Soil microbes and associated extracellular enzymes play an integral role in nutrient dynamics in acidic and nutrient poor KwaZulu-Natal grassland ecosystem soils.

Purpose: This study investigated the effects of long-term phosphorus (P) fertilization and liming on soil microbe diversity and extracellular soil enzyme activities in acidic and nutrient-poor grassland soils in KwaZulu-Natal (KZN). MethodsExperimental soil samples were collected from the Veld Fertilizer Trials (VFT) initiated in 1951 at Ukulinga Research Farm in Pietermaritzburg, South Africa. P fertilizer and liming treatments comprised of superphosphate (336 kg. ha -1 ) applied once a year and dolomitic lime (2250 kg. ha -1 ) applied every 5 years (P+L), superphosphate (336 kg. ha -1 ) applied once a year (+P) and soils with no superphosphate and no dolomitic lime (-P-L). These soils were analyzed for their nutrient concentration, pH, total cation concentrations and exchange acidity, microflora and extracellular enzyme activities. ResultsSoil nutrition, pH, total cations and exchange acidity showed significant differences between the soil treatments. However, nitrogen (N) and organic carbon (C) concentrations showed no significant differences between the soil treatments. P-solubilizing, N-cycling and N-fixing microbial diversity varied among the different soil treatments. Various nutrient cycling bacteria were identified across soil treatments with the most abundant strains in the Pseudomonas genera. β-glucosaminidase enzyme activity was high in acidic soils compared to P-fertilized and limed soils. However, N reductase activity showed no significant differences between the soil treatments. Alkaline phosphatase showed increased activity in P-fertilized soils, whereas acid phosphatase showed increased activity in acidic soils. Conclusion: These experimental results show that soil microbes and soil enzymes play an integral role in nutrient dynamics in acidic and nutrient stressed grassland ecosystem soils.