Assessing Organic Nitrogen Acquisition of Ericoid Mycorrhizae in Highbush Blueberry (Vaccinium corymbosum L.) Plants by Using an 15N Tracer

Abstract

The ability of mycorrhizal highbush blueberry plants to acquire soil organic nitrogen under different organic amendment regimes was investigated in a field experiment by using an 15N tracer. Plants inoculated with an ericoid mycorrhizal isolate from the genus Oidiodendron had lower leaf 15N enrichment than uninoculated plants, indicating mycorrhizal (M) plants absorbed more unlabeled soil nitrogen than nonmycorrhizal (NM) plants. The unlabeled nitrogen was presumably from soil organic N sources which might be less available to NM plants. M plants produced more plant dry weight and larger canopy volume, presumably as a result of improved N acquisition ability. In the study, the effect of pre-plant organic amendments on the growth of highbush blueberry plants was clearly demonstrated. The forest litter amendment produced higher dry mass than either the rotted sawdust amendment or no amendment. The rotted sawdust amendment produced the smallest plants. These results suggested that organic amendments with different C:N ratios might have affected soil N availability by affecting the N mineralization process. The implication of these findings in the production of highbush blueberry in mineral soils will be discussed.