No description available.

Typescript. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1974. / Bibliography: leaves [187]-195. / xx, 195 leaves ill

Typescript (photocopy) / xx, 251 leaves, [6] leaves of plates : ill. (part col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Soil Science, 1982

Typescript (photocopy) / xx, 251 leaves, [6] leaves of plates : ill. (part col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Soil Science, 1982

Photocopy (positive) of typescript. / Thesis (Ph. D.)--University of Hawaii, 1964. / Bibliography: leaves 158-161. / xi, 171 l illus., tables

Call number: LD2668 .T4 1962 F64

Graduation date: 1991

A field tillage tool carrier was constructed using a tractor trailer, hydraulic cylinder and steel construction material. Tillage tool blades of varying lengths, widths and angles of attack were fabricated from steel and were used in the study of the effect of tool rake angle, tool width and depth of operation on soil strength properties, draft, draft efficiency, volume of soil manipulated, degree of soil loosening and penetration resistance. / The results showed that the draft increased with tool rake angle and width. Operating at a depth of 150 mm and 100 mm depth did not make any significant difference on the draft requirement. Low angles of attack were observed to have a greater potential to loosen the soil, and the loosening increased to a depth of 150 mm then decreased. The draft efficiency was affected by the angle of attack as well as the depth of operation. The cross sectional area of the furrow and hence the volume of soil manipulated was seen to depend on the width of the tool and the operating depth. / Slender tools and high rake angles were found to loosen the soil better than wide ones. No distinct trend existed between depth to width aspect ratio and draft requirement. No variation was observed between draft efficiency and d/w ratio. Penetration resistance increased with depth of operation as well as distance from the furrow centre after tillage. Some areas of residual high strength were sometimes left within the sphere of influence of the tools. Some tools dealt with these omissions better than others.

No description available.

The physical state of the seedbed is of importance to the plant environment as it influences some important processes in the soil such as seedling emergence, water and solute transport, and ease of root penetration. This is affected to a large extent by tillage process, the tillage implement type and the geometry of the implement used. / A field experiment was carried out on a clay soil to determine the effect of the geometry of bladed tillage implements on some soil physical properties after tillage. The soil properties evaluated were bulk density, mean clod size distribution and total pore space after tillage and the extent of loosening achieved. / Implement parameters considered were blade width, rake angle and depth of operation of the implement. Two blade widths of 75 and 150 mm were evaluated in combination with three rake angles of 30, 60 and 90 degrees. Each tillage implement was drawn through the soil at four operating depths of 100, 150, 200 and 250 mm. / Larger rake angles were observed to result in larger mean aggregate sizes and greater bulk density reductions when compared to smaller rake angles. Greater reduction in bulk density was observed with the wider of the two blade widths evaluated. Mean clod size after tillage was also observed to be large for the wider of the two widths evaluated. Irrespective of width and rake angle, greater operating depths resulted in larger mean clod sizes and greater reductions in bulk density as compared to shallower operating depths. Fractal analysis showed the extent of fragmentation to be greater at shallower operating depths, hence the small mean clod sizes obtained.