[en] This study was carried out to evaluate the dynamics of Nitrogen (N) and plants growth and development through the use of biofertilizer on kenaf mutant lines in the field. The kenaf mutant lines has been developed under the mutagenesis radiation program for late flowering capability. In this study, four kenaf mutant lines labeled as S1, S2, S3 and S5 were planted at the research field, National Kenaf and Tobacco Board (LKTN), Beseri Perlis. The kenaf mutant lines are grown under four (4) fertilization treatments namely, (i) Farmer Practice (FP), (ii) Biofertilizer (BO), (iii) Control (C) and (iii) Farmer Practices + Biofertilizer (FBO). The use of oligochitosan as a growth booster has been applied to all treatments. The ¹⁵N isotope dilution technique has been used in this study, whereas ¹⁵N labeled urea 3 % atom excess was used as a tracer in the study to determine N derived from fertilizer (Ndff) and atmosphere (Ndfa). The application rate of ¹⁵N Urea per treatment is 20 kg N/ ha. The presence of ¹⁵N isotope in the sample has been determined by using emission spectrometer and the percentage of N amount has been determined using Kjeldahl method. The value of ¹⁵N a.e in the sample has been used in the determination of Ndff and Ndfa. (author)