To analyze the relationship between the feature "PH" and the target variable "grain yield of this soybean cultivar," I will consider my prior knowledge about soybean cultivation. Generally, the pH level of the soil affects the availability of nutrients to plants, which can impact grain yield.

Based on my prior knowledge and experience, the appropriate ranges of pH values for soybean cultivation are typically around 5.5 to 7.5. I will use this range to assess the relationship between the pH level and grain yield.

Here is the generated dictionary showing the typical values of the "PH" feature for each target class "low" and "high":

```json
{
	"low": [5.5, 5.6, 5.7, 5.8, 5.9],
	"high": [7.1, 7.2, 7.3, 7.4, 7.5]
}
```

Please note that these values are just examples and should be adjusted based on the specific context of the soybean cultivar and the target variable.