The Gemoro near the bottom of 13a says that barley could not have grown from nothing to 1/3 growth in 5 days. The Gemoro then says that it could not even have grown from 1/4 or 1/6 to 1/3 in 5 days (but we must rely on Eretz Zvi).
My question is: maybe when the Jews came in to Eretz Yisroel, they found barley slightly less than 1/3 grown (e.g. 30% or 32%), and in 5 days it grew the small amount up to 33%!?
(In slightly different words: We are assuming that it is possible to tell when grain has reached 1/3 growth, and since the grain is continually growing, there must be a time before which people did not recognise 1/3 growth, and after which people did recognise 1/3 growth - maybe that time was during those 5 days).
Meir Eliezer Bergman, Manchester UK
This would also be considered Ketzir Nochri, as the amount that was grown by the Nochri is considered his grain regarding the Omer even after Bnei Yisrael would enter Eretz Yisrael (see Tosfos DH "v'Lo Ketzir" and Turei Even).
All the best,