The technical equipment used to apply fertilisers posess a substantial influence on the preciseness with which fertilisers are spread.
In order to prevent the pollution of surface waters, boundary and field side spreading devices enable accurate application. This is particular important for centrifugal mounted spreaders, which are used for mineral fertilisers.
Mineral fertilisers show a large variance in their physical properties. Therefore, an appropriate technical standard of the spreading vanes is one prerequisite to ensure even lateral distribution of mineral fertilisers, the other is to adjust the spreader technique to the actual mineral fertiliser which shall be spread. Uneven lateral distribution of mineral fertilisers may lead to a local oversupply with nitrogen, which might induce increased partial leaching. Fields in question show a characteristic light and dark green striped pattern (Klages et al., 2018). Especially spreaders for mineral fertilisers (centrifugal broadcasters) need regular calibration for every new mineral fertiliser used. This is due to extremely variations in physical properties of the fertilisers, e. g. grain size and grain size distribution, hardness of grain, degree of moisture or dust content (Klages et al., 2017).
Using the nitrogen in organic fertilisers more effectively reduces losses to the environment. For biodiversity protection reasons, technique for organic fertilisation is supposed to minimise gaserous losses. A large amount of nitrogen is lost as ammonia, especially under unfavourable weather conditions and in case the organic fertisers are not immediately after spreading incorporated into soil (using chisle or plough) or directly applied near (using drip hose booms) or into soil (using trailing shoe or slit technique).
Manure N efficiency may be increased by up to 15 % through a requirement to take allowance of the N conserved by reduced ammonia (NH3)-emission techniques. In comparison to application methods, which mix the liquid manure with soil, the injection of slurry reduces N immobilisation and thus increases manure-N efficiency by 10-15 %. In growing cereals, NH3 emissions can be reduced by band spreading within the canopy. Compared with undigested slurry, anaerobic digestion of slurry may also increase manure-N availability within the season of application by 10-20 %, slurry acidification may increase manure-N efficiency by 35-65% by reducing total NH3 losses by 70 % compared with unacidified slurry stored without cover and not incorporated after spreading (Webb et al., 2013).
In cases the amount of nitrogen applied with techniques reducing NH3 emissons is not adjusted to a reduced loss of N, there is an increase possibility of groundwater pollution by nitrates (Klages et al., 2018).
Precision farming connects highly resolved information on nutrient plant need and other site factors (often obtained from remote sensing) to advanced fertiliser application techniques. Precision fertilisation varies in a plot according to plant need. A N surplus due to partial weak development of a crop or existing N-reserves in the soil can be avoided. Precision fertiliser techniques are available both for mineral and organic fertilisers. For organic fertilisers, near-infrared spectroscopy (NIRS) is sometimes used to determine the nitrogen in the liquid manure or digestate during the loading procedure or even while spreading (Böhrnsen, 2007).
The indicator technical standard of fertiliser application could give a good picture on the feasibility of precise fertilisation according to plant needs. Anyhow, data are collected only sporadically. Furthermore, a good technical standard is not linked to the absolute amount of N applied, therefore this indicator cannot be used on its own for the risk of nitrate leaching.