FACTORS WHICH AFFECT THE GROWTH OF GRAIN LEGUMES ON A SOLONIZED BROWN SOIL .2. GENOTYPIC RESPONSES TO SOIL CHEMICAL FACTORS

Lupins (Lupinus angustifolius cvv. Yandee, 75A-258 and P22872, and L. pilosus cv. P20957) and field peas (cv. Dundale) were grown in the glasshouse in a sieved solonized brown soil. The soil was taken from sequentially deeper zones in the B horizon of the natural profile (8-83 cm below the surface). The pH (in CaCl2) increased from c. 6.3 to c. 8.2 with depth while sodium and chloride concentrations reached 83 and 62 mol m-3 (soil solution) respectively in the deepest unfertilized subsoil. Sodium concentrations reached 159 mol m-3 when the subsoil was fertilized. When plants were grown in the deepest subsoil, the growth of shoots and roots was inhibited by up to 75% in L. angustifolius but less severely in L. pilosus and pea. Roots of pea were affected least by the deep subsoil. Shoots of L. angustifolius, but not L. pilosus or pea, had severe chlorosis in the expanding tissue and necrosis of the oldest leaflets when grown on the deepest soil. Expanded leaflets of L. angustifolius had sodium and chloride concentrations up to 200 mol m-3 while iron concentrations were less than 20-mu-g g-1 dry weight in expanding tissues. Concentrations of manganese and zinc exceeded requirements for maximum growth but copper concentrations were sufficiently low to suggest deficiency in growing tissue of Yandee and 75A-258. No symptoms of deficiency were apparent. It is concluded that adverse chemical factors in the subsoil restrict root growth of L. angustifolius in the field. L. pilosus and field peas, on the other hand, appear to be significantly better adapted to these sodic, alkaline subsoils.