Nitrogen turnover by sequential immobilization and mineralization during residue decomposition in soils

• Published in: Soil Science Society of America journal Vol. 59; no. 4; pp. 1052 - 1058
• Main Authors: Blackmer, A.M. (Iowa State University, Ames, IA.), Green, C.J
• Format: Journal Article
• Language: English
• Published: Madison, WI Soil Science Society of America 01-07-1995; American Society of Agronomy
• Subjects: ABONOS NITROGENADOS; Agronomy. Soil science and plant productions; AZOTE; Biochemistry; Biological and medical sciences; Chemical, physicochemical, biochemical and biological properties; Clay; Clay loam; Corn; Decomposition; DEGRADACION; DEGRADATION; DOSE D'APPLICATION; DOSIS DE APLICACION; ENGRAIS AZOTE; Flowers & plants; Fundamental and applied biological sciences. Psychology; IMMOBILISATION; INMOVILIZACION; Loam soils; METABOLISME DE L'AZOTE; METABOLISMO DEL NITROGENO; MINERALISATION; MINERALIZACION; Mineralization; NITRATE; NITRATOS; Nitrogen; NITROGENO; Organic matter; Physics, chemistry, biochemistry and biology of agricultural and forest soils; RESIDU DE RECOLTE; RESIDUOS DE COSECHAS; Soil science; Soils; Stover; TECHNIQUE DES TRACEURS; TECNICAS DE TRAZADORES; ZEA MAYS; Laboratory study; Monocotyledones; Chemical analysis; Gas emission; Zea mays; Isotope labelling; Carbon dioxide; Immobilization; Isotopic composition; Decomposition; Nitrates; Mollisols; Nitrogen Isotopes; Cereal crop; Vegetal waste; Soils; Soil testing; Nitrogen cycle; Gramineae; Mineralization; Angiospermae; Turnover; Spermatophyta
• ISSN: 0361-5995; 1435-0661
• DOI: 10.2136/sssaj1995.03615995005900040014x

Additions of 15N-labeled fertilizers to soils often induce mineralization of nonlabeled N, and such mineralization poses problems when interpreting the results of isotopic analyses. We studied the effects of added 15NO3- on turnover of N during the decomposition of corn (Zea mays L.) residues in soils. Samples of a Galva silty clay loam (fine-silty, mixed, mesic Typic Hapludoll) were treated with various levels of corn stover and various levels of 15N-labeled NO3- and were incubated for 90 d. Evolution of CO2 and concentrations and isotopic composition of NO3 were monitored. Increases in rates of NO3 addition increased initial rates of immobilization of labeled N and subsequent rates of mineralization of nonlabeled N. The sequential immobilization of labeled N and mineralization of nonlabeled N resulted in substantial replacement of labeled NO3 by nonlabeled NO3-. Early added-N-induced immobilization of labeled N often was offset by subsequent added-N-induced mineralization of nonlabeled N before the end of the study. Sequential immobilization and mineralization should be recognized as a potential source of error in 15N-tracer studies because sequential processes violate the commonly held assumptions that mineralization and immobilization occur simultaneously. This error could be avoided by recognizing that sequential immobilization and mineralization can occur and that the sequential processes result in a different distribution of isotopes than does simultaneous mineralization-immobilization turnover