Relationships Between Applied Nitrogen Fertilizer and Postharvest Storage Properties of Sugarbeet Roots

Abstract

While soil nitrogen deficiencies will result in a significant reduction in root yields of sugarbeet, excessive nitrogen will increase the concentration of impurities that interfere with sucrose extraction, decrease sucrose concentration, and reduce the overall value of the crop. Almost all recommendations for nitrogen management attempt to optimize growers' returns at harvest and make no assumptions regarding the role of nitrogen fertility on sucrose losses during postharvest storage. This study examined the impact of nitrogen fertilizer rates on changes in processing quality during storage. Based upon averages over three environments, seven fertilizer rates, and two storage intervals (30 and 90 days), each additional 43.2 kg ha-1 of nitrogen fertilizer reduced recoverable sucrose concentration by 5 kg Mg-1. Differences between amino-nitrogen concentrations 30 and 90 days after harvest (DAH) increased by 100 ppm for each additional 53.4 kg ha-1 of nitrogen fertilizer. Nitrogen fertilizer rate did not have a significant effect on postharvest respiration rate or invert sugar concentration. However, respiration rates increased 0.88 mg CO2 kg-1 h-1 between 30 DAH and 90 DAH and invert sugar concentrations increased 1.37 g (100 g sucrose)-1 during the 60 days between observations.