Sesame (Sesamum indicum L.) is grown mainly in the tropics. It is typically grown by smallholders with nearly all of its production in developing countries. It is an important source of high-quality oil and protein. Inappropriate use of fertilizers and monocropping are among the major production constraints. The objective of this paper is therefore to review the effect of N fertilizers on sesame growth and productivity. Growth and yield of sesame are greatly influenced by the application of N fertilizer. In most of the sesame-producing countries, optimum seed yield of sesame was obtained from application of 46–100 kg·N/ha. Adequate nitrogen fertilization also improves uptakes of other nutrients, particularly P and K and some micronutrients. Preemergence application of mobile nitrogen (urea) is less efficient due to losses. Mobile form of N fertilizer became available within two days for the crop. Split N applications where the N fertilizer is applied at different growth stages of the crop increases productivity. Side-dress application is one of the easiest ways to maximize nitrogen use efficiency. N fertilizers should be placed 3–5 cm deeper than the seeds and 5–10 cm apart from the plant for side dress but not far than 20 cm. Under optimal environmental conditions, nitrogen fertilizer has no effect on phonological traits but on the growth parameters. In the potential areas, application of 46–100 kg·N/ha gives maximum yield and lowering the application of N to less than 46 kg·N/ha in marginal areas is economical.

Inappropriate use of fertilizers is one of the major production constraints in sesame. Studies to optimize the use of N fertilizer on sesame were conducted at Humera Agricultural Research Center (HuARC) under rain fed and irrigation conditions. Thirteen (13) N doses were evaluated in a Randomized Complete Block Design (RCBD) during 2016, 2017 and 2018. In the rain fed condition; results showed higher number of days to 50% flowering on the higher N application. The 31-121.5 kg N ha-1 have scored higher seed yield, where the lower (18 kg N ha-1) and higher (156 kg N ha-1) N doses scored lower seed yield. In the irrigation condition; higher N application rate prolonged the flowering time to some extent and days to 90% maturity was reduced as N rate increased. Heavier seed weights and maximum seed yield were recorded on 64 and 75 kg N ha-1 and the lower N doses scored low seed yield. Agronomic efficiency of N fertilizer (N-AE) was higher on 64 kg N ha-1 under both growing conditions. The partial budget analysis revealed that 64 kg N ha-1 (rain fed) and 75 kg N ha-1 (irrigation) had the higher net profit, MRR and residual ranking. Therefore, for the greater sesame productivity 64 kg N ha-1 has to be recommended for rain fed and 64 to 75 kg N ha-1 for the irrigated sesame.