Most assimilated nitrogen comes from nitrate, which is efficiently recycled from organic forms by ammonification and nitrification. The majority of nitrogen in most ecosystems is recycled locally by decomposition and reassimilation, although nitrogen exchange between the soil and atmosphere are of long-term importance. The phosphorus cycle Phosphorus is a major component of nucleic acids, phospholipids, ATP, and a mineral in bones and teeth. The phosphorus cycle is relatively simple since it does not have a gaseous form and it occurs in only one important inorganic form, phosphate. Weathering of rock adds phosphate to the soil.
Producers absorb the soil phosphate and incorporate it into molecules.
Phosphorus is transferred to consumers in organic form. Phosphorus is added back to the soil by excretion by animals and by decomposition of detritus by decomposers. Phosphorus cycling is localized since humus and soil particles bind phosphate . Weathering of rocks keeps pace so terrestrial systems are not depleted. Phosphate that reaches the oceans accumulates in sediments and becomes incorporated into rocks which may eventually be exposed to weathering.