Mechusar Ketzitza

Unfortunately, I haven't had an internet connection for a few days so I've been off. But now it's back up so I am back to work.
The gemara in Gittin 21b states that one cannot write a get on mechubar l'karka, and then cut off the get and give it to the woman. Rashi explains that it says in the pasuk "v'kasav v'nasan", that one has to immediately be able to give the get after writing it, whereas if he writes the get on mechubar l'karka, so he will have to "cut" it after the writing, and then give it. This psul is referred to as "mechusar ketzitza".
The Ramban in Gittin brings a Yerushalmi that brings a different drasha of "sefer", that it's not called a "sefer" if it is written on mechubar l'karka. The Ramban has an interesting language where he says that acc. to the Yerushalmi that darshans "sefer", so it would not be a problem of "mechusar ketzitza" if one would simply write the get on a tree and give the woman the tree and the land (rather it would only be a problem on not being a "sefer"). What's interesting about the language is that the Ramban says to give the woman the tree and that land, why not simply say the land?
A possible answer to this could be that the Chiddushei R' Shmuel writes in Kiddushin Siman 4 that if one holds that kinyanim don't work by get (as the Ramban seems to hold in Gittin 77b) so one cannot simply give land to the woman as a get, because it's not a "nesinah", and the pasuk says "v'nasan". However, see the Chazon Yechezkel in Tosefta Gittin 2:6 that some hold that mechubar l'karka (like a tree) are dragged along with the kinyan karka similar to placing a get in a chatzer and then being makneh to the woman the chatzer. This would work even in the Ramban and explains why the Ramban focuses on a tree attached to the land. There are a number of other issues related to these drashos of "sefer" and "mechusar ketzitza", but we will save this for some other time.