THE EFFECTS OF NUTRIENT SOLUTION ACIDITY (PH), ALUMINUM CONTENT AND RHIZOBIUM INOCULATION ON TAPROOT ELONGATION, ROOT-GROWTH AND NODULE FORMATION ON FIELD BEANS (PHASEOLUS-VULGARIS L) CV ROSECOCO

The effects of nutrient solution PH, aluminium concentration and Rhizobium inoculation on taproot elongation, root growth and nodule formation on field beans (Phaseolus vulgaris L). cv Rosecoco, GLP 2 type, were studied in a greenhouse. There was a highly significant reduction (p < 0.001) of the mean taproot length. With respect to nutrient solution acidity, the highest mean taproot length was observed at pH 4.0. These differences were attributed to the existence of forms of Al having varying degrees of toxicity, controlled by the pH of the nutrient solution. The concentration of Al in the nutrient solution did not affect the mean root dry matter weight significantly but affected the nodule numbers which decreased as the concentration of this element increased in the nutrient solution. The highest mean number of nodules formed was 13.12 at pH 6.8 and 0 ppm Al. Field beans cultivar ''Rosecoco'', GLP 2, showed a poor response to inoculation compared to others. Nutrient solution acidity inhibited nodulation of the beans. It is suggested that the inhibitory effect of Al may depend on the specific ionic form of this element apart from its concentration and pH of the nutrient solution