Effects of Cassava-Chili Intercropping at Different Planting Densities on Soil Bacterial Community Structure

This study established three intercropping densities of cassava and chili (chili plant spacing of 0.4 m, 0.5 m, and 0.6 m, denoted as IA, IB, and IC, respectively), using cassava monoculture (MC) and chili monoculture (MP) as controls, to systematically investigate differences in soil biochemical properties and soil bacterial community structure under different cassava-chili cropping systems. The results showed that soil pH, catalase activity, and acid phosphatase activity were higher in the IB and IC treatments than in the monoculture treatments, while alkali-hydrolyzable nitrogen (AN), available phosphorus (AP), and available potassium (AK) contents were lower in the IA and IC treatments compared to the monoculture treatments. Alpha diversity was higher in the intercropping systems than in the monoculture systems, and the soil bacterial communities exhibited greater richness and diversity. In the intercropping systems, the relative abundances of Verrucomicrobiota, Gemmatimonadota, and the common dominant soil genus Candidatus_Udaeobacter increased, while those of Actinobacteriota, Proteobacteria, and the genera Acidothermus and Chujaibacter decreased. Redundancy analysis indicated that the soil bacterial community was significantly influenced by soil catalase activity and total nitrogen. In summary, cassava-chili intercropping enhances soil nutrient levels and enzyme activity while reshaping the structure of the soil bacterial community.