Based on my prior knowledge, the pH of the soil can have a significant impact on soybean grain yield. Generally, soybeans prefer a slightly acidic to neutral pH range of 6.0 to 7.5. pH levels lower than 6.0 may indicate acidic soils, while pH levels higher than 7.5 may indicate alkaline soils.

To analyze the relationship between the feature "PH" and the target variable "grain yield" (low or high), we can make some assumptions:

1. For the "low" grain yield class, we can expect the pH values to be within the range of acidic soils. Let's assume a pH range of 4.5 to 6.0 for the "low" class. 

2. For the "high" grain yield class, we can expect the pH values to be within the range of slightly acidic to neutral soils. Let's assume a pH range of 6.0 to 7.5 for the "high" class.

Based on these assumptions, I will create a dictionary with typical pH values for each target class:

```json
{
	"low": [4.5, 4.7, 5.1, 5.8, 6.0],
	"high": [6.0, 6.5, 6.8, 7.0, 7.5]
}
```

Please note that these values are just examples and should be validated with actual data or domain expertise for a more accurate analysis.