comes up in the provided link in association with potatoes, but merely a wild guess on my part

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Note added at 16 mins (2008-06-21 15:11:32 GMT)
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http://isis.ku.dk/kurser/blob.aspx?feltid=160460

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Note added at 38 mins (2008-06-21 15:33:51 GMT)
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or is this simply something like "these three portions"??

German term (edited): Drillingsfraktion

As far as I understand, the three categories being distinguished are as follows:

Normalsortierung
Drillingsfraktionen
Bio-Pflanzen

And the text makes it clear that there are no premiums for the second and third categories (although one might expect this, since one might regard them as 'premium' categories).

I don't really know what you call these potatoes in English, but I used to work in a cafe where we served a specialty from the Canary Islands that we made using small potatoes, which we bought specially for this. I think we ordered them as "size class: extra small" or something, but we sold them as "mini-potatoes".

Drilling can also mean seeding, the term seed drill also exists in English, and therefore I think the Drillingfraktionen are the small "Grade B" (as opposed to the Grade A size) potatoes that are sorted out when potatoes are graded. The Grade A yield is the so-called marketable yield and the B yield is generally unmarketable, except in specialty markets for mini-potatoes; however, they can also be used as seed potatoes (assuming the crop has been grown virus-free). Of course seed potatoes is somewhat of a misnomer, as they are actually tubers and not true seeds, however, the term is correct. Incidentally, larger potatoes are also used as seed potatoes; they are cut and allowed to cure (cork over) and in this case are referred to as seed pieces. Factors such as the soil type, climate, rainfall, etc. determine to a large extent what is used or preferred (B grade or cut seed/seed pieces).
There is also a cull category in potato grading; they are tubers too small for anything and considered trash.