Sandy soils are among the least productive soils because of their inability to
store adequate water for plant growth. Their high percolation rate not only allows
water to move quickly beyond the root zone, but also washes nutrients below the reach
of plant roots. High evaporation occurs from the soil surface. Many acres of these
soils around the world are left out of crop production. This study is a contribution to
bring these soils into production by increasing their ability to hold more water in the
root zone. Several promising methods of enhancing these soils were simulated,
surface mulch, buried barrier layer, and a combination of both. The effects of varying
texture and thickness of these layers and varying evaporative demand were
investigated. The impact of such modifications on solute distribution in the soil was
also simulated. A simulation model of water and solute transport in layered soils was
developed for this purpose.
The Richards equation for one-dimensional water transport in unsaturated soils
was modified to account for the water jump between the layers. The solute transport
equation was also modified by implementing the same theory of water infiltration in
layered soil to the solute convective transport. The Crank-Nicolson scheme was used
to solve the transport equations with the help of the Newton-Raphson iteration method.
The results of the simulation show that the proposed methods increase water
content in the sandy soil by up to 45%. The combination of barriers, which decreases
leaching and evaporation was the most effective in conserving water. Most of the
contribution came from the influence of the mulch layer in suppressing water losses by
evaporation. The combination method traps solute in the root zone, and this decreased
solute leaching from the soil may limit plant growth in saline soils. / Graduation date: 1993
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/36742 |
| Date | 23 July 1992 |
| Creators | Mohammed, Fareed H. A. N. |
| Contributors | Warkentin, Benno P. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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