Effect of aluminium on growth and nutrient uptake of cabbage, lettuce and kikuyu grass in nutrient solution

Abstract

Some of the interactions between low pH, aluminium and calcium were reflected in the growth and nutrient uptake response of cabbage, lettuce and kikuyu in nutrient solution. Kikuyu growth, in contrast to cabbage and lettuce, was relatively unaffected by aluminium excess and a pH reduction from 4.6 to 4.0 in solution. The tolerance of kikuyu to aluminium was not associated with lower aluminium concentrations in roots, but with markedly lower concentrations in tops. Cation uptake by roots and tops of all species was reduced in the presence of aluminium or at pH 4.0. Aluminium concentration In roots was higher at pH 4.6 than 4.0, consistent with a lowering of net charge density of aluminium ions as pH is increased. The aluminium concentration in tops was higher at the lower pH. When 0.5 mM calcium (control level) was used in the culture solution, the concentration of calcium was markedly lower and that of magnesium was markedly higher in kikuyu as compared with cabbage and lettuce. When 12.5 mM calcium was used at pH 4.6 in the absence of aluminium, the root yield of cabbage and lettuce was greater and the top yield of kikuyu was lower than the control. This latter treatment overcame the inhibitory effect of aluminium on the yield of cabbage and lettuce roots and the yield of cabbage tops. The 12.5 mM calcium treatment had no effect on aluminium concentration in roots, but reduced the concentration in tops for all species. The magnesium concentration in roots and tops was similarly reduced. Aluminium caused an increase in the concentration of phosphorus in roots of cabbage and kikuyu, but had no consistent effect on the concentration in tops.