Stand outside and look underneath your feet. There, perhaps under some grass, is the soil. On a dry day, all the spaces in the soil are filled with air. And some distance further down, those spaces ...

Plants need water, light and air to thrive. But when they transport water from the soil up to their leaves, they defy gravity. Scientists describe this astonishing phenomenon as “negative water ...

Unsaturated soils occupy the zone between the water table and the ground surface, where capillary and gravitational forces govern the distribution and movement of water. Their hydraulic ...