Changing fertilizer strategies to address new challenges in sugarbeet management: Early harvest, varietal differences, and sugar quality.

Abstract

Nutrient management strategies have always been a focal point of sugarbeet production. However, with the adoption of the 30-300 Initiative (i.e., 30 T A^-1 and 300 lbs sugar T^-1), Michigan sugarbeet production continues to emphasize improving beet quality as compared to yield. New obstacles continue to impact agronomic management including a more variable climate, early harvest intervals, updated varietal characteristics, and managing an N-responsive cropping system that growers may or may not wish to respond to N applications. Although management has mostly evolved to being site- or field-specific, little work has been done investigating how nutrient management may change based on sugarbeet varietal characteristics. More defensive varieties with greater disease tolerance may respond differently compared to more aggressive varieties with greater tonnage. Field studies were established to evaluate sugarbeet varietal response (defensive vs. aggressive) to specific fertilizer management strategies and early vs. conventional harvest intervals. The study was blocked by two harvest timings (early and conventional) and two varieties (C-G675 and C-G919). All treatments received 60 lb. N A^-1 at planting applied 2×2. Four fertilizer strategies consisted of only 60 lb. N A^-1  applied 2×2 at-plant, 60 lb. N A^-1  applied 2×2 and 100 lbs. N A^-1 sidedress coulter inject at 4-leaf stage, 60 lb. N A^-1  applied 2×2 and 100 lbs. K₂O A^-1 surface applied next to row at canopy closure (~20 leaf stage), and 60 lb. N A^-1  applied 2×2 along with 100 lbs. N A^-1 sidedress coulter inject at 4-leaf stage and 100 lbs. K₂O A^-1 surface applied next to row at canopy closure (~20 leaf stage). Climate variability continued to impact growth and production in 2021 with moist autumn conditions decreasing sugar concentrations by 0.37% in October harvest as compared to August. Despite a mean yield increase of 16 T A^-1 with conventional as compared to early harvest, no interaction between variety and harvest timing occurred in 2021. Starter N was sufficient for early harvest specifically in 2021 with no tonnage differences observed compared to starter with sidedress N. Field results from 2022 will be included after harvest is complete and compared alongside 2021 field data.