Certified Crop Advisor Practice Exam

What effect does excessive tillage have on soil organic matter?

1. Increases Organic Matter

2. Reduces Organic Matter

3. Has No Effect

4. Improves Soil Structure

The correct answer is: Reduces Organic Matter

Excessive tillage has a significant impact on soil organic matter, primarily leading to its reduction. When soil is tilled frequently and aggressively, it disrupts soil aggregates and enhances the breakdown of organic matter into simpler compounds, which are more rapidly decomposed by microbial activity. This process can lead to a loss of carbon, as the organic matter is exposed to air and breaks down more quickly. Moreover, the physical disturbance associated with tillage increases the exposure of organic materials to oxidation, further accelerating the loss of organic carbon from the soil. As a result, the overall capacity of the soil to store organic matter diminishes, which can ultimately affect soil health, fertility, and productivity. In contrast, practices that minimize tillage or adopt conservation tillage techniques help maintain or even build soil organic matter by preserving soil structure and reducing disruption of the soil ecosystem. This highlights why excessive tillage is detrimental to organic matter levels in the soil.