Frequency and saturation is an important key in your lawns root development. Infrequent or insufficient watering can cause the grasses roots to develop close to the top of the soil and make your lawn more susceptible to weeds. Think about it this way, if water is being applied to the top one or two inches only, then your lawn will be more apt to grow roots in these areas. Infrequent and penetrating water is recommended when your lawn needs supplemental watering. By insuring that the water is penetrating to a depth of 4-5 inches, your grasses root system should develop deeper roots and become overall healthier.