Matric potential - that portion of the total soil water potential due to the attractive forces between water and soil solids as represented through adsorption and capillarity. It will always be negative. Osmotic potential - that portion of the total soil water potential due to the presence of solutes in soil water. It has very little effect on mass movement of water in soil, but its primary importance is in the uptake of water by plant roots. It will always be negative.
Water always moves from areas of higher potential to areas of lower potential.
Units expressing soil water potential bar or atmosphere , both of which is approximately equal to 1020 cm of water. Water movement is complicated by two additional factors Wetting and drying curves for a given soil can be different. This is called Hysteresis , which refers to the difference in the amount of moisture held by a wetting soil and a drying soil at the same soil moisture tension. The term applied to the length and difficulty of the path that water must take during unsaturated flow to get from point A to point B in the soil. Classes of Soil Water Gravitational - Drains out of the soil by the force of gravity.