Based on prior knowledge, the number of stems (NLP) in soybean cultivars can be a useful indicator of grain yield. However, without specific information about the cultivar in question, it is difficult to determine the range of values for NLP that would correspond to low or high grain yield. To generate a dictionary with specific details, we will assume some arbitrary ranges for NLP values.

```json
{
	"low": [2.5, 3.0, 3.5, 4.0, 4.5],
	"high": [5.0, 5.5, 6.0, 6.5, 7.0]
}
```

Please note that these numeric values are only for illustrative purposes and may not correspond to actual ranges for a specific soybean cultivar. To provide a more accurate analysis, it is necessary to have access to detailed data and domain knowledge specific to the soybean cultivar under consideration.