Nitrogen Spoon Feeding Effects On Seed Yield and Rust Severity in Perennial Ryegrass Seed Production.

In recent years, Northern Minnesota has become a significant region for the production of perennial ryegrass seed with total crop acreage estimated at around 16,200 ha.  Major limitations to seed production in this region are nitrogen (N) use efficiency and stem rust (Puccinia graminis subsp. graminicola).  There is a need to match crop N demand with N availability but slow release sources of N have proven to be unreliable in our region due to moisture and temperature-dependent N release.  Growers have demonstrated interest in using a “spoon feeding” approach to N applications.  The objectives of this study were: 1) to determine the effect of multiple foliar applied N applications vs. single N applications on disease pressure and seed yield, and 2) to determine how multiple foliar N applications interact with various growth regulator programs and N rates.

The trial was conducted on ‘Arctic Green’ perennial ryegrass at two locations (Roseau and Lake of the Woods County, MN) during the 2009 and 2010 growing season.  Preliminary results indicate that applying nitrogen as multiple foliar applications vs. one single application results in higher relative chlorophyll content, more vegetative biomass, and likely higher nitrogen content of the plant tissue prior to harvest.  At the Roseau location two- and three-way split N applications resulted in seed yields that were slightly lower than the single N application (1224 and 1159 vs. 1337 kg ha-1) but the three way split resulted in greater vegetative biomass yields than the one- or two-way splits (3675 vs. 3468 and 3405 kg ha-1).    At the LOW location, splitting the spring N application did not affect seed yield but a similar trend in biomass production was observed.  Seed germination, seedling vigor, plant height, lodging and rust severity were also evaluated.  The results of this study indicate that using a “spoon feeding” approach to N management in northern Minnesota may be a viable option for increasing N uptake by the perennial ryegrass seed crop.  Future research on proper rates and timing will be required.