Use of more than one chelating agent simultaneously for different micronutrients in hydroponic nutrient cultures

Abstract

Best growth with bush beans (Phaseolus vulgaris L. cv. Improved Tender‐green) in hydroponic culture was obtained with all the Fe, Zn, Cu and Mn chelated with DTPA and of solution pH 8.2, or with 110% of the Fe chelated with EDDHA and the Zn, Cu and Mn chelated with DTPA at pH 6.4. The concentration of the four elements supplied in mg.1^‐1 were 1.0, 0.6, 0.3, 0.05 for Fe, Mn, Zn and Cu respectively. In another experiment in which Zn was decreased to 0.2 ing.l^‐1 and solution pH of 5.5 and also 7.8, best growth of bush beans was with Fe only chelated with DTPA although good growth was also obtained when more than one micronutrient was chelated. In another experiment, best growth of tomatoes (Lycopersicum esculentum L. cv. Tropic) was obtained with Fe, Zn, Mn and Cu chelated with DTPA at one level of micronutrients. With a lower level of Mn and Zn and other nutrients unchanged, best growth was obtained when all four micronutrients were chelated‐½ with EDDHA and ½ with DTPA. The results of the studies strongly imply that FeEDTA is not the best source of iron for hydroponic solution cultures. They also imply that chelated Zn, Cu and Mn, as well as Fe, can also be available to plants. The best source of Fe to plants at pH 6 was FeDTPA but FeEDDHA was best at pH 7.5.