Open access publications in the SLU publication database

Abstract

Shallow injection of slurry on grassland can reduce ammonia emissions compared to surface spreading and increase plant nitrogen utilisation. Other advantages include enhanced silage quality and lower odour. Disadvantages include higher investment costs, increased draught requirements and potential crop damage. The objective of this thesis was to determine appropriate techniques for slurry injection into ley that would minimise ammonia emissions, contamination of crops and energy inputs, while resulting in high plant utilisation of slurry nitrogen. Slurry injector performance was validated in field trials. Conventional slurry tankers with different types of injectors were used to shallow-inject (less than 0.05 m) slurry into open slots after the first cut. Slurry placement after spreading, ammonia volatilisation, yield and crop nitrogen uptake were measured and compared to the results of band spreading. In the first year, silage quality and an economic analysis were also included. Only one injector, with double disc tines, could place the slurry below the soil surface in all three soils tested. Ammonia release was on average 39% of the total ammoniacal nitrogen (TAN) applied, half the level with band spreading, but this did not result in higher dry matter (DM) yield or higher apparent nitrogen recovery (ANR) for the injector by the second cut. Despite inefficient injection, silage quality tended to be better than after band spreading. However, shallow injection was less financially viable. To find a tine that shallow-injected the slurry into closed slots on grassland, six different designs of tubulator tines were compared to double disc tines by measuring horizontal and vertical forces and ammonia emissions. The tubulator tine required significantly lower vertical forces to penetrate the soil and minimised ammonia losses at similar energy requirements to a conventional double disc injector. With appropriate tine design, slurry could be injected below the soil surface even in hard soil conditions and ammonia emissions minimised, but extra energy and financial investment were required.