Intensive pastoral land use is associated with increased use of phosphate (P) and nitrogen (N) to enhance food and fibre production, but the interaction of N and P, particularly on carbon (C) storage, is not well understood. Our objectives were to determine the quantity and forms of C and N leached and also the changes in soil stocks in association with progressively increasing urea additions in two similar soils with high and low phosphate (P) fertility. A pasture cut-and-carry lysimeter experiment was established in the Waikato region of New Zealand, using soils from sheep grazed farmlets with a P management history of either no P or high P additions. Treatments imposed were a continuation of no P and high P (31.5 kg ha⁻¹ y⁻¹) inputs in combination with 0, 100, 200, 400 kg urea–N ha⁻¹ y⁻¹ in 50 kg split dressings or a single spring application of 400 kg N ha⁻¹ y⁻¹ of bovine urine. The high P soil had greater dissolved organic carbon (DOC) leaching, and DOC leaching in both soils increased with increasing urea inputs. Soil C decreased in the high P soil with N inputs, although there was no correlation between the rate of N addition and C loss. Urea addition led to increased N leaching in both soils, but was reduced in the high P soil compared with the no P soil. Greater herbage production may have utilised more dissolved N in the high P than in the no P soils, which led to less N available for leaching in the high P soil. Urine additions also led to greater C and N leaching in both the no P and high P soils.