What aspect of soil chemistry does organic matter influence directly?

Organic matter plays a crucial role in influencing nitrogen fertilizer needs. It is a significant source of nutrients and has the ability to release nitrogen slowly as it decomposes, thus contributing to the overall nitrogen supply in the soil. The decomposition of organic matter not only adds nitrogen but also affects the soil's structure and its capacity to retain moisture and nutrients, making it essential for understanding how much supplemental nitrogen fertilizer may be required for optimal plant growth.

While other factors such as water pH levels, oxygen levels in the soil, and soil temperature variation are indeed important aspects of soil health and plant growth, they are not directly influenced by organic matter in the same way. For instance, pH levels are primarily determined by the minerals and parent material of the soil, oxygen levels are influenced by soil compaction and moisture content, and temperature variations are affected by factors such as soil color, depth, and surface cover. Organic matter primarily impacts nitrogen dynamics, making it pivotal in assessing fertilizer needs.