Objective The aims were to explore the effects of different crop rotation patterns on soil fertility in newly cultivated terraced fields of rain-fed regions, in order to establish a theoretical basis for regional soil improvement.

Method Using continuous potato monoculture (P-P-P) as the control, three rotation patterns of Potato-Vetch-Potato (P-G-P), Potato-Vetch-Maize (P-G-C), and Potato-Vetch-Wheat (P-G-W) were established and evaluated for their effects on soil physical properties, organic matter content, and nutrient levels in cut and fill sections of newly cultivated terraced fields, and conducted a comprehensive evaluation for soil fertility.

Result ① Compared to P-P-P, all rotation patterns significantly reduced soil bulk density in the 0-20 cm of both cut and fill sections, while increasing total porosity in the 0-40 cm of fill section. No significant differences were observed among these rotations. ② The P-G-P rotation outperformed P-P-P by significantly increasing soil organic matter (SOM), total nitrogen (TN), total phosphorus (TP), available nitrogen (AN), and available phosphorus (AP) in the 0-40 cm layer in both cut and fill sections. Moreover, it concurrently increased three-year cumulative yield by 15.91% and 18.46%, boosting economic benefits by 21.65% and 24.80% in these respective sections, and generating net profits of 17909 and 20963 yuan hm⁻² for cut and fill sections, respectively. The P-G-C elevated SOM and TN in the 0-20cm layer, and AN and available potassium (AK) in the 0-40 cm layer of both sections. The cumulative crop yields in P-G-C for the cut and fill sections increased by 44.85% and 42.47%, the economic benefits rose by 9.73% and 10.78%, resulting in net profits of 15604 and 16770 yuan hm⁻², respectively. The P-G-W enhanced SOM and AK in the 0-20 cm layer, AN, AK and TN in the 0-40 cm layer for both sections, while TN in the 0-40 cm layer of fill section. The cumulative crop yields in P-G-W were promoted by12.78% and 20.13%, the economic benefits were increased by 0.98% and 7.70%, resulting in net profits of 16197 and 20104 yuan hm⁻² for cut and fill sections, respectively. ③ Principal component analysis (PCA) revealed that three principal components in cut sections explained 83.32% of cumulative variance, ranking by P-G-P > P-G-W > P-G-C > P-P-P; while 84.44% of explained cumulative variance in fill sections, ranking by P-G-W > P-G-C > P-G-P > P-P-P.

Conclusion Integrated nutrient and economic analyses demonstrated that the P-G-P rotation optimally enhanced soil fertility in cut sections of newly cultivated rain-fed terraced field, while P-G-W was the most effective pattern for fill sections. These findings established a theoretical foundation for rapid soil amelioration in comparable regions.