Poster: Biology & Disease Mgmt: Cultural Control
Addition of supplemental spent lime to previously limed soils for control of Aphanomyces root rot on sugar beet
J. BRANTNER (1) A. Chanda (1); (1) University of Minnesota, U.S.A.
Application of sugar beet factory spent lime to soil in fields infested with the soilborne oomycete pathogen Aphanomyces cochlioides has been shown to decrease disease and increase sugar beet yield in Minnesota and North Dakota. Sugar beet growers are inquiring about the need to reapply lime in fields where lime has previously been applied. In a field trial where lime had originally been applied in April 2004 at 0, 6, 12, 18 and 24 Mg dry wt ha-1, plots were split and an additional 7.8 Mg dry wt lime ha-1 was added to half of each plot on October 31, 2014. The following spring, sugar beet was sown and data was collected on early season stand, Aphanomyces root rot and sugar beet yield. There was significant interaction between supplemental and original rates of lime for early season stand, root rot ratings, and yield (P ≤ 0.05). At 4 and 7 weeks after planting, sugar beet stands were higher in plots that received supplemental lime where original lime rates were 0 and 6 Mg ha-1 (P ≤ 0.05), but not where original lime rates were 12 Mg ha-1 or higher. Supplemental lime reduced Aphanomyces root rot and increased sugar beet yield only in plots where lime had not been previously applied (P ≤ 0.05). Results demonstrate a benefit from adding supplemental lime to fields previously limed at low rates, but do not support a need to add supplemental lime to fields previously limed with at least 12 Mg dry wt ha-1 within the past ten years.