Influence of nitrogen application rate on sugarbeet ( Beta vulgaris L.) yield and quality along with weed emergence and growth

Field studies were conducted to determine optimum nitrogen (N) application rates for sugarbeet (Beta vulgaris L.). Linear plateau, quadratic plateau, and quadratic models were used to determine optimum N application rates based on yield, grower payment, recoverable white sucrose (RWSA), and return. Economic optimum N rates based on grower payment and RWSA are insensitive to changes in sugar and N prices. Based on economic return, optimum N rates within a range of 135 kg N ha-1 plus or minus 15 kg N ha-1 was sufficient for sugarbeet production. Three out of 14 sugarbeet field sites were non-responsive to N fertilizer. In two of three non-responsive sites, OM was greater than 4%; suggesting that organic matter (OM) may assist in predicting non-responsive sites.; Field and greenhouse studies were conducted to investigate the effect of preplant broadcast incorporated urea ammonium nitrate (UAN 28%) on early season weed emergence and growth. Emergence of common lambsquarters and ladysthumb smartweed increased as N increased in the early seeding dates in 2003 and 2004. Emergence of giant foxtail increased as available N increased in the early N application dates in 2003 and 2004. Total weed biomass increased as available N increased at all weed seeding dates in 2003 and in two of three seeding dates in 2004. Reducing available N in the weed germination and rooting zone will reduce weed emergence and the growth and competitiveness of weeds in sugarbeets.