Phosphorus and nitrogen losses associated with runoff and erosion on an Aridisol in northern Iraq

Runoff and soil erosion are known to cause a degradation in soil and water quality. Six natural runoff plots (three 10 m long and three 30 m long) wer e established on 6% uniform slope area for the study of P and N losses asso ciated with runoff and soil erosion in northern Iraq. The soil at the site belongs to the Calciorthid suborder which dominates in the low rainfall zon e of northern Iraq. Runoff, erosion, and associated P and N losses, were re corded from these plots for three rainfall seasons. Results illustrated tha t eroded sediment is always rich in available P and inorganic N compared to the original soil. Concentrations of soluble P and soluble N in runoff ill ustrated significant variability both between storms and between seasons. B oth sediment-bound P and soluble P were significantly correlated with the r atio of runoff to rainfall.