Measuring irrigation uniformity is crucial for ensuring that water is distributed evenly across a landscape, which affects plant health and water conservation. Among the choices, soil testing does not serve as a method for measuring irrigation uniformity. Instead, soil testing typically evaluates the soil's physical and chemical properties, such as nutrient levels and moisture content, which helps in understanding the soil's health and its ability to retain water, but it does not directly measure how uniformly water is applied across a specific area.
In contrast, methods like pressure mapping, visual assessment, and water audits are specifically designed to evaluate the distribution of water from irrigation systems. Pressure mapping assesses how the pressure variations affect water distribution, visual assessments involve observing the landscape to identify dry or overly wet areas, and water audits involve measuring the actual water applied to determine its efficiency and uniformity. Each of these methods directly relates to understanding how uniformly irrigation water is applied, making them relevant to the concept being tested.