Certified Professional Horticulturist (CPH) Practice Exam

What factors are most likely to influence nutrient availability and impact plant growth?

1. Fertilizer and temperature

2. Soil movement and solubility

3. Soil amendment and fertilizer analysis

4. Water quality and pH

The correct answer is: Water quality and pH

The choice of water quality and pH is crucial because both factors directly affect nutrient availability in the soil. Water quality can influence the levels of nutrients that are accessible to plants. For instance, high salinity in the water can hinder plant growth and nutrient uptake. Additionally, pH significantly impacts nutrient solubility; certain nutrients become less available to plants at extreme pH levels. For example, iron becomes less available in alkaline (high pH) conditions, while phosphorus can become less soluble in highly acidic soils. Therefore, understanding and managing water quality and pH is essential for optimizing nutrient availability and ensuring healthy plant growth. In contrast, while the other options may contribute to plant growth, they do not have the same direct and significant impact on nutrient availability as water quality and pH do. Fertilizer and temperature can enhance growth but are more about supplementation and environmental conditions rather than fundamental nutrient interactions. Soil movement and solubility affect the physical distribution of nutrients but do not inherently determine their availability. Soil amendments and fertilizer analysis are important for adding nutrients, but they rely on the existing conditions of pH and water quality for effective plant uptake.