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Item An investigation of pasture legume root and shoot properties that influence their rate of decomposition in soil : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Soil Science at Massey University, Palmerston North, New Zealand(Massey University, 2021) Walker, HelenAgriculture is the largest source of GHG emissions (47.8 %) in New Zealand. Emissions are increasing annually, driven by increasing relative productivity. Irrespective of the climate regime, grassland soils have historically sequestered large amounts of atmospheric C into SOM (soil C) raising interest in the potential for agricultural emissions to be mitigated through acceleration of soil C sequestration. Soil C sequestration is a direct result of the rate of deposition (excreta, plant litter, and roots) exceeding the rate of decomposition and can be raised by: 1) increasing the rate of input (manipulating the drivers of vegetation); or 2) increasing the longevity of C in the system. This PhD study tests the hypothesis that C sequestration in pasture soils can be accelerated, by selecting pasture species that contribute slower decomposing litter to soil. A series of laboratory incubation studies were conducted to measure the decomposition rate (CO₂ emissions) of plant shoots and roots with high (Lotus pedunculatus) and low (Trifolium repens) tannin contents. In addition the effects of residue management (fresh and freeze dried), application to soil (fresh - surface, freeze dried - surface, and freeze dried - mixed) and rate of application (2, 5, 10 mg C. g⁻¹ soil) were evaluated. The effect of species, plant management, plant part, and rate of application on C emissions were all statistically significant (P < 0.05), with large variance in CO₂ emissions associated with all treatments. Plant species and plant part influenced the amount of C retained in the soil, although not entirely as expected. Lotus pedunculatus shoot material retained significantly more C than Trifolium repens shoot material at all rates of application (2, 5, 10 mg C. g⁻¹ soil); whereas Trifolium repens root material retained significantly more C than Lotus pedunculatus root material at all rates of application (P < 0.05). Notably plant roots and particularly Trifolium repens roots had slow decomposition rates compared to shoot materials. Research showed that soil and plant residue preparation greatly influenced the total amount of C retained for both shoot and root treatments, with more C retained under conventional incubation techniques (dried - mixed application) than with fresh applications. This indicates that CO₂-C retention in a field situation may be overestimated if predicted using conventional laboratory incubation techniques. However from a research perspective it is infinitely easier to work with pre-dried incubation materials (timing, handling, chemical analysis) so it is highly likely that this style of incubation practice will continue to be the preferred method of research. Care must therefore be taken when extrapolating the results from such incubation studies. A four compartment (2 soil C pools, persistent and labile; and 2 plant C residue pools, fast and slow) computer simulation model was developed and provided an excellent explanation of the CO₂ emissions from the incubation of fresh shoot and root material. The measurement of the metabolisable energy (ME) or lignin contents of plant shoot and root were successful in parameterising (allocating C to) the fast and slow plant residue pools. Plant tannin content was not able to explain CO₂ emission rates. The experimental and modelling studies provide evidence that grazed pasture rotations in mixed farming systems could be manipulated, by careful plant pasture species selection, to accelerate soil C sequestration. Litter and root metabolisable energy (ME) or lignin contents could be useful in species selection, but further research into other pasture species and pasture management techniques is required. Field studies should focus on the role of clover (Trifolium repens) roots in building pasture soil C content.Item Climatic factors affecting herbicidal activity of sodium trichloracetate in different soils : a thesis submitted to the University of New Zealand in partial fulfillment of the requirements for the degree of Master of Agricultural Science (Horticulture)(Massey University, 1956) Pengelly, R.Trichloracetic acid (T C A) has long been known as a protein precipitant, but it was not until 1947 that research workers in the U.S.A. found it to be an effecive grass killer. Immediately it was subjected to a considerable amount of experimentation, but it is only since 1950 that any trials have been conducted with this herbicide in New Zealand. Most of this early research was of an observational or emperical nature, and the results obtained were often inconsistent. However, it was soon determined that there was little downward translocation of T C A when foliar applications were made, and that for maximum kill it was essential for the herbicide to come into contact with the grass roots. Best control of couch (Agropyron repens L.), for example, has been obtained when the T C A was sprayed on the upturned sod and light rain fell within a few days after application. Before commerical usage of any newly developed herbicide is recommended on agricultural land it is desirable to know the fate of that herbicide when applied to the soil, whether it will persist and be cumulative so that subsequent crops will be effected, if a short period of residual activity can be expected, or if the compound is rapidly dissipated. To this writer's knowledge, no attempt had been made in New Zealand to undertake a quantitative study of the effects soil type, temperature and rainfall have on the rate of inactivation and distribution of T C A when applied to the soil. Such an investigation therefore seemed pertinent, and more especially because results of similar studies overseas were not in full agreement. The published reports showed that both chemical and biological tests had been employed to determine the concentrations, or relative amounts of T C A in the soil, but in no instance had the two methods been employed for the one experiment. It was therefore considered that in a future investigation some useful purpose would be served by a comparison of results obtained by both tests. [From Introduction]Item An activated sludge based system for the treatment of leachate containing chlorophenols and phenoxyacetate herbicides : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Biotechnology at Massey University(Massey University, 1990) McAllister, Peter JamesA study was made on the biological treatment of a landfill leachate containing high concentrations of the phenoxy herbicides 2,4-dichlorophenoxyacetic acid (2,4-D), 2-methyl-4-chlorophenoxyacetic acid (MCPA) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), along with significant quantities of para-chloro-ortho-cresol (PCOC), methanol, butan-1-ol and butan-2-ol. A mixed, natural microbial population (consisting of Pseudomonas species) was developed from a soil inoculum. The culture was found to be capable of mineralising 2,4-D and reducing the toxicity of the leachate by 92 %. The culture was found to be stable in continuous culture (residence time = 14.5 h) for 872 days. The optimum concentrations for degradation were found to be 5-10% leachate (217-435 mg/l phenoxies, 33-66 mg/l PCOC, 40-80 mg/l alcohols and 0.6-1.2 g/l ash) for batch work and 10-15 % leachate (435-708 mg/l phenoxies, 66-107 mg/l PCOC, 80-120 mg/l alcohols and 1.2-1.9 g/l ash) for CSTR work. Batch studies showed sequential utilisation of the substrates: alcohols, followed by PCOC followed by phenoxies. Studies were carried out to determine the kinetics of degradation for each group of substrates. The results showed that alcohols were the most rapidly degraded (μMAX = 0.3 h-1), although growth was inhibited by PCOC and phenoxies. PCOC was inhibitory to its own degradation, with inhibition directly proportional to PCOC concentration up to 290 mg/l, above which no degradation occurred. Both alcohol and PCOC degradation were described well by a linear inhibition model. A comparison was made between the batch determination of PCOC degradation kinetics and a relatively new method, the Modified Infinite Dilution Test (MIDT). The MIDT results showed rates 50 % higher than the batch methods, indicating there was a change in the nature of the biomass in batch studies. The kinetics of phenoxy degradation indicated that there was no inhibition in the concentration range of interest for MCPA and 2,4-D. However, 2,4.5-T was apparently degraded by cometabolism, with PCOC the best stimulator of degradation. An interactive three substrate model was used to describe degradation and was found to fit measured data for CSTR systems. The model was robust and could predict the single substrate (ie pure compound kinetics) on simplification, indicating the wide range of application of the model. The model showed that the presence of the alcohols in leachate considerably accelerated the degradation of PCOC and phenoxies. Critical points for washout were significantly shifted and reversed from those of pure compounds, indicating interactions between the substrates could not be ignored. The model provides a method for quantifying the effect of a secondary substrate on the target compounds. Results from laboratory activated sludge experiments showed that this process was capable of degrading the alcohols, PCOC and phenoxies present in both 10 and 15 % leachate. Loading rates (1.9-3.0 kgsubstrate/m3.d) were high in comparison to the typical loadings quoted in the literature. The three substrate model, in association with the critical point method predicted three regions of plant operation, total substrate removal, stable operation with residual substrate and no degradation, compared with the two regions of the critical point method. The results also showed that the system could be treated as non-inhibitory for design purposes, as the Monod model gave a closer prediction of behaviour than the critical point method. However, as the composition of the leachate is expected to change, the three substrate model is required to predict the effect of these changes on an AS plant. The sludge produced by the AS plant had low concentrations of residual organic and inorganic ions, indicating it could be treated as a non-hazardous byproduct. While AS reduced the toxicity by 71 %, the effluent toxicity could be reduced further by the use of activated carbon treatment. This produced a final effluent with an EC50 (48h) of 46 %. Preliminary economic analysis showed that AS followed by activated carbon treatment was capable of treating the leachate for 42c/l. lower than the alternatives of activated carbon alone and incineration. The cost was most sensitive to leaching rate, with lower rates resulting in smaller and cheaper processes. To conclude, it was shown that a biologically based process is capable of producing non-hazardous byproducts and is economically viable as compared to alternative treatment processes.Item Biodegradation of cyanobacterial hepatotoxins [Dha⁷]MC-LR and MC-LR by natural aquatic bacteria : a thesis submitted for fulfillment of the requirements for the degree of Doctor of Philosophy in Microbiology, Institute of Food, Nutrition and Human Health, College of Sciences, Massey University at Wellington, New Zealand(Massey University, 2010) Somdee, TheerasakThe aims of this doctoral study were to: isolate naturally occurring bacteria, able to degrade microcystins (MCs), from New Zealand waterbodies; to understand the biological processes of microcystin degradation by bacteria; and to develop small scale biofilm technology for testing the effectiveness of bacteria for microcystin degradation and/or remediation. A significant amount of microcystins were required for biodegradation experiments. A modified method, using DEAE and Strata-X cartridge chromatography, was optimized for purifying microcystin variants from lyophilized bloom samples of the cyanobacterium Microcystis aeruginosa, collected en masse from Lake Horowhenua. Seven microcystin variants, MC-RR, MC-dMe-RR, MC-YR, MC-LR, [Dha⁷]MC-LR, MC-FR, and MC-AR were purified by chromatography and then identified by reverse-phase High Performance Liquid Chromatography (HPLC) with UV detector (UVD) and Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS). A mixture of [Dha⁷]MC-LR and MC-LR, the main microcystin variants present, was used for examining biodegradation of microcystins by degrading bacteria. Three isolates of bacteria—NV-1, NV-2 and NV-3—purified from Lake Rotoiti, New Zealand were capable of degrading [Dha⁷]MC-LR and MC-LR. Among these isolates, NV-3 demonstrated the strongest degradative activity and was identified as a member of the genus Sphingomonas. On the basis of 16S rRNA sequencing, and 100% nucleotide sequence homology, it aligned most closely to strain MD-1. Based on the detection of two intermediate by-products (linearized peptides and a tetrapeptide) and the identification of four genes (mlrA, mlrB, mlrC and mlrD), that encode four putative proteins (enzymes) involved in microcystin degradation, it was suggested that the degradation of [Dha⁷]MC-LR and MC-LR by the Sphingomonas isolate NV-3 occurred by a similar mechanism previously described for Sphingomonas strain MJ-PV (ACM-3962). The bacterium Sphingomonas isolate NV-3 was examined for its ability to inhibit the growth of the cyanobacterium Microcystis aeruginosa strain SWCYNO4. It was found that the bacterium did not have any significant affect on the growth of the cyanobacterium, either by means of secretion of bacterial extracellular products or cell-to-cell contact between bacterial and cyanobacterial cells. It was established that Sphingomonas isolate NV-3 was a moderate biofilm former, based on two types of biofilm formation assays, namely, microtiter plate assays and coupon biofilm assays. This was carried out in preparation for using the bacterium in a bioreactor for biodegradation of [Dha⁷]MC-LR and MC-LR. The bacterium attached most effectively to ceramic, followed by PVC, polystyrene, stainless steel, and finally glass coupons. Biodegradation of MCs by the bacterium, in an internal airlift loop ceramic honeycomb support bioreactor (IAL-CHS bioreactor), was established in batch and continuous-flow experiments. In the batch experiment, NV-3 degraded a combination of [Dha⁷]MC-LR and MC-LR at an initial concentration of 25 µg/ml at 30 degrees C in 30 hours, whereas in the continuous-flow experiment, NV-3 degraded the same concentration of [Dha⁷]MC-LR and MC-LR in 36 hours with an hydraulic retention time (HRT) of 8 hours. This study has demonstrated that microcystin-degrading bacteria are present in New Zealand waterbodies and that these bacteria could be used, potentially on a larger scale, for removing microcystins from water.