Establishment of Kentucky Bluegrass Inoculated By a Novel Nitrogen-Fixing Bacterial Endophyte.

Field research shows application of nitrogen (N) fertilizer to turfgrass is subject to leaching, volatilization, and/or denitrification. Such losses counteract the industry’s goals of efficient culture and environmental sustainability. Biological N fixation (BNF) by microbial symbionts has been confirmed to benefit several non-legume plant species; and may potentially satisfy, to some degree, N fertilizer requirements of turfgrasses. A field experiment was initiated in 2014 to: (i) assess how inoculation of Poa pratensis (Kentucky bluegrass, KBG) seed by Gluconacetobacter diazotrophicus results in colonization of root, crown, and/or shoot tissue; and (ii) quantify/estimate any contribution of BNF to shoot tissue N status by direct/indirect methods. A factorial of seed treatment (inoculated or none) by N fertility (0, 33, 67, 100, or 133% recommended N-rates) was arranged in a randomized complete block design. Seedlings were randomly sampled 14 days after germination (DAG). Nitrogen fertilizer treatments were initiated in the 3^rd month from seeding, when all plots were established and mowing had been initiated. Beginning Fall 2014, multispectral radiometers were used to measure KBG canopy density and color. Clippings were collected over the 2015 season to assess shoot growth and N status. PCR analysis of surface-sterilized root and crown tissue, collected from inoculated plots 14 DAG, confirmed colonization by G. diaz. The main effect of inoculation (pooled across N levels) expressed significantly greater mean canopy density in Fall 2014 and Spring 2015. Results of PCR, shoot growth, and N status analysis on samples collected in 2015 will be presented.