Based on my prior knowledge, the feature "IFP, plant height" can be related to the grain yield of soybean cultivar as follows:

1. Low IFP values (short plant height) may indicate stunted growth and potentially lower grain yield.
2. High IFP values (tall plant height) may indicate healthy and vigorous growth, potentially leading to higher grain yield.

With this understanding, let's create a dictionary that includes typical values of the feature "IFP" for each target class, namely 'low' and 'high'.

```json
{
	"low": [10.5, 11.2, 12.1, 9.7, 10.2],  
	"high": [18.9, 21.3, 20.5, 19.8, 22.1] 
}
```

In this example, the values presented are just hypothetical and should be replaced with actual values based on the relationship between IFP and grain yield in soybean cultivars.