The effect of ethylene oxide-sterilization on homoionic (Na+, K+, Ca2+, Cu2+, Al3+, and Fe3+) montmorillonite samples was examined. The results indicate that ethylene oxide polymerized to polyethylene glycol in the interlayer of Cu2+-, Al3+-, and Fe3+-saturated clays, as substantiated by the increase in the d(001) values, as well as by the decrease in the cation-exchange capacity after reaction. On the contrary, ethylene oxide failed to react in the presence of the Na+-, K+-, and Ca2+-clays, likely due to the lower acidity of the exchange cations.

Field and greenhouse studies were performed to examine the influence of various surfactants with glyphosate on whole plant efficacy. Relationships were examined between glyphosate phytotoxicity and surfactant properties, including ionic form, degree of ethoxylation, and hydrophobe composition. Cationic tertiary amine surfactants enhanced glyphosate performance in both field and greenhouse studies. Nonionic allinol and octoxynol surfactants were not effective in combination with glyphosate. In field studies, glyphosate efficacy increased with increasing surfactant ethylene oxide (EO) content. Soybean and velvetleaf responded similarly to glyphosate-surfactant spray applications, as both demonstrated significant linear and quadratic relationships between increasing surfactant ethoxylation and phytotoxicity, while common lambsquarters showed a significant linear relationship only. Cationic surfactants were evaluated in the greenhouse and a significant quadratic regression of glyphosate phytotoxicity to common lambsquarters on increasing surfactant ethoxylation indicated an optimum surfactant EO content of about 10 moles. Both tertiary and quaternary ethoxylated fatty amines were effective with glyphosate in decreasing common lambsquarters' fresh weight. Fatty amine hydrophobe composition did not correlate with glyphosate phytotoxicity to common lambsquarters.

Growth chamber studies were conducted to examine the soil residual properties of DPX-A7881, a new sulfonylurea herbicide. The phytotoxic residue levels in the soil were determined by a lentil radicle bioassay. The duration of activity was prolonged in soil adjusted to pH 7.6 and 8.1 relative to more acidic levels. The rate of breakdown in the soil was enhanced with increased temperature and soil moisture content; a significant temperature by moisture interaction was noted over the duration of the incubation period. The dissipation of DPX-A7881 in soil obeyed first-order kinetics in both studies. An accelerated rate of breakdown in unsterilized versus sterilized soil (pH 7.6) indicated that microbial degradation was an important factor affecting the persistence in alkaline soils. Herbicide residues in the soil caused a reduction in taproot length and number of primary lateral roots of canola seedlings 15 days after planting but there were no other morphological effects observed on the root. The secondary laterals, however, had generally recovered by this time.

A nonionic surfactant with the appropriate structure and concentration increased rimsulfuron activity 10-fold. Surfactants sharply increased rimsulfuron activity as concentration increased up to 0.05% (w/w) with slightly more enhancement up to 0.1% (w/w). Surfactants with a wide range of 14 chemical, physical, and surface properties were evaluated on giant foxtail, velvetleaf, and corn. Two properties, HLB (hydrophilic-lipophilic balance) and the physical form of the spray deposit, explained the biological variation. The most active surfactants had an HLB from 12 to 17 and formed a moist gel spray deposit on the leaf on all three species. A separate study with 13 chemically pure linear alcohol ethoxylates supported these conclusions and additionally showed that increasing molecular size increases activity. Because crop injury correlates with weed control, the best surfactant strategy is to maximize weed control at the lowest rimsulfuron rate.