Shevi'is, Chapter 2, Mishnah 2. The Mishnah opens: "Hatomen es haluf ba'shevi'is" - a person who buries luf in the ground, luf being a species similar to an onion. This burying is done during the Shemittah year, since it was the practice of people to store onions and similar species in the ground, and this was one of the accepted ways of preserving them.
The reason for the conditions the Sages established:
One may not bury the luf when it is spread out over the entire field, because that looks like planting anew during Shevi'is. Therefore measurements were set for the manner of burying, from which it is evident that the whole purpose is storage alone and not planting.
The view of Rabbi Meir:
"Lo yifchos mi'sa'sayim" - one may not bury less than two se'ah in the ground, which are twelve kavin, that is, a large quantity together.
"Ad govah sheloshah tefachim" - the thickness of the pile should be three tefachim.
"Ve'tefach afar al gavav" - and afterward he places a tefach of earth on top of the luf.
Only with such a large quantity, in Rabbi Meir's opinion, is it clear to everyone that this is not a planting of the luf but storage alone.
The view of the Sages:
The Sages hold that such a large quantity is not necessary:
"Lo yifchos me'arba'ah kabin" - four kavin are enough, which are a third of the measure specified by Rabbi Meir (twelve kavin).
"Ad govah tefach" - with regard to the height as well, and the area the pile takes up in the ground, the measure is only a third of Rabbi Meir's view, who said three tefachim.
"Ve'tefach afar al gavav" - on this point the two Tannaim agree: the amount of earth placed on top of the luf is a tefach, the same measure that Rabbi Meir stated.
The place of burying:
The Mishnah concludes: "Ve'tomnan bimkom derisas adam" - the luf must be buried in a place where people are accustomed to tread, and this is in order to ensure that it will not sprout: the treading of feet there prevents it from growing.
In summary: in this Mishnah we learned the laws of burying luf in the ground during the seventh year for the purpose of storage, and the conditions that were set so that it would not appear to be planting: according to Rabbi Meir - two se'ah, at a height of three tefachim with a tefach of earth on top; and according to the Sages - four kavin, at a height of a tefach with a tefach of earth on top. We also learned that the burying is done in a place where people tread, so that the luf will not sprout.