The best known types of natural fertilizer are manure, mulch, and compost. Other types of natural fertilizers include seaweed, grass clippings, and commercially packaged organic fertilizers sold at nurseries and garden supply stores. Ashes left behind in fireplaces and stoves, cold coffee, and other kitchen leftovers can also be used as natural fertilizers.
Manure, primarily from livestock and poultry, is probably the oldest type of fertilizer used by humans and one of the most common ways to fertilize crops and gardens. Manures are usually buried in the soil around plants to avoid losing the nutrient potential before it gets to the plants. Manure contains all of the components of a good fertilizer. This includes nitrogen, phosphorus, and potassium, along with many different types of nutrients.
Mulching is one of the most common types of natural fertilizer. Mulching materials can include bark, pine needles, or even grass clippings from mowing the lawn. In addition to serving as a fertilizer, many mulching materials will also help water and air to penetrate the soil around plants, which will promote growth.
Grass clippings are spread in the sun to dry for a few days before application. The same principle can be applied with leaves that are raked up in the autumn. As both grass clippings and decomposing leaves generally have a high moisture content, they should be applied sparingly when used as a natural fertilizer. If used too heavily, the decomposition process can lead to soil that is too acidic.
Some gardeners are creating their own natural fertilizers and recycling kitchen waste in the process. Compost is a type of mulching. A compost pile is created that usually includes yard debris, kitchen waste, and other natural materials that will decompose. The compost pile is turned periodically as the items decompose. Once decomposition has taken place, the decomposed matter that is left behind is known as compost and makes an excellent natural fertilizer for yards, gardens, and crops.
Seaweed is often used as natural fertilizer by gardeners who live near the ocean. The seaweed is collected when it washes up, and the gardener then washes away the salt before applying it to soil. It is also available in many nurseries and gardening supply stores.
Another less common natural fertilizer is the ash left behind in fireplaces and stoves. The ash left behind from a wood fire has many of the nutrients plants need. Wood ash shouldn’t be used on plants that need high levels of acid, however. In addition to serving as a fertilizer, ash in the garden will protect plants against snails, slugs, and some insects.