Nitrogen is said to be “fixed” from the atmosphere and is also “fixed” by vermiculite clays and humus. Differentiate between these two processes and indicate the role of microbes, if any, in each...

Nitrogen is said to be “fixed” from the atmosphere and is also “fixed” by vermiculite clays and humus. Differentiate between these two processes and indicate the role of microbes, if any, in each process.

Chemical fertilizers and manures with high N contents are commonly added to agricultural soils. Yet these soils are often lower in total N than are nearby soils under natural forest or grassland vegetation. Explain why this is the case.