Nutrient fluxes in runoff on reseeded blanket bog, limed and fertilized with urea, phosphorus and potassium

Abstract. Studies have been made of the effects of 15 g N/m² as urea in two dressings during April and June on annual nutrient fluxes in runoff from reseeded blanket bog also receiving annually 6 g P/m² as granular superphosphate and 6 kg K/m² as potassium chloride. Urea applications increased significantly ( P < 0.05) the mean annual ammonium-N flux from 17 mg/m² for the P + K plots to 245 mg/m² for the N + P + K plots. Annual fluxes of total P, K and Ca were also increased ( P < 0.05) by the addition of urea. This was attributed to the effects of increased acidity around grass roots following N uptake as ammonium-N. In contrast, nitrate-N was removed from rainwater throughout the year and concentrations in runoff were at the limit of detection (< 0.01 mg/1) on many occasions. Concentrations of organic-N in runoff exceeded those of ammonium-N, but were not significantly changed by fertilization.