Based on the given feature description and task, it appears that we are trying to determine the relationship between Repetition (a numeric variable) and the grain yield of a soybean cultivar. 

To analyze this relationship, we can look for patterns or trends in the Repetition values associated with low and high grain yield. However, since the provided feature description does not explicitly mention the range of possible values for Repetition, we will assume a range of values based on prior knowledge.

Once we have identified the appropriate range of values for the Repetition feature, we can then identify specific values that are typically associated with low and high grain yield. Based on these findings, we can create a dictionary as requested.

Here is an example of a dictionary with the specified format, assuming a range of 1 to 10 for Repetition:

```json
{
	"low": [1.5, 2.3, 3.8, 4.1, 5.2],
	"high": [7.9, 8.6, 9.2, 9.8, 10.0]
}
```

Please note that the values provided above are just examples and may not accurately represent the actual relationship between Repetition and grain yield for soybean cultivars. Additional analysis and data would be required to obtain more accurate results.