The effects of adhesion to surfaces on the specific growth rates of <I>Nitrosomonas europaea </I>and <I>Nitrobacter </I>sp. were determined in batch culture systems both in monoculture and co-culture. It was found that the presence of a glass slide in co-cultures of these bacteria significantly reduced the specific growth rates of both species of bacteria. In monoculture, the specific growth rate of <I>N. europaea </I>was significantly lower in a mature biofilm system. The specific rates of production of ammonia by these four species of <I>Pseudomonas </I>were investigated in minimal medium. All four species converted approximately 60 - 80% of the provided L-alanine to ammonia, and this production of ammonia raised the pH of the medium. All four strains were capable of this when the initial pH of the medium was 5.5 or 7.5, however, lowering the initial pH of the medium reduced the specific rate of production of ammonia for <I>P. cepacia, P. fluorescens </I>and <I>P. syringae, </I>and reduced the final concentration of ammonia produced by <I>P. cepacia. </I>Ammonia produced by <I>P. fluorescens </I>could support the growth of <I>N. europaea </I>in liquid batch culture. The growth of the pseudomonad increased the pH of the medium from 5.5 to 6.8 and this increase in pH allowed growth of the nitrifier in the medium with the lower initial pH. The growth of <I>N. europaea </I>and <I>P. fluorescens </I>in continuous flow biofilm reactors was examined, and the addition of <I>P. fluorescens </I>to a nitrifying biofilm raised the pH of the bulk medium, thus removing the effects of pH inhibition on the ammonia oxidiser. Further investigations were carried out in continuous flow sand column systems and it was found that the rapid growth of the pseudomonad caused obstruction of the column.

(Poly)-maleic acid (PMA) was obtained by the pyridine-catalysed homopolymerization of maleic anhydride, followed by acidification with resin. PMA was found to show many structural similarities with the humus extracted from a locally-derived podsol Bh horizon; spectroscopic (IR, NMR, U.V./Visible) and chemical degradation studies of PMA showed that although a degree or aromaticity undoubtedly exists, the predominant structural feature was an aliphatic or alicylic backbone substituted predominantly by vicinal carboxyl groups. Pyrolysis of PMA yielded as a major product, 2-cyclopenten-1-one, which has hitherto not been detected from any natural source other than soil pyrolysates. Elemental and functional group analyses, and potentiometric titration of the molecular size fractions of PMA revealed that the low molecular weight fraction resembled a "typical" fulvic acid, whereas the high molecular weight fraction resembled a "typical" humic acid. 14C-labelled radioisomers of PMA were added to soil and incubated in a closed system. Estimation of the labelled carbon dioxide liberated showed that PMA did not grossly alter microbial respiration compared to unlabelled control samples. The polymer was only slowly degraded in soil, with less than 1 per cent of the radiolabel being released as 14CO2 during eight weeks. Organic and inorganic soil components were found to adsorb PMA. The clay mineral montmorillonite strongly adsorbed PMA, which produced expansion of the interlayer. Adsorption mechanisms were discussed. The secondary clay mineral proto-imogolite was found to inhibit the incorporation of PMA into the soil humic fraction, by the production of an acid-soluble complex. It was postulated that such a complex might occur in the podsolisation process. PMA was found not to cause any gross effects on soil processes. Ryegrass grown in soil was found to be tolerant to high levels of PMA amendment. Small amounts of radioactivity, monitored in the shoots and roots of ryegrass grown in soil amended with 14C-labelled PMA, probably arise via 14C-carbon dioxide.

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Manure nitrogen (N) mineralization is the process that converts organic N to plant available N and is influenced by environmental and soil factors. Field and laboratory incubation studies were conducted to determine the N mineralization and fertilizer equivalence of locally available manures. Available N from solid beef manure amendments (SBM) increased as the studies progressed due to mineralization. Liquid swine manure (LSM) behaved similarly to commercial fertilizer with high initial concentrations of ammonium N which declined continuously as the studies progressed. Manure N mineralization varied significantly (p<0.01) due to the influence soil moisture, manure types and study period as well as their interaction. The fertilizer equivalence of SBM in loamy soil was initially low compared to LSM and finally approached 80 % of ammonium nitrate fertilizer. These studies suggested that manure N mineralization requires emphasis on the initial form of N in manures besides soil moisture, soil temperature, and aeration.

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No description available.