Sugar Beet N Fertilization and Economic Optima: Recoverable Sucrose vs. Root Yield1

Abstract

AbstractSugar beet (Beta vulgaris L.) yields are frequently measured in terms of root yield but recoverable sucrose is the marketable product. The response of recoverable sucrose content to N fertilization differs from that of whole root yield. The rationale for this study was to compare N fertilization rates and associated returns under two decision rules: (1) fertilize to optimize recoverable sucrose yield and (2) fertilize to optimize whole root yield. Sets of response functions were estimated using both whole root yield and recoverable sucrose as measures of yield. Three years of data (1976‐1977‐1978) from the Northern Plains Soil and Water Research Center, Sidney, Mont., were used to derive these physical relationships. The estimated response functions were then combined with price and cost data to determine economically optimal N fertilization rates. Finally, returns for each optimal combination were calculated and compared. The results show substantially lower levels of N are required to optimize recoverable sucrose. Over the years of this analysis, it required approximately 90 kg less N per ha to optimize recoverable sucrose than whole root yield. More importantly, under the conditions of this analysis, producer returns would increase by an average of $460 per ha by using N rates consistent with recoverable sucrose rather than root yield. These observations suggest substantial economic benefits from use of recoverable sucrose in N fertilization decisions.