What type of sampling method is essential for accurate soil test results?

Random sampling is essential for accurate soil test results because it ensures that samples are collected from various parts of the field without bias. This method helps to capture the variability in soil properties throughout the area, providing a representative snapshot of the soil's nutrient status. By avoiding selective sampling, random sampling reduces the risk of skewed results caused by unusually high or low nutrient concentrations found in localized areas, which might not reflect the overall conditions of the field.

In contrast, visual sampling involves making decisions based on what is observed, which can lead to biased results. Combined sampling and targeted sampling have their uses, such as focusing on specific areas or combining samples for a bulk test, but they do not ensure a broad representation of the field's overall nutrient conditions like random sampling does. Thus, for reliable soil test results that can guide nutrient management decisions effectively, random sampling is indispensable.