Certified Professional Horticulturist (CPH) Practice Exam

What irrigation problem could result from overwatering at the end of a container bed?

1. Diverse growth rates

2. Leaching of nutrients

3. A rootbound container

4. Friction loss

The correct answer is: Leaching of nutrients

Overwatering at the end of a container bed can lead to the leaching of nutrients, which occurs when excess water causes soluble nutrients in the growing medium to wash away. In container gardening, proper moisture levels are critical for maintaining an optimal balance of nutrients available to plants. When the soil is overly saturated, it can create conditions where water movement is excessive, leading to the loss of essential nutrients like nitrogen, phosphorus, and potassium. This nutrient leaching not only diminishes the soil's fertility but can also result in nutrient deficiencies for the plants as they are unable to uptake the nutrients they require for healthy growth. The other issues identified in the choices, such as diverse growth rates, a rootbound container, and friction loss, may arise under different circumstances relating to irrigation and container management but are not direct results of overwatering. Diverse growth rates can occur due to various factors such as genetics or differing light conditions, a rootbound container commonly results from inadequate container size or lack of repotting, and friction loss refers to pressure drops in a fluid system that don’t specifically relate to overwatering. Thus, the phenomenon of nutrient leaching is a direct consequence of overwatering, making it the most relevant problem associated with this situation.