Sugarbeet yield and quality when substituting compost or manure for conventional nitrogen fertilizer

To profitably produce sugarbeet (Beta vulgaris L.) by maximizing recoverable sucrose, producers must effectively manage added nitrogen (N), whether it be from inorganic sources such as urea or from often readily available and sometimes less expensive organic sources such as manure or composted manure. Our multi-site study’s objective was to determine if equivalent sugarbeet root and sucrose yields could be achieved when substituting composted dairy cattle manure or stockpiled manure for conventional N (urea) fertilizer. Treatments at Site 1 (Parma, ID), for 2 y included a control (no N applied), urea (202 kg N/ha), compost (1089 and 2175 kg total N/ha), and manure (350 and 701 kg total N/ha). Treatments at Site 2 (Kimberly, ID), were a control, urea (82 kg N/ha), compost (403 and 913 kg total N/ha), and manure (433 and 850 kg total N/ha). Compost and manure were applied, then incorporated into two silt loams, a Greenleaf (Xeric Calciargid) at Parma in fall 2002 and 2003 and a Portneuf (Durinodic Xeric Haplocalcid) at Kimberly in fall 2002. Sugarbeet was planted the following spring. Site 1’s sugarbeet sucrose yields, averaged across years and organic N source rates, were 12.24 Mg/ha for urea, 11.88 Mg/ha for compost, and 11.20 Mg/ha for manure, all statistically equivalent. Corresponding one-year sucrose yields, still equivalent, were ca. 44% less at Site 2 than 1. Doubling the organic N application rates at Site 1 increased sugarbeet root yields by 15 to 26% and sucrose yields by 12 to 21%. Applying organic amendments in place of urea affected neither root nor sucrose yields but at one location decreased sugarbeet crop quality by increasing brei nitrate and conductivity, though without hindering sucrose recovery. Sugarbeet producers can use either compost or manure to satisfy their crop’s N needs without sacrificing sucrose yield.