N2 Fixation (C2H2 reduction) by epiphylls on coffee,Coffea arabica

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Abstract
Nitrogen fixation (C2H2 reduction) by epiphylls on coffee,Coffea arabica, grown in sites with different degrees of shade, was determined. Coffee leaves with nitrogen-fixing epiphylls were found in all sites in approximately equal numbers. Rates of C2H2 reduction were similar for all sites and throughout the year, averaging 3.21 nmoles C2H2 reduced leaf with epiphylls−1 day−1. Apparently, neither rates of activity nor abundance of leaves with nitrogen-fixing epiphylls is related to the degree of shade in a site. No correlation was found between percent epiphyll cover and the presence or magnitude of nitrogen-fixing activity. Calculated annual fixation by epiphylls on coffee was low, ranging from 0.7 g N2 ha−1 year−1 for the shadeless site to 1.4 g N2 ha−1 year−1 for the site withIngajinicuil shade trees. These results suggest that epiphyll fixation is not an important source of nitrogen for the coffee ecosystem studied.