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.