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Irrigation Water Management: Soil-Water Potential and Crop Water Stress Index

 Plant-available water $(\theta_{PAW})$ in soil lies between Field Capacity $(\theta_{FC})$ (suction pressure $\approx 0.33\text{ bar}$) and Permanent Wilting Point $(\theta_{PWP})$ (suction pressure $\approx 15\text{ bar}$):

$\theta_{PAW} = \theta_{FC} - \theta_{PWP}$

​To prevent yield reduction, irrigation is applied when soil moisture reaches the Management Allowed Depletion (MAD) level, typically set at $50\%$ of available water. The Crop Water Stress Index (CWSI) quantifies plant moisture deficit using canopy-to-air temperature differences $(T_c - T_a):$

$CWSI = \frac{(T_c - T_a) - (T_c - T_a)_{lower}}{(T_c - T_a)_{upper} - (T_c - T_a)_{lower}}$

​Where subscript lower represents a non-water-stressed baseline (transpiring at potential rate) and upper represents a fully stressed non-transpiring canopy.

​In water-scarce agricultural belts across Western India, conventional scheduled rotational canal irrigation frequently causes either root-zone waterlogging or severe crop stress.

​Under state-level climate-smart agriculture initiatives, farmers deploy IoT-based soil matric potential sensors and thermal infrared camera sensors mounted on agricultural drones. Computing continuous real-time CWSI allows automated micro-irrigation systems to deliver precise water doses directly to root zones, maximizing crop water productivity $(\text{kg/m}^3).$

​Note: This technical content was curated and structured with AI assistance to support technical education.

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