Which of the following is not a contribution of soil organic matter to soil properties?

Soil organic matter plays a crucial role in enhancing various soil properties, contributing significantly to soil health and productivity. One key aspect of soil organic matter is its ability to improve soil structure. This is achieved as organic matter helps bind soil particles together, creating aggregates that enhance porosity and aeration.

Additionally, soil organic matter increases the water-holding capacity of soil by improving the soil's ability to retain moisture, which is vital for plant growth and sustainability. The presence of organic matter helps to create more pore spaces in the soil, allowing it to hold water better after rainfall or irrigation.

Furthermore, organic matter enhances nutrient retention by acting like a sponge, effectively holding onto nutrients and preventing them from leaching away, thereby making them available for plant uptake over time.

In contrast, the availability of micronutrients such as molybdenum is not directly improved by soil organic matter. While organic matter can influence the overall nutrient dynamics in the soil, molybdenum availability is primarily affected by soil pH, moisture content, and the chemical form of molybdenum present, rather than by the organic matter itself. This is why the option regarding increased molybdenum availability is not considered a contribution of soil organic matter to soil properties.