Certified Crop Advisor Practice Exam

A major way calcium is supplied to plants is by _________.

1. Mineralization

2. Cation exchange

3. Phosphatation

4. Soil compaction

The correct answer is: Cation exchange

Calcium is a vital nutrient for plants, playing a crucial role in cell wall structure, membrane stability, and signaling functions. The primary way calcium becomes available to plants is through cation exchange processes in the soil. In soil, calcium is present in the form of positively charged ions (cations). During cation exchange, roots of plants release hydrogen ions into the soil, which in turn displace calcium ions from soil particles or from the soil solution. This freed-up calcium is then available for uptake by the plant roots. The cation exchange capacity (CEC) of the soil determines how much calcium and other cations can be held and exchanged, making this process essential for ensuring adequate calcium availability for plant nutrition. Other processes, such as mineralization, involve the breakdown of organic matter, releasing nutrients, but they play a lesser role in the direct supply of calcium compared to cation exchange. Similarly, soil compaction does not facilitate the movement of nutrients to plant roots and can actually hinder root growth and nutrient uptake. Phosphatation is not a recognized process relevant to calcium supply in the context of plant nutrition. This understanding of nutrient dynamics is critical for effective crop management and ensuring adequate nutrient availability for optimal plant health.