Summary: Slurry injection has agricultural and environmental benefits, compared to surface spreading which is a significant source of nutrients runoff especially in rainy conditions. If slurry is injected into the soil these runoffs can be minimized. At the same time the nitrogen loss through ammonia evaporation can be effectively prevented.
Operation and Applicability: In Finland the farms use usually contractors for slurry injection. Contractor costs starts from 2,5 / m3 plus tax.
Efficiency: Slurry injection reduces nitrogen volatilization up to 30-40%. It also decreases phosphorus loss in surface runoff especially in wet conditions.
Efficiency and functionality Costs of the Practice Ease of Operation
Potential for nutrient recovery
Basics of the good practice:
- Slurry injection is performed by injector equipment e.g. disc or knife. With injector equipment slurry can be shallow-injected (ca. 5 cm).
- The injection equipment increases the resistance force of tractor thus it is important to minimize soil compaction by using low pressure tires and avoiding injecting slurry into wet soil.
- Slurry should be injected to strong roots because cutting slopes and injected slurry can cause root damages when the roots of cultivated plants are small.
- In Finland, according to nitrate directive every arable hectare can be fertilized yearly up to 170 kg nitrogen, including manure.
- In Finland liquid manure cannot be spread from 1st of November until 31st of March or any other time when the soil is frozen, snow covered or saturated with water. Environmental board can allow spreading in the end of November according to weather or growing conditions.
- Unspread areas:
- Distance to water bodies must exceed 5 meters.
- Zone around drinking water well or spring must exceed 30-100 meters.
- Slurry must be injected over 15% slope area.
Costs of the Practice: In Finland most costs come from buying the slurry injector or using contractor for slurry application. Environmental support system pays compensation only for slurry injection, 40€/hectare.
Ability for climate chance mitigation: The greatest benefits of slurry injection in climate change mitigation is in minimizing and reducing surface runoffs and gaseous emissions which are sources of greenhouse gases. The risk for nutrient losses may increase in the future over the climate change.
Potential for nutrient recovery: Nutrient availability increases which is opportunity to reduce fertilizer use.
Evidence of Success: Slurry injection benefits
Benefits of slurry injection compared to surface spreading:
- It reduces nitrogen volatilization and nutrients surface runoffs
- It reduces odour emissions significantly
- It makes better hygiene quality of silage
- Higher grass D value
- Better availability of nutrients
- Support compensation 40€/ha
- Longer slurry application season in autumn
In a Finnish study (Uusi-Kämppä et. al 2010) up to one third of the ammonium nitrogen was lost through ammonia volatilization when compared surface spreading and injection techniques in slurry application.
Table: Nitrogen lost through ammonia and supplementary fertilizer costs.
