Soil structure restoration in Vertisols under pastures in Texas /
| Main Author: | |
|---|---|
| Other Authors: | , , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1990.
|
| Subjects: | |
| Online Access: | ProQuest, Abstract Link to OAKTrust copy |
| Abstract: | Productivity of Vertisols is closely correlated with the evolution of their structural condition. Porosity is the best guide to structural status. Structural degradation under cultivation is mainly due to: (1) tillage and traffic; (2) changes in soil moisture regime; and (3) altered biotic activity. The dynamic nature of soil structure in Vertisols could enhance its ability for recovery once disturbance from cultivation ceases. The objectives of this study were: (1) to analyze changes in porosity and pedality which characterize a structural recovery process associated with a shift in land use from continuous cultivation to pastures for several Vertisols in Texas; and (2) to develop and test different procedures for direct evaluation and quantification of soil microporosity in Vertisols with emphasis on microfabric analysis coupled with image processing techniques. Three sites were selected at the USDA Research Station at Riese, Texas. Each site consisted of homogeneous soils and topography, but with contrasting long-term, land management systems: cultivated fields and regenerated pastures located a few meters apart. The cultivated treatments have been under continuous annual crops for at least 50 years. The pasture treatments consisted of permanent, regenerated pastures, from 15 to 50 years old. The analysis of variance components of porosity-related features (microfabric analysis) showed that properties differ in their variability at different levels of sampling (Kubienas, sections, and microscopic frames). Some properties show high variability at the Kubiena level; other properties are highly variable at the section level. The analysis of this data set indicated that a sampling scheme with four Kubienas and four sections from each Kubiena is adequate for the simultaneous analysis of several porosity properties. Image analysis (IA) of high-contrast negatives of polished blocks was advantageous in terms of time and labor requirements. Pore identification was facilitated with a UV dye included in the impregnating mixture. A high correlation (r = 0.8) was observed between porosity measurement by fully automated and manual IA systems. Fully automated systems are particularly appropriate for total macroporosity determinations. Some of their automatic features, however, cannot be used for object specific measurements such as pore orientation, when pore topology is complex... |
|---|---|
| Item Description: | Typescript (photocopy). Vita. "Major subject: Soil science." |
| Physical Description: | xii, 230 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references. |