For an average fertilized area of 20 acres ( 162,000 m²), using a "light" spread typical Indiana farm, a total of 5.9 million Bq (MBq) is distributed annually. To what extent does this fertilizing effort enrich the soil in radioactive content if you assume a fertilization depth of 30 cm. Compare the radioactivity level with the natural soil activity of 400 Bq/kg. Average density of soil is 1500 kg/m³.

NOTE: Definition of density: d=m/V, where m is mass in kg and V is volume in m³.