The relationship between soil organic matter (SOM) and water holding capacity is complex and influenced by various factors, including soil texture, structure, and the type of organic matter. However, a general rule of thumb is that an increase in soil organic matter leads to improved water holding capacity.

In summary, the relationship between soil organic matter and water holding capacity is significant, with increased organic matter generally leading to improved water retention. However, the extent of this improvement depends on various factors, including soil type, initial organic matter content, and soil structure. Soil management practices that enhance organic matter content, such as adding compost or cover cropping, can contribute to better water management in soils.

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This is because the addition of organic matter increases the number of micro pores and macro pores in the soil either by “gluing” soil particles together or by creating favorable living conditions for soil organisms. Certain types of soil organic matter can hold up to 20 times their weight in water. "Each 1 percent increase in soil organic matter helps soil hold 20,000 gallons more water per acre." The source of soil organic matter is photosynthesis resulting in plant growth either root or aboveground. Therefore, the organic matter content cannot increase more than the amount of plant growth that can be produced in a year. Every 1% increase in organic matter results in as much as 25,000 gallons of available soil water per acre. Each pound of soil organic matter (SOM) can hold up to 18 to 20 pounds of water and 1% of SOM can hold up to 1 inch of water in the soil. Soils with smaller particles (silt and clay) have a larger surface area than those with larger sand particles, and a large surface area allows a soil to hold more water. In other words, a soil with a high percentage of silt and clay particles, which describes fine soil, has a higher water-holding capacity. The soil's ability to retain water is strongly related to particle size; water molecules hold more tightly to the fine particles of a clay soil than to coarser particles of a sandy soil, so clays generally retain more water. Conversely, sands provide easier passage or transmission of water through the profile. Soils are made up of three main components: sand, silt and clay. The proportion of each component determines the soil texture. Each soil texture has its own Water Holding Capacity (WHC). The amount of organic matter in the soil also affects water holding capacity to a degree.