Organic fertilizer is good for gardens, lawns, landscaping and houseplants. There are a large array of ingredients available for mixing your own organic fertilizer. Many of these add the basic fertilizer components of nitrogen, phosphorous and potassium to your garden soil, but many organic fertilizer components do much more than that, adding trace minerals and humus material to improve soil tilth, fertility and drainage.
Nitrogen, Phosphorous, Potassium
All fertilizers begin with the three primary components necessary for plant growth: nitrogen (N), phosphorous (P) and potassium (K). All three are necessary building blocks for plant growth, flowering and, in the case of vegetables, setting fruit. Soybean and other seed meals include all three, with a particular emphasis on nitrogen, and also add organic matter to the soil.
Organic fertilizer ingredients high in nitrogen include fish emulsion, coffee grounds and blood meal. High-phosphorous ingredients for organic fertilizers include bonemeal and the slower-acting but more complete rock phosphate.
Potassium may be added to organic fertilizers from wood ashes, granite meal or kelp meal and other seaweeds, which are also rich in a large number of micronutrients.
Trace Minerals and Nutrients
In addition to nitrogen, phosphorous and potassium, plants require calcium, which they use as the actual building material for constructing the cells that form tomatoes, peppers and other garden produce. Calcite limestone adds pure calcium, while dolomite limestone also adds magnesium.
Eggshells from home kitchen use add calcium to small quantities of home-produced organic fertilizer. Using the ingredients of eggshells for calcium, coffee grounds for nitrogen and banana peels for potassium, you can make a balanced organic fertilizer smoothie in the blender and clean up your breakfast table at the same time.
Seaweeds and Jersey greensand add iron, copper and dozens of trace minerals to your organic fertilizer. Gypsum or Epsom salts add magnesium and the much-needed trace element sulfur. One hard-to-find ingredient needed for beets, chard, and sunflower growth is boron--include it in your organic fertilizer by adding just a tiny amount of unscented laundry borax.
Organic matter improves soil tilth, the texture and structure of soil. Soil with good structure does not compact like clay does. It holds on to water and nutrients instead of letting them drain right out like sand does. Peat moss, shredded leaves, shredded pine needles and straw all add organic matter to garden soil.
The most important organic fertilizer ingredients for soil structure are compost and manure. Well-aged compost and composted livestock manure both improve tilth but also include substantial, accessible quantities of nitrogen, phosphorous and potassium, as well as trace minerals and nutrients. Compost or composted manure make a reasonably well-rounded organic fertilizer when used alone, and can form the core of a top-notch organic fertilizer when used as the base for the addition of other ingredients to boost nutrient and trace mineral elements.