Abstract
Earthworms are commonly known as essential modifiers of soil carbon (C) and nitrogen (N) cycles, but the effects of their species on nutrient cycles and interaction with soil microbial activities during the decomposition of organic materials remain unclear. We conducted an incubation experiment to investigate the effect of two different epigeic earthworms (M. hilgendorfi and E. fetida) on C and N concentrations and related enzyme activities in agricultural soils with added barley residues (ground barley powder). To achieve this, four treatments were included; (1) M. hilgendorfi and barley, (2) E. fetida and barley, (3) barley without earthworms, and (4) without earthworms and without barley. After 32 days incubation, we measured soil pH, inorganic N, microbial biomass C (MBC), water or hot-water soluble C, and soil enzyme activities. We also measured CO2 emissions during the incubation. Our results indicated the earthworm activity in soils had no effect on the cumulative CO2 emissions. However, M. hilgendorfi had a potential to accumulate MBC (2.9 g kg−1 soil) and nitrate-N (39 mg kg−1 soil), compared to E. fetida (2.5 g kg−1 soil and 14 mg kg−1 soil, respectively). In conclusion, the interaction between soil microbes and earthworm is influenced by earthworm species, consequently influencing the soil C and N dynamics.
Highlights
Organic amendment can be used to increase soil carbon (C) and nitrogen (N), which are the indicators of agricultural production [1,2]
Better understanding of the impact of epigeic earthworms on C and N dynamics in agricultural soils will provide basic information to evaluate the efficacy of organic amendments to maintain soil health
Two types of earthworms were used; one was M. hilgendorfi sampled from the forest in Hokkaido University in August 2017 and the other was E. fetida obtained from a private company (Iwase farm, Ibaraki, Japan)
Summary
Organic amendment can be used to increase soil carbon (C) and nitrogen (N), which are the indicators of agricultural production [1,2]. Barley is one of the major crop species in the world and it is important to fully understand how the C from barley cycles in agricultural soils. A study will be required to understand interactions among earthworm and soil C dynamics, using barley as organic materials. Epigeic earthworms are litter dwellers and inhabit the surface level of soils. These earthworms enhance decomposition rates of their habitats interacting with microorganisms and other organisms [8,9,10]. Better understanding of the impact of epigeic earthworms on C and N dynamics in agricultural soils will provide basic information to evaluate the efficacy of organic amendments to maintain soil health
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