Effects of Long-Term Inorganic and Organic Fertilization on Soil Micronutrient Status

Soil micronutrients were studied on loess soil with an 18-year long-term experiment. The results indicated that total soil iron and copper contents were similar under all treatments, but total soil manganese and zinc contents were significantly greater at the surface soil in the fertilized plots than in the controls, and total manganese contents were significantly greater in the whole soil profile under manure plus inorganic fertilizers than under controls. Generally, application of inorganic fertilizers had no effects on available soil micronutrient contents. The straw plus inorganic fertilizers significantly increased available manganese content at surface soil and available iron in subsurface soils. However, manure plus inorganic fertilizers significantly augmented soil-available iron contents throughout the profile, and raised available manganese, copper, and zinc contents, respectively, at surface soil relative to controls. The results suggest that long-term input of organic amendments alter the properties of soil and increase its plant-available micronutrient contents.