Mineralization of Organic Nitrogen in Soil

Abstract

This chapter reviews important papers of research in the field of mineralization of organic nitrogen in soil, beginning with the years preceding World War II. Although mineralization of nitrogen must consequently be recognized as a very old problem—even the overestimation of the importance of humus for plant nutrition by Albrecht Thaer at the beginning of the 19 th century was a result of the conviction of mineralization of organic compounds in soil—it still occupies a prominent position in studies about plant nutrition. The general character of the nitrogen balance in grassland has been investigated long ago, but the spectacular ability of perennial grass to absorb even very high amounts of applied nitrogen and to retain nearly all mineralized and added nitrogen in organically bound form is still considered surprising. Consequently, much attention is paid to this characteristic of grassland and the whole problem of nitrogen mineralization in grassland remains unsolved. Investigations on nitrogen mineralization in uncultivated virgin bogs are very scarce. Cyplenkin and Schilin showed NO 3 -N formation in the waterlogged peaty soil of the tundra only locally on some hill crests and southbound slopes. Ammonification is much more common in the tundra soil, but is still very slow compared to well-drained neutral soils. Michniewicz determined the rate of nitrogen mineralization and the number of nitrifying organisms in the upper layers of the forest floor and of peat bogs.