This paper describes the relationship between the micro-structure and hydraulic conductivity of simulated sand-bentonite mixtures (SSBMs) prepared with powdered and granular bentonite. Glass beads were used to simulate sand grains because of their superior optical properties. The micro-structure of SSBMs was observed using optical micrography and scanning electron microscopy. For mixtures prepared with powdered bentonite, the indications are that bentonite coats the particles. As the bentonite content increases, the thickness of bentonite coating increases and reduces the area available for flow. For mixtures containing granular bentonite, the dry bentonite granules occupy the space between the particles and then swell to fill the void space. As the bentonite content increases, the number of granules increases, leading to more void spaces being filled with bentonite. At higher bentonite content (>8%), flow paths devoid of bentonite are unlikely, and the hydraulic conductivity appears to be controlled by the hydraulic conductivity of bentonite. The changes in micro-structure that were observed are consistent with the decrease in hydraulic conductivity that occurs with increasing bentonite content. However, the relationship between hydraulic conductivity and bentonite content differs depending on whether a mixture contains powdered or granular bentonite.

Scanning electron micrographs of spray droplet residual on wheat, sunflower, and kochia indicated that salts and various adjuvants applied with glyphosate affected deposit crystal content, thickness, and contact with the leaf surface. Spray deposits of glyphosate applied with diammonium sulfate contained distinct crystals, which related to enhanced toxicity of glyphosate applied alone, or to overcoming antagonism of glyphosate toxicity by calcium chloride, when applied to wheat. In general, glyphosate applied with antagonistic calcium chloride salt formed spray deposits that were amorphous, thick, and without crystals. Glyphosate sprayed with nonantagonistic diammonium sulfate and ammonium chloride salts had deposits with crystals and an evenly spread residue beneath the crystals. The various micrographs indicate that the antagonism of glyphosate phytotoxicity by salts may be in part from physical entrapment of glyphosate in the spray deposit. Glyphosate spray droplet residue contact with wheat, sunflower, and kochia surfaces related to observed differences in glyphosate toxicity to these species.