Nitrates are the salts and esters of nitric acid (HNO3). They serve plants as nutrients and a direct nitrogen source. In agriculture, nitrate fertilizers are also used in the form of liquid manure (slurry). These so-called economic fertilizers contain nitrogen partly as nitrate (calcium nitrate in Blaukorn), and partly in the form of ammonium compounds (ammonium nitrate, ammonium phosphate) or organic nitrogen compounds (proteins, amines, urea). Organically bound nitrogen can be naturally mineralized in the soil by releasing ammonium compounds first and nitrates later. It can also penetrate the soil humus supply, from which it is gradually mineralized. In particular, as a result of the manure economy – partly also due to excessive fertilization and leaking sewage pipes – the nitrate content of groundwater has increased significantly in recent decades. Legal regulations on the type, quantity and timing of fertilization as well as appropriate further training and remediation measures are intended to lead to a gradual, albeit highly delayed, remediation of groundwater.