Nutrients and pollutants can enter agricultural soils via animal manure, mineral and waste fertilisers, pesticides and atmospheric deposits. Through sorption processes, they adhere to soil particles or are transported into deeper soil layers or the ground water. With harvested material, nutrients and pollutants are removed from the soil. Avenues of inputs and outputs of each nutrient or pollutant depend on the soil properties and land use types.
The surface balance includes the above mentioned element fluxes into and out of the soil at individual sites in simplified form. The sorption and desorption processes in the soil are not considered. Furthermore, element translocations into deeper soil layers, surface run-off or losses through erosion are not considered. Nonetheless, the surface balances give a good overview of the element fluxes that exist relative to management and crop rotations.