Changes in DTPA‐Extractable Zinc, Iron, Manganese, and Copper in Soils Following Fertilization

Summary

Abstract Eleven soils were fertilized with Zn, Fe, Mn, and Cu and examined periodically with the DTPA micronutrient soil test. The study continued for 14 weeks while the soils were cropped in the greenhouse first with oats ( Avena sativa ) and then with corn ( Zea mays ). During this period fertilizer Cu declined to 61%, Zn to 44%, and Mn to 14% of their initial values. Only 20% of the Fe added as FeSO 4 · 7H 2 O remained extractable after 1 week. With chelated Fe as FeEDDHA, 70% was extractable at 7 weeks and 26% at 14 weeks. The results are in general agreement with reported residual response from these fertilizers and suggest that the DTPA soil test may be useful for monitoring the availability of micronutrient cations in fertilized as well as unfertilized soils.