A field study integrating plant physiology-soil response for quantifying wilting and plant survival time in a polymer-amended soil

Water deficiency caused by climate change is a global challenge for food security. Viable sustainable alternatives for enhancing water storage in the soil is a necessity for arid and drought prone regions. Water-absorbing polymer (WAP) is capable of improving the water storage in soil pores, and its efficacy can be ascertained by evaluating the resilience of plants towards wilting. The main objective of this study was field demonstration on the usefulness of fly ash-based WAP (FA-WAP) in prolonging wilting and plant survival time of beans (Phaseolus vulgaris) and radish (Raphanus sativus) in a silt loam. This was achieved by following a novel methodology for determining plant permanent wilting point (PWP) by integrating both soil response (suction) and plant response (stomatal conductance and photosynthetic yield), as against the common practice of considering a reference negative water potential (or soil suction) value of 1500 kPa. Using the proposed methodology, the PWP was 1300 kPa and 1150 kPa for beans and radish, respectively. The measured soil water retention curves (SWRC) demonstrated higher water availability in the WAP-amended soil compared to the control soil for both plant species, thereby prolonging plant survival time. The presence of WAP positively influenced the plant biochemical parameters (such as H₂O₂, MDA, proline, CHL A+B) under water deficit conditions. The WAP amendment resulted in 2.3 and 1.4 times crop yield for beans and radish, respectively, compared to the unamended soil. The use of FA-WAP has a high potential to reduce the irrigation water demand without compromising the yield of two vegetable species considered in this study.