Effect of N Fertilizer and Growth Stimulating Bacteria on Growth Traits of Sugar Beet (Beta vulgaris L.) under Delayed Sowing Condition

Delayed planting of sugar beet, use of nitrogen fertilizer and growth promoting bacteria are important in accelerating growth and compensating time loss. To study this subject, a split split plot experiment was conducted in a randomized complete block design with 3 replications and 8 treatments in 2018 at the Research Farm of Ferdowsi University of Mashhad. The factors under study consisted of planting date with two levels (regular planting, D1, and delayed planting, D2) as the main factor, nitrogen fertilizer with two levels (use of nitrogen fertilizer based on recommended rate, N1 and 25% less than recommended rate, N2) as a subfactors and bacterial growth stimulant with two levels (bacterial inoculation, B2, and without its use, B1) were considered as sub-sub- factors. Growth indices under study were leaf area index, total dry matter, crop growth rate, relative growth rate and net assimilation rate. In this study, highest leaf area index (3.5) and dry matter accumulation (2898 g.m-2) in thermal unit, as well as growth rate, relative growth rate and net assimilation rate under regular and delayed planting dates were due to the use of recommended rate of nitrogen fertilizer and bacterial inoculation treatments. The least amounts of these traits were obtained at both planting dates and use of nitrogen fertilizer, 25% less than the recommendation, and without using bacteria. Root yield and sugar content sugar beet under treatment of bacterial and nitrogen use, based on recommended rate, showed 8 to 10% higher than other treatments, under both regular and delayed planting date. It seems that the combined use of chemical and biological fertilizers is useful in delayed sowing, to compensate delayed time loss planting of sugar beet.