NITROGEN MINERALIZATION FROM ORGANIC RESIDUES: RESEARCH OPPORTUNITIES

Authors: CABRERA, M - UNIV OF GEORGIA; KISSEL, D - UNIV OF GEORGIA; Vigil, Merle

Submitted to: Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/1/2004
Publication Date: 3/1/2005
Citation: Cabrera, M.L., Kissel, D.E., Vigil, M.F. 2005. Nitrogen mineralization from organic residues: research opportunities. Environmental Quality. v34:75-79.

Interpretive Summary: The essential plant/crop nutrient nitrogen (N), when found in excess of crop need has potential to become an environmental contaminant. Research on nitrogen (N) cycling in natural soil/plant systems then becomes important. Here we review research on the release of N from microbial decomposition of organic residues. This process is known as net N mineralization. We evaluate field, laboratory and field modeling efforts, with the objective of highlighting areas with opportunities for additional research. The factors controlling net N mineralization include composition of the residue, soil temperature and water content, drying and rewetting events, and soil characteristics. Because C to N ratio of the residue cannot explain all the variability observed in N mineralization among residues, considerable effort has been dedicated to the identification of specific compounds that play critical roles in N mineralization. Spectroscopic techniques are promising tools to further identify these compounds. Many studies have evaluated the effect of temperature and soil water content on N mineralization, but most have concentrated on mineralization from soil organic matter, not from organic residues. Additional work should be conducted with different organic residues, paying particular attention to the interaction between soil temperature and water content. Additional work with more complex simulation models is needed to simulate both gross N mineralization and N 'tie-up' by microbial biomass to better estimate net N mineralized from organic residues.

Technical Abstract: Research on nitrogen (N) mineralization from organic residues is important to understand N cycling in soils. Here we review research on factors controlling net N mineralization as well as research on laboratory and field modeling efforts, with the objective of highlighting areas with opportunities for additional research. Among the factors controlling net N mineralization are organic composition of the residue, soil temperature and water content, drying and rewetting events, and soil characteristics. Because C to N ratio of the residue cannot explain all the variability observed in N mineralization among residues, considerable effort has been dedicated to the identification of specific compounds that play critical roles in N mineralization. Spectroscopic techniques are promising tools to further identify these compounds. Many studies have evaluated the effect of temperature and soil water content on N mineralization, but most have concentrated on mineralization from soil organic matter, not from organic residues. Additional work should be conducted with different organic residues, paying particular attention to the interaction between soil temperature and water content. One-and two-pool exponential models have been used to model N mineralization under laboratory conditions, but some drawbacks make it difficult to identify definite pools of mineralizable N. Fixing rate constants have been used as a way to eliminate some of these drawbacks when modeling N mineralization from soil organic matter, and may be useful for modeling N mineralization from organic residues. Additional work with more complex simulation models is needed to simulate both gross N mineralization and immobilization to better estimate net N mineralized from organic residues.