If you want to use more natural products and save money at the same time, you can make your own organic fertilizer and compost with little work. By creating a compost pile, you will also reduce the amount of household waste you drag to the curb every week for the garbage collector to haul away, and you'll be helping our over-filled landfills at the same time.
Take a Hint from Your Great Grandparents
Before the advent of large chemical companies, all farmers made their own fertilizer. From collecting animal manure to allowing plant parts and household food scraps to decompose into a rich, earthy, loam substance, our ancestors as long as 10,000 years ago never needed to go to the store to buy fertilizer of any kind. That wasn't an option. They lived a much more sustainable lifestyle than we do today and they wasted nothing.
Compost Is Fertilizer
When plants and foodstuffs break down, they form nutrients that are beneficial to cultivated plants. Creating compost was not only common, but also practiced by all farmers before the 20th century. We create compost instead of simply digging food waste directly into the soil because that method will take needed nitrogen out of the soil, whereas composting adds nitrogen. It not only provides nutrients to the plants to which you apply it--compost also improves soil texture and quality.
Animal Manure Is Strong Fertilizer
Animal manure of many types---cow, horse, pig, rabbit and goat---contains strong nutrients such as nitrogen, phosphorus and potash, among others. When you use animal manure as fertilizer, allow it to rot, or decompose, in a compost pile before you spread it around your plants. You can also make a fertilizer "tea" by mixing animal manure with water and then watering your plants with it. This way, you can use it right away and not have to wait for it to decompose. Do not use pet feces for fertilizing any plants.
Worm Castings Are Good for Houseplants
Compost worms are easy to raise, even in an apartment, and work well to fertilize houseplants. Special worms are used for worm castings---they are called red wiggler worms. Regular nightcrawlers are not appropriate for a worm compost system. You can make a worm bin out of plastic storage bins into which you drill holes and stack. Feed your worms kitchen scraps and give them "bedding" of damp newspaper strips. Within two or three months, you'll harvest a nice amount of rich, non-smelly worm castings, which you can mix with water to feed your plants.
Fish Emulsion Is One of the Best Fertilizers
If you recall your grammar school education, the Native Americans in the eastern U.S. taught the pilgrims how to place a fish in the planting hole of their corn stalks and other crops. This was a simple way of providing the nutrients that fish contains to the growing crops. Today, we can buy bottles of fish emulsion at any garden center, mix it with water in the correct proportions, and use it to nourish our plants. Although you probably won't need to make your own fish emulsion, it is made by mixing fish parts with water and then straining it before use.