Clay fixation of metal chelates as a factor in their usability by soil application to correct micronutrient deficiencies

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Abstract
Yolo loam and Hacienda loam soils were extracted with 10‐2, 10‐3, and 10‐4 M solutions of the three chelating agents, DTPA, EDTA and EDDHA, to further evaluate quantities of iron, zinc, manganese and copper that can be fixed in soil after chelation. Aliquots of the extracts were analyzed after 4, 24, 95 hours and 11 and 25 days. EDEHA was only effective in maintaining iron in solution for 4 days with calcareous Hacienda loam (fine‐loamy, mixed, thermic Aquic Natrargid) while it was effective for up to 21 days with Yolo loam (fine‐silty, mixed, thermic typic Xerorthents). All chelating agents resulted in an increased concentration of iron in solution throughout most of the test except that FeEDDHA peaked at 4 days. Manganese seemed to be readily lost from solution with time. Zinc and copper had little tendency to disappear from the solutions especially with. the calcareous Hacienda loam soil.