Animal Grazing and Forage Effect on Soil CO2 Fluxes in a Semi-Arid Pastureland in Northern Nevada.

Agricultural practices like animal grazing and forage management can influence soil greenhouse gas fluxes in semi-arid pastureland. Cattle grazing and forage treatments impact soil respiration and carbon dioxide emission. Gas samples were collected in a rotational grazing pasture at the University of Nevada, Reno Main Experiment Station in Reno Nevada. The objective of this study was to evaluate animal grazing and forage management impact on soil CO₂ emission in a semi-arid ecosystem. Soil gas samples were collected before and during cattle grazing to determine grazing and forage effect on soil CO₂ fluxes. Soil temperature and moisture were measured during each sampling period. Six forage systems (treatments) were used in this study (i) Alfalfa Mix [contained: alfalfa (40%), tall fescue (30%), and smooth bromegrass (30%)], (ii) White clover Mix [contained: white clover (40%), tall fescue (30%), and smooth bromegrass (30%)], and four spatially separated (SS) adjacent monocultures of grass and legume (50:50 ratio) within the same paddock (iii) Tall fescue-alfalfa, (iv) Smooth bromegrass-alfalfa, (v) Tall fescue-white clover, and (vi) Smooth bromegrass-white clover. Soil gas samples were collected from each paddock about 60m distance from the water source. Gas was sampled bi-weekly in each paddock and analyzed for CO₂ emission. There was pasture and period effect in the emission of CO₂ between October and November respectively (P = 0.0244). CO₂ emission differs significantly among the various pasture treatments. The mixed pasture with white clover and smooth bromegrass are the only forage component significantly different in the October and November period (P=0.0164 and 0.0564). The soil CO₂ fluxes per day were positively correlated to soil temperature (0.0183) but showed a negative correlation with soil moisture (0.2165). Results from this study are preliminary as the study is still in its infancy stage and on-going.