School of Agriculture, Food and Ecosystem Sciences - Theses
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ItemA study of the effects of high stocking rates on the production of perennial pasture and its utilization by dairy cattle( 1973)The work in this thesis consists of a study of the effects of increasing the stocking rate from 2.2 to 3.2 cows per hectare on the production of dairy cattle and perennial pastures from 1966-70. (a) Milk production per cow was significantly reduced (P < 0.05) by the increase in.:stocking rate with the exception of the first year. (b) The yield of milk and milk components per hectare was increased (P< 0.05) by the increase in stocking rate except for 1968-69 when a drought occurred and the increases were not large enough in most components to attain significance (P)00.05). The yield of nitrogen in milk per hectare was significantly increased (p<0.05) in all years with stocking rate. (c) There was a tendency for the high stocking rate to lower the percentage of all components in milk with the exception of nitrogen which remained unaltered. However significant differences were not recorded consistently in any one component over the four lactations studied. (d) No significant differences (p>0.05) in seasonal or annual net pasture production were recorded between stocking rates. (e) The increase in stocking rate caused significant increases (1).<0.01) in grazing pressure, reductions in pasture availability (P<0.01) and higher contents of crude protein (1).<0.01) in pasture excepting spring and on two occasions in winter. (f) Estimates of feed intake at the higher stocking rate showed a significant increase in pasture harvested (P < 0.01) per unit area every year. However with the exception of the first year feed intake per cow was significantly reduced (P<0.01). (g) The ratio of pasture consumed per hectare to milk production per hectare was not significantly affected (P>0.05) by the increase in stocking rate.
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ItemSome effects of botanical composition of pasture on the liveweight and wool production of sheep( 1972)Until recently, the main evidence on which to base pasture mixture. recommendations in Victoria, has been district experience and the results from dry matter ( "mowing") experiments. The grazing experiments described in this thesis, were initiated by Messrs. R. Twentyman, R. Newman, R. Allen and K. Maher of the Department of Agriculture during the period, 1960-196. Their aim was to develop some objective appreciation of the relative value for animal production of some of the sown and unsown species in Western district pastures. In addition to pasture species evaluation, they sought information on the relationship between pasture growth and animal production. Such information is needed so that Agrostologists can better evaluate the many pasture management factors (such as fertilizers, seeding rates, seed. treatments, herbicides, insecticides and defoliation treatments) that affect pasture growth and for which advice is frequently sought.
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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.
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ItemA partial analysis of border check irrigation( 1956)The Border Check method of irrigation, widely used in Australia and overseas for the irrigation of pasture crops, may be described as a method of applying water to land between parallel ridges or checkbanks. Under ideal conditions the land should have no cross slope between the banks, but there is usually a slope in the direction of irrigation. Water is admitted at the head of the strip or irrigation bay, and the flow is diverted when, in the operator's estimation, the ponded water will carry to the end of the strip without wastage. With experience it is possible to judge the cut-off point with considerable accuracy. Depending upon soil type and the natural slope of the ground, bays may be up to 1,200 feet long; and 70 feet wide, with average dimensions of 600 feet by 30 feet. It is the purpose of this thesis to examine some of the factors influencing the movement of water down a border strip, and the infiltration of this water into the soil. It is hoped that such studies will lead ultimately to a more critical assessment of border check layout in relation to soil type, topography, etc., and that it may be possible to determine accurately the dimensions needed for efficient use of irrigation water in a particular case. That efficient irrigation is necessary is brought out by the fact that one inch of excess water passing down to the water table may raise it by as much as one foot (49). The major factors influencing the movement of water down a border strip are as follows :- (1) The infiltration characteristics of the soil. (2) The flow per unit width of border strip. (>) The slope of the land in the direction of flow. (4) The resistance of the plant cover to water movement. Minor factors involved include the soil and water temperatures, the salt content of the irrigation water, the head of water during irrigation, the turbidity of the water, the nature of the soil colloids, etc. Most of these, however, influence irrigation by their effect on the infiltration at a particular point. In the work reported upon herein an attempt has been made to evaluate the influence upon pasture irrigation of the infiltration characteristics of the soil, and the density of pasture cover.
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