The quick answer to this question is YES! Here's some information on why:
A common misconception in regard to Hydretain is that it pulls moisture down into the soil straight from the air above and then creates water droplets for our plants to soak up, however, the reality is that the outside air isn't Hydretain's source to draw from to condense moisture vapor. Instead, the source is actually the humid air within soil pore space.
Here is a PDF you can download with more details:
Keywords: Hydretain, moisture, desert, dessert, soil moisture, humid air, dry air