MODELING OF WATER AND NITROGEN DYNAMICS ON AN UNDISTURBED SOIL AND A RESTORED SOIL AFTER OPEN-CAST MINING

The water movement, mass transport and nitrogen transformations were e valuated on a restored and on an undisturbed soil. During the opencast coal-mining at Acklington in north-east England the soil-layers were removed and stored in large heaps. After the completion of the coal ex ploitation the soil was restored layer by layer. An identical and undi sturbed soil in the vicinity of the opencast mine served as a benchmar k. The same experimental treatments were given to both soils. The wate r and nitrogen dynamics were evaluated by an one-dimensional model bas ed on the Galerkin finite element method. The nitrogen submodel incorp orates mineralization, immobilization, nitrification, denitrification, ammonium exchange, uptake and mass transport. The simulations of wate r content and nitrogen in the soils were compared with the biweekly wa ter content and irregular inorganic nitrogen measurements. Good a,agre ement was found between measured and simulated water distribution duri ng simulation period. At 10 cm depth, the simulation was not as good e specially during the autumn period. The soils received the same amount of inorganic nitrogen fertilizer and agronomic treatment. The dynamic s of the simulated and observed ammonia and nitrate concentrations can be largely explained as a result of differences in soil structure. (C ) 1998 Elsevier Science B.V.