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

This Article Figures Only Full Text Free Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (23) Citing Articles via Google Scholar Google Scholar Articles by Kristensen, H.L. Articles by Meisinger, J.J. Search for Related Content PubMed Articles by Kristensen, H.L. Articles by Meisinger, J.J. Agricola Articles by Kristensen, H.L. Articles by Meisinger, J.J.

DIVISION S-6-SOIL & WATER MANAGEMENT & CONSERVATION

Effects of Soil Structure Disturbance on Mineralization of Organic Soil Nitrogen

^a USDA-ARS Environmental Chemistry Lab., Beltsville, MD 20705 USA
^b Dep. of Terrestrial Ecology, National Environmental Research Inst., Vejlsøvej 25, DK-8600 Silkeborg, Denmark

gmccarty{at}asrr.arsusda.gov

Disturbance of soil structure by tillage operations is thought to make soil organic N accessible for mineralization which was otherwise protected from degradation. The origin of N released by disturbance of soil structure is, however, poorly understood and needs to be related to microbial activity. This study was performed to investigate the effect of soil structure disturbance on the release of active or protected organic N pools in surface soils (0–2 cm) under plow- (PT) or no-tillage (NT) management. Active soil N was defined as the pool participating in mineralization–immobilization turnover during short-term incubation (6 d) while protected pools were considered inactive during this period. The active pool of soil N was labelled with ¹⁵N in intact samples of PT and NT soils. The samples were either kept intact or sieved and repacked, and then leached weekly during a 35-d incubation period. The disturbance of soil structure increased mineral N release from 6 to 15 mg kg^-1 in the NT soil within the first week after disturbance. This release was found to originate from both active and physically protected N pools as could be assessed by the relative differences in ¹⁵N content of mineralized N by intact and disturbed soil samples. In contrast, the release from the PT soil was 7 to 9 mg N kg^-1 after disturbance, with only a minor contribution from protected N pools. These results support the theory that disturbance of soil structure by tillage may destabilize and release protected pools of soil N. Over the entire period of incubation, protected N accounted for 27% of total N release in the NT soil and 12% in that of PT. The calculation of availability ratios, defined as the ratio between the ¹⁵N enrichment of mineralized N and that of total soil N, showed that recently added ¹⁵N was less available for mineralization in the NT soil as compared to that of PT. The probable cause for this difference was the higher C/N ratio of organic matter in NT surface soil indicating more nonhumified organic matter when compared to PT organic matter.

Abbreviations: PT, plow-tillage • NT, no-tillage • MIT, mineralization–immobilization turnover • AR, availability ratio

This article has been cited by other articles:

				A. Bono, R. Alvarez, D. E. Buschiazzo, and R. J. C. Cantet Tillage Effects on Soil Carbon Balance in a Semiarid Agroecosystem Soil Sci. Soc. Am. J., June 18, 2008; 72(4): 1140 - 1149. [Abstract] [Full Text] [PDF]