Manipulating sugar beet plant population to compensate for high nitrogen fertility in southern Minnesota.

Abstract

As the sugar content of sugar beet crops increase, profitability increases. An obstacle to raising a high sugar content sugar beet crop in the southern Minnesota growing region is high levels of total available soil nitrogen. Sugar beet yield increases with soil nitrogen, but sugar beet quality is detrimentally impacted by soil nitrogen. The objective of this study was to determine if a producer can increase harvest plant population in high nitrogen situations and mitigate the negative impacts of the excess nitrogen. This study was conducted in two environments during the 2019, two environments in 2020, and one environment in 2021 in a replicated complete block design with a split plot arrangement of six replications.  Four nitrogen rates comprised the whole plot and two plant populations comprised the split plot arrangement and were applied at both locations. Fertilizer was applied by hand to reach a total available soil nitrogen level of 120, 160, 200, and 240 lbs ac^-1 and incorporated with a field cultivator.  Sugar beets were planted at a rate of 120,000 plants ac^-1 to ensure adequate establishment, and stands were thinned to populations of 43,800 and 71,300 plants ac^-1 28-38 days after planting.   The highest sugar content sugar beet crops were produced on soil fertilized to 120 lbs total available soil N ac^-1.  Plant populations did not significantly impact sugar beet quality. Extractable sugar per acre was highest at 240 lbs available soil N ac^-1 and 71,300 plants ac^-1. Extractable sugar per ton was highest at 120 lbs available soil N ac^-1.