Researchers at Harper Adams University College have been investigating how cattle and tractors affect soil compaction, grass yields and the emission of the greenhouse gas, nitrous oxide. The work is part of a project funded by DairyCo and involves academics from Reading University, the Scottish Agricultural College (SAC) and Harper Adams. On-going field experiments at the University College in Shropshire, and at the SAC, Dumfries, are investigating the impact of cattle and tractor compaction on soil microbial processes affecting the nitrogen cycle. Harper Adams Research Lecturer in Soil Ecology, Dr Samuel Bonnett, said: "Soil compaction by cattle and tractors can result in reduced aeration of the soil. This increases denitrification -- a process that turns nitrates into nitrous oxide (N2O)." "To investigate this, we have nine plots grouped into three main areas -- a control, a tractor compaction plot and a cattle compaction plot. We also have additional treatments of aeration and nitrification inhibitors within each of these. "The research should give an indication of the impacts of tractor and cattle compaction on N2O emissions, and also indicate whether aeration and nitrification inhibitors can be used to reduce the impact."