Whether you enjoyed studying chemistry in your scholastic past or not, there is a method for making good fashioned organic fertilizers, for all experience levels. Because, as the saying goes, “you are what you eat,” you’re also, “that what you eat as well.” Clearly it’s a good idea to start participating more in what your plants are consuming. Here are a few tips to get you started.
Fertilizer, organic or synthetic, is a substance that provides specific nutrients plants need to grow. Fertilizers contain two categories of nutrients: macro-nutrients, namely calcium, magnesium, sulfur, (and the most common) nitrogen, phosphorus and potassium (displayed on fertilizer bags as NPK) are all required in large concentrations. Whereas, micro-nutrients, such as chlorine, boron, iron, copper, manganese, molybdenum, and zinc are only needed in trace amounts.
What differentiates an organic fertilizer from a synthetic or inorganic fertilizer is where the nutrients come from. Synthetic fertilizers are usually made by chemical reactions that produce ammonia, the basic building block used for the synthesis of other needed compounds. Inorganic fertilizers can also be made from natural sources, like rocks and minerals.
Organic fertilizers are made from materials derived from animals or plants. Plant based nutrient providers include: compost, alfalfa meal, cottonseed meal, soybean meal, wood ash, kelp and seaweed. Animal based nutrients include: worm castings, livestock manure, bat guano (don’t ask), fish meal, blood meal, and bone meal.
Pros of organic fertilizers
They release nitrogen slowly, giving the plants a more stable and steady growth period.
They promote natural nutrient storage mechanisms in the soil, giving your microorganism’s food storage, longevity (which means you’ll need to fertilize less often).
Organic fertilizers help the soil to retain more moisture, thus reducing the need to water.
Organic materials help to maintain the structure of the soil and prevent soil erosion.
Cons of organic fertilizers
They can easily contain pathogens and other disease causing organisms (if not properly composted) with potentially harmful effects on humans, animals, and plants.
Their nutrient contents are variable and complex, and require greater management, as the specific nutrients release may not be in sync with your plants’ current developmental needs.
Unlike the more user friendly synthetic fertilizers getting the right ratio of organic nutrients for your specific soils requires testing of the soil. 
The most effective way to measure your fertilizer needs is to start with an evaluation of your soil. You can take a sample and send it to a lab for analysis or purchase a more general at-home test from your local nursery. This will tell you what nutrients you have, and which ones your garden is lacking and the appropriate additives you’ll need.
But, before we look at some DIY fertilizer recipes, it is important to address two techniques used to maintain nutrients in the soil – crop rotation and cover crops. Both of which are a highly recommended practices to accompany any fertilizing routine.
Crop rotation helps manage soil fertility and also assists in avoiding or reducing problems with soil-borne diseases and aggressive soil-dwelling insects. Different crops have different nutrient requirements and affect soil balance differently. A general guideline for regulating soil nutrients is to avoid planting the same general category of crop (leafy, root, and legume) back-to-back in the same location. For example, it is recommended to follow nitrogen-fixing legumes with nitrogen-craving leafy crops. And follow heavy feeding crops, like tomatoes, with light-feeding root crops, like potatoes.
Another way to participate in the natural cycle of nutrients in your soil is the use of cover crops, such as clover – which takes nitrogen from the air and puts it back into the soil. Planting a cover crop will help suppress weeds, build a productive, fertile soil, and assist in managing water, pests and diseases.
Although there is no quick remedy for plant health problems, caused by poor soil health, improper plant selection and management, these handcrafted fertilizers will nevertheless act as a stable bridge between Big-Ag dependency and empowered self-reliance. The awareness of your plants’ chemical needs alone will make your gardening experience more fruitful and mindful. Remember what you feed your plants, you feed you and your family!
Do-it-Yourself Fertilizers Recipes
1. Compost Tea
Caution: Be sure to use finished compost. Unfinished compost may contain harmful pathogens, and compost that is too old may be nutritionally deficient.
Fill a 5 gallon bucket 1/3 full of quality finished compost.
Fill with water to a few inches below the top.
Let the mixture steep for 3-4 days.
Stir the tea as often as you can.
Strain the mixture, through cheesecloth or any other porous fabric, into another bucket. Add the remaining compost to your garden or put it back in your compost bin.
Dilute the remaining liquid with water using a 10:1 ratio of water to tea. (Your watering cans contents should have the look of a weak iced tea.)
Fertilizer the soil or use with a foliar sprayer and spray the leaves.
2. Grass Fertilizer
Grass Fertilizer is rich in nitrogen, oxygen and phosphorus. Caution: Be careful not to use grass treated with herbicides. 
Fill a 5 gallon bucket 2/3 of the way full with fresh grass clippings.
Fill with water to a few inches below the top.
Let it sit and steep at room temperature for 3 days, making sure to stir it once a day.
Strain the liquid off.
Dilute the “tea” with equal parts water.
Fertilizer the soil or use with a foliar sprayer and spray the leaves.
3. Fish Tank Water Fertilizer
Your used fish tank water contains nitrogen and other nutrients that plants require. Caution: Make sure that you remove all your little fish friends first. Do not use the contents from a saltwater tank.
Use the dirty (untreated) water from your fish tank to water your plants.
Smile, knowing that you’re doing your part to return water to the earth.
4. Vinegar Fertilizer
The acetic acid in vinegar works great for acid-loving plants and can be used to replace houseplant fertilizer and rose plant food.
Combine the 1 tbs white vinegar and 1 gallon of water.
Water your plants.
Repeat about every three months.
5. Fireplace Ash Fertilizer
Fireplace ash fertilizer is a great source of potassium and calcium carbonate and will replace your need for lime (if needed). Caution: Do not use fireplace ash around acid-loving plants or if your soil is alkaline.
Place fireplace ash over your garden beds, and massage it into the soil.