Abstract
Biochar has the potential for improving soil properties and supporting ecological functions, but it has negative impacts on soil organisms in some cases. This study aimed to assess the effect of biochar application at rates of 0 (B0), 5 Mg ha−1 (B5), 20 Mg−1 (B20), and 40 Mg ha−1 (B40) on soil nematode community under upland and flooded conditions in a short-term microcosm experiment. After biochar application, soil was incubated for 2 to 8 weeks and nematodes were identified for community composition, trophic structures, functional guilds, maturity index and metabolic footprints. The chemical properties of the soils were also analyzed. General linear model revealed that biochar increased soil pH, EC, NO3−-N, available phosphorus, total C, and C/N ratio, particularly in the highest application rate and shifted the composition of nematodes. The greatest abundances of omnivores (Mesodorylaimus, Thornenema), predator (Nygolaimus) and functional guilds of cp5 were observed in B5, resulting in greatest structure footprint and composite footprint, (omnivorous + predator) footprint and total biomass in B5. While abundances of nematodes tended to decrease with the biochar applicate rates, the abundance of Prismatolaimus was the highest in B40. During the 8-week incubation period, the abundances of Achromadora, Alaimus, Aporcelaimellus, Cryptonchus, Mononchus, and Tobrilus remained stable in upland conditions. Under flooded conditions, the abundances of almost all taxa were markedly lower than those under upland conditions irrespective of biochar application, except for Acrobeloides, Alaimus, Aphelenchoides, and Ditylenchus. We highlighted that 5 Mg ha−1 of rice husk biochar can be the optimum in shaping the nematode community.
Highlights
Biochar is a pyrolysis product of various organic resources, such as agricultural residue biomass and livestock waste, under limited oxygen conditions [1]
Such contrasting effects of biochar on soil organisms may depend on the rates, material sources, processing conditions, and timing of application, and soil conditions, e.g., pH, soil moisture and temperature [17,18]
To clarify the effects of biochar on soil nematode community under upland and flooded conditions, this study aimed to find out (1) the responses of species-specific nematode community to biochar application rates, and (2) the changes in its trophic structures, functional guilds, and metabolic footprint as well as soil physicochemical properties
Summary
Biochar is a pyrolysis product of various organic resources, such as agricultural residue biomass and livestock waste, under limited oxygen conditions [1]. Contrasting effects by biochar addition are reported on soil organisms [10], including nematodes [11,12,13,14], and higher trophic levels of consumer fauna [15]. Liu et al [16] reported that the application of 4.5 Mg ha−1 peanut shells biochar increased the total abundance of nematode communities, that of bacterivorous nematodes. Such contrasting effects of biochar on soil organisms may depend on the rates, material sources, processing conditions, and timing of application, and soil conditions, e.g., pH, soil moisture and temperature [17,18]. The biochar addition needs to be carefully considered based on the overall effects on soil organisms [13]
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