Temperature and water potential effects on the growth,
transpiration, total nonstructural carbohydrate (TNC) content, and
nutrient uptake of sudangrass (Sorghum vulgare var. piper) were
investigated in laboratory experiments. The effect of nitrogen supply
on the growth and nutrient uptake at constant soil water potential was
also investigated in this study....
One of many important physical properties that must be known
to understand transport phenomena in soils is pore size distribution.
Presently the pore size distributions of soils are most commonly
obtained from soil water characteristic curves. The soil water characteristic
curves are usually obtained by the pressure plate technique.
It...
Several investigators have recently called attention to the
fact that the flux equation for water movement in unsaturated soils
may not be an appropriate mathematical model for the development
of the theory of unsaturated flow phenomena.
An analytical theory is developed for the purpose of testing
the validity of the...
Experiments were conducted to study the effect of pore size
distribution on the diffusion of 2, 4-Dichlorophenoxyacetic acid (carbon-
14) through water saturated porous media. Eight size fractions of
glass beads were used representing the porous media. It was found
that as the average particle radius, and hence pore radius,...
In regions where soil temperatures limit plant growth, artificial
soil warming may be an economically feasible practice. This hypothesis
was evaluated in a soil warming experiment near Corvallis, Oregon.
This experiment was prompted by the observation that multiple
use of waste heat discharged in the condenser cooling water of thermal...
Gaseous diffusion equations which describe the diffusion of
oxygen and carbon dioxide through soil have been studied by several
investigators. However, these efforts seldom considered gaseous
diffusion through soil together with the effects of soil environmental
factors such as soil temperature and soil water content on sink or
source strength....
The continuum theory provides a framework in which the growth
of a plant root as a dynamic process involving interactions among
transport of water and solute, cell division, and the subsequent cell
elongation can be described. A plant root is modeled as a one-dimensional,
multi-phase, mathematical continuum. The network of...
Gaseous transport through soil in the presence of soil
microorganisms has been investigated. More recently, modeling of
gaseous transport in the unsaturated zone has been investigated.
However, the problem of mathematical model of oxygen and carbon
dioxide transport through soil, as affected by the climatic
conditions, the transport of soil...
Freeze/thaw cycles are numerous in agricultural soils of the Pacific Northwest. Potential loss of soil by erosion is high whenever a soil thaws from the surface creating a saturated soil overlying an impermeable frozen layer. Field studies were conducted to investigate the effect of surface residue on soil freezing. Residue...
Rates of germination and emergence of corn were measured as
influenced by soil physical parameters using blotter paper and a sandy
loam soil as growth media. The corn seeds used were a hybrid of
Funk's (DJ7xLH93).
Experimental conditions were soil temperature of 20°C, 25°C,
30°C, and 35°C, soil water potential...
At present the adsorption kinetic of ions by soil particles is considered to be a surface reaction. When the transport of solutes in soils is described using the one-dimensional flow equation, it becomes a serious problem that lateral diffusion of ions from the bulk solution towards the soil surfaces is...
A number of investigators have proposed equations to predict
the permeability of porous media. Most of their equations are based
on the distributions of the sizes of the various contributing pores in
the medium. Presently the pore size distributions of agricultural
soils are most commonly obtained from soil water release...
Petroleum mulch applied on the soil surface over a row of
planted seeds promotes a more rapid and a more uniform germination
of seeds, enhances elongation of seedlings and in some cases increases
the yield of the crop. The beneficial effects of petroleum
mulch have usually been attributed to increased...
Laboratory experiments were used to investigate the mechanism
of plant response to water stress by determining the sensitivity of leaf
elongation, photosynthesis and transpiration in young corn plants to a
decrease in leaf water potential.
In initial experiments, 9 day old corn plants were grown at soil
water potentials of...
Sulfur-coated urea (SCU) is a slow release nitrogen fertilizer
manufactured by the Tennessee Valley Authority. Urea granules are
sprayed with molten sulfur, then holes in the sulfur coating are sealed
with a layer of wax sealant. The sulfur coatings are mixtures of
amorphous and crystalline allotropes of sulfur. Coating thickness...
The principles of continuum mechanics provide a consistent
framework for the derivation of mathematical statements describing
transport of water and solute, and growth in plant tissue. These
derivations are based upon the explicit consideration of the tissue as
a mathematical continuum composed of a cell wall matrix, water, and
solute...
Forest soils with low bulk densities are often considered less
susceptible to compaction than soils with higher bulk densities. The
objective of this study was to determine if soil strength controlled the
compression of soils with low bulk density. Four soils were selected
for this evaluation. Three of these were...
The effect of soil temperature and plant water stress on nitrogen
uptake, growth rate and transpiration rate of wheat (Triticum aestivum
VILL. , Host) seedlings was studied. A special apparatus for the control
of plant water stress and root temperature was used.
Leaf area was measured by the air flow...
The purpose of this study was to use computer analysis of soil and rainfall data to predict the possible occurrence of soil erosion in Central Tunisia. Analysis was done with the program OR-NATURE (M.Ungs et al, 1985) . Central Tunisia was subdivided into northern, central, and southern subzones. Data about...
Douglas-fir seedlings were inoculated with different species of
ectomycorrhizae-forming fungi in order to test the concept that
ectomycorrhizae enhance the drought tolerance of seedlings and to
investigate the mechanisms responsible for this effect.
Seedlings were transplanted at age 6 to 8 weeks into pots
containing pasteurized loam soil and inoculated...
Multiple use of waste heat from power plants may become an
important consideration in the development, siting, and certification
of these plants. A multiple use system of components that can
beneficially utilize waste heat may include home heating and cooling,
greenhouses, animal enclosures, open basins for single cell protein
production...
Leaf elongation is a major indicator of plant growth. It is
controlled by complex interactions of many factors including light
intensity, photoperiod, water availability, atmospheric conditions,
and plant water stress. In this study, the response of leaf elongation
to length of photoperiod and to plant water stress as indicated by...
The hydrophobicity of soils of the Deschutes National Forest was
studied. The soils are Cindery Typic Cryorthents, formed in cinders
and ash from Mt. Mazama. Ponderosa pine is the dominant overstory
vegetation. Of particular interest was the effect of prescribed
burning on hydrophobicity. Fire has been shown to cause a...
The effect of soil water suction and soil temperature on rates
of transpiration, photosynthesis, respiration and nitrogen fixation of
soybean (Glycine max. Merrill, var. Chippewa 64) seedlings was
studied. A special apparatus was developed in which the soil water
suction of several cells with soybeans growing in them could be...
The influence of soil moisture stress and soil temperature on
transpiration has never been determined explicitly. This relationship
has been neglected mainly because of the lack of a satisfactory method
to control soil moisture stress.
A technique was developed to evaluate this relationship by
controlling soil moisture stress with osmotic...
Experimental Drainfields: Standard subsurface sewage disposal systems, gravity loaded and 60 cm deep on slopes above 15% did not show signs of effluent surfacing after 14 months of operation. However, subsurface signs of failure were found on both the experimental sites and on older drainfields established in identical soils. Evidence...
There is considerable evidence that the growth and elongation of
plant roots increases linearly or almost linearly with increasing water
contents or decreasing moisture-tension of soil. If this is true it is
difficult to distinguish the effects of different water contents on absorption
phenomena such as water or ion uptake...