Injection methods to reduce ammonia emission from volatile liquid fertilisers applied to growing crops

Advanced techniques for separation of animal slurry are now available and used for optimising the use of nutrients present in manure, resulting in the production of two liquid fractions and a solid residue. One liquid fraction rich in nitrogen is used as a biofertiliser locally on the farm and the other liquid fraction with a low nutrient concentration is used for irrigation on the farm. In this study, ammonia volatilisation following landspreading of the liquid biofertiliser was investigated. Three application techniques were compared: a disc coulter injector, a spoke wheel injector and a newly developed high-pressure injector using a trailing shoe technique. Two field studies using the micrometeorological mass-balance technique and a laboratory study employing a dynamic chamber technique showed that when the liquid biofertiliser was surface applied, 20–35% of the applied total ammonical nitrogen (TAN) was lost as ammonia, whereas disc coulter injection into 5–7 cm depth reduced the loss to 2–3% of TAN. In the laboratory study, it was seen that the high-pressure injection reduced the ammonia volatilisation as much as disc coulter injection into 5–7 cm depth, but in the field experiment the high-pressure technique was not able to inject deeper than 0–2 cm, thereby it had no reducing effect on ammonia volatilisation compared to surface application. A yield experiment showed significantly higher yields from spoke wheel injection and high-pressure injection of biofertiliser compared to surface application, but significantly reduced yields compared to commercial mineral fertilisers.