Fertile soil contains abundant humus because humus, the decomposed organic matter, significantly enhances soil fertility. It provides essential nutrients, improves soil structure, and enhances water retention, all of which are crucial for healthy plant growth.
Elaboration:
Nutrient Source:
Humus acts as a reservoir of minerals and nutrients, making them readily available for plants to absorb.
Soil Structure:
Humus binds soil particles together, creating a crumb-like structure that improves aeration and water infiltration, beneficial for root growth.
Water Retention:
Humus has a high capacity to retain water, which is vital for plant survival, especially in drier conditions.
Microbial Activity:
Humus supports a thriving microbial community, which further enhances nutrient cycling and soil health.
Topsoil Layer:
Humus is particularly abundant in the topsoil (A horizon), which is the most fertile layer due to its high organic matter content.