Left:  Make a measuring cylinder using a 5-mlsyringe: Remove the piston, heat the nozzle to make it soft, press it together with pliers.
Put 2.5 ml of dried and sifted soil of the previous experiment into your cylinder.
Middle:  Add 2.5 ml of water from a second syringe.
Observations
Air bubbles leave the soil while the water penetrates.
Right: 2.5 ml soil + 2.5 ml water result in only 3.3 ml mixture.
Half of the soil is air: Roots of plants, earth worms and fungi need this air for breathing.