Title page, table of contents and abstract only. The complete thesis in print form is available from the University of Adelaide Library. / Trace element deficiencies represent an ongoing limitation to agricultural productivity in Southern Australia and in many regions of the world. Trace element deficiencies are commonly encountered on alkaline and calcareous soils due to their high metal adsorption and fixation capacities. Chelating agents, such as EDTA, have been used to reduce fertiliser fixation in these soils and increase trace element transport to the rhizosphere. However, EDTA, which is the most commonly used chelating agent, can be relatively ineffective on alkaline soils and may have negative environmental implications due to its long-term persistence. This study has identified two novel sequestering agents for use on alkaline and calcareous soils. The novel products differ significantly from EDTA in terms of their structure and functionality. For example, rhamnolipid is synthesised by Pseudomonas bacteria, is nontoxic, biodegradable and forms a lipophilic complex with cationic metal ions. The other chelating agent, polyethylenimine (PEl) can complex up to 4 times more metal (g Cu(II)/g ligand) than EDTA, which has important implications for chelate application rates and the cost effectiveness of chelate use. In solution culture experiments, rhamnolipid and PEl facilitated Zn absorption into the root symplast; the kinetic rate of Zn absorption was greater than that of ZnC12 alone. On alkaline and calcareous soils the novel products were significantly (P O.05) more effective Zn sources than EDTA or the SO24-salt. EDTA increased the concentration of Zn in soil solution. However, this did not translate to increased Zn uptake by canola plants. This was not surprising as EDT A inhibited Zn absorption by roots in the solution culture experiments. Radioisotope experiments showed that rhamnolipid and PEl increased Zn adsorption to the soils solid phase. However, PEl increased the size of the total Zn labile pool (P<0.05) and mobilised Zn from the pool of fixed native soil Zn (P<0.05). Rhamnolipid did not significantly (P>O.05) increase the total size of the Zn labile pool in either soil, but significantly (P<0.05) increased Zn uptake by canola, probably by facilitating root absorption by the formation of lipophilic complexes with Zn. These results showed that, on alkaline soils, chelates that increased the rate of trace element absorption into the root symplast were significantly more effective than EDTA, which was not readily absorbed by canola roots. Experiments were also undertaken to explore the effect of chelation on the absorption of foliar applied trace element fertilisers. Perhaps not-unexpectedly, chelation reduced the absorption of foliar applied Zn. The lipophilic chelate, rhamnolipid, quadrupled Zn absorption by enzymatically excised Citrus sinensis cuticles but did not significantly (P>O.05) increase Zn absorption by live leaf tissue. Therefore, there was no discemable relationship between the Kc/w of fertiliser solutions and Zn permeability. This body of work has important implications for future fertiliser development, the cost effectiveness of chelate use and the treatment of micronutrient deficiencies on alkaline soils in the world today. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1272776 / Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2007

From the Proceedings of the 1971 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 22-23, 1971, Tempe, Arizona / The 2 major environmental problems of Arizona and the southwest are the alkalinization of soil and water by irrigation and air pollution from copper smelting. It is proposed that the amelioration of both problems may be solved through a common process. This is the production of sulfuric acid from sulfur dioxide, which is the main pollutant of smelter effluent gases. The conversion process is cheap and easy, and the sulfuric acid could then be added to irrigation waters to increase the solubility of CA carbonate in the soil, thereby decreasing alkalinity. Lower alkalinity results in increased soil permeability and increased water use efficiency by plants. The potential market for sulfuric acid in irrigation was calculated, on the basis of neutralizing 90% of the bicarbonate ion concentration in Colorado River water and Arizona well water, to be about 1.6 million tons annually, representing about 1/3 of the sulfur now dissipated by smelters as air pollution. This market includes both the Imperial Valley of California and the Mexicali Valley of Mexico, both of which are currently experiencing mounting salinity problems. Salinity itself is not amenable to this treatment, but the cumulative increase in NA and bicarbonate may be slowed and reversed, leading to gradual soil stabilization.