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|Title:||Effects of Mulch and Rainfall Intensity on Crust Strength of Three Illinois Soils|
|Author(s):||Owido, Seth Frederick Ochieng'|
|Doctoral Committee Chair(s):||Simmons, F. William,|
|Department / Program:||Agronomy|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Abstract:||An experiment was conducted to study the effects of mulch and rainfall intensity on the crusting characteristics of the surface (0 to 15 cm) horizons of three Illinois soils: Drummer silty clay loam (fine silty, mixed, mesic Typic Haplaquoll); Cisne silt loam (fine, montmorillonitic, mesic Mollic Albaqualf); and reconstructed Blair silt loam (fine-loamy, mixed, mesic Aquic Hapludalf). Increased rainfall intensity significantly reduced rate of seedling emergence especially when the soil was bare. Mean period of ultimate emergence was significantly reduced while rate of emergence was increased by increasing mulch rates. The soils differed with respect to rate of emergence, and ultimate emergence. Under controlled moisture content, mulch rate significantly reduced crust strength of Cisne and Drummer but had no influence on strength of the Blair soil. Rainfall intensity slightly increased the strength of the Drummer soil but did not affect that of Cisne and Blair. Bulk density and gravimetric moisture content had major influence on crust strength of Cisne and Blair while in the Drummer, only bulk density had a significant influence. Multiple regression models developed to describe the effects of input variables on the modulus of rupture indicated that gravimetric moisture content accounted for 75% of the variation in crust strength of the Blair soil. Low regression coefficients obtained for Cisne and Drummer indicated that factors other than mulch rate, bulk density, orientation, and gravimetric water content may be responsible for the variation in their crust strength.
The effects of freeze-thaw and wet-dry cycles on crust strength of surface (0 to 15 cm) horizons of the three Illinois soils was also determined. Freezing at 0$\sp\circ$C and subsequent thawing resulted in a significant increase in crust strength. Blair silt loam showed significant reduction in strength at freezing temperatures of $-$5, and $-$10$\sp\circ$C, while Cisne and Drummer increased in crust strength. Freezing and thawing episodes affected crust strength by influencing the bulk density, especially for the Blair silt loam. Regression models indicated that freeze-thaw cycles, bulk density, and temperature of freezing accounted for most of the variation in crust strength. (Abstract shortened by UMI.)
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1992.
|Date Available in IDEALS:||2014-12-17|