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Accueil du site → Doctorat → États-Unis → 1984 → PARENT MATERIAL - TOPOGRAPHIC - MANAGEMENT CONTROLS ON ORGANIC AND INORGANIC NUTRIENTS IN SEMIARID SOILS (CULTIVATION, EROSION)

Colorado State University (1984)

PARENT MATERIAL - TOPOGRAPHIC - MANAGEMENT CONTROLS ON ORGANIC AND INORGANIC NUTRIENTS IN SEMIARID SOILS (CULTIVATION, EROSION)

AGUILAR, RICHARD

Titre : PARENT MATERIAL - TOPOGRAPHIC - MANAGEMENT CONTROLS ON ORGANIC AND INORGANIC NUTRIENTS IN SEMIARID SOILS (CULTIVATION, EROSION)

Auteur : AGUILAR, RICHARD

Université de soutenance : Colorado State University

Grade : Doctor of Philosophy (PhD) 1984

Résumé
Paired native grassland and cultivated landscapes were characterized to evaluate parent material and topographic controls on organic matter and phosporus along catenary sequences in southwestern North Dakota. Site selection was based on parent material (sandstone, siltstone, and shale residuum), similar cropping history (44-yr wheat-fallow rotation), and uniform range management. Parent material-soil process relationships were established by evaluating chemical and physical data for soil profiles at the native-summit landscape segments on the three contrasting parent materials. The effects of topography on the amounts and vertical distribution of organic matter and phosphorus were evaluated by studying soil profiles at various geomorphic landscape components along the catenas. The effects of 44 years of cultivation were evaluated by comparing cultivated and virgin soils at each landscape segment using the soils on native pasture as benchmarks. The finer textured soils weathered in shale were found to have much higher levels of organic C, N and Total P. Soils weathered in sandstone were found to have more uniform decreases in organic matter with profile depth and the highest quantities of organic P. On the native pastures, quantities of organic matter were much higher in the lower landscape segments because of higher moisture contents and/or the deposition of organic matter-enriched soil. Soils at lower landscape segments (lower backslopes, footslopes) have been enriched with Total P at the expense of soils at the upper portions of the catenas. Changes in organic and inorganic soil constituents resulting from cultivation were found to vary as a function of parent material and topography. Mineralization losses of organic constituents appear to have been higher in the sandstone soils. The fine-textured shale soils, which appear to have a large proportion of highly humified, clay-associated organic matter, lost the lowest quantities of organic constituents relative to total soil loss. Losses of organic matter were generally lower at the lower landscape segments in all three sites, reflecting soil deposition. Redistribution of soil material by both mechanical (tillage practices) and natural processes (wind and water erosion) must be considered when evaluating cultivation-induced changes in soil properties along catenary sequences.

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