Thesis (M.A.S.)--University of Delaware, 2008. / Principal faculty advisor: Herbert E. Allen, Dept. of Civil & Environmental Engineering. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1950. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 53-56).

Investigations are described which were carried out to analyse the way in which certain mineral element deficiencies restrict the growth and development of plants. The plant system used in this work was excised pea roots grown in sterile culture media, and the deficiencies studied were those of iron, magnesium and molybdenum. Growth was measured at the cell level and related to other characteristics of the system; two different experimental designs being employed to assess the effects of deficiencies. In the first, roots were grown in full nutrient and in deficient media and growth was measured on samples taken after growing periods of 0, 3, 5, 7, 9 and 11 days; while in the second, roots were grown for 7 days in full nutrient and in deficient media and serial one centimetre sections taken from these roots were compared. The first approach assessed the effects of the deficiency on overall growth, and the second gave an indication of the effects of the deficiency on the longitudinal differentiation of pea roots. Both experimental approaches were employed when examining iron and magnesium deficient roots, but only the second when examining molybdenum deficient roots. Roots deficient in iron and magnesium were obtained by culturing tips cut from germinated seeds in deficient media, but two successive tip passages were necessary to obtain roots deficient in molybdenum. Growth was assessed basically in terms of length, cell volume, protein nitrogen, and rate of oxygen uptake. However with iron deficient roots measurements of invertase activity, sensitivity of the oxygen uptake to cyanide, and the frequencies of cells in the different stages of division were also made. The techniques involved in the culture of deficient and full nutrient roots, and the analytical techniques are described. It has been shown that iron deficiency markedly affects the growth and development of excised pea roots. Growth in terms of length and cell number per root is stopped after 7 days and no further increases occur between days 7 and 11. Although iron deficiency stops cell division, measurements made at day 7 indicate that this deficiency does not restrict the process of cell expansion. In fact 7 day old iron deficient roots carry larger cells in the terminal centimetre than full nutrient roots. By 11 days the iron deficient roots have a pronounced swelling at the terminal end, and it is suggested that this is brought about by an abnormal expansion of the cells in the lateral direction. Some cells containing mitotic figures are present in the tips of 7 and 11 day old iron deficient roots. However there are fewer cells in the division stages of prophase and metaphase and practically no cells in the stages of telophase and anaphase in the deficient roots when comparisons were made with full nutrient roots. The protein nitrogen content of iron deficient roots is lower than that of full nutrient roots at day 7, but there is a considerable increase in both deficient and full nutrient roots between days 7 and 11. The trend of the derived quantity, average protein nitrogen content per cell, is the same in both groups of roots up to day 7, but from day 7 to day 11 it increases sharply in the deficient roots but does not change in the full nutrient roots. This result indicates that cell division was not stopped in the deficient roots by a shortage of protein nitrogen as such. At the day 7 stage the distribution of protein nitrogen along the length of deficient roots is different to that in full nutrient roots. The front sections of the deficient roots contain an increased content and the back sections a decreased content when compared with full nutrient roots. On a per cell basis the situation is the same, as the cells in the front sections of deficient roots have a higher average protein content and those in the back sections a lower content when compared with the cells of full nutrient roots. The accumulation of protein nitrogen in the front sections of iron deficient roots is most probably associated with the cessation of active cell division in the meristem. Evidence is available which suggests that under normal conditions the formation and development of cells in the apex of the root is dependent on substrates synthesised in the mature regions of the root and translocated forward. It is considered that in iron deficient roots precursors of protein are no longer removed by the demands of the meristem and they condense to form protein in the regions adjacent to the apex. Invertase activity per unit protein nitrogen is the same in both full nutrient and iron deficient roots at all stages. Further, there is no difference in invertase activity when the corresponding sections of full nutrient and deficient roots are compared at day 7. It is clear that in this one respect the protein of iron deficient roots is similar to that of full nutrient roots. The rate of oxygen intake per root of iron deficient roots is lower than that of full nutrient roots at the early day 3 stage, but there are large increases in the rates in both deficient and full nutrient roots between days 3 and 11. It is of some significance that iron deficiency clearly reduces the rate of oxygen uptake at a stage before the process of cell division is stopped. On a per unit protein nitrogen basis the rate of oxygen uptake of deficient roots is lower than that of full nutrient roots after day 3. It is suggested that the effects of days 3 and 5 are a direct effect of iron deficiency but the effects at days 9 and 11 are influenced by the fact that cell division stops at day 7. The results from 7 day roots show that the effect of iron deficiency in reducing the rate of oxygen intake per unit protein nitrogen is confined to the front three sections of the root as iron deficiency does not alter the rates in the back three sections. Iron recovery experiments show that iron deficient roots 7, 9 and 11 days old can resume cell division and grow when they are transferred to a full nutrient medium. It is of interest that in these experiments the recovery in terms of an increased rate of oxygen uptake is greater than the recovery in terms of length and protein nitrogen. Experiments in which the rate of oxygen uptake of deficient and full nutrient roots were measured in the presence and absence of cyanide show that in both groups of roots there is a large fraction of the respiration insensitive to cyanide. The activity of this cyanide insensitive system increases considerably from day 3 to day 11 in both the full nutrient and iron deficient roots. Increases, after day 3 in the activity of this cyanide insensitive system, which would not contain iron, account for the large increase in the total rate of oxygen uptake of iron deficient roots between days 3 and 11. The activity of the cyanide sensitive system involved in respiration decreases in both groups of roots between days 0 and 5. It increases from day 5 to 11 in full nutrient roots, but does not increase in deficient roots over this period. That synthesis of a cyanide sensitive system involved in respiration stops at or about the same stage as cell division in iron deficient roots is considered to be highly important. This cyanide sensitive system most probably corresponds to the iron containing cytochrome/cytochrome oxidase system, and there is other circumstantial evidence that this system is important in the process of cell division. It is important to note that the activity of the cyanide sensitive system was the same in the tips of deficient and full nutrient roots at the day 7 stage. It may be that a certain minimum level of activity per cell is necessary to maintain division; a slight reduction stopping cell division completely, but not being capable of detection by the method of measurement.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references. Also available via the Internet.

Thesis (Ph.D.)--University of Delaware, 2009. / Principal faculty advisors: John L. Gallagher, and Denise M. Seliskar, School of Marine Science & Policy.. Includes bibliographical references.

Thesis (MScAgric)--University of Stellenbosch, 2006. / Bibliography. Also available via the Internet.

The annual production of biosolids in the Perth region during the period of this study was approximately 13,800 t dry solids (DS), being supplied by three major wastewater treatment plants. Of this, 70% was typically used as a low-grade fertiliser in agriculture, representing an annual land use area of around 1,600 ha when spread between 5 and 7 t DS/ha. Loading rates of biosolids are typically based on the nitrogen (N) requirements of the crop to be grown, referred to as the N Limiting Biosolids Application Rate (NLBAR). A consequence of using the NLBAR to calculate loading rates is that phosphorus (P) is typically in excess of plant requirement. The resultant high loading rates of P are considered in the guidelines developed for the agricultural use of biosolids in Western Australia, but lack research data specific to local conditions and soil types. Regulatory changes throughout Australia and globally to protect the environment from wastewater pollution have created a need for more accountable and balanced nutrient data. Experiments presented in this thesis were undertaken to ascertain: the percentage relative effectiveness (RE) of biosolids as a source of plant available P compared with inorganic P fertiliser; loading rates to best supply P for optimum crop growth; P loading rates of risk to the environment; and the forms of P in local biosolids. Therefore, both the agronomic and environmental viewpoints were considered. Anaerobically digested and dewatered biosolids produced from Beenyup Wastewater Treatment Plant, Perth with a mean total P content of 2.97% dry weight basis (db) were used in a series of glasshouse, field and laboratory experiments. The biosolids were sequentially fractionated to identify the forms of P present and likewise in soil samples after applying biosolids or monocalcium phosphate (MCP). / The biosolid P was predominantly inorganic (92%), and hence the organic fraction (8%) available for mineralisation at all times would be extremely low. The most common forms of biosolid P were water-soluble P and exchangeable inorganic P (66%), followed by bicarbonate extractable P (19%) and the remaining P as inorganic forms associated with Fe, Al and Ca (14%). Following the application of biosolids to a lateritic soil, the Fe and Al soil fractions sorbed large amounts of P, not unlike the distribution of P following the addition of MCP. Further investigation would be required to trace the cycling of biosolid P in the various soil pools. The growth response of wheat (Triticum aestivum L.) to increasing rates of biosolids and comparable rates of inorganic P as MCP, to a maximum of 150 mg P/kg soil was examined in the glasshouse. The percentage relative effectiveness (RE) of biosolids was calculated using fitted curve coefficients from the Mitscherlich equation: y = a (1-b exp–cx) for dry matter (DM) production and P uptake. The initial effectiveness of biosolid P was comparable to that of MCP with the percentage RE of biosolids averaging 106% for DM production of wheat shoots and 118% for shoot P uptake at 33 days after sowing (DAS) over three consecutive crops. The percentage residual value (RV) declined at similar rates for DM production in MCP and biosolids, decreasing to about 33% relative to freshly applied MCP in the second crop and to approximately 16% in the third crop. The effectiveness of biosolid P was reduced significantly compared with inorganic P when applied to a field site 80 km east of Perth (520 mm annual rainfall). An infertile lateritic podsolic soil, consistent with the glasshouse experiment and representative of a soil type typically used for the agricultural application of biosolids in Western Australia was used. / Increasing rates of biosolids and comparable rates of triple superphosphate (TSP), to a maximum of 145 kg P/ha were applied to determine a P response curve. The percentage RE was calculated for seasonal DM production, final grain yield and P uptake in wheat followed by lupin (Lupinus angustifolius L.) rotation for the 2001 and 2002 growing seasons, respectively. In the first year of wheat, the RE for P uptake in biosolids compared with top-dressed TSP ranged from 33% to 55% over the season and by grain harvest was 67%. In the second year, and following incorporation with the disc plough at seeding, the RE for P uptake by lupins in biosolids averaged 79% over the growing season compared with top-dressed TSP, and by grain harvest the RE was 60%. The residual value (RV) of lupins at harvest in biosolids compared with freshly applied TSP was 47%. The non-uniform placement of biosolids (i.e. spatial heterogeneity) was primarily responsible for the decreased ability of plant roots to absorb P. The P was more effective where biosolids were finely dispersed throughout the soil, less so when roughly cultivated and least effective when placed on the soil surface without incorporation. The RE for grain harvest of wheat in the field decreased from 67% to 39% where biosolids were not incorporated (i.e. surface-applied). The RE could also be modified by factors such as soil moisture and N availability in the field, although it was possible to keep these variables constant in the glasshouse. Consequently, absolute values determined for the RE need to be treated judiciously. Calculations showed that typical loading rates of biosolids required to satisfy agronomic P requirements of wheat in Western Australia in the first season could vary from 0 to 8.1 t DS/ha, depending on soil factors such as the P Retention Index (PRI) and bicarbonate available P value. / Loading rates of biosolids were inadequate for optimum P uptake by wheat at 5 t DS/ha (i.e. 145 kg P/ha) based on the NLBAR on high P sorbing soils with a low fertiliser history (i.e. PRI >15, Colwell bicarbonate extractable P <15 mg P/kg). On soils of PRI <2 mL/g however, biosolids applied at identical loading rates would result in high concentrations of available P. Further work on sites not P deficient would be necessary to validate these findings on farmed soils with a regular history of P fertiliser. The sieving of soil samples used in the field experiment to remove stones and coarse organic matter prior to chemical analysis inadvertently discarded biosolids particles >2 mm, and thus their was little relationship between soil bicarbonate extractable P and P uptake by plants in the field. The risk of P leaching in biosolids-amended soil was examined over a number of different soil types at comparable rates of P at 140 mg P/kg (as either biosolids or MCP) in a laboratory experiment. Given that biosolids are restricted on sites prone to water erosion, the study focussed on the movement of water-soluble P by leaching rather than by runoff of water-soluble P and particulate P. In general the percentage soluble reactive P recovered was lower in soils treated with biosolids than with MCP, as measured in leachate collected using a reverse soil leachate unit. This was particularly evident in acid washed sand with SRP measuring 14% for biosolids and 71% for MCP, respectively, although the differences were not as large in typical agricultural soils. Specific soil properties, such as the PRI, pH, organic carbon and reactive Fe content were negatively correlated to soluble reactive P in leachate and thus reduced the risk of P leaching in biosolids-amended soil. / Conversely, the total P and bicarbonate extractable P status of the soils investigated were unreliable indicators as to the amount of P leached. On the basis of the experiments conducted, soils in Western Australia were categorised according to their ability to minimise P enrichment and provide P necessary for crop growth at loading rates determined by the NLBAR. Biosolids applied at the NLBAR to soils of PRI >2mL/g with reactive Fe >200 mg/kg were unlikely to necessitate P loading restrictions. Although specific to anaerobically digested biosolids cake applied to Western Australian soils, the results will be of relevance to any industry involved in the land application of biosolids, to prevent P contamination in water bodies and to make better use of P in crop production.

Thesis (M.S.)--West Virginia University, 2006. / Title from document title page. Document formatted into pages; contains xi, 145 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 101-104).

Thesis (M.S.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains ix, 115 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 78-80).

published_or_final_version / Geography and Geology / Doctoral / Doctor of Philosophy