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Fate of Nitrogen‐15 in a Perennial Ryegrass Seed Field and Herbaceous Riparian Area
Author(s) -
Davis J. H.,
Griffith S. M.,
Horwath W. R.,
Steiner J. J.,
Myrold D. D.
Publication year - 2006
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2005.0223
Subject(s) - riparian zone , perennial plant , environmental science , agronomy , riparian forest , riparian buffer , soil water , fertilizer , denitrification , biomass (ecology) , nitrogen , surface runoff , hydrology (agriculture) , ecology , chemistry , biology , soil science , habitat , geology , geotechnical engineering , organic chemistry
Intensive management of grass seed fields in the poorly drained soils of the Willamette Valley, Oregon, has prompted concern in the capacity of these landscapes and their associated minimally managed riparian areas to process and retain fertilizer N. Our goal was to determine the extent of N losses and effectiveness of a riparian area and an adjacent perennial ryegrass seed field to retain N. The fate of fertilizer 15 NH 4 and 15 NO 3 was determined with a 15 N tracer experiment. During the second year of the study, 15 N recovery in the plant and soil (0–30 cm) from the cropping system was 51% for 15 NH 4 and 43% for 15 NO 3 whereas recovery in the riparian area was only 20% of 15 NH 4 and 31% of 15 NO 3 Greater cropping system retention of 15 N resulted from both greater uptake by the crop and greater retention of 15 N in the soil. Low recovery of 15 N in the riparian area was possibly the result of two significant spring flood events saturating the surface soil of the riparian area but not the cropping system. The prolonged seasonal saturated conditions significantly reduced riparian plant biomass production and N uptake and increased the potential of N loss through overland flow and denitrification. Results indicate that the cropping system had larger available N pools and a larger potential to retain fertilizer N than the riparian zone. However, both areas were prone to substantial loss of applied N.