Nitrogen Management And Compensation For Early Harvest Sugar Beets PDF Download

Local (southwestern Ontario and Michigan) sugarbeet production practices have changed to an earlier harvest date (early/mid Sept. vs. late Oct. early Nov.) and increased plant density (114, 800 plants ha-1 at 57 cm vs. 86, 500 plants ha-1 at a row width of 76 cm) using high yielding glyphosate-resistant sugarbeet varieties. In addition, crop consultants have recommended including N fertilizer in a 5-by-5 cm band during sugarbeet planting. Nutrient management is an essential aspect of crop production, and more specifically, in sugarbeet production as quality and root yield are negatively and positively, respectively, influenced by N fertility. Therefore, the effects of these changes in crop production practices on root and sucrose yield, profit margins, N dynamics, and nitrogen use efficiency (NUE) were evaluated at two fields in 2013-2015 with two harvest dates. Application rates of 157 kg N ha-1 to optimize root yield but only 12 kg N ha-1 to optimize recoverable white sucrose per tonne (RWST) were observed at either harvest date. Conversely, profit margins calculated using Michigan Sugar Company (MSC) 5-year average payment standards favour an optimal profit margin application rate of 127-136 kg N ha-1 for early and late harvest, respectively. The effect of harvest date and N and P fertilizer placement, source, and timing was not influential on NUE and N loss indicators and a lack of difference between NUE indices and yield slightly favoured the application of N and P in a 5-by-5 cm band at planting together or alone compared to the zero N-P control. Therefore, results do not contradict current industry recommendations; however, there is no compelling evidence to suggest farmers should modify planters to include N fertilizer at planting unless already capable. Further, plant density and harvest date had no influence on N fertilizer requirements tor most profitable rate of N. However, an early harvest resulted in lower root yield, RWST, and N removal from the field. It is therefore recommended that, under current payment protocols, N fertilizer should be applied at rates 27-57 kg N ha-1 greater than the current application of 100 kg N ha-1 and can be applied at the same rate regardless of harvest date or plant density. However, NUE calculations suggest that an earlier harvest may result in higher risk of N losses compared to late, and as such, growers may wish to harvest later or consider implementing N loss mitigation strategies.