Keeping an organic garden means avoiding harsh, synthetic chemicals, but having some sort of plant fertilizer is still important. An organic garden means that most commercial fertilizers are out of the question for your garden. Luckily there are many choices available for the organic gardener, including bone meal, guano, fish emulsion and kelp. Fertilizers are best placed in healthy soil, so your fertilization plan should begin with compost.
Choose an area close to your kitchen but far from your deck and entertaining areas, and built an enclosure for your compost. Place grass clippings, kitchen waste, raked leaves and other organic material on your pile and layer with dirt. Turn over the pile periodically, to ensure that materials are decomposing at an even rate. Apply your compost to your garden before planting, and turn the compost into the dirt. This will allow your garden soil to retain water, and absorb nutrients from your fertilizers.
To be healthy, plants need nitrogen, phosphorus and potassium. Before you plant your garden, take a sample of your soil (with your compost worked in) to your garden store and ask the professionals to run a chemistry sample on your soil. This will alert you if your soil is naturally deficient in one of these nutrients. If so, you'll need to correct the soil with fertilizer before you plant.
Before you purchase organic fertilizer, look for the chemical makeup on the packaging. The ratio of nitrogen, phosphorus and potassium will be listed in order, separated by dashes (N-P-P). Nitrogen promotes leaf growth, phosphorus promotes flower and fruit growth and potassium helps the plant resist disease.
To boost the phosphorus levels in your garden, consider bone meal. This powdered fertilizer is widely available, and is easy to sprinkle onto the soil and work in with a trowel. Rock phosphate is another natural source of phosphorus.
Nitrogen levels can be increased with alfalfa meal, blood meal, canola meal and bat guano. While fresh manure is also high in nitrogen, the high levels can burn some plants (and the smell can offend some neighbors). Alfalfa and bat guano are more pleasant options.
To increase potassium levels, consider kelp meal. This brown seaweed works well to boost the growth of flowers, in particular. Greensand will also increase potassium.
Organic fertilizers are designed to break down and be absorbed by plants slowly. By using organic fertilizers, you can reduce the amount of time you spend applying fertilizer. Many organic gardeners only apply fertilizer once before planting and once mid-season.
To provide your plants with an extra boost during flowering and harvest times, apply liquid fertilizer. You can place fish emulsion or kelp extract into a sprayer and apply it directly to the leaves of your plants. This form of fertilization (called foliar feeding) allows the plants to absorb the nutrients directly, without any intervention into the soil. It's best to do foliar feeding early in the day, so the leaves have time to absorb the nutrients and dry off.