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

Abstract

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 (N₂O) emission measurements were conducted three times in spring and four times in summer, and quantitative real-time PCR was performed to determine the absolute abundances of N-cycling genes, including ammonia-oxidation (amoA-AOB, amoA-AOA, amoA-comammox), denitrification (nirS, nirK, nosZ), nitrate ammonification (nrfA), and N-fixation (nifH) genes. Long-term liming increased the absolute abundances of nitrifiers, denitrifiers, and nitrate ammonifiers. Soil N₂O emissions did not differ significantly between liming and control treatments. Additionally, liming had a buffering effect that maintained the population of N-cycling microbes against seasonal variations in abundance. Our results indicate that improving soil acidity through liming potentially facilitates microbial N-cycling processes without increasing N₂O emissions.