Long-term effect of a single application of factory waste lime on sugar beet and Aphanomyces root rot

Aphanomyces cochlioides infests over 50% of sugar beet fields in Minnesota (MN) and North Dakota (ND). Calcium carbonate aids extraction of sucrose from beet juice by precipitating impurities; by-product "waste lime" contains inorganic and organic compounds. Long-term effects of one soil-application of waste lime on sugar beet yield and Aphanomyces root rot was studied by amending plots with 0, 6, 12, 18 and 24 Mg dry wt per ha at Breckenridge (MN) and 0, 7, 15, 29 and 44 Mg dry wt per ha at Hillsboro (ND). In 2007, sugar beet was sown for the first time, 37 and 43 months after lime was applied at MN and ND, respectively. At MN, root rot was severe and interactions occurred between lime rate and cultivar (susceptible [S] and moderately resistant [MR] + hymexazol). The S cultivar had more root rot and lower yield compared to the MR cultivar in the non-limed control; for both cultivars, root rot decreased and yield increased with increasing rates of lime. At ND, soil was too dry for root rot and S and MR cultivars responded similarly; there was a trend for higher stands and yields with increasing rates of lime compared to the control. Thus, a soil amendment of waste lime that was applied over 36 months earlier, decreased Aphanomyces root rot and increased sugar beet yield (especially when A. cochlioides was active) compared to a non-limed control.