A cricket match outdoors is nearly always played on grass. Grass grows, so it has to be mowed so that playing conditions can be maintained as far as possible the same for both sides. There are regulations in the Laws for when this mowing is to take place. In a match scheduled to last for more than one day, both the pitch and the outfield must be mowed on each day - assuming that the ground and weather conditions allow it to be done. The pitch mowing must be completed not later than 30 minutes, and the outfield mowing not later than 15 minutes before the scheduled or rescheduled start of play on each day.
Any mowing done before the match starts is the responsibility of the groundsman and his team. Once play has commenced the umpires assume the responsibility for supervising it.