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Fertilized agricultural soils serve as a primary source of anthropogenic N₂O emissions. In South Africa, there is a paucity of data on N₂O emissions from fertilized, irrigated dairy-pasture systems and emission factors (EF) associated with the amount of N applied. A first study aiming to quantify direct N₂O emissions and associated EFs of intensive pasture-based dairy systems in sub-Sahara Africa was conducted in South Africa. Field trials were conducted to evaluate fertilizer rates (0, 220, 440, 660, and 880 kg N ha⁻¹ year⁻¹) on N₂O emissions from irrigated kikuyu–perennial ryegrass (<i>Pennisetum clandestinum–Lolium perenne</i>) pastures. The static chamber method was used to collect weekly N₂O samples for one year. The highest daily N₂O fluxes occurred in spring (0.99 kg ha⁻¹ day⁻¹) and summer (1.52 kg ha⁻¹ day⁻¹). Accumulated N₂O emissions ranged between 2.45 and 15.5 kg N₂O-N ha⁻¹ year⁻¹ and EFs for mineral fertilizers applied had an average of 0.9%. Nitrogen in yielded herbage varied between 582 and 900 kg N ha⁻¹. There was no positive effect on growth of pasture herbage from adding N at high rates. The relationship between N balance and annual N₂O emissions was exponential, which indicated that excessive fertilization of N will add directly to N₂O emissions from the pastures. Results from this study could update South Africa’s greenhouse gas inventory more accurately to facilitate Tier 3 estimates.