Abstract: Background, aim, and scope The Yellow River basin is one of the main agricultural production areas in China, which plays a crucial role in solving the problem of food security in China. However, with the continuous increase of irrigated area and fertilizer application amount, the problems of nutrient imbalance and low fertilizer utilization rate appear in the irrigated areas along the Yellow River. Although there have been some studies on soil quality evaluation in irrigated areas before, there are few reports on comprehensive evaluation of soil fertility in five irrigated areas along the Yellow River basin. In order to better realize the sustainable development of the irrigated areas and even the whole Yellow River Basin，our study aims to fully understand the characteristics of soil nutrient content in five major irrigated areas along the Yellow River. Materials and methods In this study, five irrigated areas in Ningxia (NX), Hetao (HT), Fenhe (FG), Guanzhong (GZ) and the North China Plain (HB) were selected as research objects. The nutrient contents of soil were measured and the soil fertility was evaluated. Results The results showed that the soil pH of the irrigated areas was higher than 8.0; The average contents of soil organic matter (SOM), total nitrogen (N), available nitrogen, total phosphorus (P), available phosphorus, total potassium (K) and available potassium were corresponding to four, four, four, three, two, three and one nutrient levels; The average contents of available Fe, Mn, Cu and Zn were corresponding to the three, four, one and one nutrient levels; The comprehensive fertility index of the five irrigated areas along the Yellow River basin is in the order of NX > FG > HB > HT > GZ. Discussion The differences of nutrient contents in five irrigated areas are related to fertilization, soil types, irrigation conditions and other factors. The contribution rate of organic matter and total nitrogen to soil comprehensive fertility was high in NX and HT. The reasons why the comprehensive index of soil fertility in GZ is low, in addition to the insufficient input of organic fertilizer, are the poor soil types, which mostly is tidal soil along the river. Conclusions The difference of soil comprehensive fertility caused by nutrient imbalance existed in five irrigated areas. Ningxia and Fenhe irrigated areas were of secondary fertility, while the rest were of tertiary fertility. Recommendations and perspectives The results indicate that we should strengthen the control of soil salinization, increase the organic matter of farmland, adjust the proportion of N, P, K and attach importance to the supply of trace elements, so as to change the current situation of soil nutrient imbalance between the five irrigated areas.
Keywords: areas irrigated by the Yellow River; soil nutrient; soil fertility; soil testing fertilization; sustainable development