| Taking brewing sorghum ‘Fenjiuliang No. 1’ as the test material, field experiments were carried out from 2018 to 2021. Six treatments were established: no fertilizer (CK), chemical fertilizer (NPK), farmyard manure (S), commercial organic manure (C), a combination of farmyard manure and NPK (SNPK), and a combination of commercial organic manure and NPK (CNPK). The yield, nitrogen, phosphorus and potassium accumulation in continuous sorghum were obtained together with soil bulk density (BD), pH value, organic matter content (OC), total nitrogen content (TN), available phosphorus (AP) and potassium content (AK) content of the soil. The results showed increases of 4.45% to 33.60% in the sorghum yield over continuous cropping for four years under treatments with NPK, S, and SNPK as compared to unfertilized crops. The yield increasing effect of the S treatment increased as continuous cropping continued, with a significant increase of 6.47% to 28.69% observed in the fourth year as compared to the other fertilizer treatments. Compared to NPK, significant reductions of 10.64% and 6.38% were observed in the coefficient of yield variation values of the S and SNPK treatments, respectively, while increases of 2.53% and 1.27% in the yield sustainability index values indicated improved stability and higher sustainability. Nitrogen accumulation was 8.36% and 3.31% higher under S and SNPK treatments, respectively, as compared to NPK, along with respective fourth year increases of 3.48% and 21.45% for potassium accumulation and only 2.22% and 0.70% for phosphorus accumulation. S and SNPK treatments also led to BD decreases of 3.78% and 4.55% in the 0~20 cm and 7.29% and 4.31% in the 20~40 cm soil layers, respectively, as compared to NPK treatment. SNPK significantly and steadily reduced the pH value in the 0~40 cm soil layer and led to a significant increase of 22.18% to 36.71% in soil OC and 9.07% to 25.62% in soil AP for the 0~20 cm soil layer as compared to NPK, while S increased the soil OC by 15.00% to 22.37% and soil AP by 41.08% to 43.91% in the 20~40 cm soil layer. However, significant decreases were observed in terms of yield and nitrogen and phosphorus accumulation under fertilizer application treatments in the fourth year of continuous cropping, with yield decreasing by 15.57% to 32.76%, nitrogen accumulation decreasing by 12.89% to 27.90%, and phosphorus accumulation decreasing by 5.89% to 25.82%. The results indicated that applying farmyard manure and farmyard manure combined with chemical fertilizer could stabilize the yield and maintain the soil fertility level; however, continuous cropping should be continued for only three years. The application of farmyard manure combined with chemical fertilizer (SNPK) is likely beneficial for improving the fertility level in the 0~20 cm soil layer and the sorghum yield over two years, while farmyard manure (S) is beneficial for improving the fertility level in the 20~40 cm soil layer and the sorghum yield over three years of continuous cropping. |