Effect of Nitrogen and Clipping On Forage and Seed Yield of Tall Fescue.

Grass pastures are essential components of western US agriculture.  The objective of this study is to find out the response of nitrogen and clipping time on forage and seed yield of tall fescue cultivars/lines under irrigation.  The study was planted in May 2009 at two locations in four replicates: Powell Research and Extension Center (PREC) and Stroh farm, Powell in Wyoming.  There were two separate experiments namely seed production and forage production.  Standard seeding rates were used for both studies (10 kg PLS (pure live seed) ha^-1 for seed production and 22 kg PLS ha^-1 for forage production).  In seed production study, seven cultivars/lines of tall fescue were planted in 56 cm rows and three nitrogen levels (0, 112, and 168 kg nitrogen ha^-1) and three clipping times (no, early, and late) were applied.  In forage production study, treatments included seven cultivars/lines and three nitrogen levels (0, 56, and 112 kg nitrogen ha^-1).  Nitrogen was applied in two-splits.  In 2010, the lowest forage dry matter (DM) yield was associated with the control treatment (no nitrogen) while 2-3 folds DM yield increase was obtained from 56 and 112 kg nitrogen ha^-1 treatment.  Similar trend was also observed for seed production study at both locations, however, clipping time had significant effect on seed yield for all cultivars/lines.  Late clipping treatment consistently produced the lowest seed yield compared to no or early clipping.  In 2011, similar but improved trends for both forage and seed yield were observed at both locations.  For example, at Stroh farm, total forage yield ranged 1,400-5,660 kg DM ha^-1 in 2010 while the range was 1,900-9,600 kg DM ha^-1 in 2011.  The ranges for seed yield were 180-1,890 kg ha^-1 and 150-2,000 kg ha^-1 at PREC and Stroh farm, respectively.  Results will be discussed in details in the presentation.