Translocation and recovery of 15N-labelled N derived from foliar uptake of 15NH3 by rice (Oryza sativa L.) cultivars

Foliar uptake of (NH3)-N-15 applied at two growth stages (tillering and anthesis) and the subsequent N-15-labelled vegetative-N distribution in different plant components at maturity was investigated in three rice cultivars, IRA NIAB-6 and Bas-385. Rice plants absorbed 22-30% and 18-24% of the (NH3)-N-15 applied at tillering and anthesis stages, respectively. Of the total (NH3)-N-15 absorbed at tillering stage, IR-6 and Bas-385 showed higher recovery (71%) in different plant components at maturity as compared to NIAB-6 (48% recovery). At maturity, percent recovery of the (NH3)-N-15 absorbed at anthesis stage was almost comparable in different cultivars, but it was lower (46-55%) than that absorbed at the tillering stage. Recovery of the absorbed (NH3)-N-15-N in the soil was negligible and ranged from 0.3-1%. At maturity, the cultivars IR-6 and Bas-385 showed a higher loss (45-53%) of (NH3)-N-15 absorbed at anthesis than at the tillering stage (29% loss), whereas for NIAB-6, the corresponding figures were comparable for the two growth stages (tillering, 51% loss; anthesis, 49% loss). Results indicated a variable potential of the tested rice cultivars for foliar uptake of atmospheric (NH3)-N-15 and distribution of N-15-labelled vegetative-N in different plant components.