Can I Make Organic Fertilizer?

Nitrogen Fertilizers

• A number of naturally-sourced fertilizers contain high levels of nitrogen, the macronutrient that makes up living cells and helps plants grow more quickly and produce better seeds, fruit and leaves. Plant sources of nitrogen include corn gluten meal, which contains 9 parts nitrogen and little to no phosphate or potassium (expressed as 9-0-0), cottonseed meal, with 6 parts nitrogen to 0.4 parts phosphate to 1.5 parts potassium and soybean meal, at a 7-2-1 ratio. High nitrogen bat guano rates at 10-3-1, while blood meal contains 12 parts nitrogen and few other nutrients. Fish emulsion has a 5-2-2 ratio, hydrolyzed liquid fish a 4-2-2 ratio, fish meal a 10-6-2 ratio and powdered fish a 12-0.25-1 ratio.

Phosphate Fertilizers

• Phosphate-heavy fertilizers provide phosphorus, an essential nutrient for successful photosynthesis. This nutrient encourages plants to grow strong root systems and healthy flowers. Many organic fertilizers contain higher concentrations of nitrogen and potassium than phosphate, but there are a few options to help balance phosphates in the soil. High phosphorus bat guano contains 3 parts nitrogen for every 10 parts of phosphate and 1 part potassium. Bone meal has a nutrient ratio of 3-15-0, and fish meal is relatively high in phosphates at 10-6-2. Gardeners can also use colloidal or soft rock phosphate, which contains about 20 percent total phosphate and 2 to 3 percent available phosphate. Over time, this material releases more phosphorus into the ground.

Potassium Fertilizers

• According to the North Carolina Department of Agriculture & Consumer Services, plants absorb potassium in larger amounts than any mineral nutrient other than calcium. This element helps plants build protein and improve fruit quality. Kelp powder is one fertilizer ingredient that's relatively high in potassium, at a ratio of 1-0-4. Alfalfa meal may also be used, as it contains 2 parts nitrogen and potassium for every 1 part phosphate.

Considerations

• One basic balanced fertilizer calls for 4 parts cottonseed meal, 1 part dolomitic lime (a source of calcium and magnesium), 1/2 part bone meal or 1 part soft rock phosphate, and 1/2 part kelp meal. This relatively simple recipe makes a balanced organic fertilizer, but not all plants need balanced nutrition. For instance, while lettuce requires a very balanced 10-10-10 fertilizer, according to Missouri State University Extension, tomatoes need fertilizers low in nitrogen but high in phosphates and medium to high in potassium. The university recommends an 8-32-16 or 6-24-24 ratio for these plants. Mix your fertilizer as appropriate for the crops you wish to grow.