Determination of the nitrogen composition of colliery spoil

Freshly exposed unameliorated spoil and vegetated spoil were analysed for their nitrogen constituents using methods devised for soils. The main components found were non-exchangeable ammonium (25%), hydrolysable nitrogen (33%) and unidentified non-hydrolysable nitrogen (62%). Summation of these exceeded 100% because hydrolysis with 6 M HCI extracted much of the non-exchangeable ammonium. Ammonium in the hydrolysate accounted for over 90% of hydrolysable nitrogen in freshly exposed unameliorated spoil and 70% of hydrolysable nitrogen in vegetated spoil. Correction for this ammonium in the hydrolysate allowed estimates of ‘recent organic’ nitrogen accumulation to be made. These estimates were significantly correlated with spoil mineralizable nitrogen levels. The nature of the nitrogen constituents of colliery spoil and the use of ‘recent organic’ nitrogen estimates in assessing site fertility are discussed.