Long-term effects of grazing, liming and nutrient fertilization on the nitrifying community of grassland soils

We found that AOB amoA gene copy numbers were significantly higher in limed soils (associated with greater pH values) whereas AOA amoA gene copy numbers were higher in grazed grasslands. The chronic addition of inorganic N fertilizer in the form of ammonium nitrate (either applied alone or in combination with other macro-nutrients) greatly contributed to increase AOB abundance. Our study brings evidence of how soil-nitrifying communities can differently respond to the long-term effect of animal (i.e. rabbit) grazing and to repeated applications of nutrient (e.g. NH4NO3) and non-nutrient (i.e. CaCO3) fertilizing materials.