During my own experience as a soccer player, and also as an agronomist, I have seen a variety of watering requirements from coaches, managers, players and grounds managers prior to a soccer game.
Why water prior to games?
Most athletic fields, particularly those built on native soils, play best when they are on the dry side. Not so dry as to create hard and unsafe playing conditions, but dry enough that the soil surface does not lose integrity and become a mud-bath. As a rule of thumb, the irrigation is turned off 48 hours prior to a game, to ensure the surface is dry enough. On sandy soils, irrigation is often used before a game to increase the shear strength of the sand. Basically, moist sand is firmer for the athlete's footing than dry sand. Another reason sand fields are watered prior to soccer games is to create moist leaf tissue that helps the soccer ball to glide smoothly over the surface. A dry turf surface can hold the ball and is considered "slower" than a moist surface.
How much water prior to games?
In the Premiership Football League in England, many of the sand-based fields/pitches are watered just prior to games, but how much water is applied and is it regulated by the sport's governing bodies (such as the FA and FIFA)?
It would appear that there are no strict recommendations from the FA or FIFA about how much water to apply. However, watering during half-time requires permission from the manager of both teams and no water is applied at UEFA Cup Games during half-time.
Watering prior to games is done at the discretion of the grounds person and in consultation with coaches and managers. The amount to apply depends upon the current weather conditions, particularly the daily evapotranspiration (ET) rate. If ET rates are low (cool, calm, cloudy weather) then fields are lightly watered early before a game. If ET rates are high (warm, windy, sunny weather) then fields are watered just prior to a game. The amount of time between the players warming-up on the field and the beginning of the game also dictates the amount of time the irrigation heads can run. Heads typically run just long enough to wet the playing surface and leaf tissue, and both sides of the field must be watered evenly.
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