Document Detail

Reduced nitrate leaching and enhanced denitrifier activity and efficiency in organically fertilized soils.
MedLine Citation:
PMID:  16537377     Owner:  NLM     Status:  MEDLINE    
Conventional agriculture has improved in crop yield but at large costs to the environment, particularly off-site pollution from mineral N fertilizers. In response to environmental concerns, organic agriculture has become an increasingly popular option. One component of organic agriculture that remains in question is whether it can reduce agricultural N losses to groundwater and the atmosphere relative to conventional agriculture. Here we report reduced N pollution from organic and integrated farming systems compared with a conventional farming system. We evaluated differences in denitrification potential and a suite of other soil biological and chemical properties in soil samples taken from organic, integrated, and conventional treatments in an experimental apple orchard. Organically farmed soils exhibited higher potential denitrification rates, greater denitrification efficiency, higher organic matter, and greater microbial activity than conventionally farmed soils. The observed differences in denitrifier function were then assessed under field conditions after fertilization. N(2)O emissions were not significantly different among treatments; however, N(2) emissions were highest in organic plots. Annual nitrate leaching was 4.4-5.6 times higher in conventional plots than in organic plots, with the integrated plots in between. This study demonstrates that organic and integrated fertilization practices support more active and efficient denitrifier communities, shift the balance of N(2) emissions and nitrate losses, and reduce environmentally damaging nitrate losses. Although this study specifically examines a perennial orchard system, the ecological and biogeochemical processes we evaluated are present in all agroecosystems, and the reductions in nitrate loss in this study could also be achievable in other cropping systems.
Sasha B Kramer; John P Reganold; Jerry D Glover; Brendan J M Bohannan; Harold A Mooney
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.     Date:  2006-03-13
Journal Detail:
Title:  Proceedings of the National Academy of Sciences of the United States of America     Volume:  103     ISSN:  0027-8424     ISO Abbreviation:  Proc. Natl. Acad. Sci. U.S.A.     Publication Date:  2006 Mar 
Date Detail:
Created Date:  2006-03-22     Completed Date:  2006-05-11     Revised Date:  2013-06-07    
Medline Journal Info:
Nlm Unique ID:  7505876     Medline TA:  Proc Natl Acad Sci U S A     Country:  United States    
Other Details:
Languages:  eng     Pagination:  4522-7     Citation Subset:  IM    
Department of Biological Sciences, Stanford University, Stanford, CA 94305.
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MeSH Terms
Environmental Pollution*
Fertilizers / analysis*
Nitrates / analysis,  metabolism*
Soil / analysis*
Soil Pollutants / analysis,  metabolism*
Reg. No./Substance:
0/Fertilizers; 0/Nitrates; 0/Soil; 0/Soil Pollutants

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