As I have mentioned before, one of the most common finds at estate sales is gardening chemicals. Just today, for instance, we picked up a big bag of E.B. Stones’ Sure Start. You can frequently pick up different fertilizers really cheaply. Often times when you come around to using this fertilizer, you will find them with numerous lumps that have hardened because the bag wasn’t securely sealed. These lumps are dangerous to use because they concentrate too much fertilizer in a small soil area and “burned” plants can result. If you save one of the plant nursery trays that are in a fine grid, you can use it to screen off those lumps. Then if you put those lumps on pavement, you can give them a good stomping to reduce them to a granular form. Sweep up the remains and you have perfectly good fertilizer.
We also keep a good supply of these small grid trays to shade new plantings. It seems that the new planting of irises always occurs during the hottest weather of the year.
By the way, I have heard that plants growers are shifting over to rectangular trays. So you might hop to it in your quest for an old square one that you can use as a sifter.
Stan, The Lumpless Man
Nursery flat used to sift fertilizer clumps