Four corn hybrids were evaluated for tolerance to sethoxydim at 110 and 220 kg ha–1 applied post-directed at two growth stages (V6–7 and V10–11). Dryland corn grain yields did not respond to sethoxydim, while irrigated corn yields were sensitive to sethoxydim treatments. Sethoxydim at 220 g ha–1 reduced the grain yield of hybrid 3377 by 12% at both growth stages. Sethoxydim at the same rate reduced grain yield of hybrid 3379 by 15% when applied to V6–7 corn. Hybrid 3475 had an 11% grain yield reduction from sethoxydim applied at either dosage to V10–11 corn. Under irrigated conditions, a trend toward reduced grain yield was observed for hybrid 3183 at all application times and sethoxydim rates. Corn ear weights and kernel weights differed among hybrids but did not exhibit a response to sethoxydim within hybrids. Visual evaluation for crop injury and measured corn heights did not indicate a response to sethoxydim. There was no yield response in any hybrid to 110 g ha–1 applied to V6–7 stage corn indicating this treatment was safe to use on all hybrids evaluated.

Field studies were conducted over 3 yr to evaluate rhizome johnsongrass control with asulam applied POST at 3.7 kg ai/ha 3 d before fertilization (DBF) or 0, 3, 7, 10, or 14 d after fertilization (DAF). Liquid fertilizer (18-6-12) was applied with injector knives at 0, 112, or 224 kg N/ha 5 cm on each side of a 60-cm line of rhizome johnsongrass present on 1.8-m-wide conventional sugarcane beds. Johnsongrass response to timing of asulam application after fertilization varied among years but was not affected by fertilizer rate. Johnsongrass control with asulam applied 3 DBF was greater than applications made 0, 3, or 7 DAF. With one exception, differences in johnsongrass control following fertilization and asulam application times were also reflected in the biomass of treated johnsongrass and its regrowth harvested 6 and 10 wk after asulam application, respectively. Reduced johnsongrass control associated with asulam application following fertilization was related to stress from root/rhizome injury during fertilizer placement rather than the quantity of fertilizer applied.