If it takes less time, it is too light. In either case, the best approach is to correct your soil by adding organic material such as compost. In the mean time, you can adjust your watering as suggested above. The test works best if you haven't watered for at least 12hrs. Water retention is also increased by covering the soil with mulch.
Most mulches help retain water as well as control weeds.
Organic mulches typically cool the soil while black plastic mulch helps warm the soil. It is helpful to know the individual watering requirements of the plants you intend to grow. I have Hale's Best Cantaloupes planted next to Sugar Baby Watermelons with black plastic mulch. Holes are poked in the plastic to allow overhead watering to penetrate. This could be a problem, because Hale's Best performs best when it is short on water and it shares a common sprinkler with the watermelon which demands continuous moisture.