A large-scale assessment on spatial variability of potato yield and soil chemical properties in northern China

Understanding the spatial variability of potato yield and soil chemical properties is critical for designing management strategies and ensuring potato sustainable production. However, there has been no detailed investigation on a large-scale variation in yields and soil nutrients in potato production areas of China. In this study, 938 soil samples and potato production information were collected from the main potato-producing areas in northern China. The results showed that potato yields and selected soil properties varied considerably, with coefficients of variation ranging between 12.2% and 110.8%. Potato yield, pH, soil organic matter (SOM), total nitrogen (TN), available potassium (AK), and electrical conductivity (EC) showed strong spatial correlations, while mineral nitrogen (MN) and available phosphorus (AP) had moderate spatial correlations based on semivariograms analysis. The spatial distribution of yields indicated that 83.3% of potato yields ranged from 20 to 60 t ha(-1). The SOM, TN, AP, and AK showed similar spatial distribution trends with high concentrations in the northeast, while pH showed the opposite trend. EC was found to be highly variable with high values in the west. The high soil pH and low SOM were the most important constraints limiting potato productivity, and the high MN implied excessive nitrogen fertilizer application. The soil quality index (SQI) was calculated using selected soil properties, and a significant correlation between SQI and potato yield was observed. The spatial distribution of SQI showed that 42.2% of the study area was of low soil quality (SQI less than 0.6). A relatively low SQI indicated that there was great potential for increasing potato productivity in northern China. After dividing soil samples into rainfed and irrigated, the effect of soil nutrients on potato yield was found to become weaker at irrigated sites, where there was no correlation between SQI and yield, suggesting that the role of soil moisture overshadowed the role of nutrients. The spatial variability of soil chemical properties provided essential information for developing rational nutrient management strategies and regional planning to achieve sustainable potato production in China.