Effect of Extending Seedling-raising Period on Yield of Transplanting Sugar Beet ( Beta vulgaris ) in Black Soil Area of Northeast China

Paper pot seedling-raising technique is generally regarded as a high-yield strategy for sugar beet ( Beta vulgaris ) because it can accelerate leaf formation in early spring. But little is known about the optimal seedling-raising period in black soil area of Northeast China. In order to investigate the effect of extension of seedling-raising duration on yield of sugar beet, two field trials were carried out in 2011–2012 in black soil area of Northeast China. The results showed that leaf and root yield formation could well be described by thermal time in the whole season. The extension of seedling-raising period was helpful to cultivate good quality seedlings. The transplanted sugar beet with 35–40 days seedling-raising period had the highest yield, with average yield ranging from 60.5 to 62.7 t ha −1 , 10.4–13.6% higher than that with 25 days seedling-raising period. There were no detectable differences in seedling-raising periods for sugar concentration. In a regular year, it was suggested that transplanting sugar beet in black soil area of Northeast China should be sown before April 8 and raised for 35–40 days in greenhouse in order to obtain a marked yield increase.