Based on prior knowledge, PH (potential of hydrogen) is a measure of the acidity or alkalinity of a solution. In the context of grain yield for soybean cultivars, the PH of the growing environment can have an impact on the yield. 

To analyze the relationship between the PH feature and the task of predicting grain yield, we can assume the following ranges for the PH values:
- Low PH: pH < 4
- High PH: pH >= 4

Now let's create a dictionary with possible PH values for each target class:

```json
{
	"low": [3.5, 3.7, 3.9, 3.8, 3.6],
	"high": [4.1, 4.5, 4.2, 4.3, 4.4]
}
```

These values represent typical PH values for each target class ['low', 'high']. Please note that these values are just examples and might vary depending on the specific study or dataset used.