Impact of Cadmium-contaminated water and irrigation levels on microbiological properties of soils with different textures

Cadmium (Cd) contamination poses a significant threat to soil health and agricultural productivity, particularly under varying water availability and soil textures. This study examines the effects of water levels (25%, 50%, 75%, and 100% field capacity) and soil textures (sandy clay loam, silty loam, and clay) on key microbiological properties, including basal soil respiration (BSR), microbial biomass carbon (Cmic), dehydrogenase activity (DHA), and catalase activity (CA), in Cd-contaminated soils. An incubation experiment was conducted under controlled conditions at 20 ± 0.5°C for 10 days. Microbiological properties were assessed using standard methods: alkali absorption for BSR, substrate-induced respiration for Cmic, spectrophotometric assays for DHA, and volumetric determination for CA. Optimal microbial activity across all parameters was observed at 75% field capacity, highlighting the importance of balanced soil moisture. Clay soils consistently exhibited the highest activity due to their superior organic matter content and buffering capacity, while sandy clay loam soils showed the lowest activity due to limited water retention and nutrient availability. Excessive moisture at 100% field capacity reduced oxygen diffusion, suppressing microbial activity, while insufficient moisture at 25% field capacity constrained microbial metabolism. These findings provide critical insights into the interplay between soil texture, water availability, and Cd contamination, offering valuable guidance for sustainable soil and water management practices to mitigate heavy metal toxicity in agricultural systems.