Leaching Losses of Ammonium and Nitrate in the Reclamation of Sand Spoils in Cornwall

Reclamation studies on sand spoils in Cornwall have shown a difficulty in maintaining adequate levels of nitrogen for plant growth. Information is presented to show that the movement of NO 3 − and NH 4 + is highly correlated with rainfall ( r = 0.89 and 0.92, respectively). Nitrate leaching (4.1 cm/cm rain) is more serious than NH 4 + leaching (2.5 cm/cm rain), and calculations show that more than 98% of the NO 3 − fertilizer applied to bare sand spoil will be leached beyond the surface 20 cm with an average month of summer rainfall (9.7 cm). Maximum inorganic‐N fertilizer recoveries of 40 kg/ha are predicted for grass swards established on spoils flattened by earth‐moving equipment, while recoveries < 20 kg N/ha are likely on steeply sloping sand heaps. Grass test crops recovered 26 and 35% of the fertilizer‐N on a level site when NaNO 3 and (NH 4 ) 2 SO 4 were applied at 125 kg N/ha.