EFFECT OF NITROGEN FERTILIZATION ON STAY-GREEN AND SENESCENT SORGHUM HYBRIDS IN SAND CULTURE

Nitrogen (N) is vital in the production of N containing compounds in cereal crops. Stay-greenness in sorghum [Sorghum bicolor (L.) Moench] is characterized by the plant's ability to retain water and chlorophyll content at maturity. A greenhouse experiment was conducted to investigate the effect of the genotypic variability between stay-green (BT x 643) and senescent (RT x 7000) hybrids for leaf senescence, dry matter partitioning and N partitioning under three N levels (0.45, 0.90, 1.80 g plant-1). The stay-green hybrid had a higher percentage green leaf area at 120 DAE with a higher residual N in leaves. The chlorophyll meter (SPAD-502) values for the stay-green hybrid during anthesis (75 and 85 DAE) were higher compared to its senescent counterpart. The results indicated that the expression of stay-green phenotype in sorghum was contingent on a minimum N supply of 1.35 g plant-1 and associated with greater N acquisition. Nitrogen use and uptake in the stay-green hybrid were higher.