The effect of nutrient solution types on soybean nodulation and growth at week 3 (a) and week 4 (b) after inoculation. The data are expressed as means and SD. H: modified Herridge nutrient solution; B&D: Broughton and Dilworth nutrient solution. In each graph, values followed by different letters are significantly (P < 0.05) different. Each value is the mean of 12 data values.