A rapid method for measuring feces ammonia-nitrogen and carbon dioxide-carbon emissions and decomposition rate constants

Abstract

A rapid approach is needed for determining the effectiveness of precision conservation on soil health as evaluated using CO2 and NH3 emissions. This study demonstrated an approach for calculating CO2–C and NH3–N emissions and associated rate constants when feces were applied to bare soil or soil + vegetation. In addition, point CO2–C emission measurements were compared with near continuous measurements. The CO2–C emissions were measured at 2 h intervals over 20 d, whereas ammonia volatilization was measured three times daily for 7 d. Total CO2–C emissions over 20 d were 5% lower [186 g CO2–C (m2 × 20 d)–1] than point measurement collected at 1100 h every day (197 g CO2–C (m2 × 20 d)–1), and about 10% lower than if collected every 2 d [206 g CO2–C (m2 × 20 d)–1]. A Fast Fourier transformation (FFT) showed that temperature and NH3–N and CO2–C emissions followed diurnal cycles and that they were in-phase with each other. Over 7 d, 20% of feces NH4–N was volatilized and that this loss was similar when feces were applied over vegetation or mixed into the soil. Feces additions increased the amplitude of the CO2–C diurnal cycle, and the fecal-C first-order rate degradation constants were higher when mixed with soil [0.0109 ± 0.0043 g(g×d)–1, p = 0.1] than applied over vegetation [0.00454 ± 0.00336 g(g×d)–1, p = 0.1].