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Natural Garden Fertilizer Ingredients

By Amber Kelsey ; Updated September 21, 2017

Natural garden fertilizers contain only natural plant, mineral and animal materials. True natural fertilizers don’t contain any herbicides, pesticides or other chemicals that can leach out into nearby water sources. Natural garden fertilizers are sometimes called slow-release fertilizers, since they typically release nutrients over a span of time instead of all at once.

Bone Meal

Bone meal, made from the sterilized bones of slaughterhouse animals, contains phosphates and calcium, which ensures the sugar supply in a plant's leaves travels down to its roots. This helps to promote root growth, which makes bone meal useful for root tubers, such as dahlias and gladiolas, and root crops, such as onions and carrots. The phosphorous also helps control rhizobium bacteria in legume root nodules. Applying a natural fertilizer containing bone meal to the soil before planting sweet peas, beans and peas promotes crop growth. Because bone meal is a base and causes an alkaline reaction in the soil, it should not be used for acid-loving plants, such as azaleas and rhododendrons.

Blood Meal

Blood meal comes from the dried blood created as a byproduct of animal processing at slaughterhouses. Blood proteins contain high amounts of nitrogen, making this an appropriate ingredient to use on greens, such as lettuce, kale and Brussels sprouts. Proteins contained in blood meal are quickly broken down into ammonia by soil bacteria. In warm, humid weather, which encourages the growth of bacteria, bone meal often decomposes too quickly. This might release large amounts of ammonia into the soil, which can damage delicate roots. Blood meal's acidic soil reaction means this ingredient should not be used for members of the cabbage family.

Kelp Meal

Kelp meal, made from dried seaweed, provides a rich source of potassium, amino acids and potash. This ingredient added to natural garden fertilizer helps stimulate root development, boost plant growth and prevent fungal infections. It can also aid in preventing transplant shock and lessening stress caused by extreme temperature fluctuations. Kelp meal also stimulates microbial activity, which acts as a soil conditioner.

Cottonseed Meal

Cottonseed, made from the hulls surrounding cotton kernels, when added to natural garden fertilizers helps lower the pH of soil as well as provide healthy amounts of nitrogen, potassium and phosphorus. Cottonseed meal costs relatively little and can be readily obtained. Despite all of its benefits, cottonseed meal often contains pesticide residue. Special pesticide-free cottonseed meal fertilizer can be purchased.

Corn Gluten Meal

Corn gluten meal, a byproduct of processing corn to make corn syrup or corn starch, works well as a natural herbicide. Corn gluten meal affects the developing roots of common weeds, such as dandelions, Bermuda grass, crabgrass, barnyard grass and creeping bentgrass. Corn gluten meal is not good to use on sprouting plant seeds since it could stop them from developing normal roots and makes them more susceptible to dehydration when the soil becomes dry.