If you water and it beads on the surface, pools, or runs off to the low spots while the lawn stays dry underneath, the soil has turned hydrophobic. It is extremely common in sandy soil and in clay that has dried and cracked through summer, and it means most of your watering is being wasted. No fertiliser fixes it, because the water carrying the nutrients is not getting in.

Restore Granular Soil Wetter is spread over the surface and watered in, breaking the water repellency so moisture penetrates to the root zone instead of sitting on top.

Before you buy:

Test first, put a cup of water on a dry patch and see whether it soaks in within a minute
Apply before the heat arrives, a wetter is far more effective as prevention than as rescue
Water in thoroughly after applying so it moves down through the profile
Repeat seasonally on sandy soil, water repellency returns