Back P. D. Millner and D. D. Kaufman
Agricultural Research Service, U.S. Department of Agriculture, Beltsville, Maryland, USA
Full Paper (PDF File: 171KB)
Abstract
Soil organic matter (SOM) undergoes continuous decomposition over many
years and the decomposition process is characterized by a series of stages.
Plant, animal, and microbial constituents and residues are the building
blocks of SOM. Soil microbial biomass (SMB) is that portion of the organic
matter associated with the living soil microbial (bacterial fungi, and
fauna) populations. SMB is a major source and sink for nutrients, and it
controls the rate of turnover and mineralization of nutrients. Soil mesofauna
(microarthropods) break residues into ever smaller particles so that they
may be accessed more easily by enzymes and, thereby, decomposition is facilitated.
The soil hyphae of mycorrhizal fungi effectively increase the rhizosphere
around plant roots, and the active nutrient absorption zone and surface
area of plants in soil. Thus, the measurement and evaluation of the biological
aspects of SOM cycling relative to soil quality are quite complex and challenging.
Recent advances in quantitative techniques need to be applied to assess
SOM and microbial interactions and their consequences.