Phosphorus is used in agriculture as one of the elements found in fertilizer. It is usable in the form of phosphoric acid. It can be made by adding phosphate rock with a 20 percent Phosporus concentration dissolved with nitric acid to make phosphoric acid and calcium nitrate. Combined with a potassium fertilizer, it makes a compound fertilizer that is easy for plants to obtain their necessary nutrients from. Organic fertilizers containing the element phosphorus can be obtained from using animal manure, composts and sewage sludge. Phosphorus, a nutrient found in healthy soil is needed for plants to grow properly. Today, many crop yields can be attributed to the use of fertilizers. Fertilizers contain six macronutrients which are needed in larger quantities by plants--nitrogen, phosphorus, potassium, calcium, magnesium and sulfur. They also have the micronutrients--boron, chlorine, copper, iron, maganese, molybdenum and zinc that are needed in smaller quantities.