Effect of Nitrogen on the Accumulation and Reutilization of Dry Mass in Grain Sorghum

Abstract

Accumulation and reutilization of dry mass until anthesis and during a grain fillingperiod of sorghum in response to nitrogen fertilization in rates 0, 60, 120, 180, 240and 300 kg N.ha-1 was studied in a field experiment. Grain sorghum hybrid ECAlize was grown under not- irrigated conditions in the experimental field ofAgricultural University of Plovdiv, Bulgaria. The experimental design was arandomized, complete block design with four replications with a size ofexperimental plots of 20 m2 after wheat as predecessor. Standard farming practicesfor the region of Southern Bulgaria were applied. It was established that nitrogenfertilization significantly increased the amount of accumulated dry mass at anthesisand total above ground dry mass at maturity compared to N0. Not significant effectof higher rates (180, 240 and 300 kg N.ha-1) on the dry mass accumulation ofsorghum was found. Average post anthesis net dry mass accumulation was 3291kg.ha-1 and its amount increased in parallel with the nitrogen rate up to N180. Thehighest dry mass translocation, translocation efficiency, and contribution of preanthesisassimilations of the grain was established at nitrogen rate N120 with values2073 kg.ha-1, 25.0 % and 41,8 %, respectively. Growth of sorghum at highernitrogen rates N180, N240, N300 significantly decreased efficiency of dry masstranslocation and contribution of pre-anthesis assimilations of the grain. Nitrogenfertilization had very strong negative correlation with dry mass translocationefficiency (-0.860*) and contribution of pre-anthesis assimilations of the grain (-0.863*). Very strong positive correlation (0.988**) was found between dry masstranslocation efficiency and contribution of pre-anthesis assimilations of the grain.