Integrating provocative irrigation and stage-specific floodwater depth to enhance rice productivity and water-use efficiency in the saline Aral Sea Basin

Rice production in the Aral Sea basin is constrained by high water demand, severe soil salinity, and heavy weed pressure. This study evaluated an integrated irrigation strategy that combines provocative pre-sowing irrigation (Stale Seedbed Technique) with stage-specific regulation of floodwater depth, as a sustainable alternative to conventional continuous deep flooding. Field experiments were conducted over three seasons (2022–2024) on saline loam soils at the Karaul-Tyube Experimental Farm (Kyzylorda region, Kazakhstan), using two locally adapted rice varieties (Syr-Sulu and Avangard) in a randomized complete block design with four replications. Complementary pot experiments were used to isolate the effects of static water depths (5–25 cm) during key growth stages. Provocative irrigation (1100–1200 m³ ha⁻¹) applied before sowing induced massive germination of Echinochloa spp. (280–336 seedlings m⁻²) and Phragmites australis (45–62 seedlings m⁻²), enabling their mechanical removal and establishing nearly weed-free, herbicide-free rice stands. Simultaneously, pre-sowing leaching reduced salinity in the 0–40 cm layer from moderately–highly saline to slightly saline, with 0–10 cm dry residue decreasing four- to fivefold over the season. Stage-specific water management—shallow flooding (≈5 cm) during emergence and tillering, deeper water (≈20 cm) at panicle initiation, and moderate depths during ripening- significantly improved stand establishment, tiller number, spikelet fertility, and final grain yield. Compared with conventional continuous flooding, the optimized regime reduced seasonal irrigation input by 15–20% (≈3,500 m³ ha⁻¹) and improved specific water use by 150 m³ per 100 kg of grain, while increasing grain yield by 15.3–20.6%. Water balance analysis showed that these gains were achieved primarily by reducing non-productive percolation and eliminating drainage discharge losses. The integrated strategy provides a robust, scalable framework for water-efficient, herbicide-free rice cultivation in arid, salinity-affected regions.