Start this level by making a row next to as many firecrackers as you can.
At the moment the mushrooms are in the four corners. With a little luck the firecracker will jump into them and then more will fall down the main board.
Its not too difficult to get the firecrackers, but it is the mushrooms, if you don't get any for ages and definitely harder for the amount of crops.
I would suggest saving shovels to move obstinate crops that are in the way of a good row. Or for using them to hit a firecracker with if you are running out of moves.
Just remember to keep making rows next to the mushrooms so they will produce more.