H. Flessa et al., INFLUENCE OF CATTLE WASTES ON NITROUS-OXIDE AND METHANE FLUXES IN PASTURE LAND, Journal of environmental quality, 25(6), 1996, pp. 1366-1370
Agricultural practices are assumed to contribute significantly to the
increase in atmospheric N2O concentrations observed in the last decade
s, and they might influence the consumption of atmospheric CH4. We rep
ort on measurements of N2O and CH4 exchange of a pasture soil, as infl
uenced by droppings of a grazing cattle (BOS taurus) herd. Nitrous oxi
de and methane fluxes in pasture soil were largely determined by the e
mission rates From cattle excrement with dung patches being hot spots
of CH4 production and urine-affected areas showing extremely high N2O
release rates. Methane emissions from dung patches (0.778 g CH4-C per
animal and day) were insignificant when compared with those from the r
umen of the cattle. Total N2O-N losses from the droppings were equival
ent to 3.2% of the nitrogen excreted. Based on global data of total ni
trogen excretion by dairy cattle, non-dairy cattle, buffalo (Syncerus
caffer), and bison during grazing, we estimate the global N2O emission
from this source to be similar to 1.18 teragrams N2O-N per year, indi
cating that grazing cattle excretory products are one of the most impo
rtant sources of atmospheric nitrous oxide. Our work suggests that the
se sources have been drastically underestimated.