Sugarbeet Yield and Quality as Affected by Nitrogen Level

This study was conducted, under several climatic and soil conditions, to determine the effect of N level on sugarbeet yield and quality and to further develop and refine both soil and tissue test methods for predicting N fertilizer needs, for efficient refined sucrose production. Previous studies indicate that N fertilizer needs for maximum sucrose production may be predicted by considering yield potential and all N sources. Sugarbeets (Beta vulgaris L.) were grown under field conditions at N fertilizer levels varying from 0 to 448 kg N/ha on six sites throughout southern Idaho to determine root yield, sucrose percentages, sucrose yield, impurity index, and plant N uptake in relation to the residual NO₃-N, mineralizable N, fertilizer N, and petiole NO₃-N. These experiments demonstrated that the N fertilizer needs of sugarbeets can be determined by relating the root yield potential to the measured residual NO₃-N plus a measured or estimated mineralizable N level for an area. Optimum N level from all available soil and fertilizer sources has been found to vary between 5 to 6 kg/metric ton of beet roots produced. Using data from the current experiment and a previous study, N fertilzer could be predicted within 56 kg N/ha of that needed for maximum sucrose yield in 83% of the sites using measured NO₃-N and mineralizable N levels, 67% using measured NO₃-N and average mineralizable N levels, and only 12.5% using recommendations by fieldmen. Linear correlations were found between the total available N, total plant N uptake, other plant N variables, and root quality factors, like percentage sucrose and impurity index. These relationships confirm previous findings and will be useful for predicting root quality, optimum harvest date, and for verifying recommended fertilization practices. The use of the proposed soil and tissue test will improve root quality and sucrose production, as well as production efficiency, that will economically benefit the consumer, producer, and manufacturer.