Field experiments were established in 1982 and 1983 on a Woodburn silt loam soil (Aquultic Argixeroll) to examine the effect of S fertilizer on dinitrogen fixation and dry matter yield of 10 week-old seedling alfalfa (Medicago sativa L. cv. 'Apollo'). Six levels of S fertilizer (0 to 67.2 kg S/ha)...
Wheat endosperm morphogenesis was studied by light microscopy
during the entire growth period of anthesis to maturity. Four
developmental stages have been described in this thesis: (1) double
fertilization, (2) formation of the lower endosperm cells, (3)
termination of nuclear divisions, and (4) initiation of protein
bodies.
The first manuscript...
A seed maturation study was conducted to determine the earliest
date seed of subterranean clover (Trifolium subterraneum L.) may be
safely harvested without reduction in yield or seed quality. In 1981
and 1982, seed and bur weight, seed and bur moisture content, germination and seedling vigor were studied to determine...
Nitrogen fertilization of seedling legumes is a controversial practice intended to provide N to the plant during periods when seed N, soil N, and N₂ fixation may not meet plant requirements; eg. prenodulation, postharvest, or in the event of an inoculation failure. Field experiments were conducted in 3 consecutive years...
Roughstalk bluegrass (Poa trivialis L.) (RB) is a weed species that increased very quickly in grass seed production fields of the Willamette Valley. The invasion of RB in grass seed crops often occurs in waterlogged soils. In waterlogged areas, RB exhibited better competitiveness and had greater population densities than other...
Volunteer winter wheat (Triticum aestivum 'Daws')
severely suppressed growth of fall-planted alfalfa
(Medicago sativa (L.) 'Vernal') seedlings. Wheat
competition began soon after alfalfa emerged and continued
until the first forage harvest the following May. Alfalfa
yield at the first cutting was reduced by 1% for each day
volunteer wheat was...
Scouringrushes (Equisetum hyemale L.; E. xferrissii Clute; E. laevigatum L.) are ancient perennial seedless vascular plants historically associated with wetlands, low-lying roadsides or field margins with more plant available water. There has been little research conducted on scouringrush species in the context of agricultural production because traditional farming practices confined...
The influence of certain environmental and edaphic
factors on the germination and emergence of downy brome
(Bromus tectorum L.) was investigated in the laboratory. A
preliminary study was conducted to determine the osmotic
stability of mannitol and polyethylene glycol 20,000 (PEG)
solutions, which are commonly used to simulate water stress...
Spring grazing of annual ryegrass (Lolium multiflorum L.) seed
fields with sheep is a common practice in the Willamette Valley of
Oregon. However, the effect of grazing on seed yield in Oregon has
not previously been investigated. This experiment was designed to
determine the effects of duration of spring grazing...