AMMONIUM FIXATION AND AVAILABILITY IN HARPSTER CLAY LOAM F. ALLISON;JANET DOETSCH;E. ROLLER; Soil Science

Ammonium fixation and availability in harpster clay loam

Inorganic Forms of Nitrogen

Publisher Summary 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 19th 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 NO3-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.

Mineralization of Organic Nitrogen in Soil

Soil is undoubtedly the most complex of all microbial habitats. Primarily because of this complexity, there is insufficient information on how and where most microbial events occur in soil in situ and which microbes are the major and, physiologically, the most important participants in these events. Soil differs from most other microbial habitats in that it is dominated by a solid phase consisting of particulates of different sizes and which is surrounded by aqueous and gaseous phases that fluctuate markedly in time and space. The solid phase is a tripartite system composed of finely divided minerals (both primary and secondary); plant, animal, and microbial residues in various stages of decay; and a living and metabolizing microbiota. These particulates exist as both independent entities and mixed conglomerates. The aqueous phase surrounding the particulates is normally discontinuous, except when soil is saturated, and this restricts the movement of microbes, especially of bacteria and other nonfilamentous forms, and results in local accumulations of nutrients and toxicants, escape of cells from grazing predators, a low probability for genetic transfer, etc. These particulate-aqueous associations constitute the "microhabitats" wherein microbes reside and function in soil. The abiotic components of soil have been relatively well defined, both qualitatively and quantitatively. However, the microgeographic distribution and the geometric relations of abiotic components to each other-and to the microbiotic components-and the interactions among and between the abiotic and microbiotic components are not clearly defined. Most of what is known about the composition of the abiotic components has been obtained by dispersing soil-either chemically or physi-

Influence of Soil Mineral Colloids on Metabolic Processes, Growth, Adhesion, and Ecology of Microbes and Viruses

Retention and Fixation of Ammonium and Ammonia in Soils

Fixed NH
 4
 +
 (NH
 4
 +
 f) and fixation and defixation of NH
 4
 +
 in soils have been the subject of a number of investigations with conflicting results. The results vary because of differences in methodology, soil type, mineralogical composition, and agro-climatic conditions. Most investigators have determined NH
 4
 +
 f using strong oxidizing agents (KOBr or KOH) to remove organic N and the remaining NH
 4
 +
 f does not necessarily reflect the fraction that is truly available to plants. The content of native NH
 4
 +
 f in different soils is related to parent material, texture, clay content, clay mineral composition, potassium status of the soil and K saturation of the interlayers of 2:1 clay minerals, and moisture conditions. Evaluation of the literature shows that the NH
 4
 +
 f-N content amounts to 10–90 mg kg−1 in coarse-textured soils (e.g., diluvial sand, red sandstone, granite), 60–270 mg kg−1 in medium-textured soils (loess, marsh, alluvial sediment, basalt) and 90–460 mg kg−1 in fine-textured soils (limestone, clay stone). Variable results on plant availability of NH
 4
 +
 f are mainly due to the fact that some investigators distinguished between native and recently fixed NH
 4
 +
 while others did not. Recently fixed NH
 4
 +
 is available to plants to a greater degree than the native NH
 4
 +
 f, and soil microflora play an important role in the defixation process. The temporal changes in the content of recently fixed NH
 4
 +
 suggest that it is actively involved in N dynamics during a crop growth season. The amounts of NH
 4
 +
 defixed during a growing season varied greatly within the groups of silty (20–200 kg NH
 4
 +
 -N ha−1 30 cm−1) as well as clayey (40–188 kg NH
 4
 +
 -N ha−1 30 cm−1) soils. The pool of recently fixed NH
 4
 +
 may therefore be considered in fertilizer management programs for increasing N use efficiency and reducing N losses from soils.

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Ammonium fixation and availability in harpster clay loam

Citations

Inorganic Forms of Nitrogen

Mineralization of Organic Nitrogen in Soil

Influence of Soil Mineral Colloids on Metabolic Processes, Growth, Adhesion, and Ecology of Microbes and Viruses

Retention and Fixation of Ammonium and Ammonia in Soils

Fixation and defixation of ammonium in soils: a review

Related Papers (5)

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