ABSTRACTEffects of Fe sources, levels of added Fe, and incubation time on the availability of micronutrients in a slightly acid (normal) and a calcareous (Fe-deficient) soil were determined. Twenty, 40, and 80 ppm Fe, as Fe-EDDHA,1 Fe-PF, and Fe-LS, were mixed with soils and incubated at field capacity at room temperature. DTPA extraction of soil samples collected at 1,2,4, and 8-week intervals indicated that, in general, proportional Fe recovery decreased with increasing Fe application. After 8 weeks, Fe recovery from Fe-EDDHA applied to the normal soil at rates of 20, 40, and 80 ppm Fe was 46, 34, and 21%, respectively. Iron retention by the soil increased with time, and was higher in Fe-deficient soil than in normal soil. Iron-EDDHA was found to be the most stable compound in both soils. Iron-PF was more stable in Fe-deficient soil than Fe-LS, and the reverse was true in the normal soil. Extractable Mn increased with increasing Fe application. Extractable Zn and Cu varied with soil and source of Fe. Iron-LS produced the highest increase in extractable Cu and Zn; Fe-PF increased Mn, but Fe-EDDHA had little or no influence on extractable soil micronutrients. The results generally suggest that Fe-EDDHA has a superior efficiency to Fe-LS and Fe-PF in both soils. The results also confirm the suitability of DTPA as a soil extractant for available Fe.
Effects of Fe sources, levels of added Fe, and incubation time on the availability of micronutrients in a slightly acid (normal) and a calcareous (Fe-deficient) soil were determined. Twenty, 40, and 80 ppm Fe, as Fe-EDDHA,1 Fe-PF, and Fe-LS, were mixed with soils and incubated at field capacity at room temperature. DTPA extraction of soil samples collected at 1,2,4, and 8-week intervals indicated that, in general, proportional Fe recovery decreased with increasing Fe application. After 8 weeks, Fe recovery from Fe-EDDHA applied to the normal soil at rates of 20, 40, and 80 ppm Fe was 46, 34, and 21%, respectively. Iron retention by the soil increased with time, and was higher in Fe-deficient soil than in normal soil. Iron-EDDHA was found to be the most stable compound in both soils. Iron-PF was more stable in Fe-deficient soil than Fe-LS, and the reverse was true in the normal soil. Extractable Mn increased with increasing Fe application. Extractable Zn and Cu varied with soil and source of Fe. Iron-LS produced the highest increase in extractable Cu and Zn; Fe-PF increased Mn, but Fe-EDDHA had little or no influence on extractable soil micronutrients. The results generally suggest that Fe-EDDHA has a superior efficiency to Fe-LS and Fe-PF in both soils. The results also confirm the suitability of DTPA as a soil extractant for available Fe.
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