Based on my prior knowledge, the number of stems (NLP) in soybean cultivars can have a significant impact on the grain yield. A higher number of stems usually translates to a higher grain yield. However, there are certain ranges of values that can be considered typical for low and high grain yield.

After analyzing the relationship between the NLP feature and the task, I have determined the following dictionary:

```json
{
    "low": [0.5, 1.2, 0.8, 0.7, 0.9],
    "high": [2.5, 2.1, 2.3, 2.7, 2.2]
}
```

These are example values and should not be considered as specific values for a particular soybean cultivar. The values provided above are meant to illustrate the typical range of NLP values for both low and high grain yield.