Mobilization of aluminium in soil by acid deposition and its uptake by grass cut for hay-a Chemical Time Bomb

Analyses of soil and hay samples collected from the Park Grass Experiment at Rothamsted during the last 137 years indicate slow but significant increases in KCl- and EDTA-extractable aluminium in soil and a sudden and very large recent increase in the concentration of aluminium in the herbage. The latter is associated with a sudden increase in the rate of acidification of the soil over the last 10-15 years and the mobilization of aluminium as the soil enters the aluminium buffer range - a Chemical Time Bomb. Such severe acidification from atmospheric inputs on a well-buffered soil illustrates how quickly an apparently stable situation can change as a result of acid deposition. It highlights the need to protect soils and plants from the effects of acidification by decreasing acid inputs or by liming.