HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Legg, J. O. Articles by DeMar, W. H. Search for Related Content PubMed Articles by Legg, J. O. Articles by DeMar, W. H. Agricola Articles by Legg, J. O. Articles by DeMar, W. H.

Incorporation of ¹⁵N-Tagged Mineral Nitrogen into Stable Forms of Soil Organic Nitrogen¹

ABSTRACT

Transformation of ¹⁵N-tagged mineral N into organic forms was accelerated by growing a series of oat crops (Avena sativa L.) in the greenhouse, with each crop growing to sufficient maturity for the seed to be used for the next crop. The plant material was returned to the soil, except for triplicate pots which were removed for analysis at each cropping period. Availability ratios (fraction of plant N that is ¹⁵N divided by the fraction of soil N that is initially ¹⁵N for each cropping period) declined from an initial value of 10.4 for the Chester surface soil to approximately 2 after 11 crops.

During long-term mineralization tests with soil samples taken after two, five, and eight cropping periods, availability ratios were also stable, or soon became stable, at approximately 2. When similar soil samples were extracted after autoclaving in 0.01M CaCl₂ or subjected to acid hydrolysis, however, the "extractability ratios" approached unity. It is hypothesized that about half of the indigenous N in the Chester soil is biologically unavailable because of inaccessibility to microorganisms of organic N compounds or complexes incorporated within microaggregates.

¹ Contribution from the US Soils Lab., Soil and Water Conservation Research Division, ARS, USDA, Beltsville, Md.

² Research Soil Scientists and Agricultural Research Technician, respectively.

Received for publication July 31, 1970. Accepted for publication October 15, 1970.