Regulation of Soil Microorganisms in Protected Cultivation by Straw Decomposition Products Treated with Calcium-Containing Additives

Objective The aims were to explore the effects of rice straw decomposition products treated with different calcium-containing additives on soil microorganisms in protected cultivation, and to provide a theoretical basis for soil improvement in protected cultivation.

Method A greenhouse pot experiment was conducted with protected cultivation soil as the research object. Three treatments were set up, with chemical fertilizer alone (CK) used as the control. Based on CK, two additional treatments were established: one with rice straw decomposition products treated with Ca(OH)₂ (HCa) and the other with rice straw decomposition products treated with CaC₂O₄ (OCa). Thirty days after the pot experiment, soil physical and chemical properties as well as soil microbial community structure were determined.

Result The addition of rice straw decomposition products treated with Ca(OH)₂ and CaC₂O₄ significantly increased soil pH and reduced exchangeable acid (EA) content. Among them, the addition of Ca(OH)₂-treated decomposition products also significantly decreased total soluble salt (TSS) content, while CaC₂O₄-treated decomposition products significantly increased total nitrogen (TN) and available phosphorus (AP) contents. The dominant bacterial phyla in the soil were Proteobacteria, Gemmatimonadota, and Actinobacteriota, and the dominant fungal phylum was Ascomycota. The treatment with Ca(OH)₂-treated decomposition products enriched Cellvibrionaceae (Gammaproteobacteria) and Saprospiraceae (Bacteroidota), whereas the treatment with CaC₂O₄-treated decomposition products enriched Nocardiaceae and Microbacteriaceae. The bacterial community was regulated by pH, available potassium (AK), and EA, while the fungal community was mainly affected by pH.

Conclusion Rice straw decomposition products treated with different calcium-containing additives improve the nutrient status and microbial diversity of protected cultivation soil to varying degrees. The addition of Ca(OH)₂-treated decomposition products significantly increases soil pH, reduces soluble salt content, and enriches beneficial bacterial families, while the addition of CaC₂O₄-treated decomposition products significantly increases soil AP content.