Nitrates and Phosphates in Plants

Nitrogen in the form of nitrates and phosphorous in the form of phosphates are two essential macronutrients that all green plants require to live. A lack of these critical plant nutrients can lead to stunted growth, failure to fruit and even plant death. Plants also need 15 other important nutrients for healthy growth.

Nitrate is a compound made up of one atom of elemental nitrogen and three atoms of elemental oxygen. Nitrate is the form of nitrogen that plants can use in their metabolism. Plants need nitrate to develop leaves, stems, immune systems and seeds. Although elemental nitrogen gas, or N2, makes up nearly 79 percent of Earth’s atmosphere, it is chemically inactive and cannot be used by plants. Nitrogen must be converted into the chemically active nitrate form through a process called nitrogen fixation before plants can absorb it.

Nitrogen fixation occurs in nature through metabolic action by certain species of soil bacteria or through high-energy atmospheric events such as lightning strikes, meteorite trails and cosmic radiation. About 90 percent of the fixed nitrogen naturally added to soil each year comes from bacterial action. The remainder comes from atmospheric events. If additional nitrates are needed, they can be applied to soil in the form of natural nitrate-rich materials, such as animal manure, or as manufactured nitrate fertilizer made from ammonia.

Phosphate is the form of phosphorous readily taken up by plants. It is made of two elemental phosphorous atoms bonded to five elemental oxygen atoms. Phosphate is essential for regulating protein synthesis, cell division and tissue development in plants. It also is one of the agents that regulate various other energy transformations as a plant grows. Phosphate promotes root growth and overall hardiness, and it hastens maturity.

Phosphate fertilizers are manufactured from raw phosphate rock laid as sediments in prehistoric seas. Florida’s phosphate mines are the major source of phosphate rock in the United States, producing roughly 75 percent of the phosphate used in the United States and about 25 percent of the world's phosphate supplies. The phosphate rock is separated from the sand and clay of the ancient seabed and sent to a processing plant where the rock is treated with sulfuric acid to create phosphoric acid. The phosphoric acid in turn reacts with ammonia, producing the phosphate fertilizer bought by gardeners and farmers.