Water in The Soil-Plant System

Rainfall, precipitation, evapotranspiration, groundwater flow…

Conc grad, gravitational, pressure, solute and matric

Adhesion/Cohesion properties of clay/colloidal material

Determine surface are for which soil can be held

Amount/proportions/continuity

Relative energy level of water in a volume of soil, being 0 when saturated, water potential decreasing as soils dry

Evapotranspiration Soils gradients

Gradients in height, pressure, solutes and soil wetness, surface friction or poor constriction

Ease of water movement through pores

Stronger capillary/surface forces in small pores, little flow until pressure forces movement, improving water holding capacity, impeding drainage

This says flow of a liquid at any point is given by fluid pressure gradient, viscosity of the fluid and effective permeability

Gravity, pressure, matric and solutes

Drives water movement, osmotic effect, suction or tension on water surfaces

Binding of water to materials and enclosure in capillaries/other fine pores

Proportional

Leaf/Soil surface roots

Dominates beneath water table, flooding soils, and irrigation/heavy rain infiltration

Air obstructs it in largest pores, thus flows through the smallest pores remaining filled with water

Upper limit of which water is useful to plants: permanent wilting point with further drying

Drying soils, low evaporation due to uncoductivity and dryness, with large surface area allowing dominant transpiration