Effect of phosphorus and aluminium in the response of spring barley to soil acidity

SUMMARY Soil chemistry in relation to yield of spring barley (Hordeum vulgare, cv. Golden Promise) was investigated in three field experiments in north-east Scotland in 1982. Previous treatments had produced a range of soil pH values from 4·0 to 6·0 (measured in 10mM-CaCl2 solution). The experiments demonstrated the values for soil acidity components below which yields were reduced. Large additions of phosphate fertilizer allowed barley to withstand larger concentrations of soluble and exchangeable aluminium (the principal acid soil toxin), thus decreasing the critical soil pH from 5·2 to 4·8 (corresponding to about 5·9 and 5·5 if measured in a water suspension), and increasing the critical soluble Al concentration from 10 to 50 UM and the critical Al saturation of the cationexchange complex from 0·025 to 0·1.