Fig. 3. Concentration of malate and citrate in the rhizosphere of maize, soybean, and faba bean. Harvests were at 35 and 45 days after emergence, respectively. Data from two samplings were combined into one data set as replicates because no significant difference was found between the two samplings. Differences among the letters above the bars indicate a significant (P < 0.05) difference in organic acids between crops (n = 11) (Greenhouse Study 3).