Soil physicochemical and microbial characteristics of contrasting land-use types along soil depth gradients

Soil physicochemical properties can be regarded as an important tool to assess soil health, which further form a base for biological activity in soil. These soil physicochemical properties are comparable in identical land-uses and so reflect similar soil microbial properties. However, the changes in land-use types and their effects on soil physicochemical and microbial properties are largely debated and rather unclear. The aim of this study is to assess the impact of land-use types and soil depth on physicochemical properties (Organic C, total N, C/N ratio, available phosphorus, bulk density, pH and electrical conductivity), nitrogen forms (Nitrate-N, ammonium-N, organic N, mineralizable N, microbial biomass N and extractable organic N) as well as microbial indices (basal respiration, respiratory quotient, microbial quotient, microbial biomass). Land use types- farmland, orchard, grassland and abandoned land served as horizontal factors while soils at 0-10 cm, 10-30 cm and 30-60 cm depth were used as vertical factors for accessing the physicochemical and microbial properties. Discriminant analyses (DA) indicated that soil microbial properties were affected by both land-use types and soil depths than nitrogen and physicochemical properties in our study. We found that the overall trend of percentage of discriminant function 1 (DF1) was highest for microbial indices (similar to 90%) > nitrogen (similar to 80%) > physicochemical properties (similar to 70%). All investigated soil properties differed with higher significance by land-use types than by soil depths. The results further indicated that among all investigated soil properties in different land-use types, electrical conductivity, mineralizable nitrogen and microbial biomass carbon served as best discriminating indices. Regarding soil depths, total organic carbon followed by mineralizable nitrogen and basal respirations were found to be the decisive indicators of soil conditions. Overall, our results demonstrate the sensitivity of various soil properties and their differential provenience along horizontal and/or vertical gradients. These outcomes suggest that differences in land-use types are reflected in soil physicochemical properties that are actual drivers of soil microbial properties in this region. Thus they are promising guideline tools for further studies related to soil quality, soil management and sustainability in long run.