I have been thinking about the argument between Ula and R. Yochanan. To Ula, if one has a fruit bearing tree within 16 amot [cira 16 yards] of the border of his field with his neighbor he can not bring first fruits because he is a thief. To R.Yochanan he can. At first Rav Shach said the argument is who owns the fruit. To Ula the source of the sustenance is what matters, while the tree itself is just to process the sustenance, So the fruit belong to who owns the ground. [And so in our case the roots of the tree get sustenance partly from the nearby ground partly from that of his neighbor.] To R. Yochanan the owner of the tree owns the fruit. Later Rav Shach brought a different explanation of Ula.The reason is that he shows the roots of the tree up until 16 amot are owned by the owner of the tree. This he sees as a contradiction to what he wrote before. This point has eluded me for weeks already.
If the roots are owned by the owner of the tree., what has that to do with the fruit?
I am being a bit short here, for this is really based on Rabainu Chananel
