in the clay soil.