What soil factor can directly influence the occurrence of plant diseases?

Moisture is a critical soil factor that directly influences the occurrence of plant diseases. Various pathogens, including fungi, bacteria, and nematodes, thrive in specific moisture conditions. Excessive moisture can create an environment conducive to root rot and other water-related diseases, as it promotes the growth of pathogens that attack the roots and lower plant structures. On the other hand, insufficient moisture can stress plants, making them more susceptible to disease.

While pH level is also an important factor affecting plant health and disease susceptibility, it generally influences nutrient availability and the overall biology of soil rather than directly facilitating disease occurrence like moisture does. Soil color can indicate certain soil properties and conditions but does not have a direct impact on disease occurrence. Soil depth can affect root growth and nutrient availability, but it is not a primary factor that directly influences the prevalence of diseases compared to moisture levels. Therefore, moisture stands out as a primary determinant in the dynamics of plant diseases.