Influence of Crop Sequence, Nitrogen Fertilizer and Herbicides on Weed Seed Populations in Sugar Beet Fields¹

The crop sequence in which sugar beets followed beans had lower weed seed populations than did sugar beets following barley and corn. The rate and time of application of nitrogen fertilizer had a significant effect on weed seed numbers in sugar beet fields. Where high levels of N were applied, high densities of weed seed occurred. Chemical weed control treatments significantly reduced populations of all weeds studied when compared to mechanical cultivation treatments. Significant differences between interactions were found for N fertilizer and crop sequence, weed control and crop sequence and weed control and N fertilizer.