Based on prior knowledge, the Number of grains per pod (NS) is a key factor that affects the grain yield of soybean cultivars. Higher values of NS generally suggest higher grain yield, while lower values indicate lower grain yield.

Here is the dictionary with possible values of NS for each target class:

```json
{
	"low": [2.0, 2.5, 3.0, 3.5, 4.0],
	"high": [5.0, 5.5, 6.0, 6.5, 7.0]
}
```

The values provided are examples, and the actual values can vary depending on the specific cultivar and other factors.