Phosphate rock is incredibly nutrient-dense, ensuring robust, vigorous plants. Because of the rock minerals in them, these fertilizers are sometimes known as "rock dust." Phosphate rock fertilizers are commonly used to promote healthy flowers and veggies. They provide phosphorus, which is needed by plants to make DNA and other important molecules, and they supply other nutrients too.
The most common type of phosphate fertilizer is bone meal. This ingredient is made by grinding up old bones from meat factories or fish farms. It contains a large amount of phosphorous, plus some calcium and magnesium. When applied as a soil supplement, it helps plants absorb other nutrients such as nitrogen and potassium.
Rock phosphate has the same chemical formula as human blood plasma and acts as a source of phosphorus for plants. It is derived from mineral deposits found in rocks containing phosphate of lime (H3PO4). The stone is processed into a powder that can be spread on lawns or sprinkled into soil around plants. It promotes root growth and increases yield when used with other nutrients.
Phosphate rock and bone meal are not equivalent forms of phosphorus. They have different effects on plants because they contain different amounts of other elements too. Rock phosphate is very high in calcium and magnesium while bone meal is high in phosphorus.
Phosphorus is now an important component of commercial fertilizer. Ninety percent of the world's mined phosphate rock is utilized in agricultural and food production, primarily as fertilizer, with a smaller proportion used as animal feed and food additives. Phosphate fertilizers contain either elemental phosphorus or compounds which can be converted into phosphorus oxides when applied to soil.
In agriculture, phosphorus plays an essential role in plant growth because it is required for cell division and expansion. Without phosphorus, plants would grow but they would not produce seeds or fruit. In fact, plants cannot move away from phosphorus once they have found it, so if you remove most of the phosphorus from your soil, the remaining bits will be used by the plants instead. The more phosphorus there is in the soil, the more fruits and seeds that will grow.
Phosphorus is also needed for healthy leaves, flowers, and roots. If you don't give plants enough phosphorus, they will appear pale and weakly-rooted. The top few inches of soil near plants' growing tips contains about half of all the phosphorus available to the plant. Above this depth, the concentration of phosphorus decreases rapidly. That's why it is important to add phosphorus whenever you fertilize your garden.
Besides being useful for plants, phosphorus is also necessary for healthy animals. Humans need phosphorus too, but we get it from food rather than fertilizer.
Rock phosphate is not necessarily a good fertilizer. Because the majority of it is insoluble, it might be difficult for the roots to absorb the maximum quantity of phosphorus. Aside from its weight, it is slower to act than fast-acting synthetic chemical fertilizers.
Phosphate rock contains various other elements in addition to phosphorus. These other elements may or may not be present in equal amounts with phosphorus. For example, iron phosphates are used as pigments and additives for steel. They also tend to be more soluble than pure phosphate rock. If iron levels are high, it might be best to use separate sources for nitrogen and phosphorus.
Another disadvantage of rock phosphate is its price. It can cost up to $20/ton while urea is sold for $6/ton. A third factor is its location. Phosphate rocks can be found only in a few countries including Mexico, Morocco, Canada, and United States. As for urea, it comes from agricultural crops such as corn and soybeans which means it's widely available in most parts of the world.
Finally, some people are allergic to rock phosphate. It might cause skin rashes or respiratory problems if you are sensitive to dust particles.
As for urea, it is completely hydroscopic and will dissolve in water quickly.