Application of Livestock Slurry Significantly Influences Microbial Biosynthesis and Cumulative Respiration in Agricultural Grassland Soil

Abstract

The long-term application of livestock slurry to intensive grassland soils may lead to positive effects, including an increase in soil organic matter and plant nutrient supply to soils. Further, there is increasing interest in the potential of biological slurry additives (mixtures of selected living or latent microorganisms added to slurry) to enhance soil fertility through mobilisation of key elements in slurry and soil. However, significant uncertainties remain surrounding the potential impacts of slurry amended with biological additives on carbon (C) partitioning within three pools: respired CO2, microbial biomass C (Cmic) and C retained in the soil, as well as composition of the microbial community in temperate grassland soils. We examined how slurry that has received a biological additive ultimately affects the partitioning of C within these pools and the composition of the soil microbial community, based on phospholipid fatty acid (PLFA) analysis. Four short-term incubations in which soil collected from a grassland field that has received livestock slurry treated with a commercial biological additive, alongside 14C-labelled carbohydrates of different complexity (14C-glucose, 14C-glucose 6-phosphate (G6P), and 14C-cellulose) were undertaken. Our results indicate that the addition of slurry to soil alongside carbohydrate compounds led to lower 14C biomass uptake and cumulative respiration of carbohydrate compounds, as well as greater residual 14C activities in soil, compared to the treatments in which slurry was not applied. A dominance of bacteria over fungi characterised soil microbial community composition in all treatments through time, with a prevalence of gram-negative over gram-positive bacteria. Our results also indicate that the addition of biological additives during slurry storage increased 14C biomass uptake following application of slurry to agricultural grasslands. Therefore, biological additives have the potential to create a favourable environment for maintaining and increasing soil fertility through modification of the microbial community associated with the slurry and influence of the soil microflora.

Keywords

Identifiers

DOI

10.31219/osf.io/zuxab

Journal

Unknown journal

Year

2021