Development and evaluation of biopolymer-fly ash amended sand for improved water holding capacity, abrasion resistance, and plant growth in desert ecosystem.

Desert sand, although mineral-rich, is unsuitable for agriculture due to its low water holding capacity and weak particle cohesion. In this study, a sustainable sand amendment approach was developed using Fly ash (FA) in combination with biopolymers, such as Guar gum (GG), Xanthan gum (XG), and Carboxymethyl cellulose (CMC), to enhance water retention and support plant growth in desert ecosystem. Sand and FA were blended at ratios of 90:10, 75:25, and 60:40, followed by the addition of 0.1% of biopolymer solution. The amended systems were evaluated for water holding capacity (WHC), evaporation rate (ER), and plant survival efficiency etc. Among the tested formulations, GG-amended sand-FA mixtures (60:40 and 90:10) exhibited 70% WHC that was equivalent to a 25% increase when compared with unamended sand. Evaporation losses were significantly reduced in all amended systems, with the lowest evaporation rates observed in the 90:10 sand-FA mixture treated with XG (48.68%), followed by CMC (53.16%) and GG (59.2%), compared to unamended sand (95%). The WHC-to-ER ratio, an indicator of effective water availability, was highest for XG and GG sand-FA amendments. SEM micrographs also revealed that GG and XG sand-FA amendments demonstrated superior performance due to their continuous, homogeneous matrix and strong inter-particle adhesion. Plant survival efficiency studies using a two-layer model demonstrated the 90:10 sand-FA amendment of GG and XG exhibited 61.9 and 57% plant survival efficiency. Overall, the findings demonstrate the potential of GG Sand -FA amendments as sustainable strategy for transforming desert sand into arable soil-like structure.