Life cycle assessment of environment benefits in wheat production under water-saving and nitrogen-reducing practices in the North China Plain

Winter wheat cultivation faces yield reductions in the North China Plain due to drought and excessive nitrogen fertilizer use, exacerbated by climate change. This study employed a life cycle assessment approach, integrating economic and material input-output data, to evaluate the eco-efficiency of reduced irrigation and nitrogen fertilizer inputs. Field experiments were conducted with four irrigation regimes at the jointing stage (W0: no irrigation; W1: 75 mm), heading stage (W2: additional 75 mm), and filling stage (W3: additional 75 mm), in combination with three nitrogen fertilization levels (conventional, N250: 250 kg ha−1; 20 % reduction, N200: 200 kg ha−1; 40 % reduction, and N150: 150 kg ha−1). The interactive effects on environmental benefits were comprehensively assessed. Results showed irrigation frequency had higher effect on yield than nitrogen application, with nitrogen reduction causing a maximum yield loss of 11.7 %, while reduced irrigation led to 34.0–48.9 % yield losses. Under conditions of sufficient water availability, total environmental costs were inversely correlated with wheat yield and did not increase with higher irrigation frequency. Specifically, increasing irrigation frequency reduced total environmental costs by an average of 32.4 %, 26.9 %, and 23.7 % under N250, N200, and N150 fertilization levels, respectively. Nitrogen fertilizer inputs represented the largest contributor to environmental costs, accounting for 25.6–60.1 % of the total environmental burden. Nitrogen reduction strategies enhanced overall eco-efficiency and lowered environmental costs, whereas water-saving measures involving reduced irrigation decreased eco-efficiency and increased environmental costs. The optimal strategy for high-quality wheat production involved applying 150 kg ha−1 nitrogen and irrigating twice (W2), balancing yield, sustainability, and eco-efficiency. This approach effectively balances yield, environmental sustainability, and eco-efficiency, providing a practical solution to address the environmental challenges of wheat production in the region.