Degree Type


Date of Award


Degree Name

Doctor of Philosophy



First Advisor

Nick E. Christians

Second Advisor

Dave D. Minner


Inorganic soil amendments have been suggested for use in sand-based golf and sports turf root zones to alleviate soil compaction, increase water retention and hydraulic conductivity. The overall objectives of my research are to investigate the physical properties of sand-based media modified by soil amendments and to quantitatively evaluate sand particle shape and roundness for sports turf surface stability.;On a flat green study we found that porous ceramic clay (PCC) increased both Ksat and water retention. Hydraulic conductivity of the sand/inorganic mixtures decreased over two years, although some increase were observed each spring.;In a laboratory study simulating freeze/thaw effects, we found that after 20 freeze/thaw cycles, sand amended with polymer coated clay (PC) had a 7.6% decrease in bulk density from the compacted sample. The percentage weight of the finest particles increased due to freeze/thaw cycles. After 20 cycles of freeze/thaw, Ksat values of sand amended with PCC and calcined diatomaceous earth (CDE) were 25 and 33% higher than the control, respectively.;A sloped research green was topdressed with mixtures of sand and soil amendments. During most of the growing season in 1999, the preloaded fertilizer in zeolite clinoptilolite might be responsible for the better quality of this product during non-stressed period. Its low turf quality after water stress and in the spring of 2000 could have been caused by toxicity from its high Na and K contents.;In the study of sand shape and roundness evaluation, mason sand, concrete sand, silica sand, crushed brick, crushed glass, and crushed stone were used to cover a wide range of shapes and roundness. We used glass beads as the base line. A roughness index (Ir) was proposed as the ratio of the particle surface area to the area of a sphere of the same volume. Angle at repose, coefficient of uniformity (CU), coefficient of friction (CF), and two-dimensional image analysis were also included in the evaluation of the materials. Principle component analysis indicated that only three factors---angle at repose, CU, and Ir---are necessary to explain 98.5% of the variance contributing to surface stability of sand-based media.



Digital Repository @ Iowa State University,

Copyright Owner

Deying Li



Proquest ID


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116 pages