Analysis:

To analyze the relationship between the NLP (Number of stems) feature and the grain yield of the soybean cultivar, we can make some assumptions based on prior knowledge regarding soybean cultivation. Typically, an increased number of stems in a soybean plant leads to higher grain yield. 

Based on this assumption, we can hypothesize that higher values of NLP will be associated with a high grain yield, while lower values may be associated with a lower grain yield.

Considering the above analysis, we can create the following dictionary:

```json
{
	"low": [1.0, 1.5, 2.0, 2.5, 3.0],
	"high": [3.5, 4.0, 4.5, 5.0, 5.5]
}
```

In this dictionary, we provide five possible values for NLP for each target class ('low' and 'high'). These values are represented as floats in the list.