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Phosphorous Fertilizer

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Sources of Phosphorus Fertilizer

Plants require many nutrients and minerals to survive, which are supplied either from the soil or via fertilizer. One of these minerals, phosphorus, aids plants with bud set and fruiting. Commercial fertilizers usually supply phosphorus to soil and plants, though there are many organic and inorganic sources of the mineral.

Rock Phosphate

The most common source of phosphorus in commercial fertilizer blends, rock phosphate is quarried then ground into grit prior to use. Rock phosphate contains up to 35 percent pure phosphate and provides the base source for all phosphate. Sulfur treatments prior to packaging improve the solubility of rock phosphate so that plants can absorb more of the mineral from the soil.

Bone Meal

Animal bones contain approximately 10 percent phosphorus, making them a suitable source for the fertilizer. Bones are crushed and ground into a fine grit then added to the soil alone or added to other fertilizers. Bones are often steamed before crushing, as this releases more phosphorus from the material and may increase the amount to 13 percent. Bone meal is considered suitable as an organic fertilizer compound.


Manure provides not just phosphorus but nitrogen as well. Usually only manure from herbivores is used in gardens, as other manures tend to burn plants. Composting the manure first prevents most issues with plant burning and ensures all the nutrients are broken down and easily accessible by the plants. The amount of phosphorus in manure is variable, depending on the animal it came from, the diet of the animal and whether the manure is composted or not.

How to Water Plants With Vitamins

Buy a multivitamin high in vitamin C, calcium, potassium, iron and phosphorus. For best results, choose one that is organic and derives its minerals from plants. This will make it easier for the plants to absorb and process the nutrients.

Crush four multivitamins with a mortar and pestle. If you don't have one, use the back of a sturdy tablespoon and a flat surface. Keep working the vitamins until they form a fine powder. Chunks will not dissolve well.

Mix the powdered vitamins with 1 gallon of water until the vitamins have completely dissolved. Pour the mixture into your watering can.

Water your plants with the multivitamin mixture once every two to three months.


Some stores sell liquid vitamins that you can also use for this project. Just add 2 to 3 drops to a gallon of water.

What Is a High Phosphorus Fertilizer?


Phosphorus is often responsible for proper root growth, fruit production and blooming.

Fertilizer Labels

When purchasing commercially available fertilizers, the middle number on the label indicates phosphorus. Fertilizer labels express the percentage, by weight, of each nutrient.

Common Uses

High-phosphorus fertilizers are often popular with vegetable gardeners. A high-phosphorus fertilizer used in a typical vegetable garden would have a ratio of 5-10-5, or double the weight than nitrogen and potassium.

When To Apply

Phosphorus is slow to move through the earth. For this reason, it is advisable to add phosphorus before or during planting.

Phosphorus Deficiency

Phosphorus deficiency often presents itself with a usually green plant turning purple. Soil tests are also beneficial for determining whether you have the optimal balance of nutrients for your garden. Soil tests can be arranged through your state’s Cooperative Extension Service. These are usually offered at little or no cost.


High levels of phosphorus can lead to premature flowering, which could in turn lead to a weaker plant later.

The Best Blooming Fertilizer

The best plant fertilizer for larger and healthier blooms is one high in phosphorus. This nutrient also produces stronger roots and overall plant development. Generally, on fertilizer packaging, phosphorus is the middle number. Nitrogen is first and potassium is last. These are the three major fertilizer nutrients.

How to Correct High Phosphorus Levels in Soil

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Step 1

Stop adding organic products that increase phosphorus levels in the soil. The worst culprits include manure and other organic composts. If you must have an organic mulch or an organic nitrogen-builder, substitute pine bark or blood meal. These products are low in phosphorus.

Step 2

Stop using phosphorus-containing commercial fertilizers. Fertilizer containers normally describe the formula with three numbers -- the middle one indicates the amount of phosphorus. A fertilizer with a middle number of zero does not contain phosphorus or phosphates. For example, choose fertilizers such as ammonium sulfate or magnesium sulfate.

Step 3

Add iron and zinc to help restore health to the garden. Because a high phosphorus level prevents absorption from the soil, use a sprayer to apply a solution of these minerals to plant leaves.

Step 4

Test your soil regularly. Many state agricultural extension offices provide inexpensive soil-testing services. Avoid phosphorus-containing fertilizers or amendments as long as your soil remains high in phosphorus.

What Vitamins Do Plants Need?


Nitrogen, one of the primary nutrients for plant growth, helps plants turn carbohydrates into energy. It also helps plants produce the protein that keeps them strong and healthy.


Plants also need phosphorus, another primary nutrient. Phosphorus strengthens plants, allowing for faster growth. Phosphorus also encourages bloom and root growth.


Potassium is the third primary nutrient for plant growth and is the "K" in the NPK nutrient balance. Potassium aids in the photosynthesis process, provides immunities to plant diseases and increases the quality of fruit in fruit plants.


Plants also need trace elements (micronutrients) for chlorophyll formation and seed germination. Trace elements include copper, boron, copper, iron, manganese, zinc, molybdenum and chlorine.


Even with all the proper nutrients in place, plants will not prosper without light, air and water. These essential elements help provide plants with the necessary energy and support for growing strong and healthy.

What Are the Functions of Phosphorus Fertilizer?


Phosphorus fertilizer provides one of the main nutrients of plant growth. It helps plants convert other nutrients into usable building material. (Reference 1)


Phosphorus is the "P" that is listed in the NPK balance of plant nutrients and is essential to the process of photosynthesis.


A deficiency in phosphorus will stunt the growth of a plant. It will also cause the plant to produce little or no flowers. This means no fruit in fruit-producing plants.


Organic phosphorus fertilizers, such as animal manures, have been used for centuries as the ideal phosphorus source for crops. Inorganic or chemical fertilizers have evolved over the last several decades and are widely used as a nutrient supplement.


A good nutrient fertilizer will have a high phosphorous value that is nitrate soluble as well as water soluble. It will also have a high availability percent. (Reference 1, 2)


Phosphorous fertilizer can run off into the water supply and become a major pollutant if used in excess.

Organic Fertilizer Information

Soil Testing

Having your soil tested tells you if your soil needs one or more of the “Big Three”--nitrogen, phosphorus or potassium (N-P-K)--as well as various trace minerals. Your local extension service can provide an extremely detailed list of what your garden needs in order to thrive.

Manure for Nitrogen

Chicken, rabbit, horse and cow manures all make excellent sources of nitrogen. Always use aged manure or spread the newer stuff at least three months before planting.

Other Nitrogen Sources

Blood meal, alfalfa meal, soybean meal and liquid fish emulsion all make great sources of “vitamin N.” You can alternate a slower-release fertilizer, such as blood meal, with one like liquid fish emulsion, which doesn't last quite as long but gives drooping plants a pick-me-up.

Organic Phosphorus

Leftover slaughterhouse products tend to yield good sources of phosphorus, including bone meal and the lesser-known horn and hoof meals. For those seeking a non-animal source, use rock phosphate.

All-natural Potassium

Kelp, woodstove ash, crushed greensand and granite are good choices for adding potassium organically.

Trace Minerals

Ground rocks, salt and other “hard stuff” make the best natural sources for the various nutrients your soil test may specify. One supplier of an all-around fertilizer adds “glacial rock dust, Azomite, lignite, copper sulfate, zinc sulfate and manganese sulfate” to its basic N-P-K ingredients.

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