MINERALIZATION RATE CONSTANTS AND THEIR USE FOR ESTIMATING NITROGEN MINERALIZATION IN SOME CANADIAN PRAIRIE SOILS

Abstract

There is a need to provide quantitative relationships that will allow agronomists to estimate accurately the nitrogen-supplying power of soils while taking into account both temperature and soil moisture variations. The procedure for estimating net nitrogen mineralization proposed by Stanford and co-workers was used to determine Arrhenius relationships between the rate constants (k) and absolute temperature (°K) for 33 virgin and cultivated Western Canadian prairie surface (0–15 cm) soils. There was no significant difference in Arrhenius relationship between soils within each soil zone; thus, a single average Arrhenius equation was calculated per soil zone. Average Q10 for the Brown chernozemic soils was 2.75, for the Dark Brown, thin Black and thick Black chernozems, 2.18, and for the Gray luvisols, 2.0. These Q10 values are as high or higher than those reported in other parts of the world and may be related to the degree of degradation of the soil organic matter in these various soils. Culture had no marked effect on Q10 but sandy soils had higher Q10 than loams and clays. An equation for estimating net nitrogen mineralization for the Wood Mountain loam (a Brown chernozem) was tested using data from a previous study. The results were quite satisfactory, especially when the test data were derived under laboratory conditions where moisture was well controlled. The temperature functions presented herein can be used together with moisture functions and potentially mineralizable nitrogen results published earlier to make first estimates of net nitrogen mineralized during the growing season in the soils tested. Key words: Q10, Arrhenius relationship, potentially mineralizable nitrogen