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.