C. Vankessel et al., SEASONAL-VARIATIONS IN DENITRIFICATION AND NITROUS-OXIDE EVOLUTION ATTHE LANDSCAPE SCALE, Soil Science Society of America journal, 57(4), 1993, pp. 988-995
This study was conducted to examine the seasonal and spatial variabili
ty of denitrification in various landform elements in a pea (Pisum sat
ivum L.) field at Blaine Lake, Saskatchewan, Canada. The distributions
of denitrification activity and N2O evolution were highly skewed, and
could not be log-transformed to yield normal distributions. Consequen
tly, ordinary statistical procedures (i.e., those based on a normal di
stribution) were considered inappropriate for this study, and nonparam
etric statistics were used to describe the data. Denitrification activ
ity and N2O evolution exhibited similar temporal and landscape-scale p
atterns and were highly correlated, suggesting that denitrification wa
s the main source of N2O evolution. In general, N2O evolution accounte
d for almost-equal-to 41% of the denitrification activity. Maximum rat
es of denitrification were low prior to spring tillage and seeding, in
creased during the first half of the growing season (following the add
ition of fertilizer N), and decreased toward the end of the growing se
ason; denitrification had essentially ceased by the fall sampling. Sta
tistical outliers for denitrification activity, i.e., hotspots of acti
vity, occurred predominantly at low levels of denitrification activity
and were completely absent when denitrification activity was at its m
aximum. Therefore, the importance of hotspots of activity for estimati
ng seasonal rates of denitrification appears to be limited. Soil water
content was the most dominant factor controlling denitrification acti
vity, followed by the concentration of NH4+, total soil respiration, a
nd NO3-. The intensity of denitrification was controlled largely by hy
drologic processes, which, in turn, were influenced by the topography
of the landscape. Nevertheless, the landscape-scale patterns of denitr
ification and N2O evolution were intensity-independent and remained co
nsistent throughout the season.