School of Agriculture, Food and Ecosystem Sciences - Theses
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ItemThe effect of applied N and P under mowing and grazing on the yield and botanical and chemical composition of irrigated pasture and on the nutrient status of a red-brown earth at Kyabram( 1978)A split plot experiment was conducted over 4 years to study the effect of method of harvesting (grazing and mowing) and applied N and P (5 rates of nitrogen ranged from 0 to 112 kg N ha -1 cut-1 and 6 rates of superphosphate ranged from 0 to 188 kg P ha 1 year year-1) on the yield, botanical and chemical composition of irrigated phalaris (Phalaris tuberosa x Phalaris arundinacea)/white clover (Trifolium repens L. cv. Irrigation) pasture and nutrient status of a red-brown earth at Kyabram. A second experiment was conducted over 2 years to find out the effect of rates (0 to 112 kg N ha. 1) and frequency of N application (2, 4 or 8 times year ) o n dry matter production, botanical composition and crude protein content of paspalum (Paspalum dilatatum)/white clover pasture. Results: Mowed plots significantly out-yielded grazed plots in the first two years. However, grazed plots significantly out-yielded mowed plots in the following two years. Nitrogen application significantly (P <0.01) increased dry matter production of grass/clover mixtures. The size of response was governed by the growth rate of pasture species, clover percentage in the sward, climatic conditions and the status of other nutrients in the soil. Splitting N rates in smaller but more frequent applications had no effect on total herbage yield or seasonal distribution. Response to N (kg D.M. kg N-1 ) declined as N rates increased. Phosphorus application up to 94 kg P ha -1 year -1 significantly (P,(0.01) increased pasture production and relative response was greater in winter. Occasionally, the P and N requirements for maximum production were higher for grazing than for mowing. Both methods of defoliation and fertilizer applications affected pasture composition and IT, P and K content in the herbage. Nitrogen application decreased N in the herbage before increasing it and P application up to 141 kg P ha- 1 year -1 increased it. The return by the grazing animal increased total soil N by 106 kg ha 1 year 1 and soil P (Colwell) by 1:0 p.p.m. in four years compared with the start of the experiment. The relationship between plant P and soil P and P rates were significant (P < 0.01). The available soil P decreased with P withdrawal or the application of 23.5 kg P ha-1 year -1 under grazing and 47 kg P ha -1 year-1 under mowing. Phosphorus and nitrogen application significantly affected available soil P. 60-80% of the available P accuminulated in the 0-5 cm and the downward movement increased by increasing P rates. The continuous mowing and P application significantly reduced available soil K. Defoliation method affected C/t:N ratio. Phosphorus application increased soil N whereas N application decreased it. P application at the rate of 23.5 kg ha-1 year-1 increased total soil N by 0.068% which is equivalent to 952 kg N ha-1 in five years. It was estimated that 4 to 4.7 p.p.m of P was required to be removed or added to the soil to change the available soil P by 1 p.p.m. The application of 196 kg N ha-1 year -1 as NH4 NO3 did not change the soil pH and 784 kg N ha 1 year 1 reduced soil pH by an average of ').4 unit.
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ItemAn investigation of soil friability and plant growth( 1979)The effect of the exchangeable cations, total soluble salts, organic carbon and particle size distribution on soil friability and the relationship between soil friability and plant production were investigated. The stability percentage method was introduced to examine soil friability. The A and B horizons of three soil types belonging to three Great Soil Croups were selected for these investigations. Peach tree growth was investigated on an orchard near Kyabram, Victoria, and wheat production in a glass-house experiment. The stability percentage method was shown to be a satisfactory quantification of field assessment of friability. Exchangeable Ca and K, total soluble salts, clay sized particles and organic carbon in the soil were shown to contribute to a strongly aggregated soil (friable), while silt, fine sand and exchangeable Na and Mg contribute to a weakly aggregated soil (less friable). Fine sand and silt reduce wet aggregate stability, and they decrease the load required to crush aggregates of 1 mm diameter (dry aggregate stability). The ratio of exchangeable Ca plus K to exchangeable Na plus Mg has an important role in aggregate stability. The higher the ratio, the stronger is the soil. aggregation (friable). An exchangeable Na percentage of 5 or more has a significant effect in reducing aggregate stability. Also, the greater the aggregate stability (friability) of the soil, the better is the peach tree performance as measured by butt circumference and tree height. Exchangeable Ca and K, organic carbon and phosphorus in the soil increased grain and dry matter production of wheat, whereas high exchangeable and soluble Na and Mg as well as the chloride in the soil decrease this production. The results showed differences between wheat production and soil friability. Significantly higher wheat production was obtained with increasing friability. Wheat production between the A and B horizons was not significantly different in the uniform soils, but it was for the duplex soils.
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ItemSulphur studies in relation to yield and quality characters of wheat cultivars (Triticum aestivum L.)( 1975)This thesis contains no material which has been submitted for the award of any other degree or diploma at any university. Experimental results from two of the papers presented in this thesis have been published in international scientific research journals. Results of a study entitled "Relationship Between Free glutathione Content and Quality Assessment Parameters of Wheat Cultivars (Triticum aestivum L.)" were published in the Journal of Science, Food and Agriculture, 1972, 23, 485-491. Results of a study entitled "A Sand Culture Experiment to Compare the Effects of Sulphur on Five Wheat Cultivars (Triticum aestivum L.)" were published in the Australian Journal of Agricultural Research, 1974, 25, 369-80. Other publications from this thesis will also be in this author's name.
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ItemSalting on dryland farms in North-Western Victoria( 1972)In semi-arid north-western Victoria saltpans developing on farms are associated with seepage of rainwater and of water from earthen channels, and with a consequent rise of groundwaters from beneath the mantle of soils. Seepage is most active on land with E-W. dunes, and it has increased through the replacement of deep-rooted native vegetation with crops, pastures and fallows. As yet saltpans have developed on only a small proportion of low sites where groundwaters or clays of low permeability lie unusually close to the surface. The extent to which production on interdune flats is being reduced by rising salinity of subsoils is unknown. Of most significance is a rise of groundwaters causing large saltpans to develop in several districts. Here there is a need to dry out the soils on a district rather than a farm basis, using deep-rooted pastures. Information is urgently needed on the placement and movement of groundwaters