Today’s blog post comes to us from another grower in the Pacific Northwest. He wanted to know if the two predominant soil types in his field were giving him different crop sizes. Depending on the answer, he could change how he manages the eastern and western sections.

Raptor Maps deployed its Harvest Monitor on his field to find out. You can see the map of average potato diameter to the right. ​Each box is 1/4 acre (about 100 ft x 100 ft.). Red corresponds to smaller potatoes, while green corresponds to larger potatoes. For privacy, we have removed the surrounding satellite imagery and specific soil types that were present in the report.

​By looking at the map, you may notice that Soil B appears a bit more green, indicating larger potatoes. Is this a real phenomenon?

This is a graph comparing the two different soil types. The horizontal axis is the potato diameter, and the vertical axis is the percent of potatoes that were measured at that diameter.

But how do we know for certain that we’re seeing a difference? Raptor Maps used statistical methods to calculate a p-value for this grower. You can read about it here, but the gist is that a very small p-value is good, since it means the probability that you are seeing a difference by random chance is incredibly slim. In this case, the p-value was much less than 1%, meaning there is a greater than 99% chance that this difference is real.

What does it mean for his bottom line? Soil B yielded a 0.18″ larger diameter potato. That might seem small but it actually results in a 17% larger potato! Larger potatoes mean more money (see our previous post), so this grower can now optimize his time and inputs to maximize his return.