Sugarbeet Response to Nitrogen as Affected by Seasonal Irrigation

Abstract

Abstract Sugarbeet ( Beta vulgaris L.) responses to irrigation (I) and N have been documented but I by N interactions are less well understood. The objective was to determine if N response is dependent on the amount of seasonal irrigation. Sugarbeet root yield, fresh weight sucrose concentration, and impurities were measured in experiments involving four N rates within three irrigation levels during 1982, 1984, 1986, and 1987 on a slowly permeable Pullman clay loam (fine, mixed, thermic Torrertic Paleustoll). Irrigation by N interactions were not significant in 1982 and 1984 when residual NO 3 –N was an important N source. Significant I by N interactions for all yield and quality factors were measured in 1986 and 1987, when residual NO 3 –N was low (87 and 99 kg ha −1 , 0‐ to 2.4‐m depth) and NO 3 –N concentration was greater above than below 0.6 m. Sucrose yield increased an average of 0.54, 1.76, and 2.65 Mg ha −1 in 1986 and 1987 in response to N for irrigation levels averaging 0, 234, and 435 mm, respectively. Sucrose loss to molasses at the N rate needed for maximum sucrose yield averaged 15.2, 14.1, and 13.3 g sucrose kg −1 roots for 0, 234, and 435 mm irrigation levels, respectively. Sucrose loss to molasses averaged 20.1, 16.0, and 14.1 g kg −1 at the highest applied N rate for 0, 234, and 435 mm irrigation levels, respectively, and indicated a potential for serious impurity problems with excess residual or applied N and reduced irrigation.