Certified Landscape Irrigation Auditor

What factors determine available plant water?

1. Soil type and local rainfall

2. Soil type, water-holding characteristics, and root depth

3. Fertilizer application and soil moisture

4. Climate and irrigation method

The correct answer is: Soil type, water-holding characteristics, and root depth

The determination of available plant water is fundamentally influenced by several key factors, primarily soil type, water-holding characteristics, and root depth. Soil type plays a crucial role because different soil textures – such as sandy, loamy, or clay soils – have varying capacities to hold and retain water. For example, sandy soils drain quickly and have lower water-holding capacity, while clay soils retain water more effectively but may also limit root penetration. Water-holding characteristics refer to the soil's ability to retain moisture after it has been absorbed. This includes the soil's porosity and permeability, which affect how much water the soil can hold and how easily it can be accessed by plant roots. Root depth is equally important as it determines how much of the soil profile can be accessed by the plant for water uptake. Deeper roots can reach moisture that is unavailable to shallow-rooted plants, thus significantly impacting the overall availability of water for the plant. While other options mention relevant factors, they do not encompass the complete picture as comprehensively as soil type, water-holding characteristics, and root depth do. For instance, local rainfall and climate affect overall water availability but do not specify how water is available to the plants directly. Fertilizer can impact plant