Application timing and soil factors affect sulfentrazone phytotoxicity to two soybean (Glycine max (L.) Merr.) cultivars

Field experiments were conducted at Urbana, DeKalb, and Brownstown, IL in 2001 and 2002 to evaluate the effect of application timings and soil OC on sulfentrazone phytotoxicity to two soybean varieties. These studies were conducted on established plots where the soil pH had been incrementally adjusted across a range from 5.5 to 7.5. Sulfentrazone treatments applied at the labeled dose (0.22 kg a.i./ha) and 2× labeled dose (0.44 kg a.i./ha) at 7 days before planting (EPP) and at planting (PRE), and at 0.22 kg a.i./ha at 50% soybean hypocotyl emergence (VE), were compared with a weed-free glyphosate-treated control. Sulfentrazone-tolerant and -sensitive varieties were used to evaluate treatment responses. At Brownstown (1.1% organic carbon (OC)), injury ranged from 23% to 30% for the sensitive variety, whereas no significant injury was observed for the tolerant variety. Grain yield was decreased up to 15% for both varieties at Brownstown, depending on the application timing. At Urbana (2.3% OC), injury ranged from 7% to 17% for ‘P94B01’ and from 4% to 7% for ‘P93B53’ at the different application timings, and yield was reduced up to 6% for both varieties, depending on the application timing. At DeKalb (2.9% OC), injury ranged from 3% to 14% at the different application timings, but there was no significant yield decrease for either variety.