Effect of beef cattle manure application rate on CH4 and CO2 emissions

In a series of field experiments, emissions of two major greenhouse gases (GHGs), methane (CH4) and carbon dioxide (CO2) were measured using a closed chamber technique in summer 2010 to evaluate the effects of solid beef cattle manure land application techniques. The treatments included a control (C: no manure), two manure application rates (40 and 80 T ha−1), and two injection layers (surface vs. subsurface (5 cm)): (1) 40 T ha−1 on surface (S40), (2) 80 T ha−1 on surface (S80), (3) 40 T ha−1 at subsurface (D40), and (4) 80 T ha−1 at subsurface (D80)). The exchange patterns of CH4 and CO2 in the control were variable and showed both emission and deposition. However, only emissions were seen in the manure treatments. Emissions of CH4 were seen systematically on the ascending order of 5.35 (C), 59.3 (S40), 68.7 (D40), 188 (S80), and 208 μg m−2 h−1 (D80), while those of CO2 also showed a similar trend: 12.9 (C), 37.6 (S40), 55.8 (D40), 82.4 (S80), and 95.4 mg m−2 h−1 (D80). The overall results of our study suggest that the emissions of CH4 and CO2 are affected most noticeably by the differences in the amount of manure application.