Dryland agroecosystems face persistent challenges from low soil fertility and limited organic matter inputs. Although integrated organic-inorganic nutrient management (IOINM) is widely promoted, its interaction with water-harvesting tillage systems remains insufficiently quantified. A decade-long field trial on China's Loess Plateau investigated how three IOINM regimes, inorganic nitrogen and phosphorus fertilizer (NP), NP combined with corn straw (NPS), and NP supplemented with sheep manure (NPM), interacted with three tillage systems: flat tillage (FT), ridge-furrow (RF), and ridge-furrow with plastic mulch (RFPM). Tillage systems modified the effectiveness of organic amendments. Improvements in soil organic carbon (SOC), total nitrogen (TN), and yield with straw and manure amendments were greater under RFPM, reflecting complementary effects of improved soil moisture conditions and organic nutrient inputs rather than statistically demonstrated non-additive interactions. The RFPM-NPM treatment produced the most significant gains, increasing soil SOC by 40.6% and crop yield by 225.2% compared with FT-NP, while also mitigating excessive nitrate accumulation observed under RFPM-NP. Lower residual nitrate under RFPM despite higher total N inputs is consistent with enhanced biological nitrogen demand and altered nitrogen turnover under moisture-conserving conditions. In contrast, the benefits of organic amendments were less pronounced or inconsistent under RF and FT systems. Correlation analysis was used to assess relationships between soil properties, SOC, and crop yield across tillage and IOINM treatments, while XGBoost feature-importance analysis provided exploratory, complementary support for these relationships rather than independent validation. Overall, incorporating manure into IOINM under RFPM represents a highly productive management strategy that improves SOC accumulation and crop performance. However, long-term sustainability will depend on mitigating phosphorus drawdown driven by high crop removal, and on effective management of plastic-film residue accumulation under RFPM.