Dissertation > Excellent graduate degree dissertation topics show

Research on the relationship between erosion and soil resistance to its soil aggregate water stability

Author: LuJinWei
Tutor: LiZhanBin
School: Northwest University of Science and Technology
Course: Soil and Water Conservation and Desertification Combating
Keywords: soil aggregate water stability assess quantitatively relation soil erodibility
CLC: S152
Type: Master's thesis
Year: 2002
Downloads: 1092
Quote: 19
Read: Download Dissertation

Abstract


Soil aggregate is an important soil composition to be evaluated because it mediates many biological and physical processes in soils. Soil aggregate structure determines porosity, infiltration and soil erosion susceptibility. Soil aggregate stability has a close relation with soil erodibility, so it has been selected as a good indicator for credibility ?(Chan and Mead, 1988; Cooteetal., 1988; Wang youmin, 1994 ; et al.). Combined with soil aggregate breakdown experiment, simulated rainfall erosion experiment and the analysis of some soil physical and chemical data, factors that affected soil aggregate water stability, the mechanism of aggregate’s breakdown and the relationship between soil aggregate water stability and soil erodibility is studied in this paper. With the equation of Williams, the soil erosion erodibilty K was calculated in use of the field data. Following conclusions can be reached:(1) There are several factors affecting water stability of soil aggregate (WSA) such as soil OM (organic matter), soil nitrogen and phosphorus content, vegetation, and no-tillage years, et al. The results show that soil OM content has obviously closer relationship with >0.25mm soil water stable aggregate content (%) than that of soil nitrogen and phosphorus content. The relationship is linear. Soil nitrogen and phosphorus content (%) have exponential relationship with >0.25mm water stable aggregate content (%). No-tillage years and vegetation can also affect >0.25mm water stable aggregate content (%) accordingly. In general, Soil OM (%) and the mean weight diameter (MWD) can be used to assess the water stability of soil aggregate.(2) There are several factors which can Jesuit the breakdown of soil aggregate, but the main reasons are due to rainfall density (including single raindrop) and different prewetting rate. So they are selected to study the process and the mechanism of the breakdown of soil aggregate. The results show that energy needing in the breakdown of soil aggregate (>5mm) by single raindrop is much more than that of soil aggregate (5-2mm and 2-1mm), prewetting can increase the water stable aggregate content in given range and the rainfall is able to accelerate the breakdown of soil aggregate through affecting the soil cementing agents (OM). Furthermore, the mechanism of breakdown of soil aggregate is discussed.(3) Three methods are to be used to quantitatively assess WSA on the basis of wet -sieve methods. The first is the energy-consumption method. The energy discharged in the breakdown of soil aggregate has a close relation with soil structure and water stability ofsoil aggregate. The better the water stability is, the more the energy need. According to these relations and experimental data, one equation is put forward to assessing WSA with different aggregate size. Secondly, the nutrients in aggregates are used to quantitative assess WSA. The results show that soil OM (%) and nitrogen content (%) have a good exponential relation with the WSA, but soil phosphorous has little relation WSA. So the phosphorous content can’t be used to assess the WSA. Thirdly, air encapsulation in aggregate and the lasting time of breakdown of soil aggregate also has close relation with water stable aggregation. The longer the time, the better the water stability is. A model is founded to quantitatively assess WSA. The result shows that the time has a direct relation with soil erodibility K: ziwuling < yangling < ansai.(4) The relation between WSA and soil erodibility is studied in this paper. The result indicates that the relation is very close and >0.25mm water stable aggregate content (%) even can be used to assess the soil erodibility. In the first time Williams equation is used to calculate soil erodibility K of the main type of soils in Loess Plateau and the soil cultivated different years in ziwuling forest area on basis of data available. K huangmiamu >K heiiutu >K loutu >K heigaitu>K senlinhetu >K ligaitu. Result indicates that the forest soil has smaller soil erodibility K than that of other type of

Related Dissertations

  1. Financial Relations between the German government,F815.16
  2. Distribution of Volatile Acid and Volatile Alkali and Its Relationship with Quality Indexes,S572
  3. Middle School Students Self-consciousness and Class of Relationships between Social Psychology,G632.0
  4. Analysis of Concrete Durability under Combined Action of Freeze-thaw Cycles and Chloride Ion Erosion,TU528
  5. Effects of Continous Super Rice Planting on Contrnt of Organic Carbon and Aggregates Stability in Paddr Soils,S511
  6. Study on Weediness Characteristics and Allelopathic Potential of Weedy Rice (Oryza Sativa L.) and Competitive Relation with Cultivated Rice (O. Sativa L.),S451
  7. Relationship between Aroma Constituent, Sensory Quality and the Alkaloid Content in Different Genotypes of Flue-cured Tobacco,S572
  8. Research on the Construction of a Harmonious Community in Xuanwu District, Nanjing,D669.3
  9. Impact of Group Counseling about International Interaction on New Junior Students’ Adaptation to School,G444
  10. Comparative Research on Different Scale Enterprises of CSR Focus on Employer-Employee Relation in China,F249.26;F224
  11. The Research of Soil Organic Carbon Sequeatration under Conservation Tillage in Maize Land,S513
  12. Study on Relationship between Urbanization and the Service Industry of Xinjiang,F719;F224
  13. Experimental study emulsified asphalt mixture to resist water damage,U414
  14. Research on the Rode Performance of Broken Gravel,U414
  15. Snow Change in Manas River Basin and Its Relation to Runoff of Manas River,P333
  16. The Laboratory Experimental Study of Rubber Modified Asphalt,U414
  17. The postal transportation information resources integration of research for dynamic scheduling,F626
  18. Metamodel based model transformation method in MDA,TP311.52
  19. Service Relation Mining and Network Analysis,TP393.09
  20. Auction-Based Multi-Agent Task Allocation in Smart Logistic Center,TP242
  21. Preference Representation and Revision in Intelligent Information Processing,TP18

CLC: > Agricultural Sciences > Agriculture as the foundation of science > Soil > Soil physics
© 2012 www.DissertationTopic.Net  Mobile