In a forest parasitic plants may exist on living plants extracting phosphorus from the living plant. In a forest dead plant material remains on the forest floor and eventually returns phosphorus to the lithosphere. Agricultural crops are harvested and do not return any phosphorus to the lithosphere. Without artificial inputs of phosphorus through fertilizers, crops would reduce the phosphorus levels in the lithosphere. Agricultural crops will increase the rate of phosphorus removal from the geosphere.
Crop plants grow faster and take up more phosphorus faster than do most forest plants.
Also, as mentioned previously, crops do not return phosphorus to the lithosphere or geosphere. Agriculture frequently increases erosion. Increasing erosion increases the transfer of phosphorus to the hydrosphere. The application of inorganic fertilizers may also increase the transfer of phosphorus to the hydrosphere. How has agriculture changed the global rates of nitrogen fixation.