Transformation of Incubated Micronutrient Chelates in Calcareous Soils
1983
Ryan, John | Hariq, S. N.
Micronutrient chelates have been introduced as fertilizing materials to overcome deficiencies mainly in calcareous soils, and to maintain effectiveness for a significant period of time. However, few studies have examined changes in applied chelates over a normal growing season, and some selected soil and environmental properties which influence these changes. Laboratory incubation studies, up to 168 d, were conducted to evaluate the influence of associated properties in several soils and, added CaCO₃ (0, 2.5, 5.0, and 10.0% wt/wt), temperature (5, 15, 25, and 35°C) and wetting-drying (up to four weekly cycles) on the persistence of applied FeEDDHA and Zn-, Mn-, and CuEDTA. Incubated samples were extracted with water and then with DTPA-extraction solution. Recovery varied with the metals in each soil. After 168 d, 32 to 56% of the applied Fe and <13% of the applied Cu and Zn was extracted by both solutions. Loss of Mn from MnEDTA was essentially complete within 2 d. Decreased metal extractability appeared to be related to the organic matter content of each soil. Applied CaCO₃ depressed recovery with no significant difference between application rates. Metal extraction also decreased consistently with increasing temperature and with the number of wet-dry cycles compared to constantly moist samples. The results have implications for arid-region soils where chelates are used under irrigation and high soil temperatures.
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