Liming does not counteract the influence of long-term fertilization on soil bacterial community structure and its co-occurrence pattern

Chemical fertilizer application is a common agronomic practice to improve crop productivity and liming is often used to counteract the soil acidification caused by long-term fertilization; however, it is unclear whether liming will counteract the effect of long-term fertilization on soil bacterial community structure and its co-occurrence pattern. Here, we examined the influence of long-term fertilization (NPKS) and liming (L) on soil bacterial community structure and its co-occurrence networks by sequencing 16S rRNA gene amplicons. Our results showed that liming counteracted the influence of long-term fertilization on soil pH, but not on soluble organic carbon (SOC) and electrical conductivity (EC). Long-term fertilization affected the abundance of Acidobacteriia, Deltaproteobacteria and Gammaproteobacteria in the 0-10 cm soil, and that of Deltaproteobacteria, Gammaproteobacteria and Gemmatimonadetes in the 10-20 cm soil; whereas liming affected the abundance of Acidobacteriia, Gammaproteobacteria, and Chloracidobacteria in the 0-10 cm soil and that of Deltaproteobacteria in the 10-20 cm soil. The bacterial community structure in soils with the NPKS-L treatment was different from that with other treatments, and was mainly affected by SOC, EC, and NO3- concentration. The link numbers in bacterial co-occurrence networks were decreased by long-term fertilization or liming alone, but were increased by the NPKS-L treatment. Notwithstanding the fact that liming alleviates fertilization-induced soil acidification, this study indicates that liming did not counteract the effect of long-term fertilization on soil bacterial community structure and its co-occurrence pattern, hence cannot recuperate the soil microbial functionality that is changed by long-term fertilization.