Plant Available Water and Plant Water Stress

The 1983 growing season in Kentucky was a vivid reminder that water is essential for good plant growth. And the water used by plants is taken from the reserve or water stored in soil

Effect of Soil Water Stress and Irrigation on Growth, Yield and Quality of Burley Tobacco

An experiment was conducted for a period of three years, 1982, 1983 and 1984, in order to evaluate the effects of soil water stress and irrigation on growth, yield and quality of burley tobacco at Spindletop Farm, Lexington. The variety KY 21 was grown all three years. Three treatments were used in the experiment: (1) check, rainfall only, not irrigated, (2) well watered, rainfall plus supplemental irrigation, and (3) water stressed beginning 50 days after transplanting. The soil of treatment 3 was covered with black plastic to prevent rainfall from entering the soil

Water Relationships of Kentucky Soils

Plant water stress is the most limiting single factor in crop production in Kentucky. It almost always occurs sometime during July and/or August even though it\u27s variability makes it hard to predict. Even though the 1979 growing season was an exception to this generalization the 1980 growing season was a vivid reminder of this fact especially in Western Kentucky

Capillary-Diffusion and Self-Diffusion of Liquid Water in Unsaturated Soils

Capillary-diffusion coefficients were measured by use of inflow and outflow methods. With both methods the capillary-diffusion coefficients decreased very rapidly with decreasing water content. The lighter textured soils were found to have the higher diffusion coefficients over the entire moisture content range studied, 0 to 1 bar tension. Self-diffusion coefficients were measured over a moisture content range from air dryness to saturation using 3H as a tracer of water. Each of the soils gave the same diffusion characteristics when the self-diffusion coefficients were expressed as a function of either water content or average number of water layers on the external surface of each mineral. As the water content decreased from saturation to near field capacity, the self-diffusion coefficients decreased very rapidly. An attempt was made to separate the self-diffusion coefficients into a liquid and a vapor component by use of 36Cl as a tracer of liquid water. The results showed 36Cl not to be a good tracer of liquid water movement in soil. The results suggest that a functional relationship exists between capillary-diffusion and self-diffusion; however, before this relationship can be firmly established, the liquid and vapor components of water movement must be separated

Predicting Infiltration and Surface Runoff from Reconstructed Spoils and Soils

A laboratory system was fabricated to measure infiltration and runoff from spoil and soil profiles constructed in rectangular bins. Construction, calibration and operation of a rainfall simulator is discussed and instrumentation used to measure transient infiltration and transmittance of water through experimental profiles is described. Spoil and soil materials from surface mines in Eastern and Western Kentucky were transported to the laboratory and used in constructing experimental profiles in rectangular bins (0.91 x 1.83 x 1.07 m). An extensive series of infiltration experiments were conducted utilizing a rainfall simulator and soil moisture monitoring instrumentation. A dual probe gamma density gauge was used to measure moisture content and tensiometers were used to measure soil matric suction. Initial moisture content, bulk density and rainfall rate were varied and respective responses of infiltration characteristics determined. Extremely low infiltration rates in Western Kentucky spoil material was attributed to relatively high bulk densities and well-graded particle constituency. Conversely, extremely high infiltration rates were observed for Eastern Kentucky shale material even at very high bulk densities. The sandstone material, however, exhibited infiltration rates of the same order of magnitude as that of Western Kentucky spoil material. Soil water characteristic curves were developed using the Brooks-Corey and Gardner procedures, based upon desortpion tensiometer data. Unsaturated hydraulic conductivity values were determined using the plane of zero flux procedure and compared with predictions resulting from models described by Campbell, Burdine and Mualem for situations involving reconstructed soil and spoil materials. There was generally good agreement between the models and plane of zero flux results, and excellent agreement with Campbell\u27s predictions. The infiltration process was modeled with the SCS curve number method, a modified form of Holtan\u27s equation, the Green-Ampt model and Richard\u27s equation. SCS curve numbers were determined by fitting the method to the observed results. Richards\u27 equation gave very good estimates of the infiltration process through the spoil profiles, but was only slightly better than the Green-Ampt model. None .of the models worked well for the profiles where macropore flow occurred through a two layer topsoil over spoil system

Modeling Soil Water Contents and Their Effects on Stream Flow in Kentucky

Soil water contents of eight important soil series in Kentucky were measured periodically during the summer growing season for four years, 1977 through 1980. The soils divided into three groups according to their behavior. The first group (Maury and Crider) is well-drained and never showed excess water above field capacity at any time during the four seasons. The second group (Zanesville, Lowell, Calloway, Grenada and Shelbyville) showed perched water tables at times, especially during the early part of the growing season. The third group was represented by the Huntington soil which has a permanent water table. The in-situ field capacity or upper limits was determined on numerous samples of the Maury, Crider and Shelbyville soil series. Variation within series was rather low, indicating that samples taken at one site are representative of the soil in general. A model for estimating the soil water in each 15 cm layer was developed and proved to work very well with both Maury and Crider soils. Lowell soil was predicted poorly by the model, with other soils being intermediate. A variation of the model which assumed that the lowest layer of the Huntington was always at the upper limit due to a permanent water table also worked well. The water calculated from the model as deep drainage was used as a measure of increase in streamflow and compared to measured streamflow on three watersheds and four soils in 1978 and 1979. The R2 values ranged from 0.41 to 0.95 and the slope, which ideally should be 1.0, ranged from 0.54 to 1.36. The quantitative measure of streamflow was not satisfactory but the prediction of events was quite good. Modifications in the model that seem to be required include provisions for evaporation from foliage with small rains, higher evapotranspiration at lower soil water contents, less deep drainage with small rains and an aquifer storage factor

New Clock Comparison Searches for Lorentz and CPT Violation

We present two new measurements constraining Lorentz and CPT violation using the Xe-129 / He-3 Zeeman maser and atomic hydrogen masers. Experimental investigations of Lorentz and CPT symmetry provide important tests of the framework of the standard model of particle physics and theories of gravity. The two-species Xe-129 / He-3 Zeeman maser bounds violations of CPT and Lorentz symmetry of the neutron at the 10^-31 GeV level. Measurements with atomic hydrogen masers provide a clean limit of CPT and Lorentz symmetry violation of the proton at the 10^-27 GeV level.Comment: 11 pages, 5 figures. To appear in the Proceedings of the 3rd International Symposium on Symmetries in Subatomic Physic

High Redshift Supernovae in the Hubble Deep Field

Two supernovae detected in the Hubble Deep Field using the original December 1995 epoch and data from a shorter (63000 s in F814W) December 1997 visit with HST are discussed. The supernovae (SNe) are both associated with distinct galaxies at redshifts of 0.95 (spectroscopic) from Cohen etal. (1996) and 1.32 (photometric) from the work of Fernandez-Soto, Lanzetta, and Yahil (1998). These redshifts are near, in the case of 0.95, and well beyond for 1.32 the greatest distance reported previously for SNe. We show that our observations are sensitive to SNe to z < 1.8 in either epoch for an event near peak brightness. Detailed simulations are discussed that quantify the level at which false events from our search phase would start to to arise, and the completeness of our search as a function of both SN brightness and host galaxy redshift. The number of Type Ia and Type II SNe expected as a function of redshift in the two HDF epochs are discussed in relation to several published predictions and our own detailed calculations. A mean detection frequency of one SN per epoch for the small HDF area is consistent with expectations from current theory.Comment: 62 pages, 17 figures, ApJ 1999 in pres

Diffusion-induced Ramsey narrowing

A novel form of Ramsey narrowing is identified and characterized. For long-lived coherent atomic states coupled by laser fields, the diffusion of atoms in-and-out of the laser beam induces a spectral narrowing of the atomic resonance lineshape. Illustrative experiments and an intuitive analytical model are presented for this diffusion-induced Ramsey narrowing, which occurs commonly in optically-interrogated systems.Comment: 4 pages, 8 figure

Optimal control of light pulse storage and retrieval

We demonstrate experimentally a procedure to obtain the maximum efficiency for the storage and retrieval of light pulses in atomic media. The procedure uses time reversal to obtain optimal input signal pulse-shapes. Experimental results in warm Rb vapor are in good agreement with theoretical predictions and demonstrate a substantial improvement of efficiency. This optimization procedure is applicable to a wide range of systems.Comment: 5 pages, 4 figure