Fertilizers are used to add plant nutrients that are not abundant in the soil. There are 16 nutrients essential to plant growth. Carbon, hydrogen and oxygen are found in water and air. The remaining 13 nutrients must come from the soil and include nitrogen, phosphorus and potassium, which are the most important nutrients for plant growth. Secondary nutrients include calcium, magnesium and sulfur. The remaining nutrients are referred to as micronutrients because very little is required. These nutrients include zinc, manganese, iron, boron, molybdenum and chlorine. Making fertilizers at home allows gardeners to control which nutrients they are adding for the best possible results.
Mother Earth News (MEN), a sustainable living news source, offers a recipe for homemade organic fertilizer that boosts the soil nutrient content and helps spawn plant growth. The recipe includes 4 parts seed meal, 1/4 part ordinary agricultural lime, 1/4 part gypsum, 1/2 part dolomite lime, 1 part bone meal and 1/2 part kelp meal. According to MEN, these ingredients should be mixed uniformly and measured in parts by volume. This fertilizer should be used at least once a year, generally in the spring, before planting crops or bedding plants. This recipe is full of phosphorus, potassium, nitrogen, calcium, sulfur and magnesium.
Grass clippings can provide your lawn or garden area with massive amounts of nitrogen, phosphorus, potassium and other nutrients. According to the University of California Cooperative Extension (UCCE), grass clippings are a good ingredient for a backyard compost pile. However, they can also be used as mulch to discourage weed growth and fertilize the soil. According to UCCE: "When left on the lawn, properly mowed grass clippings filter down to the soil and decompose rapidly, usually within a few weeks. During the breakdown process, the clippings feed soil organisms, recycle plant nutrients, and contribute organic matter to the soil."
When most people think of salt they do not think of a natural plant fertilizer. However, according to the University of Tennessee, epsom salt works well as a houseplant, garden or rose fertilizer. The university recommends combining 1 tbsp. epsom salt with 1 gallon water. Epsom salt provides an abundant supply of magnesium and sulfate. And common houseplants, tomatoes roses, peppers and potatoes are magnesium-loving plants that will benefit from an extra dose.