Enhancement of Cashew (Anacardium occidentale L.) Seedlings Growth in Semiarid Regions Using a Superabsorbent Hydrogel Composite

Abstract

In arid and semiarid regions, agricultural producers, including cashew growers, grapple with the challenges of cultivating crops in harsh environmental conditions. To address this issue, conditioning materials capable of maintaining soil moisture levels even during droughts presents a promising solution. Herein, we synthesized a superabsorbent hydrogel composite comprised of starch-grafted-poly(sodium acrylate) embedded with 20% (w/w) kaolin (KAO), designed to enhance the quality of cashew seedlings. Characterization of the composite through Fourier transform infrared (FTIR) and X-ray diffraction (XRD) analyses confirmed its successful synthesis. The incorporation of KAO influenced the thermal, morphological, and swelling properties of the composite, as a result of the interaction between the clay and starch. Moreover, the composite exhibited improved water absorption capacity and kinetics, demonstrating a superabsorbent behavior. Our findings demonstrated that the addition of just 1% (w/w) of the composite effectively enhanced soil moisture retention. Notably, the placement of the composite within the soil column proved critical in extending the interval between irrigation cycles. Field experiments revealed that cashew seedlings cultivated in soil conditioned with the composite positioned deeper in the pot exhibited notable improvements in morphological parameters such as plant height, stem diameter, and leaf count, especially over prolonged cultivation periods. Besides, these seedlings displayed increased vigor and overall quality, essential for the establishment of robust and healthy cashew orchards. Overall, this study underscores the potential of this composite as a promising and cost-effective soil conditioning material for enhancing cashews and other crop yields in arid and semiarid regions with limited water availability.