Soil microbial biomass, activity and community structure as affected by mineral phosphorus fertilization in grasslands

Nutrient availability is an important indicator of nutrient balance and affects soil microbial processes and functions. However, few studies have explored the effect of short-term application of mineral phosphorus (P) on grassland soils. This study evaluated the effect of mineral P fertilization on soil microbial biomass, activity and community composition in the soil of timothy (Phleum pratense L.) swards at two sites (established in 2010) in eastern Canada with P fertilization rates of 0, 20, and 40 kg P ha(-1). Soil samples were collected at the top 10 cm three times in 2013 and 2014. Results revealed that P application has significantly increased soil Mehlich-3P and microbial biomass P at both sites tested, but soil microbial biomass C and N were not affected. Phosphorus application has increased dehydrogenase activity, but it had no significant effect on alkaline phosphomonoesterase activity. The total soil bacterial biomass decreased with P application at the Levis site but not at the Normandin site. Permutational multivariate analysis of variance (PERMANOVA) analysis and principal component analysis (PCA) revealed that soil microbial community structure varied between sites and among sampling dates, but was not significantly affected by P fertilization, suggesting that P was not a major limiting factor to soil microbial community structure. We conclude that short-term P application had limited influence on changing the microbial community structure, but did affect the processes of the microorganisms involved in soil P cycling.