Changes in the forms and availability of applied phosphate over a twelve-month period in two soils of the Manawatu-Rangitikei sand country : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science at Massey University

A feature of New Zealand agriculture is the requirement for regular applications of phosphate fertilizer to maintain high producing pastures. This is reflected in the large amounts of phosphate fertilizer sold annually, which for the 1971-72 season reached a level of 2,041,000 tonnes. The soils of the Manawatu-Rangitikei sand country, being naturally deficient in phosphate, are no exception to this requirement for regular applications of phosphate. However, these soils, especially those of the sand plains are potentially fertile. Thus trials conducted by the Department of Agriculture have shown that, on Himatangi sand, pasture production in the range 15,700-16,800 kg D.M./ha can be realized (Blackmore, pers. comm.). The need for regular, preferably at least annual, application of phosphate to these sand country soils implies a fall in the level of availability of the applied phosphate within the zone of action of the pasture roots due either to:- (i) actual loss of phosphate from this zone by leaching a distinct possibility in such light-textured soils; or (ii) a change in the soil/soil solution equilibrium distribution of phosphate as a result of changes in the nature of the fixed forms with time; or (iii) a combination of those factors. The object of the present study was to investigate the operation of these factors for two representative sand country soils, the differing moisture regime and pH status of which might be expected to exert some influence on the course of phosphate fixation. At the same time, it was hoped to reach some conclusion as to the relative sensitivity of a number of commonly used chemical "quick tests" for evaluation of phosphate availability in these soils and to determine whether changes in these values were paralleled by demonstrable changes in the forms of phosphate binding

Extended Water Quality Monitoring of the Lincoln Lake Watershed

For seven years, the Lincoln Lake (Moores Creek and Beatty Branch) watershed was monitored for improvements in water quality resulting from agricultural best management practices (BMP) implemented to reduce nutrient transport. During the first three years of monitoring (1991 to 1994), nitrogen transport declined significantly (Edwards et al., 1994, 1996, and 1997) under both base and storm flow conditions. This decline in nitrogen transport was again observed in the three-year period following 1994 (Vendrell et al. 1998). This monitoring effort has demonstrated that water quality bas improved in the Lincoln Lake watershed. However, since the nitrogen transport continued to decline and there was some indication that phosphorus may begin to decline, monitoring was extended for another year (1998)

Imaging Transport Resonances in the Quantum Hall Effect

We use a scanning capacitance probe to image transport in the quantum Hall system. Applying a DC bias voltage to the tip induces a ring-shaped incompressible strip (IS) in the 2D electron system (2DES) that moves with the tip. At certain tip positions, short-range disorder in the 2DES creates a quantum dot island in the IS. These islands enable resonant tunneling across the IS, enhancing its conductance by more than four orders of magnitude. The images provide a quantitative measure of disorder and suggest resonant tunneling as the primary mechanism for transport across ISs.Comment: 4 pages, 4 figures, submitted to PRL. For movies and additional infomation, see http://electron.mit.edu/scanning/; Added scale bars to images, revised discussion of figure 3, other minor change

Land use change detection with LANDSAT-2 data for monitoring and predicting regional water quality degradation

The author has identified the following significant results. Comparison between LANDSAT 1 and 2 imagery of Arkansas provided evidence of significant land use changes during the 1972-75 time period. Analysis of Arkansas historical water quality information has shown conclusively that whereas point source pollution generally can be detected by use of water quality data collected by state and federal agencies, sampling methodologies for nonpoint source contamination attributable to surface runoff are totally inadequate. The expensive undertaking of monitoring all nonpoint sources for numerous watersheds can be lessened by implementing LANDSAT change detection analyses

Utilization of the Multiple Access Communications Satellite (MACSAT) in Support of Tactical Communications

Two MACSATs were launched on May 9, 1990 on a Scout launch vehicle from Vandenberg Air Force Base, California. After a short on-orbit check-out, these research and development satellites were placed into service providing operational communications support to 2d Marine Aircraft Wing units deployed to the Persian Gulf in support of Operations Desert Shield and Desert Storm. This support was provided from August 1990 until Operation Desert Storm was completed in April 1991. During this time, many lessons were learned that are directly applicable to the design and fielding of future small tactical communications satellites. This paper will highlight some of the lessons learned from supporting Operation Desert Shield, as well as other communications support missions

Spatiotemporal dynamics in a spatial plankton system

In this paper, we investigate the complex dynamics of a spatial plankton-fish system with Holling type III functional responses. We have carried out the analytical study for both one and two dimensional system in details and found out a condition for diffusive instability of a locally stable equilibrium. Furthermore, we present a theoretical analysis of processes of pattern formation that involves organism distribution and their interaction of spatially distributed population with local diffusion. The results of numerical simulations reveal that, on increasing the value of the fish predation rates, the sequences spots $\rightarrow$ spot-stripe mixtures$\rightarrow$ stripes$\rightarrow$ hole-stripe mixtures holes$\rightarrow$ wave pattern is observed. Our study shows that the spatially extended model system has not only more complex dynamic patterns in the space, but also has spiral waves.Comment: Published Pape

Adsorption of Xe and Ar on Quasicrystalline Al-Ni-Co

An interaction potential energy between and adsorbate (Xe and Ar) and the 10-fold Al-Ni-Co quasicrystal is computed by summing over all adsorbate-substrate interatomic interactions. The quasicrystal atoms' coordinates are obtained from LEED experiments and the Lennard-Jones parameters of Xe-Al, Xe-Ni and Xe-Co are found using semiempirical combining rules. The resulting potential energy function of position is highly corrugated. Monolayer adsorption of Xe and Ar on the quasicrystal surface is investigated in two cases: 1) in the limit of low coverage (Henry's law regime), and 2) at somewhat larger coverage, when interactions between adatoms are considered through the second virial coefficient, C_{AAS}. A comparison with adsorption on a flat surface indicates that the corrugation enhances the effect on Xe-Xe (Ar-Ar) interactions. The theoretical results for the low coverage adsorption regime are compared to experimental (LEED isobar) data.Comment: 12 pages, 8figure

Space station automation of common module power management and distribution

The purpose is to automate a breadboard level Power Management and Distribution (PMAD) system which possesses many functional characteristics of a specified Space Station power system. The automation system was built upon 20 kHz ac source with redundancy of the power buses. There are two power distribution control units which furnish power to six load centers which in turn enable load circuits based upon a system generated schedule. The progress in building this specified autonomous system is described. Automation of Space Station Module PMAD was accomplished by segmenting the complete task in the following four independent tasks: (1) develop a detailed approach for PMAD automation; (2) define the software and hardware elements of automation; (3) develop the automation system for the PMAD breadboard; and (4) select an appropriate host processing environment