Loam soil is ideal because it has a good absorbing rate and can also hold water well. Clay soil can be hard to water because it absorbs the water very slowly. Clay also holds water well and dries slower than sand or loam type soils. The average turfgrass consumes about one inch of water a week. If there isn't enough rain to meet the need, then watering is the only answer.
Soil dries out from the surface downward.
By deep watering you encourage deeper rooting of the grass. If possible, apply most of this inch of water at one time. Summer temperatures may affect your watering time due to evaporation. Evaporation may require you to water up to three inches in one week to give the plant an actual inch of water. A dense thatch layer, surface crusts, or a non-wettable sand can severely reduce water infiltration rates.