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Effects of Alfalfa Proportions and Clipping Frequencies on Timothy‐Alfalfa Mixtures. II. Nitrogen Fixation and Transfer 1
Author(s) -
Ta T. C.,
Faris M. A.
Publication year - 1987
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj1987.00021962007900050013x
Subject(s) - medicago sativa , phleum , loam , agronomy , nitrogen , biology , legume , pasture , zoology , chemistry , soil water , ecology , organic chemistry
The inclusion of legumes in grass pastures often increases grass yields due to the contribution of the N fixed by the legume to the associated grass. This benefit was evaluated in field experiments under different management conditions at Ottawa, Ontario, Canada, on a Manotick mixed sandy loam soil (Typic Dystrochrett) labeled with 15 N. Timothy ( Phleum pratense L.) and alfalfa ( Medicago sativa L.) were grown in pure stands and in mixtures at two proportions (1:1 and 1:2) and harvested at three alfalfa maturity stages (early, mid‐, and late bloom). Nitrogen fixed by alfalfa and N transfer from alfalfa to timothy were calculated from the differences between the isotopic compositions of the two species in mixture and timothy in pure stand. The highest amounts of N in alfalfa shoots originating from N fixed were 192 and 215 kg N ha −1 yr −1 in the first and second year, respectively, when harvested at mid‐bloom (four cuts). The inclusion of timothy in alfalfa stands increased the proportion of N fixed by alfalfa. Nitrogen transfer from alfalfa to associated timothy contributed up to 22% (first year) and 30% (second year) of the total N yield of timothy and amounted to up to 13 kg N ha −1 yr −1 . This transfer increased with progressive cuts and with an increased proportion of alfalfa in the mixture. Growing alfalfa in mixture with timothy at a high proportion to timothy is an ideal system for maximum N transfer and for reducing N fertilizer usage.