• slurry injection;
  • crop damage;
  • N fertilizer;
  • perennial ryegrass;
  • red fescue;
  • red clover;
  • yield


Slurry injection into grassland has advantages as it decreases ammonia losses, but may harm grassland plants. In two field experiments, four different types of knife/tine equipment were tested on three different grassland species (monocultures of red clover, perennial ryegrass and red fescue), with or without added mineral nitrogen (N), but without slurry application. During 2 years, in two separate experiments, the injection treatments were applied in spring or in summer to different plots. Crop damage was assessed by a range of methods. It was concluded that both the timing and the design of the knife/injector equipment had a significant influence on yield when used in grassland, with the greatest decrease in yield after spring use. Mean total yield over 2 years (no treatment = 100) for timing and species, with N added, was 94 (vertical knife), 92 (vertical and horizontal knife), 96 (double disc tine) and 94 (tubulator tine). With no N added, the relative yield decrease caused by equipment was less. Red fescue seemed to be a little more sensitive than the other species at spring treatment in one of the 2 years. Leaf area index could be useful for measuring crop damage.