Combined influence of water-absorbing polymer and vegetation on soil water characteristic curve under field condition

Aims: Water-absorbing polymer (WAP) is recognized as a suitable soil additive for enhancing water retention and storage in the root zone under arid condition. The presence of such additives may alter the soil water characteristic curve (SWCC) and hence, may affect the plant growth. The effect of WAP on SWCC particularly, with the presence of vegetation is rarely explored. Therefore, this study investigates the combined influence of WAP and vegetation on SWCC for unraveling the soil-plant-WAP-atmosphere interaction. Methods: Two different WAPs along with vegetation species Solanum Lycopersicum species, were considered. The SWCCs along with its model parameters (Air entry value (AEV); Plant available water content (PAWC), FC (Field Capacity) and Permanent Wilting Point (PWP)) were established for silty loamy soil considering the different combinations of WAPs and vegetation. The changes in root structure were analysed with and without the presence of WAP. Results: Parameters such as FC, PWP and PAWC are increased by more than 1.5 times with the presence of WAP and vegetation compared to control soil This is mainly attributed to the alteration in pore volume in the soil matrix. Root-induced soil showed higher moisture retention than control soil at a specific suction which is affected by the root biomass/architecture. Conclusions: The study indicates that the WAP helps to reduce water demand during arid condition. This study also demonstrates the usefulness of SWCC as a tool to unravel the combined influence of WAP and vegetation on soil-water storage and water retention characteristics of soil associated with soil-WAP-root-atmosphere interaction.