No description available.

A range of adsorbents have been evaluated for the adsorption of selected herbicide compounds from aqueous solution. The adsorption performance of LF -1, a carbonised polymer produced in the laboratory, Amberlite XAD-4, a commercially available polymeric adsorbent produced by Rohm and Haas and MN-200, a HypersolMacronet polymer produced by Purolite, were compared with a commercial activated carbon, Chemviron F -400. The pore size distributions of the adsorbents have been investigated using nitrogen adsorption. F-400, LF-1 and MN-200 were found to contain similar microporous structures. The carbons also possess a significant degree of mesoporous structure, which may enhance the diffusion of organic species into the micropores. The pore size distribution for XAD-4 shows an almost exclusive meso/macroporosity with very little microporous structure. Spectroscopic analysis and titration of the adsorbents indicated a number of different oxygen functional groups. XPS and elemental analysis suggested higher oxygen concentrations than those obtained using direct titration, which was attributed to bound oxygen within the structure of the adsorbents. The adsorption capacity of phenol was assessed as a characterisation technique. The capacity of the carbons was much greater than the polymeric adsorbents. Analytical techniques were developed and validated for the determination of trace levels (0.1 parts per billion) of five herbicides; atrazine, benazolin, bentazone, imazapyr and tric1opyr. Single and multi-component adsorption isotherms are presented for trace concentrations of the herbicides in aqueous solution. The effect of pH and fulvic acid upon the adsorption was also investigated. Mini-column experiments were performed using multi-component mixtures. In all cases, the uptake of herbicides on F -400 is greater than on the other adsorbents. Regeneration of F-400 and MN-200 was investigated usmg solvent stripping techniques. Significant regeneration efficiencies were observed using ethanol at pH 12 and 50°C to make the technique a viable option.

No description available.

No description available.

Intercropping of a short-cycle legume crop and a longer-cycle non-legume crop has been suggested as a potentially beneficial intercrop combination. Most studies have concerned cereal and legume corps. Few have involved horticultural crops. In 1990 and 1991, a 56-day semi-leafless pea crop (Curly) and a 75-day lettuce crop (Paris Island Cos) were grown both as monocrops and as intercrops. Intercrops consisting of alternating rows of each crop, represented additive populations (56:100) of peas and lettuce. Three lettuce transplanting dates (June 19, 25 and July 4) and three nitrogen fertilizer rates (0, 50, 100 kg ha$ sp{-1}$) were tested. Peas were all sown on May 18. In addition, a new pea/lettuce intercropping pattern (45:82), consisting of alternating double rows of peas and lettuce, was tested in 1991. The $ sp{15}$N dilution method was also used to test for nitrogen transfer. Alternate row intercropped lettuce plant$ sp{-1}$ yields were, on average, 76% and 46% lower than their corresponding monocrop yields for the early and late transplanted lettuce, respectively. Declines in yield of 63% and 55% were reported for the double row intercropped lettuce for the early and late transplanting dates, respectively. Nitrogen fertilization significantly improved intercropped fresh lettuce yields but had no effect on monocropped lettuce. Pea yields m$ sp{-1}$ row were unaffected by intercropping. Alternate row land equivalent ratios (LER) ranged from 0.87 to 1.05 and from 1.06 to 1.63, in 1990 and 1991, respectively. The double row LER's ranged from 1.06 to 1.21 in 1991. The higher LER's in 1991 reflected higher pea yields. No evidence of nitrogen transfer to the lettuce crop was detected.

No description available.

No description available.

Typescript. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1990. / Includes bibliographical references (leaves 164-173) / Microfiche. / xi, 173 leaves, bound ill. 29 cm

Typescript. / Thesis (Ph. D.)--University of Hawaii, 1967. / Bibliography: leaves 124-137. / xiv, 159 l graphs, tables

Typescript. / Bibliography: leaves [97]-105. / xiii, 105 l graphs, tables