Liming enhances the abundance and stability of nitrogen-cycling microbes: The buffering effect of long-term lime application

Lime application (liming) has historically been used to ameliorate soil acidity in grasslands. Liming effectively improves soil pH, plant productivity, and soil physicochemical properties, but the long-term impact of acidity control by liming on key microbial nitrogen (N)-cycling genes in semi-natural grasslands is unknown. We investigated the effect of 65 years of liming on N-cycling processes in the limed and control plots of the Ossekampen long-term grassland experiment in the Netherlands. These plots have not received any other fertilizers for 65 years. Soil sampling and nitrous oxide (N 2 O) emission measurements were conducted three times in spring and four times in summer, and quantitative real-time PCR was performed to determine the abundances of N-cycling genes, including ammonia-oxidation ( amoA ), denitrification ( nirS , nirK , nosZ ), and N-fixation ( nifH ) genes. Long-term liming increased the abundances of nitrifiers and denitrifiers but did not increase N 2 O emissions. Additionally, liming had a buffering effect that stabilized the population of N-cycling microbes against seasonal variations in abundance. Our results indicate that improving soil acidity through liming facilitates microbial N-cycling processes without increasing N 2 O emissions. Highlights: 65 years of liming increased bacterial but not archaeal and fungal community abundance. Liming increased the abundance of microbial N-cycling genes. The buffering effect of liming reduced seasonal variations in the abundance of N microbes.