Kentucky Bluegrass Seed and Vegetative Responses to Residue Management and Fall Nitrogen

Open‐field burning to remove post‐harvest residue from Kentucky bluegrass ( Poa pratensis L.) seed fields was essentially eliminated in Washington in 1998, and may be banned in Idaho and Oregon because of health concerns. Regulations banning burning necessitated exploring non‐thermal residue management. Seed and vegetative responses of six Kentucky bluegrass cultivars to three post‐harvest residue removal methods, and three timings of fall applied N in second‐ and third‐year seed crops were evaluated. Residue removal methods were burn, vacuum, and rake. Split fall timings of N applications were 70% September, 30% October; 30% September, 70% October; and 100% October. Post‐harvest residue management did not significantly influence second‐year seed crop yields; however, with mechanical residue removal, third‐year seed crop yields of ‘Glade’, ‘Huntsville’, and ‘South Dakota’ were 42 to 62% of seed yields with open‐field burning. Seed yield of ‘Baron’, ‘Limousine’, and ‘Georgetown’ was not affected by residue management in the third‐year seed crop. As larger portions of N were October applied, second‐year seed yields of Georgetown and Huntsville were higher. Third‐year seed crop yields were not influenced by timing of N application. Overall, seed production was correlated with panicle number( r = 0.77** ), but not with above ground biomass, rhizome biomass, or weight per 100 seeds. These data suggest that seed yield of relatively short‐statured, small‐seeded cultivars producing modest amounts of above ground biomass may be sustained by mechanical residue removal through three seed crop years when 70 or 100% the N is applied in October.