Objective The aim was to understand the basic information of soil nutrients in Nanchong, and the difference of nutrient content among different soil types.

Method The 14 physicochemical indicators of 872 cultivated land soil samples collected in Nanchong in 2020 were measured. The test results were classified by using the nutrient grading standards of the second national soil survey, and the soil types were classified according to the Chinese Soil System Classification.

Result The results of soil testing and nutrient grading indicated that the overall soil compaction was alkaline, the available phosphorus (AP) and available iron (Fe) were in the first grade. The available copper (Cu), available sulfur (S) and available zinc (Zn) were in the second grade, and the total nitrogen (TN), available potassium (AK), available manganese (Mn) and available boron (B) were in the third grade. The contents of soil organic matter (SOM), alkali-hydrolyzed nitrogen (AN) and available molybdenum (Mo) were in the fourth grade. The soil classification results showed that the soil types in Nanchong were yellow earths, neo-alluvial soils, purplish soils, fluvo-aquic soils and paddy soils, with sampling site proportions of 3.78%, 0.46%, 50.23%, 2.63% and 42.89%, respectively. The soil bulk density of neo-alluvial soils was the highest, with an average of 1.75 g cm^-3. At the same time, the average contents of nutrients, such as available Zn, available Fe, available B and available S, were also the lowest. The average pH of yellow earths was 6.94, but the average contents of available Mn and available B was the highest. Typical yellow earth had higher contents of SOM, AN and trace elements, while bleached yellow earth had higher average contents of AP and AK. Purplish soil had the highest alkalinity, but the average contents of SOM, TN, AN, AP and AK were the lowest. Lime purplish soil accounted for 78.08% of the samples in purplish soil, which not only has a high alkalinity, but also had a higher average contents of SOM and trace elements. Neutral purplish soil had an advantage in the average content of large elements. Paddy soil has the highest average contents of SOM, available Cu, available Fe and available S, but with the lowest soil bulk density. Among the four subgroups of paddy soil, percogenic paddy soil samples accounted for the highest proportion of total paddy soil samples (52.95%). The average values of TN, AN, available Zn, available Mn, available B and available S in submergenic paddy soil were the highest. The average content of SOM in hydromorphic paddy soil was the highest, and the average contents of AP and AK in gleyed paddy soil were the highest.

Conclusion The soil types of farmland in Nanchong were mainly purplish soils and paddy soils, containing a small amount of neo-alluvial soils, yellow earths and fluvo-aquic soils. The purplish soils were mainly calcareous purplish soils, while the paddy soil was mainly gleyed paddy soil. The soil as a whole was alkaline, with low average contents of SOM, AN and available Mo, and abundant average contents of AP and available Fe. The physical and chemical properties of different types of soil also have their own characteristics, such as high alkalinity in purplish soils, higher SOM in paddy soil, more bulk density in neo-alluvial soils, higher available Mn in yellow earths, and abundant N in fluvo-aquic soils. At the same time, there are differences in the distribution of nutrient contents among soil subgroups.