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An index for plant water deficit based on root-weighted soil water content

Shi, Jianchu, Li, Sen, Zuo, Qiang, Ben-Gal, Alon
Journal of hydrology 2015 v.522 pp. 285-294
arithmetic, drought, greenhouse experimentation, irrigation scheduling, plant characteristics, plant-water relations, rhizosphere, rice, roots, soil water, soil water content, subsurface irrigation, surface irrigation, wheat
Governed by atmospheric demand, soil water conditions and plant characteristics, plant water status is dynamic, complex, and fundamental to efficient agricultural water management. To explore a centralized signal for the evaluation of plant water status based on soil water status, two greenhouse experiments investigating the effect of the relative distribution between soil water and roots on wheat and rice were conducted. Due to the significant offset between the distributions of soil water and roots, wheat receiving subsurface irrigation suffered more from drought than wheat under surface irrigation, even when the arithmetic averaged soil water content (SWC) in the root zone was higher. A significant relationship was found between the plant water deficit index (PWDI) and the root-weighted (rather than the arithmetic) average SWC over root zone. The traditional soil-based approach for the estimation of PWDI was improved by replacing the arithmetic averaged SWC with the root-weighted SWC to take the effect of the relative distribution between soil water and roots into consideration. These results should be beneficial for scheduling irrigation, as well as for evaluating plant water consumption and root density profile.