Microbial Biomass Carbon Distribution under Agroforestry Practices and Soil Depth Variations in Southern Ethiopia

Abstract

<title>Abstract</title> The land-use change from agroforestry (AF) to monoculture-based agriculture has the potential to change soil microbial biomass carbon (MBC). The MBC has been used as an indicator of soil quality as well as to determine the microbial status of soil. The aim of this study was to analyze the distribution of soil MBC across different agroforestry practices (AFPs) at two depths in southern Ethiopia. Soil samples were collected from cropland/parkland, woodlots, home gardens, and trees on soil and water conservation-based AFPs. The MBC was determined using the difference in fumigated and non-fumigated extracted carbon contents. The MBC and soil microbial biomass quotient <bold>(</bold>MBQ) were significantly different among the different AFPs (P &lt; 0.05). The highest contents of MBC were reported from homegarden on topsoil (505.36 ± 12.45 mg kg ^{− 1}) and subsoil (401.88 ± 7.26 mg kg ^{− 1}) soil depths (surface = 0–30 cm, subsoil = 30–60 cm), followed by woodlot (surface: 464.37 ± 9.19 mg kg ^{− 1}) and (subsoil: 380.24 ± 6.88 mg kg ^{− 1}), while the lowest result was registered from the subsoil of the croplands (153.10 ± 46.44 mg kg ^{− 1}). The higher percentage of MBQ was recorded under the woodlots in topsoil layers (1.48%) and subsoil (1.37%), followed by homegarden (surface = 1.41%, subsoil = 1.25%), while the lowest was found under the cropland in subsoil (0.57%). The highest content of soil organic carbon was found under homegarden in topsoil (3.62%) and subsoil (3.23%) followed by woodlot (topsoil: 3.16%, subsoil: 2.87%) and trees on soil and water conservation structures (topsoil: 2.69%, subsoil: 2.51%), while the lowest value was registered under cropland/parkland AF practices (topsoil: 2.67%, subsoil: 2.46%). The distribution of MBC was significantly related to soil organic carbon in soil depth categories, soil total nitrogen, and soil pH in topsoil. Homegarden and woodlot AFPs were suitable for soil MBC improvement among the different AFPs studied, implying that tree-based systems are important for increasing of MBC and ecosystem stability.