Integrating super water absorbent with reproductive-stage irrigation enhances peanut (Arachis hypogaea L.) productivity under reduced irrigation in lahar-derived soils

Water limitation is a major constraint to peanut production in highly permeable lahar soils, yet the effectiveness of integrating super water absorbents (SWA) with stage-specific irrigation under these conditions remains poorly understood. This study investigated whether combining SWA with strategically timed irrigation could improve peanut productivity while reducing irrigation inputs under drought-prone lahar-affected sandy loam. A randomized complete block design was used to compare conventional irrigation (emergence, VE; beginning flowering, R1; pod formation, R3; seed filling R5) with two reduced-irrigation strategies incorporating SWA: irrigation at VE alone and irrigation at VE plus pod development (R3). Irrigation management altered reproductive traits with minor effect on vegetative growth, flowering time, biomass production, or harvest index. The combination of SWA with irrigation at VE and R3 produced the highest pod number (32.35 pods plant⁻¹), pod yield (2.17 t ha⁻¹), and seed yield (1.35 t ha⁻¹), corresponding to increases of 26.9% and 25.0% over conventional irrigation, while reducing irrigation input by 50%. Complementary analyses consistently indicated that treatment differences were driven primarily by reproductive sink establishment, particularly pod number and seed size, rather than vegetative growth or phenological development. Collectively, these findings demonstrate that the agronomic effectiveness of SWA in highly permeable lahar-derived soils depends on its integration with strategically timed reproductive-stage irrigation, highlighting the importance of maintaining temporal continuity of water availability during critical reproductive development to achieve greater irrigation efficiency and peanut productivity under limited water supply.