Iowa Soil Judging Practice Test

A soil with high organic matter content is characterized by a dark color and a crumbly texture. The dark color arises from the decomposition of organic materials, such as plant and animal matter, which contributes to the formation of humus. This dark pigmentation is a strong indicator of nutrient richness and biological activity, key components of fertile soil.

The crumbly texture results from the aggregation and structuring of soil particles influenced by organic matter. This texture indicates good soil health, allowing for better aeration, water retention, and root penetration, all of which are essential for plant growth.

In contrast, lighter colored soils often lack organic materials, which means they may have lower fertility. Furthermore, sandy soils do not retain organic matter well, and the presence of large rocks and gravel indicates poor soil structure and is generally less conducive to high organic content. These factors collectively distinguish the properties of soils with high versus low organic matter.