Identifying agronomic options for better potato production and conserving water resources in the agro-pastoral ecotone in North China

Potato is a main food crop in the agro-pastoral ecotone (APE) of North China, but its yield is low and highly variable. Agronomic managements, such as irrigation, fertilization and intensive cropping systems, has been used for increasing potato yield but resulted in negative environmental sequences (e.g., soil dryness and groundwater table decline) in such arid and semi-arid regions. This study aims to quantify the agronomic options for better potato production and groundwater conservations based on field experiments together with APSIM-Potato model. The long-term simulated crop yield, economic income and environmental impact (surface soil water content and groundwater table) were analyzed for the different cropping systems of potato (continuous planting, CP; alternating planting and fallowing, APF; long-term continuous fallowing, LF) and irrigation scheduling (rainfed and one-four irrigations). The calibrated APSIM-Potato performed well in simulating the responses of soil water dynamics, leaf area index (LAI), biomass, evapotranspiration (ET) and yield of potato to different irrigation treatments. Long-term (1981-2010) simulated potato yield could be increased by 43.4-90.2% from rainfed yield if irrigation was applied from 60 to 240 mm and the yield gap between the potential and rainfed yields could be narrowed by 41.5-85.9%. Across the APE, CP with four irrigations (240 mm) produced the maximum income of 18,445 Yuan.ha(-1) while WUE was the highest for both CP and APF with two irrigations (120 mm). However, such irrigation amounts would decrease the groundwater table by 4.1-42 m across the APE during this period. Rainfed CP could enhance the groundwater table by 0-3 m but decrease available soil water content in 1 m depth by 15.5 mm per decade from 1981 to 2010. Rainfed APF and LF increase available soil water content in 1 m depth by 2-79 mm and 100-143 mm respectively. The study suggested that CP would decrease the soil moisture significantly and increase the risk of soil desertification in the APE. APF with one irrigation by harvesting rainwater could be a feasible way of maintaining soil moisture and groundwater conservation if government subsidy could guarantee the incomes of local farmers in the APE in North China.