How to Garden With Organic Fertilizers

Supply your plants with nitrogen from blood meal or well-rotted manure. Blood meal is a richer source of that macronutrient, but it doesn't improve air and water circulation underground as animal manure does. In general, incorporate 5 to 10 pounds of blood meal per 100 square feet 6 inches into the soil. If using manure, spread a 2- to 4-inch layer on your garden bed and work it in with a shovel or rototiller to a similar depth.

Apply bone meal, a rich source of phosphorous, to your garden to promote vigorous root development, but only if the soil pH is below 7.0. One application of 10 pounds of bone meal per 100 square feet releases phosphorous into the soil for up to four months. Incorporate bat guano labeled as "High P" into neutral and alkaline soil to provide phosphorous. Use 5 pounds per 100 square feet. Work either fertilizer 6 inches deep into the ground.

Add an organic source of potassium to your garden to boost your plants' immune system and to get perennials ready for the winter. Your options include compost, kelp meal and greensand among other products. Hardwood ashes from your fireplace also contain potassium, but they're only suitable if you need to lower your soil pH. In the absence of free ashes, compost is the most affordable potassium source. Incorporate a 2- to 4-inch layer 6 inches deep into the garden bed at planting.

Give your plants an organic supplement that provides micronutrients. Seaweed is a complete source offering trace minerals, amino acids and vitamins, as well as growth hormones. You usually find kelp-based seaweed fertilizers in liquid, powder and meal form. Mix kelp meal 6 inches below the soil at the rate of 1 pound per 100 square feet. Alternatively, water your plants to the root zone with dissolved kelp powder. Mix ¼ to ½ tsp. of the product with 1 gallon of water. Use liquid kelp as a foliar spray, blending 1 to 2 tbsp. with 1 gallon of water to mist your plants' leaves.