Draught requirement of trailing-foot and shallow injection equipment for applying slurry to grassland

Surface spreading of slurry leads to the inevitable emission of ammonia int o the environment. Injection of slurry on grassland reduces these emissions . However, injection of slurry by deep working injector tines with goose fo ot chisels (wings) requires high draught forces. This type of injection has the risk of the crop dying back under dry soil conditions and is not possi ble on all soil types. In recent years, new slurry application techniques f or grassland have been developed that achieve a large reduction in emission s of ammonia, but require less draught force. These techniques include cutt ing a shallow slit in the sward, into which slurry is applied, and applicat ion of the slurry in bands on the soil surface using a trailing foot implem ent. In a series of experiments on sandy loam, day and peat soils, the drau ght force requirement of single elements of five new slurry application tec hniques was investigated. The application techniques were a trailed sliding foot element and four shallow injection elements: angled-disc coulters (do uble-disc opener), thick-disc coulter, flat disc coulter followed by a vert ical injection coulter and knife coulter followed by a vertical injection c oulter. The application technique, working depth and soil conditions had a significant influence on the draught force. For a working depth of 5 cm, th e required draught forces per shallow injector element, measured in this ex periment, were in the range of 202-706 N for a double-disc opener, 284-991 N for a thick-disc coulter, 361-1260 N for a flat-disc coulter plus injecto r and 389-1358 N for a knife coulter plus injector. The lowest draught forc es occurred on peat soil and the highest forces on dry clay. The trailing f oot required an average draught force of 39 N. The draught force of the tra iling foot did not relate to the soil conditions but an effect of the grass sward condition was suggested. (C) 1998 Silsoe Research Institute.