MDARD Michigan Core Pesticide Applicator Practice Exam

How does organic matter in soil affect leaching?

1. Higher organic matter increases leaching

2. Higher organic matter decreases leaching

3. Organic matter has no effect on leaching

4. Organic matter increases soil texture

The correct answer is: Higher organic matter decreases leaching

Higher organic matter in soil plays a significant role in reducing leaching due to its capacity to enhance soil structure and improve its water-holding capabilities. Organic matter contributes to the formation of aggregates in the soil, which can create pore spaces that help retain water and nutrients. When soil has more organic content, it typically also has better cation exchange capacity, meaning it can hold onto positively charged nutrients more effectively. This ability to retain nutrients and water reduces the likelihood that they will be washed away by excessive rainfall or irrigation, which is a process known as leaching. Additionally, organic matter can help promote microbial activity, which aids in the breakdown of nutrients into forms that plants can use, thereby minimizing nutrient loss through leaching. The result is that soils rich in organic matter are generally more resilient and productive, leading to less nutrient movement beyond the root zone.