Wood ash application increases pH but does not harm the soil mesofauna

doi:10.1016/j.envpol.2017.02.041

Environmental Pollution

Volume 224, May 2017, Pages 581-589

https://doi.org/10.1016/j.envpol.2017.02.041 Get rights and content

Highlights

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Wood ash applied to agricultural soil had effects on collembolans at 15 g kg⁻¹/17.4 t ha⁻¹.
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Wood ash had no effect in organic soil.
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The wood ash effect is mainly due to osmotic stress.

Abstract

Application of bioash from biofuel combustion to soil supports nutrient recycling, but may have unwanted and detrimental ecotoxicological side-effects, as the ash is a complex mixture of compounds that could affect soil invertebrates directly or through changes in their food or habitat conditions. To examine this, we performed laboratory toxicity studies of the effects of wood-ash added to an agricultural soil and the organic horizon of a coniferous plantation soil with the detrivore soil collembolans Folsomia candida and Onychiurus yodai, the gamasid predaceous mite Hypoaspis aculeifer, and the enchytraeid worm Enchytraeus crypticus. We used ash concentrations spanning 0–75 g kg⁻¹ soil. As ash increases pH we compared bioash effects with effects of calcium hydroxide, Ca(OH)₂, the main liming component of ash. Only high ash concentrations above 15 g kg⁻¹ agricultural soil or 17 t ha⁻¹ had significant effects on the collembolans. The wood ash neither affected H. aculeifer nor E. crypticus. The estimated osmolalities of Ca(OH)₂ and the wood ash were similar at the LC₅₀ concentration level. We conclude that short-term chronic effects of wood ash differ among different soil types, and osmotic stress is the likely cause of effects while high pH and heavy metals is of minor importance.

Graphical abstract

Introduction

Wood ash from combustion of various types of wood in power plants is currently regarded as a waste product to be recirculated to plantations and cultivated fields in small amounts (Miljøstyrelsen, 2008a). Environmental effects of ash application due to its complex mixture of beneficial and detrimental compounds have been observed in several studies (e.g. Augusto et al., 2008, Nabeela et al., 2015, Nieminen, 2011). Burning of mixed organic fuels such as straw, woodchips, green waste and logs, produces a mixed quality ash of variable chemical content (Pitman, 2006). It contains a mixture of salts, mostly with cations of Ca, K, Fe, Al, Mn, Na, Mg and various trace elements in lesser amounts (Ozcan et al., 2013). Due to its high content of oxides and hydroxides, the wood ash has alkaline properties and is frequently used as a pH raising agent in acidic soils (Heviánková et al., 2014, Neina and Dowuona, 2014, Ohno and Susan Erich, 1990, Ozcan et al., 2013). Because of the liming effect we hypothesize that the soil pH increase from ash application could be a main contributor to toxicity, as it is know that pH above 7 inhibits collembolan reproduction (Greenslade and Vaughan, 2003, Jänsch et al., 2005). Otherwise, osmotic stress from soluble salts and heavy metal are among candidates explaining responses to bioash by soil invertebrates.

Bioash affects soil invertebrates and their food and habitat conditions (Haimi et al., 2000, Liiri et al., 2002, Nieminen et al., 2012). Mesofauna, i.e. invertebrates 0.2–2 mm in size, plays an important role in the decomposition of soil organic matter, not only by consuming litter, but also by regulating the microbial community. Thereby, and via direct predation on other faunal groups, they are essential components of the soil food web (Sackett et al., 2010). The collembolans Folsomia candida (OECD, 2009) and Onychiurus yodai, the mite Hypoaspis aculeifer (OECD, 2008) and the enchytraeid-worm Enchytraeus crypticus (ISO, 2004, OECD, 2004) are soil mesofauna model organisms that are widely used to uncover ecotoxicological effects of xenobiotics (Arp et al., 2014, Ke et al., 2004, Larsen et al., 2008, Nakamori et al., 2008, Sverdrup et al., 2007). The four species represent dominant types of mesofauna.

Apart from the composition of ash, the soil type and application rate are important factors determining how the ash affect the soil biota (Pitman, 2006). Hence, we used the four species F. candida, O. yodai, H. aculeifer and E. crypticus as indicators to test the ecotoxicological effects of ash in two types of soil either from an agricultural field or from a spruce plantation. Therefore, we will assess the effects of ashes on the population performance of these four species in two types of soil and in addition assess effects of an increase in pH through liming. Hence, our study addresses the following hypotheses: Wood ash could potentially affect soil mesofauna, and the species F. candida, O. yodai, H. aculeifer and E. crypticus could respond differently; effects of the wood ash could differ depending on the soil type, and factors involved could be liming and osmotic changes. This is essential knowledge needed to improve the management of ashes and thus minimize damage to the soil ecosystem.

Section snippets

Test substances and test soil

We used a mixed bottom and fly ash made from burning mixed wood chips at a district heating plant located in Galten, Denmark. For comparison an additional type of wood bottom and fly ash from burning Picea abies wood chips at a district heating plant located in Brande, Denmark, was employed to test if similar types of ashes elicited the same ecotoxicological response. Prior to use, ash samples were crushed and subsamples were chemically analysed (Hovmand et al., 2008, Miljøstyrelsen, 2008b).

F. candida

Ash amendment in the loamy sand resulted in significantly different reproduction between treatments and control (one-way ANOVA, F_{6, 25} = 45.1, p < 0.05) (Fig. 1). The NOEC value was 17 g kg⁻¹ and the LOEC value was 20 g kg⁻¹ (Table 4). Adding ash to the loamy sand inhibited the reproduction of F. candida resulting in an EC₅₀ value of 19.5 [-3.82–42.8] g kg⁻¹. No effects were observed on the survival in any of the two soil types within the range of the tested concentrations. Neither were there

Discussion

We observed that effects of wood ash are highly dependent on the properties of the testing substrate. Only high concentrations of wood ash (>15 g kg⁻¹/17.4 t ha⁻¹) applied to agricultural soil had significantly negative effects on collembolans but no effect on the enchytraeid and the gamasid mite. Alkaline soil conditions are harmful to collembolans (Greenslade and Vaughan, 2003, Jänsch et al., 2005), and as the wood ash increased the pH of the loamy sand from 7 to 9 (Fig. 4) it caused

Conclusions

We tested four taxonomically distant representatives of the soil mesofauna fungivores, detrivores and a predator inhabiting different niches, thus our ecological effects assessment presented here is robust. Wood ash did not have negative effects for neither survival nor reproduction of F. candida, O. yodai, H. aculeifer and E. crypticus in the test in organic soil. Wood ash applied to agricultural soil had statistical significant effects for both reproduction and survival for both collembolan

Acknowledgement

We thank Mette Hansen for sharing information on the Gedhus soil property. This work was partly funded through the ASHBACK project funded by the Danish Council for Strategic Research. Jiayi Qin was partly funded by the Graduate School of the Science and Technology faculty at Aarhus University (GSST) through a Screening Grant and a PhD grant.

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Wood ash application increases pH but does not harm the soil mesofauna☆

Highlights

Abstract

Graphical abstract

Introduction

Section snippets

Test substances and test soil

F. candida

Discussion

Conclusions

Acknowledgement

Pedobiologia

For. Ecol. Manage

Min. Eng.

Environ. Pollut.

Pedobiologia

Pedobiologia

Soil Biol. Biochem.

Pedobiologia

Plant Physiol. Biochem.

Ecotoxicol. Environ. Saf.

For. Ecol. Manage

Geoderma

Agric. Ecosyst. Environ.

Pedobiologia

Soil Biol. Biochem.

Ecotoxicol. Environ. Saf.

Ecotoxicol. Environ. Saf.

Standardization of test Methods with terrestrial terrestrial invertebrates for assessing remediation procedures for contaminated soils

Ecoinforma

Der einfluss des pH-Werts und von PCB52 auf reproduktion und besiedlungsaktivität von terrestrischen enchytraeen in PAK-, PCB-und schwermetallbelasteten rieselfeldböden

Verh. Ges. Ökol

Native Oxy-PAHs, N-PACs, and PAHs in historically contaminated soils from Sweden, Belgium, and France: their soil-porewater partitioning behavior, bioaccumulation in Enchytraeus crypticus, and bioavailability

Environ. Sci. Technol.

Wood ash applications to temperate forest ecosystems—potential benefits and drawbacks

Plant Soil

Water vapor absorption in arthropods by accumulation of myoinositol and glucose

Science

Wood ash potential for Colorado potato beetle control

Am. J. Potato Res.

Populationsentwicklung von Enchytraeus crypticus (Enchytraeidae, Oligochaeta) und einfluss subletaler pestizidbelastungen unter laborbedingungen

Chapter 11: hypothesis testing: do my samples come from the same population? Non-parametric data

Scheirer-Ray-Hare Test in R. Research Methods for the Biosciences

Simultaneous inference in general parametric models

Biom. J.

Package ‘multcomp’. Simultaneous Inference in General Parametric Models. Version 1.4–4