Soil nitrogen. III.—Mineralizable nitrogen determined by an incubation technique

Abstract

Abstract ‘Mineralizable‐N’ values were determined by incubating at 18° a series of 27 soils of medium and heavy textures at 50% of their moisture‐holding capacity for 30 days. Increases in nitrate levels following incubation of soils which had been previously air‐dried were, on average, three times as great as increases given by incubating corresponding freshly‐sampled soils. In all soils the levels of nitrate and total mineral nitrogen increased appreciably on incubation; corresponding changes in ammonium levels were smaller, were irregular and were not related to other soil characteristics. Increases in nitrate and in total inorganic nitrogen on incubating air‐dried soils were approximately related to the initial levels of nitrate present in the soils when they were sampled, and to their percentages of total nitrogen.