Effects of manure history and nitrogen fertilizer rate on sugar beet production in the northwest U.S.

Past manure applications effects on sugarbeet production needs to be assessed in the areas where manure applications to crop land are common. A study was conducted in Kimberly, Idaho in 2014 and 2016 to assess the effects of manure application history and N rates on sugarbeet production on a Portneuf silt loam (coarse-silty mixed mesic Durixerollic Calciorthid) soil. From 2004 to 2009, manure was applied to plots every two years (M1, total application = 60 tons per acre), every year (M2 total application = 106 tons per acre), or no manure (F, commercial fertilizer only). In spring 2014, the manure main plots were split in half with one half receiving a commercial fertilizer N rate treatment superimposed on the main plots in 2014 and the other half receiving the superimposed N rate treatments in 2016. In 2014 and 2016, the commercial fertilizer N rates were 0, 30, 56, 77, 100, 141, 180, and 202 pounds per acre. The study design was a randomized block split-plot with manure history as the main plot and N rate as the subplot. During both years of the study, N rate did not affect sugarbeet yields, but M1 and M2 treatments had higher sugarbeet root yields compared to the F treatment. Averaged across all N rates, root yields from both manured treatments were 12% and 36% greater than the F treatment in 2014 and 2016, respectively, although sugar yield was only significantly greater in 2016. Manure applications will impact sugarbeet production for several years after manure applications have ceased