The role of microaggregation in physical edaphology

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Sokoine University of Agriculture


Soil type and the previous tensile strength and penetration resistance as a (PR) should allow the soil compared ranging fail to failure planes in between the microaggregates. function of easily along Five Tanzanian soil hardsetting Paleustalf from a extreme of strength behaviour, through a Paleudoll, Paleustult, both It was expected (the strength characteristics). that microaggregation types were can I characterized soil strength by measuring affect soil strength. matric potential cultivation history of one at Paleudalf and a to a strongly microaggregated Orthox expected to be at At each site soils that had a history of the weak end of the scale. 7 or more years of cultivation and cropping were compared with newly cultivated soils. The and Orthox Paleustult had the best PR characteristic for ease of root growth and the Paleustalf had the worst characteristic which suggested that it would not permit root growth at matric suctions exceeding 100 kPa. The Orthox also had much the most favourable tensile strength characteristic. At air dryness (100 MPa suction), the previously uncultivated and previously cultivated Orthox topsoils strength. compressive) Paleustalf topsoils. Paleustult) a previous had 3 and respectively, 9 times than less the tensile (and corresponding For three of the soils (Orthox, Paleudoll and history of cultivation was found to have significantly and substantially reduced the tensile strength of the topsoil at any given matric suction compared to the newly cultivated soil


PhD Thesis


microaggregation, edaphology, physical edaphology