Multi-objective optimization of agronomic practices to balance soil fertility, water productivity, and economic returns in saline-alkali farmlands

Optimizing agronomic management is crucial for improving soil fertility , crop growth, and resource efficiency. However, the interactions between precision irrigation, organic amendments, and straw incorporation in salinized soil remain underexplored. This study aimed to evaluate the combined effects of irrigation on crop demand (IOD), organic substitution (OS), and straw return (SR) on soil fertility, crop growth, water productivity (WP), and net profit (NP) in salinized farmland, while identifying the optimal agronomic strategy through multi-objective optimization. A 2022–2023 field experiment evaluated eight treatment combinations (CDI (conventional drip irrigation), SNR (straw not return), CK (chemical fertilizer only), IOD, SR, and OS) in saline-alkaline soils of arid regions. Key indicators included soil fertility, sunflower growth, salt leaching efficiency, WP, and NP. Data analysis integrated Pearson correlation, EWM-TOPSIS-AISM optimization, and partial least squares path modeling to assess variable relationships, rank treatment performance, and clarify causal pathways. IOD+SR+OS significantly enhanced soil fertility, increasing soil mineral nitrogen by 6.87–59.54 %, available phosphorus by 4.96–152.93 %, and exchangeable potassium by 7.02–83.07 % compared to other treatments, which in turn promoted sunflower growth, leading to improvements in plant height (9.92–63.32 %), stem diameter (7.59–47.39 %), leaf area index (19.59–176.50 %), and above-ground dry matter (7.43–68.01 %). Additionally, this integrated approach exhibited the highest salt leaching efficiency (0.0032 g kg⁻¹ mm⁻¹), effectively mitigating soil salinity . Although IOD+SR+CK achieved the highest short-term NP (22.94 and 22.74 (Thousand Chinese yuan) ha⁻ 1 in 2022 and 2023), IOD+SR+OS demonstrated superior long-term sustainability by optimizing WP (1.42 kg m⁻³, increasing by up to 26.12 %). Multi-objective optimization further confirmed IOD+SR+OS as the most effective strategy for balancing soil fertility, WP, and NP in salinized farmland. By highlighting the synergies among IOD, SR, and OS, this study provides empirical evidence for improving soil fertility, optimizing resource efficiency, and enhancing farm profitability in arid regions. These findings contribute to the advancement of precision agriculture strategies that foster sustainable agriculture development. • Combined precision irrigation, straw return, and organic substitution improved soil N/P/K by 4.96–152.93 %. • Combined precision irrigation, straw return, and organic substitution got the best multi-objective balance. • Optimal strategy promoted the growth and dry matter accumulation of sunflower. • Optimal strategy maximized salt leaching (0.0032 g kg mm −1 ) and water productivity (1.42 kg m −3 ).