Final answer:
The dominant limitation in the soil on John's land is erosion problems.
Step-by-step explanation:
The dominant limitation in the soil on John's land, according to the test results, is erosion problems.
Soil erosion can occur due to factors such as topography and climate, which can strip away parent material and affect plant growth. Erosion can lead to thinner soils and loss of fertility, making it difficult to cultivate crops.
Additionally, the information provided states that agricultural production in many places has been associated with soil erosion and land degradation, further supporting the idea that erosion is a major limitation in soil for agriculture.