Survey of Winter Wheat (Triticum aestivum) Stubble Fields Sprayed with Herbicides in 1998: Cultural Practices1

摘要

A survey of 174 fields was conducted during August and September of 1998 to investigate effects of cultural and herbicide practices on postharvest weed control in winter wheat stubble fields across western and southern Nebraska. Seventy-four percent of the fields were seeded at rates of 67 to 100 kg/ha, with 60% of the wheat seeded in rows spaced 25 cm apart. Wheat seeded in east–west rows contained 98% more stinkgrass and 82% more tumble pigweed than wheat seeded in north–south rows. Sixty-nine percent of winter wheat stubble fields were rated excellent for weed control. Postharvest weed control with herbicides was not affected by row spacing. In western Nebraska, density of tumble pigweed and Russian thistle was greater when wheat seeding rate was 50 kg/ha than at higher seeding rates. Short-stature winter wheat cultivars had greater densities of Pennsylvania smartweed and toothed spurge than taller cultivars. The most common winter wheat cultivars were ‘Arapahoe’ (34%) and ‘Alliance’ (17%). Weed control was positively correlated with number of winter wheat stems per square meter (r = 0.22**). Density of several weed species was greater in fields seeded with a disk than with a hoe drill. The most common crop rotations sampled were winter wheat–corn–fallow (50%), winter wheat–fallow (18%), and winter wheat–corn–soybean (13%). Winter wheat yields and wheat stem densities were greater and weed density was less when winter wheat was seeded after an 11- to 14-mo fallow period rather than a 0- to 5-mo period.