Loss of organic matter and potentially mineralizable nitrogen from Saskatchewan soils due to cropping.

Abstract

Cropping caused large losses of organic C (41-53%) and N (31-56%), but losses of potentially mineralizable N (N0) were even greater for the Chernozems (55-67%) though not for the Gray Luvisols. N0 in virgin soils ranged between 133 and 401 mu g N/g soil and increased from Gray Luvisol to Brown to Dark Brown to thin Black Chernozem. In cultivated soils, N0 was generally similar among soil zones and values ranged between 66-141 mu g N/g soil. Medium-textured soils generally had the greatest organic matter content and N0. The active N fraction (N0/N) ranged between 4-20.5% and was greatest in brown soils and in the coarser-textured soils. Losses of organic matter, N0, and N0/N were greatest from the coarser-textured soils. Findings help to explain why a significant portion of prairie soils now require N fertilizer even after being summer-fallowed. -from Authors