Sugarbeet Response to Nitrogen at Four Harvest Dates

Abstract

Early sugarbeet (Beta vulgaris L.) harvest in the Northern Great Plains extends the processing period by a month or more. Early harvest starts before optimum sugarbeet yield and quality are achieved, so practices which increase yield or quality of early harvested sugarbeet are valuable. Nitrogen (N) management is an important component of sugarbeet production that may be a way to improve yield and quality of both early and late harvested sugarbeet. Yield and quality of sugarbeet to three rates of fertilizer N were evaluated when harvested at different dates. The study was conducted under furrow fl ood irrigation from 1992 to 1995 at the Eastern Ag­ ricultural Research Center in Sidney, Montana. AppJied N was based on a budget that considered residual soil N to 120 cm, N expected to be mineralized from organic matter, and expected yield. Three rates of N, 75%, 100%, and 125% of the recommended N rate (5 kg for each Mg of expected root yield ) were applied in random strips through the field prior to planting by knifing liquid N (28-0-0) between rows. Four harvest dates were the beginning of early harvest, the begin­ ning of main harvest, a date midway between the first and third dates, and a date near the end of the main harvest cam­ paign. The lowest N rate usually resulted in greater sucrose content, and greater extraction than the recommended and increased N rates. Economic returns for sugarbeet fertilized with each N rate varied from year to year, but on average, the recommended N rate resulted in greatest income per acre at the earliest harvest date and the latest harvest date, the low­ est N rate resulted in greatest income at the later date of the early harvest period, and increased N rate resulted in the