NITROUS-OXIDE EMISSION IN RELATION TO SOIL FACTORS AT LOW TO INTERMEDIATE MOISTURE LEVELS

The objective of this study was to investigate the N2O emission from agricultural soils (14 field plots/38 measurements) as a function of environmental and soil factors-clay content, soil temperature, soil moisture, total organic C and N, water-soluble organic C, nitrate and ammonium concentrations, and pH-that are considered of significance for N2O production in soil. Possible relations were tested by multiple linear regression and multivariate data analysis (PIS). A significant (P less-than-or-equal-to 0.05) relation (linear regression) was obtained only between N2O emission rates and NO3- concentration in soil. However, the degree of explanation was low (R2 = 13%). If one field, with N2O emission rate several orders of magnitude higher than from the others, was excluded from the analysis a significant relation with the NH4+ concentration was obtained. In this case the degree of explanation was 17%. The results from the PLS analysis were similar to those from the regression analysis. If clay soils (>40% clay) were analyzed separately, NH4+ concentration and soil moisture for 65% (P less-than-or-equal-to 0.05) of the variability of the N2O emission rates. In the medium- and low-clay soils no similar relationships were found. In conclusion, the obstacles caused by the complexity of the soil system and the different scale of measurement of N2O emission rates and soil factors probably obscured the possibility to relate the N2O emission rates to single or combinations of soil factors.