Balancing yield, quality, and resource efficiency in potato production: A global meta-analysis identifies an optimal deficit irrigation and fertilization strategy

Investigating the effects of water and nitrogen reduction on potato production performance has emerged as a crucial challenge for sustainable agricultural development, given that global agriculture is confronted with the twin issues of resource scarcity and climatic variability. To systematically assess the changes in yield, quality, and resource use efficiency under varying reduction intensities, this study compiled a comprehensive meta-analysis database comprising 3397 observational datasets from 72 field experiments across 11 countries. Furthermore, a path model was employed to identify the primary regulatory pathways, and the TOPSIS multi-objective decision model was utilized to evaluate and rank the water and nitrogen management strategies. The findings demonstrated a strong synergistic effect, with yield remaining essentially constant under mild reduction conditions (70%-90% of maximum water and fertilizer inputs). On average, water use efficiency (WUE) and nitrogen partial factor productivity (NPFP) increased by 7.69% and 12.94%, respectively. However, yield dropped by an average of more than 24.83% under severe reduction conditions (≤50%). Quality indicators exhibited directional divergence under deficit irrigation and fertilization: although Vitamin C content exhibited a marginal increase under mild resource deficits, it yielded a significant negative response overall (-0.0957). In contrast, protein content remained relatively stable, whereas reducing sugar and starch concentrations generally declined across the treatment groups. Subgroup analysis revealed that optimal treatment results occurred under soil conditions of neutral pH (6.5–7.5), an annual average temperature of 8–12 °C, annual rainfall of 400–800 mm, and organic matter content≥ 15 g kg−1. Regression analysis revealed a significant binary quadratic relationship and positive interaction between water and nitrogen inputs and yield. While single-factor analysis indicated that peak yields required inputs of 0.91 FI (FI: the amount of irrigation for full irrigation) and 0.96 FF (FF: the local maximum nitrogen application rate), the water-nitrogen coupling demonstrated that maximum yields could be achieved with significantly reduced inputs (0.82 FI and 0.87 FF). This confirms the substantial advantages of coupled water and nitrogen management for resource conservation and synergistic yield enhancement. Path analysis indicated that planting density was the strongest direct factor influencing production (path coefficient 0.4463), outperforming fertilizer (0.2915) and irrigation (0.3646), while also indirectly increasing crop output by modulating organic matter and microclimate. The TOPSIS comprehensive evaluation showed that sufficient irrigation coupled with a mild reduction in nitrogen application (FIFFL) was the optimal combination to balance potato yield, quality, and water and nitrogen use efficiency. The regression model predicted that the best balance point for maximizing the comprehensive benefits of potatoes is 0.83 FI and 0.87 FF. In conclusion, under appropriate environmental and management conditions, potatoes possess the physiological capacity to adapt to reduced water and nitrogen inputs. This study provides quantitative evidence and mechanistic support to encourage precise input reduction, stabilize output, and boost resource efficiency in global potato-producing regions.