Improving Forage Production on Claypan Soils

Mechanical range improvement practices such as contour ripping and furrowing have been used to increase forage production on a variety of range sites in the northern Great Plains. These improvement practices seem to have particular promise on Claypan and Thin Claypan range sites in western South Dakota. Soils on these range sites have a sodium dispersed layer (claypan) at or near the surface. This layer severely reduces the rate of water infiltration, thus causing a greater amount of the precipitation to run off or pool up and evaporate from the soil surface than would happen on soils of similar texture without the claypan layer. Because more precipitation water is lost to runoff and evaporation, less water is available for plant growth. The compact nature of the claypan layer also tends to restrict root growth, further reducing plant growth. Thus, claypan soils are inherently lower in forage production potential than similar soils without the claypan layer. The difference between productivity of the claypan soils and normal soils represents the potential increase in forage production if the effects of the claypan layer could somehow be removed

Range Renovation

Mechanical treatments of rangelands are designed to increase water infiltration and increase forage quantity and quality. Storing precipitation where it falls is important to stabilize in annual forage production, especially on sites with water uptake problems due to slope, shortgrass sod cover and/or high salt concentrations in the upper horizons Soil moisture and vegetation data accumulated over five growing seasons following mechanical renovation of Thin Claypan range sites indicate a great potential exists for increasing range carrying capacity. Both soil moisture and forage production can be improved

Polarons in semiconductor quantum-dots and their role in the quantum kinetics of carrier relaxation

While time-dependent perturbation theory shows inefficient carrier-phonon scattering in semiconductor quantum dots, we demonstrate that a quantum kinetic description of carrier-phonon interaction predicts fast carrier capture and relaxation. The considered processes do not fulfill energy conservation in terms of free-carrier energies because polar coupling of localized quantum-dot states strongly modifies this picture.Comment: 6 pages, 6 figures, accepted for publication in Phys.Rev.

Cool Season Grass Variety Comparisons in Jackson County

The purpose of the plant nursery trial in Jackson County, South Dakota, was to (1) provide information for landowners on planting a special use pasture for grazing or hay production, (2) assimilate longterm comparative yield and longevity data to support seeding reconmendations and (3) provide a visual comparison of sufficient size plantings for area residents, agency technicians and others to observe growth and survival characteristics of various grasses

Influence of carrier-carrier and carrier-phonon correlations on optical absorption and gain in quantum-dot systems

A microscopic theory is used to study the optical properties of semiconductor quantum dots. The dephasing of a coherent excitation and line-shifts of the interband transitions due to carrier-carrier Coulomb interaction and carrier-phonon interaction are determined from a quantum kinetic treatment of correlation processes. We investigate the density dependence of both mechanisms and clarify the importance of various dephasing channels involving the localized and delocalized states of the system.Comment: 12 pages, 10 figure

Western Wheatgrass Recovery From Drought

Native grasses are predictably taller in wet years than in dry years and their density also increases with favorable precipitation. These responses of western wheatgrass are more dramatic on mechanically treated rangeland when precipitation is adequate. Measurements taken in July 1991 confirmed that western wheatgrass was slightly taller and density at least two times greater on mechanically treated claypan soils compared with untreated soils 13 and 18 years following treatment. Increases of this magnitude constitute a potentially greater carrying capacity which livestock producers should be prepared to utilize. This report briefly summarizes the effects of mechanical treatment on height and density of western wheatgrass 13 and 18 years following treatment and in a wet year following several dry years

Cool Season Grass Variety Comparisons in Harding County

The purpose of the plant nursery trial in northwestern South Dakota was to (1) proivde information for landowners on planting a special use pasture for grazing or hay production; (2) assimilate long term comparative yield and longevity data to support seeding recommendations; and (3) provide a visual comparison of sufficient size plantings for area residents, agency technicians, and others to observe growth and survival characteristics of various grasses