Ammonia (NH₃) volatilization and loss from nitrogen (N) fertilizer in agriculture negatively impacts crops, farm profitability, human health and surrounding ecosystems where it is deposited. A significant source of NH₃ volatilization occurs from surface application of urea on sandy soils with low pH buffering capacity such as those in the...
Ammonia (NH₃) volatilization can result in a substantial amount of surface applied nitrogen (N) being lost into the atmosphere, making it an environmental pollutant as well as reducing plant-available N. However, N can also be easily lost from the soil through leaching,
and nitrous oxide (NO₂). Enhanced efficiency N fertilizers...
Previous studies indicated that fertigating with nitrogen (N) was more effective than using granular N fertilizers in production of northern highbush blueberry (Vaccinium corymbosum L.). To build on these findings, four studies were conducted in western Oregon to determine whether fertigation was also an effective method for applying other nutrients,...
Interest in measuring soil quality continues to increase worldwide in view of demands on land productivity and the necessity to preserve soil resources, yet identification of suitable indicators for soil quality assessment is still evolving. This study adapted 10 biological, physical, and chemical indicators of soil quality identified by the...
Mechanical thinning and prescribed fire are widely used to restore western forests after a century of fire suppression, yet we know little about
how these treatments affect understory communities where plant diversity is highest. We followed understory plants and environmental factors in
old-growth, Sierran mixed conifer for two pre-treatment and...
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 goal of the work in this dissertation was to identify alternative soil amendments to improve plant growth and yield during establishment of highbush blueberry (Vaccinium hybrid). Woody materials, such as sawdust and wood chips, have a high carbon to nitrogen (C:N) ratio and low water holding capacity, which can...
Douglas-fir [Pseudotsuga menziesii (Mirbel) Franco] bark (DFB),
sphagnum peat moss, and pumice are the most common substrate components used
in the Oregon nursery industry. Despite the widespread use of these three
components, little information is available on the effect of physical and hydraulic
properties of peat moss and pumice on...
The impact of fertilizer source and cultivar on growth, fruit quality, and yield was evaluated in organic blackberry (Rubus L. subgenus Rubus Watson) from 2011-2013 in three studies. In all studies, plants were drip irrigated, and weeds were managed using a woven polypropylene, permeable landscape fabric (weed mat). At a...
Although the potato (Solanum tuberosum L.) is a global crop, few growing regions rival the high yields of the Columbia Basin of Eastern Oregon and Washington. Two research projects were conducted in Hermiston, OR to contribute to best management practices for the region. The first project evaluated the efficacy of...