Remove drop of a crop when breaking the farm land.

Hey! Here's what I want to do: When you break a beetroot crop, I only want the crop to drop beetroot seeds. But I discovered that when you break the farmland under it, it drops a beetroot. Here's what I came up with, but it dosen't seem to work.

Code:

    public function onBreak(BlockBreakEvent $event){
        $block = $event->getBlock();
        $player = $event->getPlayer();
        $level = $player->getLevel();
        $under = $block->add(0, -1, 0);
        $above = $block->add(0, 1, 0);
        if ($block->getId() == Block::BEETROOT_BLOCK and $block->getDamage() >= 4) {
            $event->setDrops([Item::get(458, 0 , mt_rand(1, 2))]);
            $event->setDrops([Item::get(457, 0, 0)]);
        }
        if ($block->getId() == 60 and $block->getLevel()->getBlock($above)->getId() == Block::BEETROOT_BLOCK and $block->getLevel()->getBlock($above)->getDamage() >= 4) {
            $event->setDrops([Item::get(458, 0 , mt_rand(1, 2))]);
            $event->setDrops([Item::get(457, 0, 0)]);
            $event->setDrops([Item::get(3, 0, 1)]);
        }
 

60 is the id of a farm land block by the way.
Sorry for my bad english, I am french.