How super absorbent polymers boost crop yield in direct-seeded rice: a surface vs. subsurface drip irrigation analysis

The global water deficit has highlighted the necessity of direct-seeded rice (DSR). Furthermore, the role of Super Absorbent Polymers (SAP) in water retention has been determined. This experiment was conducted in 2019 and 2020 to determine the effect of two irrigation systems (surface drip irrigation (DI) and subsurface drip irrigation (SDI)) and two types of soil (containing SAP at a rate of 125 kg/ha and Non-SAP) on grain yield, yield components, and irrigation water use efficiency (IWUE) in DSR for three rice genotypes (Firuzan, Juzdan, and Sazandegi) in semi-arid regions of Iran (Najafabad-Isfahan). The experiment was carried out as a split-split plot in a randomized full block design, with three replications over two years. According to the variance analysis, DI’s grain yield in 2019 was 2673 kg/ha, whereas SDI’s was 2169 kg/ha. In 2020, the yield for DI was 2767 kg/ha, while for SDI it was 2337 kg/ha. Actually, DI yielded 19% more grain in 2019 and 15% more in 2020 than SDI. In addition, the IWUE exceeded the SDI by 22% in 2019 and 32% in 2020. Rice grain production in SAP-containing soils was 2550 and 2695 kg/ha in 2019 and 2020, respectively, while Non-SAP soils yielded 2292 and 2409 kg/ha. In fact, in both years, soil with SAP produced 10% more grain than Non-SAP. IWUE increased by 12% in 2019 and 10% in 2020 compared to Non-SAP.