Here are some of the results I've compiled of our large project classifying soil types and investigating the influence of soil, climate, and varietal on cup quality in Puerto Rico.
These graphs and comments are part of a much larger report, with databases and maps, which will be released soon. Just a little preview, which I hope you find interesting. The purpose of this project is to help farmers improve quality and prices in Puerto Rico. All the data collected, and all of the analysis, will be published and distributed to farmers (in Spanish and Enlgish), so that they can put our findings into action for their own benefit.
How did I arrive at these data points? The altitude and varietal information was provided by the USDA researchers in Puerto Rico. Each sample was collected individually, and sample collectors made a GPS recording on-site, standing next to the trees from which the cherries were taken. These readings include latitude, longitude, and altitude above sea level. The cupping scores are the result of a week of extensive blind cupping done by a team of Q-graders (myself included) in California, in May. Each sample was cupped multiple times, in random order, and the scores you see here are means taken from all the individual scores recorded.
The portion quoted here refers to other sections of the document which are not publicly available yet. Sorry, you'll just have to wait!
(click on graphs to embiggen)
There is a strong correlation between the quality of the samples and the altitude at which the coffee was grown at. As one would expect, generally speaking, the higher the coffee was grown, the higher it scored on the cupping table. This is one of the strongest relationships we found in all the data.
While not all of the high-grown coffees were in the very upper echelon of cupping scores, most of them were. And the relationship is even stronger at the low end of the spectrum. All of the lowest scoring coffees belonged in the lower altitude categories.
The following graph illustrates the relationship between coffee quality and altitude, across all varietals and soil types:
This graph shows an average gain in quality of just over 2 points from the lowest altitudes to the highest.
Altitude by varietal
One of the most interesting findings in all of the data we collected and analyzed was that improvements due to altitude were much stronger when certain varietals were used. This leads us to the conclusion that producers at higher altitudes would benefit even more by switching to the preferred varietals.
Once again, the average improvement (shown above) for higher altitudes was just over 2 points.
The next graph shows what that improvement looked like when we limit the analysis to just limaní, fronton, and catimor (three low-scoring varietals):
We can observe the same general upward trend that we saw in the comprehensive data set. However, if we read the graph closely, we can observe that the improvement is much less dramatic. In fact, there is barely 1 point of quality improvement in over 2000 feet of altitude increase. Producers who plant these varietals (fronton, limani, and catimor) at high altitude are not receiving the full benefit of their natural altitude advantage.
Let us now contrast this with the data from a different subset, using the high-scoring varietals pacas, bourbon, and caturra.
Once again, we see the expected increase in quality as altitude increases. However, in this case, the increase is far more dramatic. The low-altitude coffees score just above 80 points. But the high-altitude coffees are nearly at 84. That is nearly a 4 point gain in cup quality due to altitude, the kind of quality gains that tend to bring much higher prices in the specialty market.
Producers who are planting pacas, bourbon, and caturra at high altitude are getting a much better return on the natural advantage of high altitude.
Conclusion: As we saw in the first section, all coffee producers can expect an increase in quality by switching to higher-quality varietals. However, this switch is even more crucial for higher altitude producers. The higher the altitude, the more benefit producers can see from using these better varietals. Producers who plant lower quality varietals at higher altitudes are missing out on the huge benefit that altitude can provide.
More to come...