The Influence of Shallow Injector Design on Ammonia Emissions and Draught Requirement under Different Soil Conditions

Incorporation of manure into soil can effectively reduce ammonia emissions after spreading. This study was aimed at finding an appropriate tine design, which shallowly injects slurry in closed slots on grassland, with relatively low draught forces and minimal emissions of ammonia. Hollow ‘tubulator’ tines were developed in six different designs and compared with a double disc tine. Horizontal and vertical forces were measured in an indoor sand bin and in field experiments. In some field tests slurry placement and ammonia emissions were also measured. With the sharp tip of the smallest tubulator (application rate of 25 t ha–1; depth of 5 cm) the draught forces in the field were from 520 to 1080 N, depending on soil. Draught forces for the double disc tine were similar or slightly lower. However, under all soil conditions, the tubulator required significantly lower vertical forces to penetrate the soil than the double disc tine. For an application rate of 35 t ha–1, draught and vertical forces for the medium-sized tubulators were about half those for the double disc tine at 8 cm depth. Ammonia losses after injection with the tubulator were 1·6% and for the double disc tine 27% of applied ammonia nitrogen. Thus, appropriate tine design can minimise ammonia losses while maintaining similar energy requirements to a conventional injector.