Reducing potato water footprint by adjusting planting date in the agro-pastoral ecotone in North China

Reducing the water footprint per unit of crop production reduces the pressure on the limited freshwater resources. This study used data from a four-year field experiment conducted in the agro-pastoral ecotone (APE) of Northern China, to calibrate and validate the APSIM-Potato model, and determine the impacts of planting dates on the water footprint (WF) of potatoes under rain-fed and irrigated conditions. Results showed that the rain-fed potato yields were 14.6, 18.9, and 19.9 t ha−1, under the early, normal, and late planting dates, respectively, and the irrigated yields were 19.7, 31.8, and 30.9 t ha−1 under the three planting daets. The blue WF of the potatoe were -25.6–0 m3 t−1, -27.2–0 m3 t−1, and -26.4–0 m3 t−1 in early, normal, and late planting dates, respectively, under rainfed condition, and the value was highest in normal planting date. Green WF of the potato was 24.4 m3 t−1, 16.0 m3 t−1, and 13.5 m3 t−1 under early, normal, and late planting dates, respectively. The total WF was 20.3 m3 t−1 under the early planting dates, which was 50.3% and 87.9% higher than that under normal and late planting dates, respectively. Under the irrigated conditions, early planting exhibited the highest blue WF (33.2–77.9 m3 t−1), followed by normal (32.1–67.4 m3 t−1), and late planting dates (26.6–61.3 m3 t−1). The green WF was 104.9 m3 t−1 under the early planting dates, which was 48.8% and 45.9% higher than that under normal and late planting dates. Furthermore, the total WF of potatoes decreased with delayed planting, with the average values of 161.1, 117.8, and 114.2 m3 t−1 under early, normal, and late planting dates, respectively. These findings suggest the potential of reducing potato WF across the APE by adjusting the planting dates.