Perennial Ryegrass Seed Production in Minnesota: The Effect of Seeding Rate, Row Spacing, and Nitrogen On Yield, Agronomic Characteristics, and Stem Rust.

Perennial ryegrass seed, produced for sale around the world as turf and forage grass seed, is grown in rural agricultural areas of northern Minnesota.  Currently there are around 60,000 acres of perennial ryegrass seed production in northern Minnesota which contribute $15-20 million annually to rural Minnesota economies.  Previous research in turfgrass and small grains copping systems provides evidence that farmer’s cultural practices (i.e. nitrogen fertilization, plant density, and seeding rate) can affect seed yields and crop tolerance to fungal pathogens.  The effects of perennial ryegrass seeding rates and row spacing in a seed production setting in northern Minnesota have not been previously evaluated.  We evaluated five seeding rates (1.4, 2.8, 5.6, 8.4, and 11.2 kg ha^-1), three row spacing widths (10.2, 20.3, and 30.5 cm), and 3 nitrogen rates (67.2, 112, 157 kg N ha^-1). The experimental design was a randomized complete block with 4 replications and treatments were arranged as a split-split plot with seeding rate as the main plot, row spacing as the sub-plot, and nitrogen rate as the sub-sub-plot.  The effect of seeding rate, nitrogen rate and row spacing on seed yield, seed quality characteristics, and stem rust disease in an ‘Arctic Green’ perennial ryegrass seed crop was evaluated at two locations in northern Minnesota during the 2010 and 2011 harvest seasons.  The 2.8, 5.6, and 8.4 kg ha^-1 seeding rates produced the most consistent seed yields while the 1.4 and 11.2 kg ha^-1 seeding rates at times exhibited poor seed yield and agronomic performance.  However, the data suggest that N rate had a greater effect on seed yield than seeding rate or row spacing and that adequate seed yields can be obtained from a sparse perennial ryegrass stand seeded at 1.4 kg seed ha^-1 if higher N rates are applied in the spring of the harvest season.