Soil solution samplers have certain inadequacies that limit their range of possible applications. Passive Capillary Samplers (PCAPS), which apply suction to the soil pore-water via a fiber glass wick, have shown promising results in preliminary experiments in regard to collection efficiency of water and of bromide tracers. The objectives of this study were to evaluate PCAPS under non-steady state field conditions with respect to (1) effect of installation procedure and operational characteristics, (2) ability to estimate the soil-water flux, and (3) ability to estimate the mean concentration of agrochemicals. At the same time, samplers were used to (4) evaluate the effect of a cereal rye (Secale cereale (L.)) cover crop on NO₃⁻ leaching. Thirty-two PCAPS and 32 suction cup samplers were installed below the root zone at a depth of 120 cm in a Willamette Variant loam wet soil (fine loamy mixed mesic Pachic Ultic Argixeroll). Samplers were installed in an ongoing cover crop/crop rotation study. Regarding overall performance, flux measurements were within 20 % of the native values as determined by a water balance. The air release from the sample bottles was a point of concern and might have slowed down the sampling rate. The installation procedure introduced bias into volume and concentration measurements of the part of the PCAPS closest to the refilled trench. The leachate concentration as calculated using the arithmetic mean of suction cup sampler measurements holds a significant bias, deviating by up to 97 % for bromide concentrations. Phosphate was not detected by the suction cup samplers indicating that ceramic cups should not be used for phosphate sampling. Matrix and preferential flow could clearly be distinguished using the PCAPS, showing that PCAPS are a valuable tool to assess the hydrology and solute transport mechanisms of a field site. The cover crop reduced NO₃⁻-N leaching significantly at the recommended N rate as evaluated by PCAPS. The cover crop reduced the seasonal mean NO₃⁻-N concentration at the recommended N rate from 13.5 mg LI to 8.1 mg L⁻¹, which is under the E.P.A. drinking water quality standard of 10 mg L⁻¹. The total NO₃⁻-N mass lost under the fallow treatment at the recommended N rate was 48 kg N ha⁻' which compares to 32 kg N ha⁻' under the cover crop treatment. Given the increasing problems with nitrate contamination of ground water, programs to support the cultivation of catch crops in conjunction with nitrogen soil testing should be considered as a relatively easy, effective, and biologically sound means to reduce nitrate concentrations in the recharge to the ground water in agricultural settings. / Graduation date: 1994

No description available.

No description available.

Bibliography: leaves 116-127.

Twenty-five piston cores 6 to 12 feet long were obtained from the deepwater sediments of Bear Lake, Utah-Idaho. Analyses of these cores revealed that the deep-water sediments of the lake are divided into two major S('f]Uflnces: a younger sequence rich in carbonate minerals, here called the carbonate sequence, and an older sequence rich in silicate minerals, referred to in this paper as the silt sequence. The carbonate sequence is composed of clay-sized quartz, aragonite, calcite, dolomite, montmorillonite, illite, kaolinite, chlorite, and amorphous material. The silt sequence consists of both silt- sized and claysized particles of quartz, calc ite, dolomite, montmorillonite, illite, kaolinite, chlorite, and amorphous material. Aragonite is absent in the silt sequence. The carbo nate sequence is rich in ostracod exoskeletons and pollen grains. Small quantities of woody material and dark, organic-rich wnes occur within the silt sequence. Chemical analyses for Mg, Ca, Fe, Mn, K, Zn, Na , and Sr were reformed on the sediments. Unusually high concentrations of Fe (8.25 percent) were found in the silt sequence, and of Sr (0 .110 percent), in the carbonate sequence. Isotopic analyses for o18 and c13 in the lake sediments indicate that formation of the authigenic carbonate minerals occurred under normal lake-bottom conditions. From the data collected, the following conclusions or inferences are made. The carbonate sequence was deposited in water depths similar to, or grea ter than, those of the present. Within this sequence, aragonite is precipitating at present from solution in such quantities that it is responsible for the inversion of the average Ca/ Mg mole ratio of inflowing water of 2:1 to a Ca/ Mg mole ratio of 1:5 in the lake water. The high concentration of Mg +2 and possible high concentration of Sr+2 in the lake water have resulted in conditions favorable for development of protodolomite. Atypical X-ray diffraction patterns for calcite and dolomite, and the relative abundances of aragonite, calc ite, and dolomite reveal that protodolomite probably is, or has been, forming in Bear Lake. The silt sequence was deposited in water shallow enough for rooted plants to establish themselves . In this shallow environment detrital sediments rich in kaolinitic clay derived from the· Bear Lake Plateau were altered to sediments rich in montmorillonitic clay and amorphous materials. The sharp contact between the silt sequence and the overlying carbonate sequence apparently represents abrupt termination of widespread swampy depositional conditions in the Bear Lake graben, caused by flooding, which possibly resulted from the most recent major episode of downfaulting of Bear Lake Valley.

Thesis (MScAgric)--University of Stellenbosch, 1955. / No Abstract Available

Various aspects of myrmecochory were investigated. Effect of different storage methods on atractiveness of seeds with elaiosomes for ants was examined. Viable seed bank of refuse piles (places where ants deposit unused objects from ant nests, e.g. seeds after the elaiosome was eaten) and places outside them were compared. Chemical content of five major chemical groups, specifically amino acids, free fatty acids, organic acids, polyols and sugars, of elaiosomes and seeds of selected species was determined, and compared with respect to their taxonomic relatedness.

Various aspects of myrmecochory were investigated. Effect of different storage methods on atractiveness of seeds with elaiosomes for ants was examined. Viable seed bank of refuse piles (places where ants deposit unused objects from ant nests, e.g. seeds after the elaiosome was eaten) and places outside them were compared. Chemical content of five major chemical groups, specifically amino acids, free fatty acids, organic acids, polyols and sugars, of elaiosomes and seeds of selected species was determined, and compared with respect to their taxonomic relatedness.