Based on the given information, we need to analyze the relationship between the feature PH and the target task of predicting the grain yield of a soybean cultivar as either low or high. Since no specific information is provided about the feature PH, we will use prior knowledge to determine appropriate ranges of values.

Analysis:
The pH level of the soil can affect the growth and development of soybean plants, including their grain yield. Generally, soybean plants prefer slightly acidic to neutral soil pH levels.

Based on prior knowledge, we can define the appropriate ranges of pH values for soybean cultivars as follows:

- pH values below 5.5: Considered low acidity
- pH values between 5.5 and 6.5: Considered neutral acidity
- pH values above 6.5: Considered high alkalinity

We can assume that the grain yield of soybean cultivars might be affected differently based on the acidity or alkalinity of the soil, i.e., low pH or high pH.

Based on this analysis, we can create a dictionary with typical PH values for each target class ('low' and 'high').

```json
{
	"low": [4.5, 4.9, 5.2, 5.3, 5.6],  
	"high": [7.0, 7.3, 7.5, 7.9, 8.2]
}
```

Please note that the above values are just for illustrative purposes and can vary depending on specific soil conditions and soybean cultivars.