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Estimated N 2 –Fixation of Cool‐Season Annual Clovers by the Difference Method
Author(s) -
Evers G. W.,
Parsons M. J.
Publication year - 2011
Publication title -
crop science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.76
H-Index - 147
eISSN - 1435-0653
pISSN - 0011-183X
DOI - 10.2135/cropsci2010.10.0597
Subject(s) - lolium multiflorum , biology , trifolium subterraneum , agronomy , dry matter , growing season , horticulture , pasture
Information on the N 2 –fixation (NF) capacity of cool‐season annual clovers in the southeastern United States is lacking. Estimates of NF were determined on arrowleaf ( Trifolium vesiculosum Savi), crimson ( Trifolium incarnatum L.), rose ( Trifolium hirtum All.), and subterranean ( Trifolium subterraneum L.) clovers using the difference in N accumulation of the clovers and annual ryegrass ( Lolium multiflorum Lam.) as the nonfixing plant at 2‐wk intervals for 2 yr. Initial estimates of NF were negative because N accumulation in ryegrass exceeded that in clovers. The general trend was for NF and percent plant N from NF to increase as dry matter (DM) yield increased. Percentage of plant N fixed from the atmosphere exceeded 75% for all clover species at some point in spring. The 2 yr average maximum NF values using herbage mass (HM) were 296 kg N ha −1 for arrowleaf clover, 189 kg N ha −1 for crimson clover, 215 kg N ha −1 for rose clover, and 192 kg n ha −1 for subterranean clover. Using HM plus roots increased maximum NF values from 4 to 12 kg N ha −1 . The root NF contribution was greatest during the winter after NF values turned positive ranging from 8 to 83% of plant NF. Then they decreased with plant maturity from 1 to 9% of total plant NF. Crimson clover had the greatest NF values until mid March after which the later‐maturing arrowleaf clover had the greatest NF value.