Based on prior knowledge and understanding of the feature "IFP" (plant height) and the task of predicting grain yield for a soybean cultivar as low or high, here is the requested analysis and dictionary:

- Analysis:
Plant height (IFP) is likely to have a positive correlation with grain yield. Generally, taller plants tend to have higher yields. However, there could be a range of optimal plant heights beyond which the yield might decrease due to factors like lodging or nutrient availability. 

- Dictionary:

```json
{
	"low": [15.2, 16.5, 17.3, 18.1, 19.4], 
	"high": [25.7, 26.9, 27.8, 28.6, 30.2]
}
```

Note:
The above values are just examples and should be interpreted as possible values within each target class. These values are not based on actual data, but rather fictional samples to demonstrate the format and fulfill the request.