School of Agriculture, Food and Ecosystem Sciences - Theses
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ItemA study of wheat crop physiology in relation to time of sowing, rate of sowing and fertilizer application( 1963)A crop physiological study upon yield in wheat was undertaken at Wagga, located in the wheat belt of southern New South Wales, in 1961 and 1962. The effects of time of sowing, rate of sowing and fertilizer application were investigated. The variety, Heron, was used throughout. Comprehensive measurements during the growth cycle of the crops were made upon total dry weight and its components, photosynthetic area, evapotranspiration, soil moisture stress and plant moisture stress (using the leaf relative turgidity technique). Time of sowing had little effect on the soil moisture available to the crop at flowering. However post flowering climatic conditions were hotter and drier for the later sown crops, and consequently plant moisture stress occurred sooner after flowering. Yields fell in both years with later sowings,at an average rate of 2 bushels/acre for each week' s delay in sowing. Increased fertilizer application and increased rate of sowing increased the vegetative growth, and the potential yield at flowering, but this was associated with small reductions in the soil moisture at flowering and an earlier onset of plant moisture stress. The increased vegetative growth usually resulted in increased grain yields, but under drier conditions grain yields were reduced. Nitrogenous fertilizer appeared to have additional effects on the crop which may under some conditions be detrimental to grain yield. Certain interrelationships within the soil/crop system were evident from these trials. Evapotranspiration increased as photosynthetic area index increased when soil moisture was adequate. Leaf relative turgidity at sunrise was closely related to soil moisture stress. Grain yield variation was highly correlated with variation in photosynthetic area duration after flowering. Photosynthetic area duration was related to photosynthetic area index at flowering and to the level of plant moisture stress after flowering, which governed the rate of senescence of this photosynthetic tissue. These results and the value of this type of crop physiological study of yield in wheat are discussed. The application of some aspects of the results to wheat agronomy and breeding is apparent.
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ItemExperiments in animal husbandry( 1961)
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ItemEffects of irrigation on the roots of pastures( 1969)An experiment was conducted in order to investigate the effects of wetting the soil to a range of depths, on the root growth and top growth of some pasture species. The experiment was done within a glasshouse, using a sandy loam soil; the pasture species studied were white clover, ryegrass and subterranean clover. Gypsum block readings, and visual assessment of the moisture status of the soil (as seen through the transparent walls of the containers) were used to decide when to apply water. The soil was maintained within the wetter 2/3 of the available moisture range, so that the effects of drying cycles were avoided. For each species the depth of wetting had a marked effect on the depth of roots; in all treatments, the roots completely occupied the depth of wetted soil. With the deeper wetting treatments both of the perennial species showed a marked increase in the weight of tops, but the annual subterranean clover showed no significant differences. On the other hand, the effect of deeper wettings on the weight of roots was significantly greater for white clover; it was not significantly different for ryegrass; but it was significantly less for subterranean clover.