OPEN ACCESS | Published on : 06-Jan-2026 | Pages: 24-40 | Doi : 10.37446/edibook222025/24-40
Water in soil plays a crucial role in the soil-plant-atmosphere system and it has an effect on processes which determine crop yield and the stability of the ecosystem. The chapter gives a clear-cut review of the soil water, beginning with the physical characteristics of water in regard to soil behaviour. It branches into discussing the soil water potential, the description of which includes explanation of the role of matric, gravitational, osmotic and pressure potentials in the retention, movement and availability of water to plants. The major processes, including infiltration, percolation, permeability, drainage, and hysteresis, are looked into and the importance of the processes in relation to the soil texture, structure, pore-size distribution, and management practices are brought to light. The water flow in the soil profile is investigated both in a saturated and unsaturated state and the importance of Darcy law and hydraulic conductivity are emphasized. The retention curves of soil moisture and constants, which include saturation, field capacity, permanent wilting point, and available water capacity are explained and the means of determining the soil moisture content. The soil plant atmosphere continuum (SPAC) framework illustrates water flow from soil to atmosphere. Lastly, the principles of plant–water relations, including root uptake and transpiration, are explored, connecting soil processes with plant physiological responses for effective soil and water management in agricultural systems.
Soil water constants, potential, movement, retention, soil-plant-atmosphere continuum
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