Actually it has already been found out and is in the turnip guide.
"The 'long turnip' trick:
This trick is when peach consistently grabs a turnip, and does many standard smash throws at an opponent, then regrabs the turnip with a standing A, what happens is that the distance from which peach begins to be able to reclaim the turnip is quite far. It gets to the point where Peach can throw the turnip off the edge and then reclaim it by pressing 'A'
The way this works is that turnips have a grabable hitbox, when you throw a turnip and it hits the enemy, for whatever reason, the grabbable hit box (which starts off roughly slightly bigger than the turnip) will double in size, meaning that you wont need to be as close to it to grab it again. Every successive throw keeps doubling the hitbox in size, where soon the turnip's grabbable hit box takes up half the screen (thus allowing her to throw it off the edge and reclaim it) unfortunately, the turnip usually expires at this point, so it has no practical use. Mr saturn works in a similar fashion, but the hit box grows in size very slowly."