Exploratory profiling of soil bacterial communities and fertility in tropical maize amended with diatomaceous earth

Soil bacterial communities are sensitive indicators of biological condition in tropical agroecosystems, yet field information from acidic maize soils in Ecuador remains scarce. This study provides an exploratory profile of soil bacterial communities and fertility indicators in maize amended with diatomaceous earth under field conditions. A randomized complete block field experiment was established with three treatments and five replications: untreated control without fertilization or diatomaceous earth (T1), conventional fertilization (T2), and conventional fertilization plus diatomaceous earth (T3). Grain yield was measured from replicated plots, whereas soil chemistry and 16S rRNA bacterial profiles were obtained from composite analytical profiles and interpreted descriptively. One composite baseline soil profile was obtained before treatment differentiation, and one composite profile per treatment was obtained at 60 and 120 days after sowing. Soil was sampled from the 0-30 cm layer in the inter-row zone. The diatomaceous earth product was applied edaphically at 12 kg ha-1 and contained 73.60% w/w SiO2 according to the product certificate. The 16S rRNA V3-V4 region was sequenced using an Illumina workflow, and raw FASTQ files were deposited in NCBI SRA. Grain yield differed among treatments (F = 18.18; P = 0.0011), with T2 and T3 statistically similar and both higher than T1. Bacterial profiles were dominated by Acidobacteria, Actinobacteria, Proteobacteria, Firmicutes and Verrucomicrobia. T3 at 120 DAS showed the highest numerical Shannon index and provider-reported species-level classifications among treatment-time profiles, but these patterns were not tested inferentially. The study offers a transparent baseline for future replicated microbiome work in tropical acidic maize soils.