Ideally that's what the sensor is for but you could try changing the soil type/ head/ or grading on the zone so it applies more water. 

Hi Scott,

This is not supported. As a workaround, you can go to settings->zones->specific zone number->smart zone-enabled->Mode ,select "customized" mode to adjust watering by providing the preferred moisture level to add/skip watering and flow rate of your sprinklers. 

Thanks,

Netro Support