Biochar, a carbon rich solid obtained via pyrolysis and intended to be used as a soil amendment material, is currently the most efficient tool available for carbon sequestration and mitigation of climate change. Further, some biochars can also improve soil properties and increase crop yield. Before the concept of using biochar as soil amendment can be implemented in a bigger scale, it is useful to know how biochar affects in the long-term key components of soil decomposer web, earthworms being one important indicator of effects on soil animals.

Majority of previous studies on biochar effect on earthworms have been short-term laboratory or greenhouse experiments and long-term effects of biochar on earthworm have not yet been elucidated in field conditions. Lack of studies is noticeable also for boreal zone, where the conditions differ strongly (e.g. high soil organic matter (SOM), high humidity, short growing seasons) from tropical zones, where the most biochar studies have been conducted so far. Four short-term field experiments investigating effects of biochar on earthworms have been conducted to our knowledge, but only two of those contained replicated treatments [1, 2, 3]. For these reasons, the aim of this study was to elucidate in boreal conditions the effects of different levels of biochar application and nitrogen fertilization on earthworm abundance, biomass and community composition in two separate field experiments, four and five years after the first application of biochar. To our knowledge this is the first study, set out to find the long–term biochar effects on an earthworms in a replicated field experiment.

Materials and methods
Biochar: Biochars for this study were produced from spruce (Picea abies (L.) H. Karst. in Umbrisol field) and a mixture of spruce and pine (Pinus sylvestris L. in Stagnosol field). Both patches of biochars were made of wooden chips in a continuous process for 10–15 min at 550 ºC [4].

Umbrisol field: The effect of biochar was investigated in a nutrient deficient soil, classified as Endogleyic Umbrisol where earthworms were sampled twice since the beginning of experiment, 4 months and 4 years after the application of spruce biochar chips [4]. The field was cropped with timothy and red clover during 2014-2015 undersown to barley (Hordeum vulgare L.) in May 2013 and application rate of biochar was 0 and 30 t ha–1, with or without inorganic fertilizer. The fertilizer was a mixture of Agro 28-3-5 and K2SO4 providing 100 kg ha–1 of N, 10.8 kg ha–1 of P, and 19.5 kg ha–1 of K in easily soluble form. Earthworm sampling was conducted in September 2011 and 2015. Three samples were taken from each 10 m x 2.2 m plot, one from each end and one in the middle. The sampling area was 25 cm x 25 cm and the sampling depth 28 cm. Earthworms were hand-sorted, weighted and identified.

Stagnosol field: Second field experiment was conducted in a fertile soil, classified as Luvic Stagnosol. This experiment started in 2010 and earthworm were sampled only once, 5 years after the application of spruce and pine biochar chips. Biochar was applied at rate of 0 and 10 t ha-1 with 100% or 30% of recommended N fertilizer (NPK). History of crops and earthworm sampling methods were the same as in Umbrisol study site.

Results and discussion
The species composition of earthworm community was on both soils typical for Finnish arable soils with the dominance of endogeic species, Aporrectodea caliginosa Sav., followed by epigeic Lumbricus rubellus Hoff. The total earthworm density and biomass was higher in Stagnosol field compared to Umbrisol field (Fig. 1) but the proportion of earthworm species was similar in both study sites. Biochar and fertilizer treatments or their interaction had no statistically significant effects on the species composition in either field. Significantly higher earthworm densities were measured in 2015 compared to 2011 in Umbrisol field. This change may be attributed to no tillage management practice, change of cropping from barley to timothy and red clover and optimal climate condition, where the average monthly precipitation over the last two years was higher than the long-term average. No detected effects of biochar on earthworm suggesting biochar to be a safe method for carbon sequestration in Southern Finland conditions.
TilaJulkaistu - 9 tammik. 2017
OKM-julkaisutyyppiEi sovellu
TapahtumaIX Maaperätieteiden päivät - IX National Symposium of Soil Science: Maaperä kiertotalouden perustana - Helsinki, Suomi
Kesto: 9 tammik. 201710 tammik. 2017


KonferenssiIX Maaperätieteiden päivät - IX National Symposium of Soil Science


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