Atzitz Nakuv on Yesaidos

The Rambam in Hilchos Shabbos 8:4 says that if one lifts a mound of dirt with grass in it on shabbos from the ground and places it onto poles he is chayav due to tolesh.
Tosafos in Gittin 7b writes that this chiyuv is only d'rabbanan because an atzitz nakuv (a pot with a plant in it that has a hole on the bottom) is really considered mechubar (attached to the ground) m'dioraysa. So too, if you were to lift this mound of dirt up and place it on poles it would be no worse than atzitz nakuv and would still be mechubar m'dioraysa. Thus, the chiyuv for telisha according to Tosafos is only d'rabbanan. The Rambam however uses the word chayav. This indicates that the chiyuv is d'oraysa acc. to the Rambam and indicates that the Rambam holds that atzitz nakuv on yeseidos is considered talush (detached from the ground) on a biblical level. Therefore, the Rambam holds that one is chayav m'doraysa in this case.
There is a mishna in uktzim (2:9) which states that a kishus (type of vegetable) that is planted in an atzitz and grows outside the atzitz is tahor. The idea is that it is tahor because it has a din of mechubar l'karka. From the Rambam in his peirush hamishnayos it is clear that it is tahor because the atzitz is nakuv and that is what makes it mechubar l'karka. In the Rambam in Tumas Ochlin 5:9 it further becomes clear that it is only considered mechubar because it is resting on the surface of the ground. Had the atzitz been raised in the air it would not be mechubar. This Rambam is l'shitaso that atzitz nakuv on poles is considered talush.
The Rash on the mishna, however, states that that its only the part of the vegetable that is overgrown outside the pot that is mechubar. The rest isn't (because he learns the atzitz isn't nakuv - i.e. there is no hole in it). The Raavad in his hasagos argues the same. This is because they hold like tosafos that atzitz nakuv on yeseidos is considered mechubar.
This summary can be found in the chidushei hagrach stencils under atzitz nakuv al gabay yesaidos.
Interestingly, R' Chaim there mentions another way acc. to the Rambam that the atztitz can be considered mechubar, even without a hole. This would be in a case where the atzitz has no "shem kli". Let's say for instance that it was so filled with earth that it was mevatel the shem kli. Then the atzitz becomes batel to the earth and it has a din of mechubar.
Acc. to the Rambam that atzitz nakuv on yesaidos is considered talush we can ask what the din would be in terumos and maasros. The pashtus is that it would not be chayav in tru"m midioraysa, because it is like talush. A priori, it is similar to a atzitz sheaino nakuv (without a hole) that is only chayav on a drabanan level.
There are many different Rambam's to bring on this issue, but for now we will just state that R' Chaim proves otherwise in the Rambam. He concludes that the Rambam would hold that atzitz nakuv on yesaidos is chayav in tru"m on a d'oraysa level even though it has a din of talush. The question is why?
R' Chaim explains this with his classical approach. There are two separate dinim. There is talush and mechubar. And then, there is gidulo min haaretz. By terumos and maasros you don't need the food to be mechubar l'karka, attached to the ground. Rather, you merely need it to derive yenikah min hakarka... it has to get its sustanence from the ground. This is a totally separate category from mechubar which applies in hilchos shabbos in the laws of telisha.
However, R' Chaim leaves off with a question, because he assumes that in a regular atzitz nakuv the dirt itself would certainly not be considered mechubar l'karka... only the plant would be. Thus it should be a food that grew in bothe aretz and chutz laaretz and be tevel and chullin mixed together. Basically, R' Chaim could not accept the fact that the dirt in the atzitz would ever have a din of mechubar and thus ran into problems.
I found that the ri malki tzedek in challah 2:2 in fact holds that the dirt can have kedushas haaretz. See also the afikei yam in chelek 2:43 that says the same idea.
I see in my notes quite a bit more on this subject which I will hopefully be able to write on some other time.