The use of antibiotic-containing manure as fertilizer raises concerns about its impact on soil nutrient cycling. Particularly, the antimicrobial effects on soil nitrogen (N) cycling are unclear in soils with different textures. We hypothesized that finer soils would significantly reduce antibiotic bioavailability, thus reducing the negative impacts on the abundance of N cycling microbes, nitrification, and N 2 O emissions expected in coarser soils. To test this, we conducted a 46-day incubation experiment using three soil textures (sandy, sandy loam, and loam) and four treatments: a control without manure, antibiotic-free manure, manure with oxytetracycline, and manure with sulfadiazine. We quantified total and bioavailable antibiotic residues, soil N 2 O emissions, soil mineral N pools, and N cycling functional genes. Our results showed that the bioavailability of sulfadiazine in sandy soil was approximately double that of loam soil, whereas oxytetracycline bioavailability was independent of soil texture. In sandy soil, the high bioavailability of sulfadiazine reduced the abundance of ammonia-oxidizing bacteria and transiently inhibited nitrification. Conversely, low sulfadiazine bioavailability in loam soil was linked to an increased abundance of complete ammonia-oxidizing bacteria (Comammox A). Oxytetracycline also increased Comammox A abundance in sandy loam and loam soils. Our findings suggest that the influence of soil texture on antibiotic bioavailability is compound specific. The antimicrobial impacts on soil N cycling are also considerably dependent on antibiotic types. Therefore, predicting the environmental impact of antibiotic residues in manure requires considering both the specific antibiotic properties and the soil characteristics. • Effects of soil texture on antibiotic bioavailability are compound specific. • Sulfadiazine inhibited AOB in sand but increased Comammox abundance in loam. • Persistent oxytetracycline showed no inhibitory effects on N cycling microbes. • Soil and antibiotic properties co-determine antimicrobial impacts on N cycling.
Yang et al. (Mon,) studied this question.