Sugar Beet Root Yield and Quality with Leaf Seasonal Dynamics in Relation to Planting Densities and Nitrogen Fertilization

This study aimed to analyze the seasonal dynamics of sugar beet leaf and root yield and quality in different plant populations and the nitrogen fertilization rate. The field trials were set as four different planting densities (60,000 to 140,000 plants ha−1) and three different spring nitrogen fertilization rates: no fertilization, pre-sowing (45 kg ha−1 N), and pre-sowing with top dressing (99 kg ha−1 N in 2014 and 85.5 kg ha−1 N in 2015. The changes of leaf growth were done measuring leaf area (LA), leaf area index (LAI), specific leaf area (SLA), and leaf area ratio (LAR). The highest LAI in 2014 was determined on 30 July at 140,000 plants ha−1 (9.35 m2 m−1) and in 2015 on 20 June at 100,000 plants ha−1 (4.83 m2 m−2). In both years, the SLA and LAR was highest at the end of May. In relation to plant density, higher plant densities had on average the highest root yield, sucrose content, and white sugar yield. In both years, pre-sowing with top dressing spring nitrogen fertilization resulted in the highest root (95.0 t ha−1) and white sugar yield (11.4 t ha−1), whereas the highest sucrose content was after pre-sowing fertilization (14.9%).