A Holistic Agronomic Assessment of Slurry Application Methods in Grassland: Implications of Distribution Equipment, Consistency and Timing for Forage Production

ABSTRACT The use of low ammonia emission equipment for slurry distribution has become mandatory in a number of countries. However, the effects of different application methods on dry matter (DM) yield, nitrogen (N) utilisation, botanical composition and forage quality are still debated. This study offers a comprehensive assessment of the effect of various slurry application methods on forage production. Slurry distribution equipment (broadcast; band‐spread; trailing‐shoe), as well as slurry consistency (unaltered or extra dilution), timing (immediately or delayed after preceding cut) and sward types (with or without legumes) were tested at two sites. Low‐emission equipment significantly increased DM yield and N utilisation at one of the two sites. Slurry dilution proved positive for N utilisation and DM yield, while early application timing had marginal effects. Low‐emission equipment had no effect on the proportion of legume species, and at one site, it had only irrelevant effects on the proportion of undesired species. Silage quality was not negatively affected by low‐emission equipment but was indicated to be positively influenced by extra diluted slurry and early application. We conclude that the use of low‐emission slurry distribution equipment can be advantageous in intensively managed grasslands in terms of N utilisation and yield. However, these positive effects are not guaranteed. Negative effects on forage quality are very unlikely with such equipment, provided that the general recommendations for silage production are followed. Slurry dilution is also advantageous, particularly when broadcast or band‐spread equipment is used.