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Production of applicable and homogeneous biochar for soil amendment purposes would benefit from knowledge on how feedstock heterogeneity impacts key biochar pore properties and how the properties are transformed due to pyrolysis. This study aimed (1) to quantify how clonal differences and within-tree heterogeneity of a hybrid aspen feedstock (wood) impact biochar pore properties and (2) to estimate how pore properties of non-pyrolysed wood materials are transformed when pyrolysed into biochar. The study was conducted by collecting samples from a hybrid aspen (Populus tremula L. × Populus tremuloides Michx.) clonal field trial. Key pore properties of non-pyrolysed and pyrolysed wood samples were quantified with 3D X-ray imaging and quantitative image analyses. The results demonstrated how pyrolysis shifted distinctively bi-modal pore size distributions of the wood samples towards smaller pore size regions. The bi-modal wood tissue structure controlled the pore structure also in the biochars. Due to decreasing cell wall thicknesses, the pyrolysis increased the porosity of the materials. While the thermal process homogenized differences in the wall thicknesses, the thicknesses of the feedstock were also shown to control the resulting thicknesses in the biochars. Mechanisms of biochar pore property formation can be considered important when designing applicable biochars for a chosen purpose. Clonal differences and within-tree heterogeneity had a direct impact only on the wall thicknesses and the pore diameters of vessels. These impacts can be of interest when planning feedstock utilization in biochar production. However, the results suggest that relatively homogeneous biochar can be produced from hybrid aspen feedstocks.

Purpose Charred materials are low in bioavailable nitrogen (N) due to gaseous losses and the formation of recalcitrant structures during pyrolysis. Enriching chars with N from wastewaters offers a possibility to upgrade the agronomic value of the chars and manage the liquids. For assessing the practical feasibility of the approach, more information on the extent of the retention and release of the loaded N is needed. Methods The ammonium-N (NH4-N) retention capacity of chars derived from sewage sludge (SS_A-C), Salix wood (SA), broiler manure (BR) and coal (LG85) was determined via equilibrations in solutions containing 400, 1500 and 5000 mg NH4-N L−1. Plant availability of the loaded N in SS_C, SA and BR was studied in a pot experiment with ryegrass. Results Differences in the total N retention of moist chars were small. The amount of N retained increased with increase in the solution N and was at the highest 2–4 g NH4-N L−1 char. In four consecutive ryegrass harvests, the apparent N recoveries were 67, 47 and 34% for SA, BR and SS_C treatments. No slow release of N was observed. Conclusion Considering crop production, the amounts of N retained within the studied chars in bioavailable form were small. Chars with a higher N retention capacity would be needed for an efficient cascade from water purification to fertilizer use. Graphical Abstract

Viimeaikaiset tulokset massa- ja paperiteollisuuden sivuvirroista ja tehtaan jätevesien puhdistusprosesseista syntyvien kuitulietteiden käytöstä maanparannusaineina hienojakoisilla viljelymailla ovat olleet lupaavia. Kuitulietteiden sato-, hiilisyöte- ja maanparannusvaikutusten selvittämiseksi karkeilla kivennäismailla (KHt) perustettiin Biosfääri-hankkeessa (Biosfääri Pohjois-Savo; Biomassan ja biojalostusteknologioiden hyödyntäminen liiketoiminnan kasvattamisessa) Luke Maaningalle kaksivuotinen, lohkoittain satunnaistettu ja neljänä kerranteena toteutettu kenttäkoe. Timotei-nurminatanurmi perustettiin kesäkuussa 2020 suojaviljan alle. Ennen kylvöä kuitulietteet levitettiin maan pintaan (21–28 tuore-t ha-1, liukoinen-N n. 15 kg ha-1, kokonais-P n. 26 kg ha-1) ja äestettiin noin 7 cm:n syvyyteen. Toinen metsäteollisuuden kuitulietteistä oli tyyppinimeltään kalkkistabiloitu puhdistamoliete (kalkkikuitu Kuopio; Fortum Waste Solution Oy; jatkossa maanparannuskuitu A), kun taas toinen oli hygienisoimaton ja tuotteistamaton (Stora Enso Oyj, Varkaus; jatkossa maanparannuskuitu B). Kuitulietteistä otetuissa näytteissä ei todettu salmonellabakteereita ja Escherichia coli -pitoisuudet (

Declining carbon (C) content in agricultural soils threatens soil fertility and makes soil prone to erosion, which could be rectified with organic soil amendments. In a 4‐yr field trial, we made a single application of three different organic sludges from the pulp and paper industry and studied their effects on cereal yield, soil C content, and fungal and bacterial composition. In laboratory rainfall simulations, we also studied the effects of the soil amendments on susceptibility to erosion and nutrient mobilization of a clay‐textured soil by measuring the quality of percolation water passing through 40‐cm intact soil monoliths during 2‐d rainfall simulations over four consecutive years after application. A nutrient‐poor fiber sludge reduced wheat yield in the first growing season, but there were no other significant effects on cereal yield or grain quality. An input of ∼8 Mg ha−1 C with the soil amendments had only minor effects on soil C content after 4 yr, likely because of fast microbe‐mediated turnover. The amendments clearly changed the fungal and bacterial community composition. All amendments significantly reduced suspended solids (SS) and total phosphorus (TP) concentrations in percolation water. The effect declined with time, but the reduction in SS and TP was still >25% 4 yr after application. We attributed the lower tendency for particle detachment in rain simulations to direct interactions of soil minerals with the added particulate organic matter and microbe‐derived compounds that stabilize soil aggregates. In soils with low organic matter content, pulp and paper industry by‐products can be a viable measure for erosion mitigation.

Amending growing media with biochar has the potential to sequester carbon and enhance the properties of the receiving substance. However, knowledge of the mechanisms of how biochar amends the physical properties of the material is incomplete. By combining 3D image analysis and more conventional methods, this study aimed to (1) characterise the pore structure properties of three different plant-based biochars and (2) quantify their impact on Sphagnum moss growing media physical properties. The 3D imaging showed that irrespective of the feedstock, the majority (0.80–0.94 m3 m−3) of the biochar pore volume resided in pores with diameters 2–11 μm. Biochar pore properties shared similarities due to the structure of plant tissue. The application of biochar increased the water retention of the growing media by a maximum increase of 0.06 m3 m−3 in the pore diameter range 1–8 μm. This is relevant for plant-available water and microbiological activity, which indicates the usability of the biochar amendments. From methodological point of view, the benefits of combining 3D imaging with conventional measurements and impacts of the water table continuum discontinuity between the biochar and the surrounding growing media were demonstrated. The design of biochar for optimal water retention would benefit from further studies quantifying pore structure characteristics of biochar produced from a wide range of feedstocks.

Replacement of synthetic pesticides with biochemical alternatives and other biological and mechanical control methods represents a future need in plant protection. We investigated if slow pyrolysis liquids (PL) originating from hardwoods, which contain a wide range of organic compounds, can be used to control giant hogweed (Heracleum mantegazzianum) either by (i) spraying directly on the seeds (Carum carvi seeds used as substitute) and seedlings or by (ii) covering seedlings with PL-containing mulching material (PLM). The effectiveness of the methods was evaluated in laboratory and greenhouse experiments using seedlings of various ages, PLs produced from aspen (Populus sp.), birch (Betula sp.) and willow (Salix sp.) and various PL/PLM application doses. In addition, the biodegradation of birch-derived PL was investigated. All tested liquids inhibited C. carvi seed germination effectively when used at > 20% concentrations and only slight differences existed among PLs produced from different biomasses. Direct spraying of PL on H. mantegazzianum seedlings was ineffective. PLM (containing 7.5%-40% of PL) inhibited seedling development effectively. Birch PL was readily biodegradable. Further product development is needed because the chemical composition of the PLs in PLM and their modes of action are poorly understood. The weed-inhibiting effect of PLM likely results from the PL and the mechanical barrier constituted by PL-bound peat fibers. (C) 2020 The Author(s). Published by Elsevier B.V.

Novel bioeconomic approaches call for increasingly faster production of lignocellulosic biomass and its bettertailored use for higher added value. The high-yield capacity and structural properties of willows (Salix spp.) suggest their excellent potential for the production of designed biochar for use in agronomic, electronic and technical applications. All these applications rely on the internal pore structure of biochar. However, we lack an in-depth quantitative understanding of the interlinkages between the feedstock properties and the physical quality of the biochar produced. We studied quantitatively how the clonal and within-plant properties of five different willow clones (hybrids of Salix schwerinii E.L. Wolf) affected the micrometre-scale pore properties of the produced biochars (pyrolyzed at + 462 ?C). The porosity and pore size distribution were analysed before and after slow pyrolysis by X-ray microtomography and image analysis. We also studied the potential of conventional low-cost fibre analysis techniques to be used to predict biochar pore properties directly from fresh feedstock. The total porosity (0.55?0.62) and the pore size distribution of willow wood and derived biochars varied between clones. Approximately two-thirds of the biochar total porosity was associated with pores formed by wood fibres. Pyrolysis levelled off the structural variation detected between and within the clones. Pyrolysis-induced shrinkage reduced the pore sizes and narrowed the pore size distribution. The results suggest that conventional fibre analysis techniques could be utilized to predict biochar homogeneity. Short rotation coppice willows are suitable feedstock to produce homogenous biochar precursor for production of bio-based carbon materials to be used in high value-added technical applications. The structural homogeneity of the feedstock and produced biochar can be enhanced by selecting proper harvesting strategy and clones used in plantations. From the industrial perspective, comprehensive understanding of feedstock properties helps to control quality of the produced biochar.

The feasibility of thermochemical biomass conversion technologies can be improved if value-added applications for all fractions can be developed. One of such approaches is the use of liquid by-products from slow pyrolysis and hydrothermal carbonization (HTC) in plant protection. Liquids produced from slow pyrolysis of pine bark, pine forest residues, wheat straw, and willow, and from hydrothermal carbonization of willow, were analyzed in this study. In particular, potential active compounds were analyzed, covering the main volatile, simple organic compounds and numerous phenolic substances. Effectivity tests of the liquids as pest repellent (Arianta arbustorum), herbicide (Brassica rapa), and insecticide (Rhopalosiphum padi) indicated that slow pyrolysis liquid from willow was the most effective pesticide, followed by the liquid from wheat, bark, and forest residues. HTC liquid did not show any pesticidal activity due to low concentration of organic compounds. High content of acetic acid and other carboxylic acids, and the presence of dozens of different phenolic compounds seem to be the main reason for the higher pesticidal activity of willow-derived pyrolysis liquid. Temperature-separated slow pyrolysis liquids proved to be suitable to be used as pesticides. Consequently there is possibility to improve the feasibility of thermochemical biomass conversion technologies remarkably by developing the liquid factions to value-added pesticides. Graphical Abstract: [Figure not available: see fulltext.].

The pulping industry generates vast amounts of bark residues and wastewater treatment sludges, which are combined and stored for varying periods in stacks, often in the open air, prior to utilization for energy via combustion. In order to optimize the storage strategy, the effects of incorporating sludge into bark on heating value and storage-related environmental impacts were investigated in laboratory and outdoor studies. Biological degradation activity was found to be higher in treatments containing 25% sludge (B75S25) and 50% sludge (B50S50) on a fresh mass basis, in comparison with pure bark (B100). Mean monthly dry mass loss was 2.1% (B100), 3.3% (B75S25), and 3.7% (B50S50) in the laboratory and 2.7%, 4.2%, and 4.8%, respectively, outdoors. Sludge addition was found to maintain degradation activity at low temperatures (+ 3°C). Co-storage of sludge and bark led to loss of energy, mainly due to increased loss of biomass and increased moisture content. Overall, biomass moisture content governed the heating value. Cumulative methane emissions over the storage period were higher from the sludge-containing treatments than from pure bark, but emissions of nitrogen-containing gases (N2O and NH3) were negligible throughout. Sludge addition roughly halved the cumulative chemical oxygen demand (COD) of leachate and minimized its concentration of phosphate-P. However, larger amounts of inorganic elements were released to the percolating water from the sludge-containing treatments. Overall, these results indicate that finding alternative uses for the sludge fraction would be beneficial.

Feasibility of pyrolysing wastewater sludge for char and energy production is dependent on the usability of the produced sludge char. This study aimed to produce mechanistic information of char impacts on amended porous media by determining (1) pore structure of sludge chars with 3D image analyses and (2) their influence on water retention and shrinkage properties of three contrasting soils. The pore structure of the chars consisted of crevices and large spheres. Their water retention impacts were minor, even though the low-porous char slightly increased porosity in the amended materials in various pore-size ranges. The dominating, though small, impacts were the increase in easily drainable interpores and decrease in smallest pore sizes relevant for plant available water. The char impacts were more visible in fine-than coarse-textured soils. The chars also significantly reduced shrinkage in clay soils. The results were insensitive to sludge feedstock or char particle size. publishedVersion

A substantial percentage of manure nitrogen (N) can be lost as gaseous ammonia (NH

Short-term agronomic and environmental benefits are fundamental factors in encouraging farmers to use biochar on a broad scale. The short-term impacts of forest residue biochar (BC) on the productivity and carbon (C) storage of arable boreal clay soil were studied in a field experiment. In addition, rain simulations and aggregate stability tests were carried out to investigate the potential of BC to reduce nutrient export to surface waters. A BC addition of 30 t ha−1 increased soil test phosphorus and decreased bulk density in the surface soil but did not significantly change pH or water retention properties, and most importantly, did not increase the yield. There were no changes in the bacterial or fungal communities, or biomasses. Soil basal respiration was higher in BC-amended plots in the spring, but no differences in respiration rates were detected in the fall two years after the application. Rain simulation experiments did not support the use of BC in reducing erosion or the export of nutrients from the field. Of the C added, on average 80% was discovered in the 0–45 cm soil layer one year after the application. Amendment of boreal clay soil with a high rate of BC characterized by a moderately alkaline pH, low surface functionalities, and a recalcitrant nature, did not induce such positive impacts that would unambiguously motivate farmers to invest in BC. BC use seems unviable from the farmer's perspective but could play a role in climate change mitigation, as it will likely serve as long-term C storage. publishedVersion

Production of organic fertilizers from poultry manure may compromise availability of phosphorus (P) to plants. This study examined the effects of granulation, feather meal addition, and pyrolysis on bioavailability of P in broiler manure in a pot experiment with ryegrass and assessed whether P availability is enhanced by inoculating arbuscular mycorrhizal fungi (AMF) into soil. Granulated broiler manure gave similar plant yield and P uptake to superphosphate. Feather meal addition had a minor negative effect on P availability, whereas pyrolysis lowered the fertilization effect of broiler manure. The yield-based mineral-P equivalences were 120%, 85% and 75% during the first harvest, and 100%, 75% and 45% during one growing season for granulated unamended, granulated amended with feather meal and pyrolyzed broiler manure. Soil inoculation with AMF did not enhance P availability. Granulated poultry manure is suitable as a P fertilizer for annual crops with comparable bioavailability to mineral fertilizer P, whereas pyrolyzed poultry manure is suitable as a slow-release or storage P fertilizer in slightly acidic soils. Knowledge on P bioavailability in organic fertilizers produced with different technologies can be used for optimizing fertilization, minimizing build-up of soil P and its adverse environmental effects. (C) 2021 The Author(s). Published by Elsevier B.V.

A substantial percentage of manure nitrogen (N) can be lost as gaseous ammonia (NH3) during storage and field spreading. Lowering slurry pH is a simple and accepted method for preserving its N. Efficiency of slow pyrolysis liquid (PL) produced from birch (Betula sp.) as an acidifying agent, and its ability to reduce NH3 emissions following surface application of cattle slurry, was studied in a field experiment. Untreated slurry (US) and slurries acidified with PL and sulfuric acid (SA) were applied to the second harvest of a grass ley. Immediate NH3 emissions, grass biomass, N-yield and possible toxic impacts on soil nematodes and enchytraeids were examined. Furthermore, the effects on soil respiration, nitrogen dynamics and seed germination were studied in subsequent laboratory experiments. In the field, over one third of the water-extractable ammonium-N (NH4-N) applied was lost through NH3 volatilization from US. SA and PL acidified slurries reduced NH3-N emission rate equally from 3.4 to

Pyrolysis is an option for enhancing the sustainable management of broiler manure surpluses by producing a concentrated, hygienic char product with a fertilizer and soil conditioner value. In this study, the impacts of pyrolysis conducted at 350, 400 and 450 °C on total nutrient and harmful element concentrations in biochars derived from peat-bedded broiler manure were examined. Emphasis was placed on the availability of phosphorus (P). In addition, the pore structures of these biochars were explored using X-ray microtomography and image analysis. During pyrolysis, 35–50%, 40–55% and 35–45% of the original carbon, nitrogen and sulfur contents, respectively, of the feedstock biomass were lost as volatiles. Mineral elements, including P, were concentrated in the biochar. Although water-extractable P was found to be converted to less labile forms due to charring, the concentration effect and notable increase in sodium bicarbonate-extractable P rendered broiler manure biochars richer in total labile P in comparison with feedstock manure (7.1, 10.0, 11.1 and 14.8 g labile P kg−1 in feedstock and biochars produced at 350, 400 and 450 °C, respectively). The pore volume of the micrometer-scale porosity of the broiler manure biochar was comparable to that found earlier in wood-based biochars. In comparison with wood-based biochars, the pore structure of broiler manure biochars was more versatile, and the pore size distribution was wider. Consequently, part of the porosity was too large to store plant-available water, which may reduce the potential of broiler manure biochars to improve soil water storage capacity.

Refining broiler manure to nitrogen (N) fertilizer products of consistent quality and balanced nutrient content could promote agronomic exploitation of this nutrient rich resource. For ensuring the effectiveness and sustainable use of such products, their plant available N supply needs to be known. In this study, the N fertilizer value of peat bedded broiler manure as pure granules (BM) and feather meal amended granules (BM+FM) was assessed in a pot experiment with ryegrass and field experiment with onion. The pot experiment examined also the performance of pure feather meal (FM) and slow pyrolyzed broiler manure (PyrBM). As measured by mineral N fertilizer equivalence, 68%, 45%–50%, 35%–43%, and 3% of the total N in FM, BM+FM, BM and PyrBM, respectively, was available to plants during the first growing season in favorable conditions. A minor (

A process model based on hot water extraction (HWE), slow pyrolysis and anaerobic digestion (AD) were used for pine and spruce bark utilisation. First tannins (32 mg/g and 11.8 mg/g, respectively) and polyphenols were recovered via HWE. Then, the residue was pyrolysed to produce biochar (marketable quality), gas (energy source) and liquid fractions. The liquid fraction was further separated into aqueous acidic fraction and to tar fraction. Bark, extracted bark residue and acidic liquid fraction from pyrolysis were treated in AD to produce biomethane and digestate. The methane yields from pine and spruce bark and extracted bark residue were low (from 42 to 96 mLCH4/gVSadded) and showed only small differences. In conclusion, cascade processing can improve the performance of subsequent single processes and utilise biomass sources with higher efficiency. The best processing chain may vary in different cases and the overall energy balance of processing needs further research.

Addition of biochar into a soil changes its water retention properties by modifying soil textural and structural properties. In addition, internal micrometer-scale porosity that is able to directly store readily plant available water affects soil water retention properties. This study shows how precise knowledge of the internal micrometer-scale pore size distribution of biochar can deepen the understanding of the biochar-water interactions in soils. The micrometer-scale porosity of willow biochar was quantitatively and qualitatively characterized using X-ray tomography, 3D image analysis and Helium ion microscopy. The effect of biochar application on clay soil water retention was studied by conventional water retention curve approach. The results indicate that the internal pores of biochar, with sizes of at 50 and 10 μm (equivalent pore diameter), increased soil porosity and the amount of readily plant available water. After biochar addition, changes in soil porosity were detected at pore size regimes 5–10 and 25 μm, i.e. biochar pore sizes multiplied by factor 0.5. The detected pore size distribution of biochar does not predict directly (1:1 compatibility) the changes observed in the soil moisture characteristics. It is likely that biochar chemistry and pore morphology affect biochar-water interactions via e.g. surface roughness and contact angle. In addition, biochar induced changes in soil structure and texture affected soil moisture characteristics. However, the approach presented is an attractive pathway to more generalized understanding on how and why biochar internal porosity affects soil moisture characteristics. publishedVersion

Biochar pore space consists of porosity of multiple length scales. In direct water holding applications like water storage for plant water uptake, the main interest is in micrometre-range porosity since these pores are able to store water that is easily available for plants. Gas adsorption measurements which are commonly used to characterize the physical pore structure of biochars are not able to quantify this pore-size range. While pyrogenetic porosity (i.e. pores formed during pyrolysis process) tends to increase with elevated process temperature, it is uncertain whether this change affects the pore space capable to store plant available water. In this study, we characterized biochar porosity with x-ray tomography which provides quantitative information on the micrometer-range porosity. We imaged willow dried at 60 $^\circ$C and biochar samples pyrolysed in three different temperatures (peak temperatures 308, 384, 489 $^\circ$C, heating rate 2 $^\circ$C min$^{-1}$). Samples were carefully prepared and traced through the experiments, which allowed investigation of porosity development in micrometre size range. Pore space was quantified with image analysis of x-ray tomography images and, in addition, nanoscale porosity was examined with helium ion microscopy. The image analysis results show that initial pore structure of the raw material determines the properties of micrometre-range porosity in the studied temperature range. Thus, considering the pore-size regime relevant to the storage of plant available water, pyrolysis temperature in the studied range does not provide means to optimize the biochar structure. However, these findings do not rule out that process temperature may affect the water retention properties of biochars by modifying the chemical properties of the pore surfaces., Comment: 10 pages, 5 figures

Conversion of dissolved P by ferric sulfate into a particulate form sparingly available to algae was studied in 15 ditches in Finland using stand-alone dispensers for ferric sulfate administration. Ferric sulfate typically converted 60-70 % of dissolved P into iron-associated form, a process which required 250-650 kg per kg dissolved P. Mean cost was 160 EUR per kg P converted (range 20-400 EUR kg(-1)). The costs were lowest at sites characterized by high dissolved P concentrations and small catchment area. At best, the treatment was efficient and cost-effective, but to limit the costs and the risks, ferric sulfate dispensers should only be installed in small critical source areas.

Pyrolysis and hydrothermal carbonization (HTC) are gaining increasing interest in the context of biomass valorization. However, these processes yield a liquid fraction with an acidic pH value challenging to productize. In this paper, the possibility of replacing concentrated acids in acidification of animal slurry with organic acids derived from thermochemical conversion of various biomasses was investigated. The acid composition of four pyrolysis and one HTC liquid fraction were characterized using capillary electrophoresis and their total acidity determined titrimetrically. The amount of each liquid needed to reduce the pH of pig and cattle slurries to 6.0 and 5.5 were recorded. The total acidity of pyrolysis liquids varied highly (850-2560 meq l-1) depending on the biomass. For HTC liquid the total acidity was low (220 meq l-1). The most concentrated liquid, which showed greatest potential for practical use, was derived from pyrolysis of willow wood. Its required application rate for decreasing the pH of the slurries from >7.5 to 6.0 was 20-50 l t-1. This study suggests that there is a possibility of using liquids from pyrolysis process for acidification of animal slurries. Producing more concentrated liquids, further concentration of these acidiferous streams and the effects of the liquid addition on the properties of slurry are worth further studying.

Vegetated buffer zones (BZs) between arable fields and bodies of water are commonly established to reduce erosion and run-off of particle-bound nutrients. Functioning of a BZ depends on soil structure, as it is important for water infiltration. Therefore, it is vital to understand how varying management practices affect soils of BZs. We studied the structural and hydraulic properties of three differently managed BZs established in a boreal Vertic Stagnic Cambisol (clay, 51%). The three management practices for vegetation were as follows: natural with no treatment, harvested yearly and grazed by cattle. We used bulk density and macroporosity, together with a pore geometry index (air permeability per unit air-filled porosity), to describe the soil structural properties. Hydraulic properties were measured at different length scales by means of an aggregate sorptivity test, saturated hydraulic conductivity of the core samples and field-saturated hydraulic conductivity. Vegetation management markedly affected the physical properties in the top 5 cm of the soil. Properties were least favourable for infiltration at the grazed site, with the greatest bulk density, least macroporosity and hydraulic conductivity or greatest pore tortuosity. In general, spatial variation in zones with restricted and good hydraulic conductivity together with reduced aggregate sorptivity in the deeper horizons made the soil prone to preferential flow when initially dry. Prolonged wetness, on the other hand, reduced saturated hydraulic conductivity significantly, resulting in surface run-off. Harvesting was considered the best management practice due to its inherent capacity for reducing the soil nutrient content and because it has minor implications for soil physical properties.

Soil test P (STP) concentration indicates whether annual P applications can be expected to give yield increases and can also indicate an elevated risk of P mobilization and potential for P transfer to surface waters and groundwater from a particular field. Changes in STP with time thus project agronomic benefits and environmental risks of different P use strategies. To predict STP changes with time, we constructed a simple dynamic model for which the input variables are P balance and initial STP. The model parameters (soil type-specific constants) were fitted using data originating from 44 P fertilizer experiments with different P rates. Model performance was evaluated using independent data sets that either had reasonably accurate input values ( = 103) or were obtained from farmers through interviews ( = 638). The simulations were in agreement with measured STP changes for both evaluation data sets when fittings were performed separately for four main soil types (clays, silts, coarse mineral soils, and organic soils). Statistical analysis confirmed that the model captured the trends in STP (NHOAc test) with acceptable accuracy and precision, with of 0.83 and 0.66 for the data with more accurate input and for farmer interview data, respectively; the corresponding model efficiency statistics were 0.88 and 0.66. The model is not restricted to use with one soil test, as fittings for several different types of soil tests can be generated. In this study, we fitted the model for Olsen P data retrieved from the literature. Agronomic use of the model includes evaluation of P use strategies, e.g., when a certain STP level is targeted or when long-term economy of P use is calculated. In an environmental context, the model can be used to predict STP changes with time under variable P balance regimes, which is essential for realistic assessment of changes in the potential for dissolved P losses.

Water infiltration is a crucial process for functioning of vegetated buffer zones (BZ). Structure of a clayey surface soil of three differently managed BZs, i.e., 1) natural with no treatment, 2) harvested once a year and 3) grazed by cattle was investigated in this study. Soil macro pores (> 50 μm) were characterized by qualitative description and quantitative image analysis of soil thin sections in order to assess their capability to water infiltration. Less than 10% of the macro pores consisted of rounded and irregular pores smaller than 300 μm indicating root activity. Instead, macro porosity was clearly dominated by elongated pores characterized by irregularity, expressing the complexity of the pore system. This pore pattern appeared in thin sections as weak or moderate ped separation suggesting good water infiltration when initially dry. Partial accommodation of pores may result in decrease of hydraulic conductivity, as these pores tend to close upon wetting and swelling. In the grazed site a platy structure was observed due to hoof pressure, which may further impair the hydraulic properties of soil. Moisture and temperature related processes (shrink–swell, freeze–thaw, and water saturation) are thought to be conducive to the aggregation and rearrangement of soil structure around the year, resulting in a complex pore system with low intra-aggregate porosity. In addition, wet periods typical of boreal soils result in clay dispersion and formation of aggregate-related pedofeatures of dense infillings, described as fine clay intrusions.

The sorption and desorption of phosphorus (P) from eroding soil particles in land runoff are important processes contributing to agriculturally-driven eutrophication. We investigated the P-exchange properties and related chemical characteristics of contrasting European agricultural soils and sediment material eroded from them under indoor (small-scale) and outdoor (larger-scale) rainfall simulations. Quantity-intensity (Q/I) relationships revealed large variation in equilibrium P concentrations at zero net P sorption (EPC 0 ) (0-10.3 mg 1 -1 ) and instantly labile P (-Q 0, the amount of P to be desorbed to obtain a P equilibrium concentration of 0 mg 1 -1 ) (2-75 mg kg -1 ), both correlating closely with Al-bound P and the P saturation degree of Al oxides (DPS Alox ). Maximum P sorption (Q max ) (43-515 mg kg -1 ) also correlated most closely with Al ox . The indoor and outdoor rainfall simulations produced sediments with different P sorption properties: in the indoor simulation (less kinetic energy, constant slope), the sediments had larger EPC 0 values, and usually larger —Qo values, than the sediments in the outdoor simulation (greater kinetic energy, variable slopes). Furthermore, the P exchange properties of the sediments differed from those of the bulk soil depending on the enrichment of soil P-sorption components (Fe/Al oxides, clay). The outdoor simulation indicated that sites with gentle slopes produced sediments that were more enriched with Al ox , Fe ox , Mn ox and organic C than those with steeper slopes. In this study, when the bulk soil had an initial EPC 0 greater than 1.3 mg l -1 , the outdoor rainfall simulation produced sediment with smaller EPC 0 and vice versa, indicating that, depending on the P status of the bulk soil, the sediment material was acting as source or sink for P during transport. However, on the basis of their EPC 0 values, most eroding sediments might be expected to desorb, rather than adsorb, P when entering surface water.

Lannan levitys sokerijuurikasmaille on ongelmallista aikaisesta kylvöstä ja myöhäisestä sadonkorjuusta johtuen, jolloin kasvukauden ulkopuolisina levitysajankohtina maa on usein märkää ja helposti tiivistyvää. Levittämällä lanta kasvukauden aikana, voidaan mahdollisesti vähentää maan tiivistymistä ja samalla vältetään ravinteiden talviaikainen huuhtoutuminen syksyllä levitetystä lannasta. Lisäksi tehostamalla lannan hyödyntämistä, voidaan vähentää väkilannoitteiden käyttöä ja niiden ostosta aiheutuvia kustannuksia.Juurikkaan kasvukausi on pitkä ja sen ravinteiden otto on suurimmillaan heinäkuussa. Siten se pystyy hyödyntämään tehokkaasti kasvukaudella levitetyn lietelannan ravinteet. Kasvukaudella 2009 toteutetussa kokeilussa peltolohkon kahta koekaistaa lannoitettiin eri tavoin. Väkilannoitekaista sai N- ja K-lannoitteina 120 kg N ha-1 ja 30 kg k ha-1 sekä lietelantakaista N-lannoitteena ja lietelantana 66 kg N ha-1, 12 kg P ha-1 ja 22 kg K ha-1. Lietteen levitystä kokeiltiin ensiksi sijoittavalla levityslaitteistolla, mutta kasvuston vioittumisen vuoksi levitysmenetelmä vaihdettiin letkulevitystä vastaavaksi.Keväällä lohkolta otettiin maanäytteet viljavuusanalyysiä varten. Juurikkaan taimettumista seurattiin taimilaskennan avulla. Kasvuston lehtivihreän määrää arvioitiin SPAD-mittarilla kolme kertaa kasvukauden aikana. Lietevaunun vaikutusta maan tiivistymiseen (35 cm) tarkasteltiin penetrometrillä. Juurisadon määrä, juurikkaan keskipaino sekä sadon sokeri-, aminotyppi-, kalium- ja natriumpitoisuudet määritettiin nostetusta sadosta.Kenttähavaintojen perusteella todettiin, ettei käytetty sijoittava levityskalusto sovellu lannan levittämiseen juurikaskasvustoon. Sijoittava kalusto vioitti juurikaskasvustoa huomattavasti, kun kaluston vannasväli oli 17 cm ja juurikkaan riviväli 45 cm. Letkulevityksessä lanta puolestaan imeytyi hyvin maahan, eikä kasvusto likaantunut merkittävästi. Kesäkuun loppupuoli osoittautui hyväksi ajankohdaksi toimenpiteelle, sillä kasvusto on vielä avointa ja voi toipua tallauksesta.Maa oli tiiviimpää lietevaunun renkaan urassa kuin sen vieressä, mikä osittain johtunee poikkeuksellisen märistä levitysolosuhteista. Lietelantakaistan alhaisempi typen lannoitusmäärä näkyi juurikkaiden aminotyppipitoisuudessa, joka oli lietelantakaistalla alhaisempi kuin väkilannoitekaistalla. Kasvukauden aikana mitatut SPAD-tulokset tukevat tulosta. Väkilannoitekaistan sato kehittyi hyväksi ilman fosforilannoitustakin.Levityskalustoa kehittämällä ja ajouria käyttämällä kasvukauden aikaisen lannanlevityksen aiheuttamaa kasvuston vioittumista voitaisiin mahdollisesti vähentää. Lietteen levityksen siirtäminen kasvukaudelle ei automaattisesti poista tiivistymisriskiä, vaan maan kosteustilaan tukee edelleen kiinnittää huomiota. Hyvä keino tiivistymisriskin pienentämiseksi on suosia mahdollisimman kevyttä levityskalustoa.

Soil cracking is a well-known phenomenon, also seen in clay soils in the boreal climatic zone. This study was carried out to quantify soil shrinkage properties in six differently managed clay soils in Finland (Vertic Cambisols, 51% clay). Cylinder samples (100 cm(3)) were taken in spring from two depths (0-5 and 5-10 cm), then saturated with water and dried as a function of applied suction. The heights of the sample were measured after each drying step and the volume of soil was calculated assuming isotropic shrinkage. The volume loss by shrinkage at a suction of -50 kPa was 1.6-3.8% and the total shrinkage was 5.2-10.5% of the total soil volume, respectively. All shrinkage curves showed structural shrinkage which occurred in the matric potential range from saturation to around -6 kPa. The shrinkage curves were characterized by minor proportional and wide residual shrinkage zones. Eight of twelve sites showed a steeper shrinkage in the proportional shrinkage zone than the theoretical 1:1 line. Large slope values, up to 3.0, reflect the collapse of inter-aggregate pore space due to shrinkage pressure. The results indicate significant particle rearrangement and structural changes, e.g. structural collapse and changes in inter-aggregate pore space due to shrinkage pressure. Continuous water saturation and variable periods of freezing between spring and autumn are mostly responsible for soil weakness against increasing effective stress as soil dries. It is presumed that shrinkage behaviour will change substantially with increases in drying and wetting cycles.

Excessive use of sodium chloride (NaCl) as de-icing chemical causes environmental problems, such as elevated chloride concentrations in groundwater. On vulnerable sites, this can be avoided by using alternative organic de-icing chemicals, such as potassium formate (KHCOO). The environmental impacts of KCHOO are, however, not well known. This study reports the potential effects of NaCl and KCHOO on mechanisms controlling the mobility of cadmium (Cd) in roadside soils as a result of vehicular traffic. Changes in the solubility of Cd in a coarse mineral soil treated with these two de-icing chemicals were studied in a 50-day incubation experiment under four different moisture and temperature combinations and an initial soil Cd concentration of 3 mg kg − 1 . After incubation, the distribution of soil Cd into different fractions was analyzed using a sequential extraction method. Soil pH and soil redox potential were recorded and the occurrence of Cd–Cl complexes in the soil was estimated using published stability constants. During incubation, KCHOO lowered the soil redox potential, but this was not accompanied by a decrease in the sorption capacity of oxides and the release of oxide-bound Cd into soil solution. On the other hand, elevated pH (from 4.3 to 6.7–8.5) in the formate treatments increased the sorption of Cd onto the oxide surfaces (up to 80% of total sorbed Cd). In the NaCl treatments, cation competition and formation of Cd–Cl complexes increased the water-soluble Cd fraction. Consequently, the amount of bioavailable Cd was 3.5 times smaller in the KCHOO than in the NaCl treatments.

Soil structure that favours infiltration is essential for successful functioning of vegetated buffer zones. We measured bulk density, air permeability and precompression stress in a clay soil (Vertic Cambisol) and a sandy loam (Haplic Regosol) in Finland, to identify management-related changes in the physical and mechanical properties in the surface soil of buffer zones. In addition, the impact of texture on these properties was studied at depths down to 180?200 cm. Soil cores (240 cm3) were sampled from a cultivated field, from buffer zones harvested by grazing (only in a clay soil) or by cutting and removing the vegetation, and from buffer zones covered with natural grass vegetation. The samples were equilibrated at a matric potential of -6 kPa and compressed at a normal stress range of 20-400 kPa (7 h), followed by stress removal (1 h). Generally, the clay soil was more compressible than the sandy loam. Due to trampling by cattle, the young grazed buffer zone (0-3 cm) had the largest bulk density and the smallest total porosity. For the grazed sites, reduced air permeability (2.7-5.1 × 10-5 m s-1) was found, compared with that of the buffer zone under natural vegetation (15-22 × 10-5 m s-1), indicating decreased pore continuity. Although the old grazed site was easily compressed, compared with the younger site, it showed a greater resilience capacity due to the protective cover of organic residues accumulated on the soil surface., Hydrologiselta kannalta suojavyöhykkeiden ja -kaistojen tarkoitus on pintavalunnan hillitseminen ja imeynnän eli infiltraation edistäminen. Koska maan rakenne vaikuttaa keskeisesti suojavyöhykkeiden ja -kaistojen toimintaan, tässä tutkimuksessa tarkasteltiin suojakaistojen hoitotoimenpiteistä aiheutuvia mahdollisia muutoksia maan fysikaalisiin (irtotiheys ja ilmanjohtavuus) ominaisuuksiin ja maan kokoonpuristumisominaisuuksiin. Tutkittuja hoitotoimenpiteitä olivat niitto ja niittojätteen poiskorjaaminen, laidunnus sekä alueen jättäminen luonnontilaan.Jokioisilla savimaan (Vertic Cambisol) ja Maaningalla hietamaan (Haplic Regosol) koekenttien maaprofiili tutkittiin 200 cm:n (savi) ja 180 cm:n (hieta) syvyyteen saakka, ja maanäytteet otettiin kustakin horisontista. Etenkin hietamaalla oli muokkauskerroksen alapuolella kyntöantura yhä havaittavissa 10 vuotta viljelyn lopettamisen ja suojakaistan perustamisen jälkeen. Savimaan syvemmissä, todennäköisesti märkinä läpi vuoden säilyvissä horisonteissa (90-200 cm) maan irtotiheys oli pieni (< 1,19 g cm-3) ja kokonaishuokostilavuus suuri (> 0,52 cm3 cm-3), vaikka orgaanisen hiilen pitoisuus (< 0,9 %) oli erittäin alhainen. Maan rakenne on yhä massiivinen ja hyvin heikosti kehittynyt. Suojakaistojen pintamaakerroksesta (0-3 cm) ja maaprofiilien horisonteista otetut häiriintymättömät lieriönäytteet (240 cm3) kyllästettiin ja tasapainotettiin hiekkapedillä (-6 kPa). Maan ilmanjohtavuus mitattiin ja näytteitä kuormitettiin 7 tunnin ajan pystysuoralla normaalivoimalla (20, 40, 70, 100, 200 ja 400 kPa), minkä jälkeen kuormitus vapautettiin (1 tunti). Jännitystilan ja vastaavan muodonmuutostilan välistä riippuvuutta eli maan kokoonpuristumisominaisuuksia tarkasteltiin puolilogaritmisella asteikolla toisen asteen polynomin mukaisesti sovitetun jännitys-puristumakuvaajan avulla. Maan sisäistä lujuutta eli kykyä vastustaa ulkoapäin tulevia voimia arvioitiin ns. esitiivistysasteen avulla, joka johdettiin graafisesti ns. Casagranden menetelmällä. Maaprofiilin eri horisonttien kokoonpuristuminen oli riippuvainen maalajista, ei niinkään hoitotoimenpiteistä, ja se oli huomattavasti suurempaa savimaalla kuin hietamaalla. Molemmilla maalajeilla kokoonpuristuminen väheni siirryttäessä pintamaasta pohjamaahan. Tämä voi osaltaan selittyä sillä, että veden poistuminen huokosista oli estynyt, mikä esti kokoonpuristumisen. Suojakaistojen hoitotoimenpiteistä laidunnus aiheutti epäsuotuisia muodonmuutoksia savimaan rakenteessa, mikä heijastui kaistojen heikentyneenä ilmanjohtavuutena (2,7-5,1 10-5 m s-1) luonnontilaisiin kaistoihin verrattuna (15-22 10-5 m s-1). Kauttaaltaan alhaiset esitiivistysasteet voivat osin selittyä varhaisella näytteenottoajankohdalla, jolloin maan rakenne on talven jäljiltä heikoin mahdollinen. Laiduntaminen vaikutti kuitenkin maan kokoonpuristumisominaisuuksiin. Vaikka nuoren laidunkaistan tiivistyminen oli jo tiiviimmästä alkutilanteesta johtuen vähäistä, myös puristuman kimmoinen palautuminen oli kuormituksen lakattua pientä. Vanha laidunkaista oli taas helposti tiivistyvä, mutta maan pintakerrokseen kerääntynyt orgaaninen aines lisäsi kuormituksesta aiheutuneen puristuman palautumista. Tulosten perusteella laidunnusta tulisikin välttää etenkin hiljattain perustetulla nurmella.

Water repellency (WR) delays soil wetting process, increases preferential flow and may give rise to surface runoff and consequent erosion. WR is commonly recognized in the soils of warm and temperate climates. To explore the occurrence of WR in soils in Finland, soil R index was studied on 12 sites of different soil types. The effects of soil management practice, vegetation age, soil moisture and drying temperature on WR were studied by a mini-infiltrometer with samples from depths of 0-5 and 5-10 cm. All studied sites exhibited WR (R index >1.95) at the time of sampling. WR increased as follows: sand (R = 1.8-5.0) < clay (R = 2.4-10.3) < organic (R = 7.9-undefined). At clay and sand, WR was generally higher at the soil surface and at the older sites (14 yr.), where organic matter is accumulated. Below 41 vol. % water content these mineral soils were water repellent whereas organic soil exhibited WR even at saturation. These results show that soil WR also reduces water infiltration at the prevalent field moisture regime in the soils of boreal climate. The ageing of vegetation increases WR and on the other hand, cultivation reduces or hinders the development of WR., Kun kuivaan, huokoiseen maahan tiputettu vesipisaraei imeydy välittömästi, maa on vettä hylkivää eli hydrofobista. Lämpimien ilmastoalueiden karkeilla mailla vedenhylkivyys on yleisesti havaittu ja tutkittu ominaisuus. Boreaalisella ilmastovyöhykkeellä ilmiötä on sen sijaan tutkittu vähän. Vedenhylkivyyden esiintyminen liitetään orgaaniseen ainekseen, vaikkakin on epäselvää, mitkä spesifit yhdisteet ilmiön synnyttävät. Vedenhylkivyys aiheuttaa veden imeytymisen heikkenemistä ja maan epätasaista kostumista. Nämä seikat puolestaan edistävät oiko- ja pintavirtauksien syntyä sekä eroosiota. Vedenhylkivyydelle on tyypillistä suuri ajallinen ja paikallinen vaihtelu. Tässä tutkimuksessa maan vedenhylkivyysindeksi (R) määritettiin mini-infiltrometrillä käyttäen kolmesta suomalaisesta maalajista, savesta, hiedasta ja eloperäisestä maasta, 0–5 cm:n ja 5–10 cm:n syvyydeltä otettuja näytteitä. Tulosten perusteella arvioitiin kosteuden, kasvillisuuden iän ja viljelymuodon vaikutusta vedenhylkivyyden voimakkuuteen sekä tarkasteltiin määritysmenetelmän soveltuvuutta eri maalajeihin. Tutkitut maanäytteet olivat näytteenottohetkellä vettä hylkiviä, ja ominaisuus lisääntyi maalajeittain järjestyksessä hieta < savi < eloperäinen maa. Kasvipeitteisillä alueilla veden imeytymisen maan pintaan todettiin heikentyneen hiedalla 3–4-kertaisesti ja savimaalla 4–10-kertaisesti vedenhylkivyyden takia. Näiden maalajien vedenhylkivyys lisääntyi kasvillisuuden ikääntyessä vuosittain kynnetyllä pellolla se oli vähäisintä. Lisäksi vedenhylkivyys oli suurempaa maan pinnalla kuin syvemmässä kerroksessa. Tämä lienee seurausta pinnalle kertyvästä orgaanisesta aineksesta ja sen runsastumisesta, kun maata ei kynnetä. Vedenhylkivyys lisääntyi maan kuivuessa. Kivennäismaat osoittautuivat vettä hylkiviksi, kun kosteus oli alle 41 tilavuusprosenttia. Eloperäinen maa taas oli lievästi vettä hylkivä jopa vedellä kyllästettynä. Kun määritettiin näytteiden potentiaalista vedenhylkivyyttä, savelle ja hiedalle sopivaksi kuivatuslämpötilaksi osoittautui +40 °C. Sen sijaan eloperäisen maan näytteiden esikäsittely potentiaalisen vedenhylkivyyden määrittämiseksi vaatii vielä lisätutkimuksia. Tulokset osoittavat vedenhylkivyyttä esiintyvän myös boreaalisen ilmastovyöhykkeen maalajeilla, vaikka sitä ei aiemmissa maan veden liikkeitä käsittelevissä tutkimuksissa ole otettu huomioon. Ilmiön merkitys korostuu etenkin kuivissa olosuhteissa kasvipeitteisillä alueilla.

Pore space characteristics of biochars may vary depending on the used raw material and processing technology. Pore structure has significant effects on the water retention properties of biochar amended soils. In this work, several biochars were characterized with three-dimensional imaging and image analysis. X-ray computed microtomography was used to image biochars at resolution of 1.14 $\mu$m and the obtained images were analysed for porosity, pore-size distribution, specific surface area and structural anisotropy. In addition, random walk simulations were used to relate structural anisotropy to diffusive transport. Image analysis showed that considerable part of the biochar volume consist of pores in size range relevant to hydrological processes and storage of plant available water. Porosity and pore-size distribution were found to depend on the biochar type and the structural anisotopy analysis showed that used raw material considerably affects the pore characteristics at micrometre scale. Therefore attention should be paid to raw material selection and quality in applications requiring optimized pore structure., Comment: 16 pages, 4 figures. The final publication is available at Springer via http://dx.doi.org/10.1007/s11356-017-8823-x