No description available.

LD2668 .T4 1948 D38 / Master of Science

Call number: LD2668 .T4 1958 T49

No description available.

No-till alfalfa (Medicago sativa L.) establishment is the only environmentally sound procedure for alfalfa production on erodable land. Surface limestone application is the only reasonable method of placement in no-til1 systems with pH below 6.5. The purpose of this research was to evaluate surface limestone application vs. incorporation throughout the plow layer for alfalfa production in acidic soils. In this study limestone placement included: 1. incorporation during tillage operations, 2. surface application after tillage and preparation of seedbed, and 3. surface application without tillage. Limestone was applied at 0, 1.25, 2.50, and 5.00 tons per acre with each placement method. Limestone treatments were imposed on 30 Sept. 1986 in Montgomery County, VA (37° 1lâ N, 80° 25â W and 1950 ft. elevation) on a Groseclose silt loam (clayey, mixed, mesic Typic Hapludult) having a pH of 5.6 in the top 9 inches. Limestone treatments were imposed at a second site on 25 Nov. 1986 in Orange County, VA (38° l3â N, 70° 7â W and 515 ft. elevation) on a Davidson clay loam (clayey, oxidic, thermic Rhodic Paleudult) having a pH of 5.7 in the top 9 inches. 'Cimmeronâ alfalfa was planted using no-till procedures on 23 March 1987 in Montgomery County and on 26 Aug. 1987 in Orange County. Soil samples were taken about 2 years after limestone application at depths of 0 to 1, 1 to 2, 2 to 3, and 3 to 6 inches for surface applied treatments and 0 to 3, 3 to 6, and 6 to 9 inches for incorporated treatments. Soil samples w0ere also taken at a depth of 18 to 24 inches where limestone was incorporated during tillage at 5 tons per acre. Four harvests were made in 1988. At both locations, limestone application increased yields by 114 to 300% as compared with the check where no limestone was applied. Yields from plots receiving surface limestone application were equal to plots with incorporation at both locations. Tillage did not increase yields as compared with no tillage except in Orange County on plots where no limestone was applied. Soil pH increased from 5.6 to 6.8 at the 1- to 2-inch depths and from 5.6 to 6.3 at the 2- to 3-inch depths where 5 tons per acre of limestone were surface applied in Montgomery County. In Orange County, soil pH increased from 5.5 to 6.5 at the 1- to 2-inch depths and from 5.6 to 6.1 at the 2- to 3-inch depths where 5 tons per acre limestone were surface applied. Above pH 5.5, Al saturation was below 2.7% in Montgomery County and 0.7% in Orange County. Aluminum saturation averaged 9.0% and 4.6% where pH was between 5.0 and 5.5 in Montgomery and Orange Counties, respectively. At both locations, in the 18- to 24-inch depths a pH of 4.8 was not influenced by limestone incorporated at 5 tons per acre. Aluminum saturation at 18- to 24-inch depths was 51% and 62% in Montgomery and Orange Counties, respectively. These data indicate that surface applied limestone can produce first year alfalfa yields similar to yields obtained with incorporated limestone. / Master of Science

The enhancing effect of K on alfalfa (Medicago sativa L.) yield has frequently been reported, but the nature of this influence has not been clearly shown. It was assumed that K contributed either to increased leaf expansion, thereby resulting in a larger photosynthetic surface, or to higher CO₂ assimilation rates per unit leaf area. Sand culture technique for growing plants was used in two greenhouse experiments, while field plants were grown in plots with soil differing in available K. Yield increases were consistently obtained with high K. Added K increased plant height and leaves per plant and per plot, The rate of leaf accumulation was higher as K increased. Leaf size and weight per unit area also increased, as did stomatal number and aperture. Larger epidermal cells and greater numbers per leaf were observed with high K nutrition. Percent K in plants was associated with rate of K application. Net photosynthesis rates of excised leaves increased with potassium application, but all K levels had similar light compensation points. Leaves from plants with added K had lower CO₂ compensation points, indicating higher efficiency of CO₂ assimilation. Based on these data, K appears to function both to increase the effective photosynthetic surface through greater leaf initiation and development and to increase the rate of CO₂ utilization per unit leaf area. The latter increase probably results from greater CO₂ diffusion into substomatal cavities. / Ph. D.

[Truncated abstract] Industrial processing to refine alumina from bauxite ore produces millions of tonnes of refining residue each year in Australia. Revegetation of bauxite residue sand (BRS) is problematic for a number of reasons. Harsh chemical conditions caused by residual NaOH from ore digestion mean plants must overcome extremely high pH (initially >12), saline and sodic conditions. At such high pH, manganese (Mn) is rapidly oxidised from Mn2+ to Mn4+. Plants can take up only Mn2+. Thus, Mn deficiency is common in plants used for direct BRS revegetation, and broadcast Mn fertilisers have low residual value. Added to this, physical conditions of low water-holding capacity and a highly compactable structure make BRS unfavourable for productive plant growth without constant and large inputs of water as well as Mn. However, environmental regulations stipulate that the residue disposal area at Pinjarra, Western Australia, be revegetated to conform with surrounding land uses. The major land use of the area is pasture for grazing stock. Hence, pasture revegetation with minimum requirement for fertiliser and water application is desirable. This thesis investigates a number of avenues with potential for maintaining a productive pasture system on BRS whilst reducing the current level of Mn fertiliser and irrigation input. Emphasis was placed on elucidation of chemical and physical factors affecting Mn availability to plants in BRS