 3 things in your kitchen that make natural fertilizers 1. Egg shells The calcium carbon in the crushed eggshells can help your soil's pH Plus, the shards from the shells help keep pestle wet 2. Coffee grounds The nitrogen in coffee grounds helps other materials within soil turn into compost They can also help acidify your soil 3. Banana pills They are a natural source of potassium, magnesium, and sodium, which is super beneficial for plants and gardens