Abstract: 【 Objective 】Soil compaction and caking can lead to a significant decrease in soil quality in agricultural farmland, and a serious lack of comprehensive agricultural production capacity. Carbon source materials may have the ability to improve the structure of clayey soil. 【 Methods 】By using field experiments, a control group (CK), farmyard fertilizer (N group), biochar (T group), biological bacterial fertilizer (B group), commercial organic fertilizer (J group), and mineral potassium humate (H group) were designed, with three gradient treatments in each group. The aim was to explore the effects of five carbon source substances on the physicochemical properties of clayey soil and plant agronomic traits. 【 Results 】(1) The input of five carbon source substances had a significant impact on soil bulk density and soil porosity, with biochar having the most significant improvement effect. (2) The input of five carbon source substances had a certain improvement effect on soil aggregates of various particle sizes. Among the 1-2 mm and 1mm soil aggregates, T₂ treatment had the best improvement effect, N₃ treatment had the best improvement effect on 0.5-1 mm soil aggregates, and J₃ treatment has the best improvement effect on 0.1-0.25 mm soil aggregates; Compared to CK, it increased by 455.70%, 504.01%, 207.41%, 65.55%, and 41.70% respectively; (3) The input of five carbon source substances could significantly improve the plant height and stem diameter of cotton plants. In terms of the improvement effect on plant height and stem diameter, the pattern presented was N>T>S>J>H and S>J>T>N>H; (4) The five carbon source substances had a significant effect on improving the dry and fresh weight of plants, and the effect of farmyard fertilizer was the best in improving the agronomic properties of cotton. 【 Conclusion 】In the overall evaluation, different carbon source inputs are beneficial for the physicochemical properties and plant agronomic traits of clayey soil, and the recommended amount of farmyard fertilizer+50% is the best. In summary, adding carbon source substances to clay soil can promote the formation of soil aggregates and alleviate the stress of compaction on soil by regulating soil structure and biochemical organic matter.