Estimations of plant water use can provide great assistance to growers, irrigators,
engineers and water resource planners. This is especially true concerning the introduction
of a new crop into irrigated agriculture. Growing hybrid poplar trees for wood chip stock
and veneer production under agronomic practices is currently being explored as an
alternative to traditional forestry practices. To this author's knowledge, no water use
estimates or crop coefficients, the ratio of a specified crop evapotranspiration to a
reference crop evapotranspiration, have been verified for hybrid poplars grown under drip
irrigation.
Four years of weekly, neutron probe measured, soil water data were analyzed to
determine averaged daily, monthly and seasonal plant water use, or crop
evapotranspiration. The plantation studied was located near Boardman, Oregon on the
arid Columbia River Plateau of North-Central Oregon. Water was applied by periodic
applications via drip irrigation. Irrigation application data, weekly recorded rainfall and
changes in soil water content permitted the construction of a soil water balance model to
calculate weekly hybrid poplar water use. Drainage was estimated by calculating a
potential soil water flux from the lower soil profile. Sites with significant estimated
potential drainage were removed from the analysis so that all sites used in the development
coefficients were calculated using reference evapotranspiration estimates obtained from a
nearby AGRIMET weather station. Mean crop coefficients were estimated using a 2nd
order polynomial with 95% confidence intervals. Plant water use estimates and crop
curves are presented for one, two and three year old hybrid poplars.
Numerical simulation of irrigation practices was attempted using weekly soil water content and soil physical characterization data. Parameter optimization and numerical simulations were attempted using the HYDRUS-2D Soil Water and Solute Transport model. Parameter optimization and numerical simulations were largely unsuccessful due to lack of adequate soil physical and root zone system representation and dimensional differences between drip irrigation processes and the model design used in this study. / Graduation date: 1998
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/33819 |
| Date | 23 January 1998 |
| Creators | Gochis, David J. |
| Contributors | Cuenca, Richard H. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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