YIELD AND QUALITY OF RS-2, A QUACKGRASS X BLUEBUNCH WHEATGRASS HYBRID

Understanding the effect of defoliation frequency and N fertilization on plant growth, Forage yield, and quality of RS-2, a quackgrass [Elyt rigia repens (L.) Nevski,] x bluebunch wheatgrass [Pseudoroegneria spi cata (Pursh.) Love] hybrid, will help promote efficient use of this hy brid in livestock production systems, Plants were fertilized with 0, 1 12, or 224 kg N ha(-1) in spring 1988 and 1989, or with a 112+112 kg N ha(-1) split in spring and summer, One see of plants was unmowed or m owed to a 5-cm stubble height once in July or August in 1988 and anoth er set was mowed initially in May, June, July, August, September, or O ctober 1989 and monthly thereafter through October, Peak standing crop of unmowed plants was 3,470 kg ha(-1) in 1988 and 5,850 kg ha(-1) in 1989. In 1989 yields of fertilized plants exceeded those of unfertiliz ed plants by 1,000 kg ha(-1). In 1988, crude protein exceeded 12% in u nmowed forage and in 1989 varied from 20% in May to 840 in August, Aft er fertilization, crude protein was increased by 2 to 4 percentage uni ts in 1988 and by 2 percentage units in 1989, but fertilization had no effect on in vitro digestible organic matter, Regrowth contained more crude protein (15-22%) and digestible organic matter (29-40%) than un mowed forage, Sequential harvesting enhanced quality of regrowth, but standing crops did not exceed 350 kg ha(-1); except in June 1989, Sixt y percent of the accumulated yield was harvested with the first mowing during May through August. Plots harvested initially in September and October were only harvested once, Our findings indicate an increase i n forage yield potential and forage quality of RS-2 after harvesting a nd fertilizing the RS-2 hybrid.