This study investigated the effects of straw layered returning combined with its decomposing agents on the transformation of soil organic carbon (C), activities of enzymes related to C metabolism, structure of microbial community, and rice yield, in order to provide a theoretical basis for organic fertilization of low-yield yellow paddy soil and rice yield improvement.
Eight treatments were designed, including no fertilization (CK), conventional fertilization (NPK), and layered straw application at 0 cm, 0-8 cm, and 8-18 cm depths (NPKSL0, NPKSL0-8, and NPKSL8-18), and layered straw application combined with decomposing agents at 0 cm, 0-8 cm, and 8-18 cm depths (NPKSML0, NPKSML0-8, and NPKSML8-18). The content of soil organic C components, activity of C metabolism-related enzymes, soil microbial community, rice yield and its yield components were investigated, and their dominant factors that affect rice yield and soil organic C were further explored.
Compared with NPK and NPKSL0-8, NPKSL8-18 treatment significantly increased the content of soil easily oxidizable organic C, microbial biomass C, particulate organic C, activity of α-glucosidase and β-glucosidase, and the relative abundance of Acidobacteriota and Ascomycota. Compared with the single straw application, the coupling application of straw and decomposing agents further increased soil organic C, easily oxidizable organic C, particulate organic C, mineral-bound organic C, and the activity of β-glucosidase in the 0-8 cm and 8-18 cm layers. Under NPKSML8-18 treatment, the abundance of Chloroflexi group was the highest, while the groups of Rozellomycota, Anaeromyxobacter, and Nigrospora were the lowest. Compared with NPK, NPKSML0, NPKSML0-8, and NPKSML8-18 increased soil organic C and rice yield, with the increments of 27.38%-37.94% and 7.97%-23.14%, and their values were highest in the NPKSML8-18 treatment. Correlation analysis showed that soil organic C and rice yield were significantly and positively correlated with soil easily oxidizable organic C, microbial biomass C, mineral-bound organic C, particulate organic C, and the activities of β-1,4-xylanase, α-1,4-glucosidase, and β-1,4-glucosidase (P<0.05), but were negatively correlated with dissolved organic C, the bacterial Shannon index and the fungal richness index (P<0.01).
Deep application of straw coupled with decomposing agents (NPKSML8-18) increases soil organic C and rice yield, mainly by enhancing the content of soil easily oxidizable organic C, microbial biomass C, mineral-associated organic C, and particulate organic C, boosting the activities of β-1,4-xylanase, α-1,4-glucosidase, and β-1,4-glucosidase, and promoting the relative abundance of Chloroflexi involved in straw decomposition.
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |