INFLUENCE OF SAMPLE-SIZE ON MEASUREMENT OF SOIL DENITRIFICATION

The influence of sample size on the magnitude and variability of soil denitrification was studied by collecting soil cores, ranging in size from 1. 7 to 5. 4 cm in diameter, from no-till and conventional-till corn plots. Estimates of natural denitrification rates were obtained by incubating intact soil cores with C//2H//2 and monitoring gaseous N//2O production. In addition, maximum denitrification potential was determined by monitoring N//2O production in anaerobic slurries amended with glucose, NO//3** minus and C//2H//2. The results of this study are consistent with the hypothesis that the source of variability associated with the natural denitrification rates is the patchy distribution of denitrifying 'hot spots' in soil. Some implications associated with the application of classical statistical methods to lognormal data are also discussed.