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Understanding the variability in soybean nitrogen fixation across agroecosystems

Permanent URL:
http://handle.nal.usda.gov/10113/41175
File:
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Abstract:
Legume-based cropping systems have the potential to internally regulate N cycling due to the suppressive effect of soil N availability on biological nitrogen fixation. We used a gradient of endogenous soil N levels resulting from different management legacies and soil textures to investigate the effects of soil organic matter dynamics and N availability on soybean (Glycine max) N₂ fixation. Soybean N₂ fixation was estimated on 13 grain farm fields in central New York State by the ¹⁵N natural abundance method using a non-nodulating soybean reference. A range of soil N fractions were measured to span the continuum from labile to more recalcitrant N pools. Soybean reliance on N₂ fixation ranged from 36% to 82% and total N₂ fixed in aboveground biomass ranged from 40 to 224 kg N ha⁻¹. Soil N pools were consistently inversely correlated with % N from fixation and the correlation was statistically significant for inorganic N and occluded particulate organic matter N. However, we also found that soil N uptake by N₂-fixing soybeans relative to the non-nodulating isoline increased as soil N decreased, suggesting that N₂ fixation increased soil N scavenging in low fertility fields. We found weak evidence for internal regulation of N₂ fixation, because the inhibitory effects of soil N availability were secondary to the environmental and site characteristics, such as soil texture and corresponding soil characteristics that vary with texture, which affected soybean biomass, total N₂ fixation, and net N balance.
Author(s):
Schipanski, M. E. , Drinkwater, L. E. , Russelle, M. P.
Subject(s):
Glycine max , soybeans , nitrogen fixation , Rhizobiaceae , nitrogen , soil fertility , nutrient availability , soil organic matter , nitrogen content , plant tissues , nutrient uptake , soil texture , biogeochemical cycles , New York
Format:
p. 379-397.
Note:
Includes references
Source:
Plant and soil 2010 Apr., v. 329, no. 1-2
Language:
English
Publisher:
Dordrecht : Springer Netherlands
Year:
2010
Collection:
Journal Articles, USDA Authors, Peer-Reviewed
Rights:
Works produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted.