Non-Kenyan SL-28?

[luca]

Hi all,

Just wondering if SL-28 is grown in countries other than Kenya and, if so, how it turns out.

Cheers,

Luca

[Peter G]

On the Santa Ana (Ilamatepec) volcano in El Salvador is an area where a bunch of Kenyan coffee trees were planted years ago. This area is now a number of different farms, most famously including Finca Kilimanjaro owned by the Batlle family and immaculately managed by Aida Batlle. We don't know if the specific variety is SL-28; the variety is known locally as simply "Kenia".

The first time I tasted this coffee was during the first El Salvador Cup of Excellence. Gee Barger was preparing the samples and when we ground the coffees, I accused him of making a mistake- someone put a Kenyan auction lot among the Salvador COEs! The coffee was delicious, filled with blackcurrant fruit and sweetness. Of course, it turned out to be Kilimanjaro. This is the first time I really understood the impact of varietal on cup profile.

Over the years, I (and others) have gotten to know this coffee better, and it is not QUITE indistinguishable from a Kenyan coffee. It has a characteristic syrupy sweetness, which could be partially because there is some Salvador-style Pacas mixed in with the Kenias on the farm.

To me, this doesn't necessarily prove that SL-types will always taste like Kenyan coffees when grown elsewhere, though. The volcanic soils of Santa Ana may very well mimic the iron-rich soils of Nyeri. It is said in Kenya that an abundance of phosphorous is especially important in developing the signature blackcurrant note in great Kenyan coffees. Certainly, the altitude is similar between the foothills of Mt. Kenya and the slopes of Ilamatepec.

Kilimanjaro is purchased primarily by Solberg and Hansen in Norway (Solberg was the buyer of the COE lot that first year, and Aida and Andreas have maintained a great, mutually supportive relationship.) Stumptown was selling it roasted for a while this year, and Sweet Maria's sells it green if you would like to taste for yourself.

Meanwhile, there are also said to be SLs in Burundi, and I reckon there must be some scattered around much of East Africa.

Best,

Peter G

[SL28ave]

If in the future it is attempted to plant SL-28 elsewhere, it should go through a good quarantine system. Seeing as Finca Kilimanjaro happened decades ago, it's an obvious exception.

It is said in Kenya that an abundance of phosphorous is especially important in developing the signature blackcurrant note in great Kenyan coffees.

am going to verge off-topic...

I've heard that this soil might not be high in Phosphorus. I haven't figured it out. A starting data point might be in Cannell's 1974 article, "Tracer Studies with 32P on the distribution of functional roots of Arabica Coffee in Kenya"
He refers to another study that says that at Ruiru, at five sample points between soil depths of 15 and 180 cm., there is a range of 15.3-11.2 ppm of NH4F/HCL extractable P.

If somebody wants to put that into context, please do! I sure the heck can't.

I imagine (keyword: imagine) there might be something about SL28 itself that could make it relatively easy for it to suck P up to the fruits, which I wouldn't be surprised if Cannell wrote about elsewhere.

[Tim Dominick]

Generally Phosphorus doesn't exceed a few hundred ppB in fertile soil and levels around 50-100 ppB are considered abundant, so 11-15 ppM would be very high P.

Typically Phosphorus is absorbed by new growth on the root tips and plants can store and concentrate up to 1000x the amounts available in the soil itself. This hinges on proper soil bio-chemistry and since most phosphorus is inaccessible to plants it requires mycorrhizal and root-stimulated chemical reactions to break the phos into digestible chunks.

Perhaps uptake is better with SL-28, perhaps it stores it better? Phosphorus is very important to flowering and less so for foliage. Is there information about root development? It could be a variety that is constantly revitalizing the root tips, therefore better able to process P?

[SL28ave]

Very interesting, Tim!

Some great info on SL28 Phosphorus in a 1971 article by Cannell called "Uptake and distribution of macro-nutrients in trees of Coffea arabica L. (SL28) in Kenya as affected by seasonal climatic differences and the presence of fruits."

The article says something like 95% of total tree P uptake during ripening goes to the fruit. A large amount of P is diverted to the fruit from other parts of the tree. And, "Only P was 'stored' and remobilized within the tree in quantity. The branches were the principal 'storage' organ."

With that great info in mind, my questions are:
In what form is it 'stored' in the branches? In what form can it make it's way through a funiculus at various times through maturation? Metabolic pathways? How does all this compare to other kinds of coffee trees?

Is there information about root development?

Will look!

Back to your regular programming? (Sorry, Luca)

[SL28ave]

Generally Phosphorus doesn't exceed a few hundred ppB in fertile soil and levels around 50-100 ppB are considered abundant, so 11-15 ppM would be very high P.

Been reading up on the "11.2-15.3 ppm of NH4F/HCL extractable P". I'm pretty sure it came from a test called the Bray-1 test. Bray-1 measures the amount of available P in a soil, but the definition of "P availability" seems to vary widely. Bray-1 uses a specific dose of NH4F and HCl to measure immediately available P such as soluble phosphate or orthophosphate ions, semi-soluble P such as adsorbed P, and various forms of P bonded with Ca, Al and Fe. That's my amateur understanding.

Look at p.390
http://books.google.com/books?id=nANhao ... #PPA390,M1
The Olsen test shouldn't be way too far off from the Bray test. Basically, the critical level is the quantity of P below which crop yields will be much less. So, if one were to assume this data could be perfectly applied to the Ruiru data, then Ruiru's soil seem to have a medium amount of P, or perhaps optimum P. However, it is probable that there wouldn't be a perfect correlation between an Olsen test in PNG and a Bray test in Kenya.

Some critical levels of other crops:
http://web1.msue.msu.edu/imp/modf1/visuals/e2567v12.jpg

More evidence in table at bottom of this page:
http://www.ipm.iastate.edu/ipm/icm/2000 ... ablep.html

I'm concluding that the ideal soil Bray-1 for coffee is a smaller range within 5-25 ppM.

I'm still curious what the "ppb" test is; I am correct to assume it's a different test, right? Maybe it's a measure of P in the "soil solution", which is the liquid phase of soil? Maybe it's a measure of immediately available phosphate ions?

[SL28ave]

The internet blows my mind. Click the pdf file in the link to read about Ruiru:
http://library.wur.nl/isric/index2.html ... isric/6459

Section 4.5 says, "Phosphorus deficiency is notable in most parts of the survey area."
But the table shows an average of something like 15ppm P, but I'm not sure what the specific method was. The test was conducted by... Scott Laboratories.

[nick]

The test was conducted by... Scott Laboratories.

I was thinking the other day that we should start a rumor among newbie baristas that the "SL" stands for Scott Lucey.

[Tim Dominick]

I'm still curious what the "ppb" test is; I am correct to assume it's a different test, right? Maybe it's a measure of P in the "soil solution", which is the liquid phase of soil? Maybe it's a measure of immediately available phosphate ions?

It is a solution test and finds the immediately available Orthophosphate (PO4). I can't track down the name of the test but I emailed a friend who can provide more details.

P can be divided into three forms in soil: Solution, active and fixed.

Orthophospate is the solution segment and represents the smallest amount, generally a fraction of a pound per acre, and is the only group that can have plant uptake and the only group that has mobility within the soil.

The active phase represents the potential contribution. This can range from a few pounds to a few hundred pounds per acre. This group requires water and microorganism mineralization before plant uptake. This P has reacted with calcium to become semi-soluble and requires just a little mineralization to complete the transition.

Finally we have fixed P which can range from a few pounds to hundreds of pounds per acre. This is locked up and entirely unavailable to plants. This can represent unused P that was applied inefficiently and then turned into crystalline variscite and strengite as they bond with Al, Mg and Fe in the soil.

If all three are measured we may see very high levels but it is entirely possible that available P will be very limited.

Reading some studies that were done 20-40 years ago I noticed some things that will undermine soil health. One in particular referred to the use of paraquat, other fungicides and pesticides. Use of microbe-killing chemicals will alter the microorganism make-up in the soil, adversely altering the transfer of active-phase P to PO4. Since most fungicides and pesticides kill indiscriminately it is a very valid concern when we discuss plant health and P metabolism at the soil level.

P is one of the most over-applied fertilizers because very little effort is made to address overall soil health. Relying on Bray-1 is a bit like flying without instruments in fog, while it does measure active and solution P and PO4 it also finds P bonded with Al and Fe. The latter two are rarely made available to plants.