Why does water stick to soil particles?

A water molecule (H2O) is called a dipole molecule that consists of covalent bonds. Due to electronegativity differences, the oxygen pulls on the electrons more than the hydrogen molecules do, as oxygen is more electronegative. read more

Since the soil contains may differently charge molecules (such as potassium and other metal ions), the oxygen in a water molecule will be more attracted to the positively charged molecules, thus allowing water to 'stick' to soil particles. read more

Essentially, cohesion and adhesion are the "stickiness" that water molecules have for each other and for other substances. You can see this in the picture to the right. The water drop is composed of water molecules that like to stick together, an example of the property of cohesion. read more

Water flowing downwards also depends on the composition of the soil, like the composition of sand, silt and clay. Consider a situation where the voids between the soil particles are large (case of sand), this would make the water go downward especially past the plant roots. read more