Weed Seed Demise in Soil in Weed-Free Corn (Zea mays) Production Across Nebraska'

An experiment was conducted at five locations in Nebraska to determine the extent of demise of weed seed in soil when seed production was eliminated from 1975 through 1979 in corn (Zea mays L.). Weed yields, weed seed production, and corn yields were determined under four weed management levels in 1980. Annual broadleaf weed seed were more prevalent than grass seed in cultivated soil throughout the study. The population of viable weed seed in soil declined 95% during the 5-yr period that weed seed production was eliminated. Weed seed buildup recov- ered to within 90% of the 1975 level during 1980 at Concord and Clay Center but remained low at Lincoln, North Platte, and Scottsbluff. Thus, seed longevity in soil was sometimes sufficient to withstand modern weed control methods and still reinfest a field after 5 yr of eliminating weed seed pro- duction. Corn yields were maintained 1 yr with minimum weed management effort following 5 yr of no weed seed