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Inefficient use of phosphorus (P) fertilizers leads to the transfer of P into water bodies, causing their eutrophication. Sediment removal is a promising lake restoration strategy that removes nutrients including P accumulated in lake sediments, and opens the opportunity to use removed nutrients in agriculture. In the present study, we investigated the effects of using a thick layer of sediment from the eutrophic Lake Mustijarv on plant growth, and estimated the environmental impacts of different sediment application methods by analyzing greenhouse gas emissions, N and P leaching, aggregate stability, and soil biota. The field experiment (2017-2020) was established on the lake shore with the following treatments: the agricultural control soil (Soil) surrounding the lake, pure sediment (Sed), biochartreated sediment (SB), and biochar and soil mixed with sediment (SSB). The sediment-based treatments resulted in a similar grass growth performance to the Soil. The availability of most macro- and micronutrients including P (75 vs. 21 g m-3) were far greater in the Sed compared to the Soil. The sediment-based growing media emitted more CO2 than the Soil (579 vs. 400 mg CO2 - C m-2 h-1) presumably due to the high rate of organic matter decomposition. The bacterial and fungal community structures of the Sed were strongly differentiated from those of Soil. Also, Sed had lower bacterial diversity and a higher abundance of the bacterial phyla associated with solubilizing P including Proteobacteria and Chloroflexi. Sediment-based growing media increased more than seven times the risk of mineral N

In acid sulfate (AS) soils, organic rich topsoil and subsoil horizons with highly variable acidity and moisture conditions and interconnected reactions of sulfur and nitrogen make them potential sources of greenhouse gases (GHGs). Subsoil liming can reduce the acidification of sulfidic subsoils in the field. However, the mitigation of GHG production in AS subsoils by liming, and the mechanisms involved, are still poorly known. We limed samples from different horizons of AS and non-AS soils to study the effects of liming on the N2O and CO2 production during a 56-day oxic and subsequent 72-h anoxic incubation. Liming to pH >= 7 decreased oxic N2O production by 97-98 % in the Ap1 horizon, 38-50 % in the Bg1 horizon, and 34-36 % in the BC horizon, but increased it by 136-208 % in the C horizon, respectively. Liming decreased anoxic N2O production by 86-94 % and 78-91 % in Ap1 and Bg1 horizons, but increased it by 100-500 % and 50-162 % in BC and C horizons, respectively. Liming decreased N2O/(N2O + N2) in anoxic denitrification in most horizons of both AS and non-AS soils. Liming significantly increased the cumulative oxic and anoxic CO2 production in AS soil, but less so in non-AS soil due to the initial high soil pH. Higher carbon and nitrogen contents in AS soil com-pared to non-AS soil agreed with the respectively higher cumulative oxic N2O production in all horizons, and the higher CO2 production in the subsoil horizons of all lime treatments. Overall, liming reduced the proportion of N2O in the GHGs produced in most soil horizons under oxic and anoxic conditions but reduced the total GHG production (as CO2 equivalents) only in the Ap1 horizon of both soils. The results suggest that liming of subsoils may not always effectively mitigate GHG emissions due to concurrently increased CO2 production and denitrification.

A 15N tracing pot experiment was conducted using two types of wood-based biochars: a regular biochar and a Kon-Tiki-produced nutrient-enriched biochar, at two application rates (1% and 5% (w/w)), in addition to a fertilizer only and a control treatment. Ryegrass was sown in pots, all of which except controls received 15N-labelled fertilizer as either 15NH4NO3 or NH415NO3. We quantified the effect of biochar application on soil N2O emissions, as well as the fate of fertilizer-derived ammonium (NH4+) and nitrate (NO3−) in terms of their leaching from the soil, uptake into plant biomass, and recovery in the soil. We found that application of biochars reduced soil mineral N leaching and N2O emissions. Similarly, the higher biochar application rate of 5% significantly increased aboveground ryegrass biomass yield. However, no differences in N2O emissions and ryegrass biomass yields were observed between regular and nutrient-enriched biochar treatments, although mineral N leaching tended to be lower in the nutrient-enriched biochar treatment than in the regular biochar treatment. The 15N analysis revealed that biochar application increased the plant uptake of added nitrate, but reduced the plant uptake of added ammonium compared to the fertilizer only treatment. Thus, the uptake of total N derived from added NH4NO3 fertilizer was not affected by the biochar addition, and cannot explain the increase in plant biomass in biochar treatments. Instead, the increased plant biomass at the higher biochar application rate was attributed to the enhanced uptake of N derived from soil. This suggests that the interactions between biochar and native soil organic N may be important determinants of the availability of soil N to plant growth.

Using biogeochemical analyses of sediments and porewaters, we investigate the legacy of a brief, intense period of eutrophication on sedimentary phosphorus (P) cycling in a boreal lake (Enonselkä basin, Lake Vesijärvi, Finland). Point-source sewage inputs in the twentieth century caused deoxygenation of the lake and accelerated the focusing of iron (Fe) and manganese (Mn) oxides into deeper areas. Early diagenesis under Fe–Mn-rich conditions now favors rapid burial of P in these areas, likely as a combination of both oxide-bound P phases and authigenic manganous vivianite. A new P budget for Enonselkä basin shows that P burial causes an annual drawdown of 1.2% (± 0.2%) of the surface sediment P inventory, supporting a long-term trend towards recovery since the construction of a wastewater treatment plant in the mid-1970s. However, remineralization of organic matter and associated dissolution of Fe–Mn oxides continues to regenerate P from a deep reactive layer (20–60 cm depth) deposited at the height of past eutrophication, leading to an upwards diffusive flux of dissolved phosphate towards the surface sediments. The magnitude of this flux is similar to that of external P loading to the lake. The combined incoming fluxes of P are likely to retard the complete recovery from eutrophication by decades, despite ongoing restoration actions.

The nitrogen availability, that affects the greenhouse gas emission and the trophic level of lakes, is controlled mainly by microbial processes. We measured in a boreal nitrate and iron rich lake how the rates of potential denitrification and dissimilatory nitrate reduction to ammonia (DNRA) are affected by degradability of organic matter and availability of aqueous ferrous iron. We also investigated the microbial community by using 16S rRNA gene and shotgun metagenomic sequencing approach, which allows taxonomic analyses and detection of metagenome-assembled genomes (MAGs) containing genes for both nitrate reduction and iron oxidation. The results show that truncated denitrification, leading to release of nitrous oxide, is favored over dinitrogen production in conditions where the degradability of the organic matter is low. DNRA rates were always minor compared to denitrification and appeared to be independent of the degradability of organic carbon. Reduced iron stimulated nitrate reducing processes, although consistently only DNRA. However, the proportion of MAGs containing DNRA genes was low suggesting chemistry driven stimulation by reduced iron. Nevertheless, the metagenomic analyses revealed unique taxa genetically capable of oxidizing iron and reducing nitrate simultaneously. Overall, the results highlight the spatial variability in microbial community and nitrous oxide emissions in boreal lake sediments.

Biochars (BC) have tremendous potential in mitigating climate change, and offer various agricultural and environmental benefits. However, there is limited information about the long-term effects of added biochars particularly from boreal regions. We studied the effects of a single application of softwood biochars on two contrasting boreal agricultural soils (nutrient-poor, coarse textured Umbrisol and fertile, fine-textured Stagnosol), both with high initial soil organic carbon contents, over eight years following the application. We focused on plant nutrient contents and nutrient uptake dynamics of different field crops over these years, as well as on soil physical properties and greenhouse gas emissions during seven to nine growing seasons. We found that, added biochars had minor long-term effects on the crop biomass yield, plant nutrient contents and plant nutrient uptake in both soil types. In terms of crop biomass yields, significant biochar × fertilization interactions were observed in barley (in 2013) and peas (in 2016), three and six years after the application of biochar in Stagnosol, respectively. In both cases, the biochar combined with the normal fertilization rate (100% of the recommended value) significantly increased crop biomass yield compared to corresponding fertilization treatment without biochar. However, the biochar had no effect at a lower fertilization rate (30% of the recommended value). Similar significant biochar × fertilization interactions were observed for several plant nutrient contents for peas in 2016, and for uptake for both barley in 2013 and peas in 2016. Thus, the ability of biochar to enhance the supply of nutrients to plants and hence to improve the crop biomass yield exists in boreal conditions, although these effects were minimal and not consistent over the years. Biochar notably increased plant K content, and also increased K:Mg ratio in plant biomass, suggesting a possible antagonistic effect of K on Mg in Umbrisol. Similar K antagonism on Na was observed in Stagnosol. The applied biochar also reduced the plant content and uptake of Al and Na in several years in Stagnosol. Furthermore, we found that, increased plant Mn content with biochar in the initial years subsequently declined over the following years in Umbrisol. On the other hand, the relative plant contents of Cd and Ni in Umbrisol, and P, K, Mg, S, Al, Cu, Fe and Ni in Stagnosol increased over the years. Despite these increased plant contents, no significant improvement was observed in crop biomass yield by added biochar over the years. The enhanced plant available water and reduced bulk density previously reported during the initial years were faded in long-term, likely due to dilution of biochar concentration in topsoil. However, the potential of biochar to affect N2O emission persisted, even seven years after the application.

To achieve appropriate yield levels, inherent nitrogen (N) supply and biological N fixation are often complemented by fertilization. To avoid economic losses and negative environmental impacts due to over-application of N fertilizer, estimation of the inherent N supply is critical. We aimed to identify the roles of soil texture and organic matter in N mineralization and yield levels attained in cereal cultivation with or without N fertilization in boreal mineral soils. First, the net N mineralization and soil respiration were measured by laboratory incubation with soil samples varying in clay and organic carbon (C) contents. Secondly, to estimate the inherent soil N supply under field conditions, both unfertilized and fertilized cereal yields were measured in fields on clay soils (clay 30-78%) and coarse-textured soils (clay 0-28%). In clay soils (C 2.5-9.0%), both the net N mineralization and the cereal yields (without and with fertilization) decreased with increasing clay/C ratio. Moreover, in soils with high clay/C ratio, the agronomic N use efficiency (additional yield per kg of fertilizer N) varied considerably, indicating the presence of growth limitations other than N. In coarse-textured soils, the yield increase attained by fertilization increased with increasing organic C. Our results indicate that for clay soils in a cool and humid climate, the higher the clay content, the more organic C is needed to produce reasonable yields and to ensure efficient use of added nutrients without high N losses to the environment. For coarse soils having a rather high mean organic C of 2.3%, the organic C appeared to improve agronomic N use efficiency. For farmers, simple indicators such as the clay/C ratio or the use of non-N-fertilized control plots may be useful for site-specific adjustment of the rates of N fertilization. Highlights We aimed to identify simple indicators of inherent soil N supply applicable at the farm level. In clay soils, the net N mineralization was found to correlate negatively with the clay/C ratio. In coarse-textured soils, agronomic N use efficiency improved with increasing soil organic C. Clay soils with high clay/C ratio are at risk of low yield levels.

In acid sulfate (AS) soils, organic rich topsoil and subsoil horizons with highly variable acidity and moisture conditions and interconnected reactions of sulfur and nitrogen make them potential sources of greenhouse gases (GHGs). Subsoil liming can reduce the acidification of sulfidic subsoils in the field. However, the mitigation of GHG production in AS subsoils by liming, and the mechanisms involved, are still poorly known. We limed samples from different horizons of AS and non-AS soils to study the effects of liming on the N

The identity of electron acceptors in promoting anaerobic oxidation of methane (AOM) in the sediments of boreal lakes is currently unknown. Here, we studied the AOM rate of sediment slurries collected from three profundal stations of a nitrate-rich, oligo-mesotrophic, boreal lake (Lake Pääjärvi, Finland), under varying nitrate concentrations using 13C-labelling. Furthermore, vertical profiles of the sediment and porewater geochemistry, and the microbial communities (16S rRNA gene and shotgun metagenomic sequencing) were analyzed. Despite geochemical data indicating that simultaneous consumption of nitrate and methane took place at the sediment layers chosen for incubations, AOM rate was not enhanced by nitrate amendments at either of the stations. AOM rate was much higher at the shallow Station 1 (0.9-6.8 nmol C cm-3 d-1) with high contents of labile phytoplankton-derived organic matter, than at the deeper stations, Station 2 (0-0.3 nmol C cm-3 d-1) and 3 (0-0.2 nmol C cm-3 d-1). Accordingly, a higher relative abundance of methanotrophic archaea (Candidatus Methanoperedens) and bacteria (Methylococcales) were observed in the layers chosen for incubations at Station 1 than at the other stations. Besides nitrate, the geochemical profiles indicated that AOM was potentially coupled with iron or sulfate reduction at all stations. Furthermore, putative nitrite-reducing methanotrophs (Ca. Methylomirabilis) were the most abundant methanotrophs above the incubation layer at Station 2 and 3, which suggests that nitrite reduction also plays a role in driving AOM in the study lake. We conclude that AOM is not uniquely coupled to nitrate reduction in sediments of nitrate-rich, oligo-mesotrophic, boreal lakes.

Mankind is taking advantage of numerous services by small shallow lakes such as drinking water supply, irrigation, and recreational function; however, many of these lakes suffer from eutrophication. Given the key role of phosphorus (P) in eutrophication process, one of the effective restoration methods especially for small shallow lakes is removal of sediments enriched with nutrients. In our study, we used interannual, seasonal, and spatial data to examine the changes in sediment P mobility after removal of sediments in 2016 from a 1-ha highly eutrophic lake. We measured the sediment redox potential, analyzed soluble reactive P (SRP) in the pore water and P fractional composition of the surface sediments, and calculated the P diffusive flux in three locations in two continuous years (2017 and 2018) after the excavation. Similar measurements were done before sediment removal at central site of the lake in 2015. Removing nutrient-rich sediment also removed 6400 kg of P, and thus the potential for release of P from sediments decreased on a long-term scale. However, a large pool of releasable P was rebuilt soon after the sediment removal due to high external P loading, resulting in extensive anoxia of sediment surface and associated internal P loading as high as 1450 mg m−2 summer−1. Moreover, the Fe-P and labile P fractions were the most important sources of P release, as evidenced by their considerable seasonal and interannual changes after the sediment removal. The sediment total Fe negatively correlated with sediment P diffusive flux, pore water SRP, and near-bottom water total P and SRP concentrations which indicated a strong linkage between sediment P dynamics and Fe after the restoration. Sediment removal could be a beneficial restoration approach, but the effects on lake water quality remain only short-term unless there is an adequate control on external loading to the lake.

Large amounts of sulfate and divalent iron (Fe) are released into the pore water of acid sulfate (AS) soils upon oxidation of sulfidic materials. The simultaneously produced acidity dissolves metals from the soil matrix. Reduced horizons of AS soils commonly have a large mineral nitrogen (N) stock in the form of NH 4 + -N, which is a potential source of N leaching and gaseous emissions. This study was carried out at three AS soil sites in Finland. Cation composition of pore water was monitored in a monolithic lysimeter experiment. Timothy samples grown in an AS soil were analysed for mineral elements and the soil was investigated for zinc (Zn) distribution in different chemical species at four depths down to 85 cm. The composition of pipestems formed in previous root channels was investigated by SEM, X-ray EDX and XRD. Emissions of CO 2 and N 2 O were measured in an AS field which had a peaty topsoil. Monitoring by closed chambers was carried out at three sites differing in the depth of peat layer (15, 30 and 60 cm). In the sulfuric horizon, large amounts of calcium and magnesium were mobilized. Reflooding stopped the mobilization of those elements but resulted in abundant dissolution of Fe, which became the dominant cation in the pore water. Timothy growing in an AS soil showed only small deviations from the average composition measured in Finland with the exception of Zn that was at the deficiency level. As Zn in the root zone had been dissolved and subsequently leached, it was recovered in easily soluble forms in the subsoil. Pipestem composition indicated accumulation of Fe and formation of a new solid phase probably mostly in the form of schwertmannite even though jarosite was also detected. The annual CO 2 emissions from the peaty AS soil were about 6000 kg C ha − 1 but the N 2 O emissions were relatively small, with a magnitude more typical of mineral rather than organic soils. Thus, large N stock of an AS soil do not necessarily contribute to abundant gaseous N emissions.

Sediment removal from eutrophicated shallow lakes may not only be an effective method for lake restoration but also provides the potential for recycling nutrients from sediments to crop production. However, finding a suitable strategy for sustainably reusing the sediment remains a challenge. Therefore, current study focused on the best practices in applying the sediment from a shallow eutrophicated lake to the soil in terms of grass yield, nutrient uptake, and nutrient leaching. During a nine-month lysimeter experiment, 100-cm high columns were filled with six combinations of soil, sediment, and biochar, with or without meat bone meal organic fertilizer. Aboveground biomass, root mass distribution in soil, nutrient concentration, phosphorus (P) uptake of perennial ryegrass (Lolium perenne L.) along with easily soluble nutrients in the growing medium, and leached mineral nitrogen (N) and P levels were measured. Plant growth conditions were improved by sediment additions, as the yield and P uptake of ryegrass nearly doubled in treatments containing sediment compared to the control soil. While the sediment was richer in macro and micronutrients (e.g. P and N) compared to the soil, the leached N and P levels from both treatments were almost equivalent (N < 830 mg m−2 and P < 3 mg m−2). In addition, applying a 2-cm layer of biochar between the sediment and soil reduced P and N leaching by 50%. According to the results, applying a 75-cm thick layer of sediments on agricultural sandy loam soils surrounding the lake seems a promising practice for improving plant yield and soil nutrient status without increasing of P and N leaching from soil.

Lake sediments are in many cases known to be rich in nutrients, organic carbon, and clay minerals. These compounds originate from eroded agricultural soils acting as primary sediment source. European countries produce about 200 million m3 y−1 of sediment removed from waterbodies which provides the potential of recycling nutrients from sediments in crop production. There are just a handful studies available exploring the potential of recycling the nutrients from sediments and none have been conducted under field conditions. Therefore, there is a need to develop efficient ways to reuse sediments on agricultural lands to preserve phosphorus and other nutrients and respond to crop demands. The aim of this research was to investigate the effects of different ways of sediments applications to soil on grass growth, soil, and environment. The study was conducted in the shore of a 1-ha heavily eutrophicated lake from which sediments were excavated. Four different sediment application methods were tested in a RCBD design with four replicates. The treatments were pure topsoil, a mixture of soil and biochar on top of the sediment, a mixture of biochar with top 20 cm of sediment, and a 75–100 cm layer of sediment directly on topsoil. In June 2017, mixture of red fescue, Kentucky bluegrass, ryegrass, and white clover was sown to all plots with meat bone meal organic fertilizer. The leaf area index, the relative leaf chlorophyll values, aboveground biomass, soil moisture content, total carbon and nitrogen, GHG emissions, and the soil penetration were measured in all plots in August 2017. The analysis of representative samples of sediments revealed that the sediments were not contaminated by heavy metals, PAHs, and PCBs. The moisture content was significantly higher in sediment plots (33±5%) than soil (19±1%). Relative leaf chlorophyll value and leaf area index were significantly 1.3 and 1.7 times greater in sediment plots than in the soil plots, respectively. Moreover, the treatments containing biochar had the highest C:N ratio. Sediment phosphorus (P) content was high, providing sufficient available P to agricultural lands. The final presentation will include data on yields of 2018, GHG emissions, and the mechanical soil resistance in different treatments. Our results emphasizes the importance of preventing the transport of nutrients to water bodies and considering the assessment of sediment nutrient contents and pollutants in the disposal of removed sediments.

Bioenergy cropping, like all agricultural practices, may lead to the release of greenhouse gases. This study was aimed at determining biomass and energy yields of reed canary grass (RCG) (Phalaris arundinacea), galega (Galega orientalis) and a mixture of these, and to relate these to fluxes of nitrous oxide (N2O), a potent greenhouse gas, emitted from the soils. Plots including a bare fallow as control were established in 2008. Gases emitted from the soil surface were collected in closed chambers from May 2011 to May 2013, except during periods of snow cover, and analysed by gas chromatography. Seasonal and annual cumulative emissions of N2O and CO2 equivalents per unit energy yield were calculated. Soil moisture content, nitrate (NO3 −)-N and ammonium (NH4 +)-N were also determined. Both species composition and crop yields affected energy yields and N2O emission from the soil. The annual cumulative emissions from mixture were marginally lower than those from fertilized RCG soils. Fertilized RCG produced twice as much biomass and correspondingly higher nitrogen and energy yields, so its low emission of N2O per Mg of dry matter was not significantly different from that of the mixtures. Cropping an RCG–galega mixture for biofuel may replace N fertilizer input since it resulted in lowering N2O fluxes, but requires management to maintain grass as the major component in order to minimize N2O emissions. In a time of climate change, low-input bioenergy crops may be a suitable strategy for land left uncropped after ploughing for one season or longer.

Nodularia spumigena is a nitrogen-fixing cyanobacterium that forms toxic blooms in the Baltic Sea each summer and the availability of phosphorous is an important factor limiting the formation of these blooms. Bioinformatic analysis identified a phosphonate degrading (phn) gene cluster in the genome of N. spumigena suggesting that this bacterium may use phosphonates as a phosphorus source. Our results show that strains of N. spumigena could grow in medium containing methylphosphonic acid (MPn) as the sole source of phosphorous and released methane when growing in medium containing MPn. We analyzed the total transcriptomes of N. spumigena UHCC 0039 grown using MPn and compared them with cultures growing in Pi-replete medium. The phnJ, phosphonate lyase gene, was upregulated when MPn was the sole source of phosphorus, suggesting that the expression of this gene could be used to indicate the presence of bioavailable phosphonates. Otherwise, growth on MPn resulted in only a minor reconstruction of the transcriptome and enabled good growth. However, N. spumigena strains were not able to utilize any of the anthropogenic phosphonates tested. The phosphonate utilizing pathway may offer N. spumigena a competitive advantage in the Pi-limited cyanobacterial blooms of the Baltic Sea.

Acid sulphate (AS) soils are most prevalent in the tropics, but the acidic discharge from cultivated AS soils also threatens water bodies under boreal conditions. Feasible options to reduce the acid load are needed. In this study, the groundwater of an AS field was monitored for 3.5 years, and the efficiency of waterlogging in mitigating the environmental risks caused by acidic discharge was investigated in a 2.5-year experiment with 10 monolithic lysimeters taken from the same field. In order to unravel the transferability of the results from lysimeters to the field scale, the Al, Fe and S concentrations in discharge water from the lysimeters were compared with those in the groundwater of the AS field (pedon and field scale), and in pore water (pedon and horizon scale). In the waterlogged bare lysimeters (HWB), the Al, Fe and S concentrations in discharge waters were broadly similar to those measured in the groundwater and followed the changes in the pore water. In the waterlogged cropped (reed canary grass, Phalaris arundinacea) lysimeters (HWC), in contrast, the discharge waters were markedly higher in Fe and lower in Al than the groundwater in the field. This outcome was attributable to the reduction of Fe(3+) to the more soluble Fe(2+) and the reduction-induced increase in pH, which enhanced the formation of Al(3+) hydroxy species. Lowering of the water table (LWC) caused soil ripening, which resulted in increased saturated hydraulic conductivity and porosity and enhanced the oxidation of sulphidic materials and acid formation. The responses of Al, Fe and S in drainage waters from HWC and LWC lysimeters resembled previous findings in AS soils. Based on this and the similarity between dissolved element concentrations in the discharge water of HWB lysimeters and groundwater in the field, we conclude that our monolithic lysimeters yielded realistic results concerning the efficiency of various methods in mitigating environmental risks related to cultivated AS soils.

Biochar is widely studied as a combined soil conditioner in agriculture and a potential carbon sink. The knowledge of the effects of field application of biochar on soil fauna remains limited. Earthworms are a globally common and important faunal group in arable soils and the purpose of our study was to determine the effects of biochar on earthworms under both laboratory and field conditions in a boreal loamy sand. An avoidance test using the earthworm Aporrectodea caliginosa Sav. was conducted for periods of 2 and 14 days with 16gkg-1 spruce chip biochar. The same biochar was mixed into the top 10cm of soil at 0 or 30tha-1 and its effect on earthworm density and biomass was studied over four and half months in a field experiment where wheat was grown with or without inorganic fertilizer application. In the avoidance test, biochar application did not affect the habitat choice of earthworms in the first 2d, but after 14d, they tended to avoid it. The avoidance was possibly the avoidance was possibly caused by a slight decline in soil water potential. Under field conditions the highest earthworm densities and biomasses were measured in biochar amended soils. None of the differences among the treatments studied were, however, statistically significant (p>0.05). The time scale of the study was sufficient for reliably demonstrating the lack of strong toxic effects and immediate avoidance reactions caused by biochar application.

Poor water retention capacity (WRC) and nutrient deficiency commonly limit crop yields in sandy soils. The use of biochar as a soil amendment has been previously reported to improve these limiting factors in subtropical and temperate soils. We studied the effects of biochar on soil properties and yield formation of spring wheat (Triticum aestivum L.) when applied together with inorganic fertiliser or meat bone meal (MBM) to an Endogleyic Umbrisol with a loamy sand texture in boreal conditions. In a two-year field experiment, biochar was applied at 0, 5, 10, 20 and 30 t ha−1 combined with three fertiliser treatments (unfertilised control, MBM and inorganic fertiliser) providing equal amounts of nitrogen (N), phosphorus (P) and potassium (K). Soil WRC and fertility as well as wheat yield, yield components and quality were analysed. Soil moisture content, leaf area index and leaf chlorophyll values (SPAD) were monitored during the experiment. Biochar increased the plant-available water content of the topsoil in the first year and reduced the bulk density in the second year after application. It also increased the contents of easily soluble K and soil organic C (SOC) in the 20 cm of topsoil, but had no effects on other soil nutrients, pH or moisture content. Biochar amendment decreased the soil NO3−-N content below control values in the first year but increased it significantly in the second year. The addition of biochar did not significantly affect the nitrogen uptake, grain yield or quality of wheat, possibly because of its low nutrient availability and the high organic matter content of the soil.

Soil productivity and other soil functions are dependent on processes in the untilled subsoil. Undisturbed soil cores were collected at the 0.3- to 0.4-m depth from a heavy clay soil in Finland subjected to a single heavy traffic event by agricultural machinery three decades before sampling. Untrafficked control plots were used as a reference. Computed tomography (CT) scanning was performed on soil cores at a field-sampled field capacity water content. Gas diffusion and air permeability were measured when the soil cores were drained to −1000 hPa matric potential (air permeability also at −100 and −300 hPa). The air-filled pore space was measured with an air pycnometer and also calculated from mass balance and CT data. Gas diffusion and air permeability were also measured on a straight model tube and on autoclaved aerated concrete. The compaction treatment had not influenced soil total porosity but had significantly lowered the volume fraction of air-filled macropores at the matric potentials investigated. The compacted soil displayed significantly lower air permeability, while gas diffusivity was not affected. Our analyses indicate that this was due to a compaction-induced reduction in the cross-sectional area of vertical, arterial macropores and in the volume of marginal pores branching from these vertical pores. We observed non-Darcian air flow during air permeability measurements and thus suggest the use of a nonlinear regression technique based on measurements at several pressure differences to arrive at true Darcian air permeability. The tests on artificial materials supported the conclusions that the dominating pores in this clayey subsoil are nearly straight, vertical macropores.

Acid sulphate (AS) soils require careful management to prevent the environmental hazards that result from the oxidation of sulphide-bearing deep soil layers and the consequent acidification of soil and waters. Management with a high water table precludes many food crops, so their suitability for perennial energy cropping was investigated in a 3-year study using reed canary grass (Phalaris arundinacea L., RCG). Monolithic lysimeters made of undisturbed AS soil and equipped with ground-water level control and measurement instruments were planted with 1- year-old RCG turfs taken from a non-AS field. Two water tables were imposed, high (HWT, 20 cm below soil surface) and low (LWT, 70 cm below soil surface, considered normal for agriculturally managed AS soils) for a 3 year period. Growth and physiological characters of RCG were determined and its ash content and the elemental composition of its dry biomass (Ca, Cl, K, Mg, and S) were analysed. The level of the water table had significant effects on crop growth and quality. Shoots were 25 to 29 % taller, consequently yielding more dry matter in HWT than in LWT lysimeters. Concentrations of K, Mg and S that can affect the combustion process were higher in biomass harvested from LWT lysimeters than from the HWT plants. At the end of the experiment, the spatial distribution of roots within the soil profile differed between treatments. Roots penetrated to the bottom of LWT lysimeters with total root dry mass nearly twice that in HWT. RCG intended for burning grows and performs well in acid sulphate soils managed with a raised water table. This management option minimizes the risk of acid flows from oxidized soils, and allows farmers to harvest a non-food crop from soils that would have to be drained to provide a food or feed crop.

The oxidation of sulphidic materials upon drainage of acid sulphate (AS) soils causes episodic hazards to aquatic ecosystems worldwide. Reintroducing a high groundwater level, in order to turn the soil reactions back to reduction, is an option to alleviate the environmental loading from these soils. In boreal conditions, with low soil temperatures and consequently slow chemical and microbial reactions, feasible tools are needed to effectively investigate the impacts of this practice on soil processes. With this aim, ten lysimeters containing AS soil monoliths (1 m high, 0.5 m wide) were set up in Finland to investigate the pore water quality and leaching of elements in response to an elevated water table. In this paper, the design of the lysimeters is described and results confirming their suitability for the purpose are presented. This paper focuses on the possible shortcomings of lysimeters in AS soils, such as unnaturally rapid oxidation of the sulphidic C horizon, side-wall flow of water in the ripening soil, and the impaired functioning of probes over time in the extremely acid soil and in the sulphidic materials. Dye and chloride tracing revealed that no significant sidewall flow occurred in the lysimeters. The continuous Eh measurements functioned unimpaired during the two-and-a-half-year experiment. Reduced conditions were preserved in the Cg horizon throughout the experiment. In drained horizons, Eh varied according to the water management practice and the growth of reed canary grass roots, but in the water-saturated horizons, Eh mainly responded to long-term changes in soil chemistry, such as the reduction of iron. Soil temperature in deep soil horizons closely corresponded to typical boreal conditions in winter, but it was a few degrees Celsius higher in summer. Our results demonstrate that it is feasible to simulate processes dependent on water management in AS soils with monolithic lysimeters.

We studied the effect of different biochar (BC) application rates on soil properties, crop growth dynamics and yield on a fertile sandy clay loam in boreal conditions. In a three-year field experiment conducted in Finland, the field was divided into three sub-experiments with a split-plot experimental design, one for each crop: wheat (Triticum aestivum), turnip rape (Brassica rapa), and faba bean (Vicia faba). The main plot factor was BC rate (0, 5 and 10 t DM ha−1) and the sub-plot factor was the N-P-K fertiliser rate. Soil physico-chemical properties as well as plant development, yield components and quality were investigated. BC addition did not significantly affect the soil chemical composition other than the increased C and initially increased K contents. Increased soil moisture content was associated with BC application, especially at the end of the growing seasons. BC decreased the N content of turnip rape and wheat biomass in 2010, thus possibly indicating an initial N immobilisation. In dry years, the seed number per plant was significantly higher in faba bean and turnip rape when grown with BC, possibly due to compensation for decreased plant density and relieved water deficit. However, the grain yields and N uptake with BC addition were not significantly different from the control in any year. Even though BC application to a fertile sandy clay loam in a boreal climate might have relieved transient water deficit and thereby supported yield formation of crops, it did not improve the yield or N uptake.

Isaac Newton's approach to developing theories in his book Principia Mathematica proceeds in four steps. First, he defines various concepts, second, he formulates axioms utilising the concepts, third, he mathematically analyses the behaviour of the system defined by the concepts and axioms obtaining predictions and fourth, he tests the predictions with measurements. In this study, we formulated our theory of boreal forest ecosystems, called NewtonForest, following the four steps introduced by Newton. The forest ecosystem is a complicated entity and hence we needed altogether 27 concepts to describe the material and energy flows in the metabolism of trees, ground vegetation and microbes in the soil, and to describe the regularities in tree structure. Thirtyfour axioms described the most important features in the behaviour of the forest ecosystem. We utilised numerical simulations in the analysis of the behaviour of the system resulting in clear predictions that could be tested with field data. We collected retrospective time series of diameters and heights for test material from 6 stands in southern Finland and five stands in Estonia. The numerical simulations succeeded to predict the measured diameters and heights, providing clear corroboration with our theory., published version, peerReviewed

We studied the impact of added biochar on the N mineralisation dynamics of two organic fertilisers by incubating loamy sand soil for 133 days in controlled conditions. Biochar made from softwood chips was added to soil at 0, 4·6, 9·1 and 13·6 g kg–1soil dry matter (DM) either alone, or in combination with meat bone meal (MBM) and composted cattle manure (CCM) fertilisers. Soil mineral N concentration was determined on days 0, 14, 28, 56, 84 and 133. Net N mineralisation in the MBM treatment was much larger than in the CCM or the unfertilised treatments. Constant soil moisture during the incubation provided suitable aerobic soil conditions for nitrification: after day 14, soil mineral N was dominated by nitrate in all treatments. Biochar additions decreased the mineral N concentrations in all treatments, probably because of immobilisation by microbes. In unfertilised soil, the immobilisation by biochar increased steadily with application rate and time, but in the MBM and CCM treatments, it started to decrease or level off after two months, possibly due to the turnover of microbial biomass. The main biochar-induced impacts on soil N mineralisation dynamics could be modelled by using standard and confined exponential models.

To examine the suitability of acid sulphate soils for perennial energy cropping and specifically to provide information on the responses of reed canary grass (Phalaris arundinacea L.) to raised water levels, a management option for these problematic soils, large core lysimeters of undisturbed field acid sulphate soil were taken into PVC tubes equipped with ground water level control and measurement instruments, planted with reed canary grass, and studied during the period 2008 - 2011. Two treatments; high water content (HWC, 20 cm below soil surface) and low water content (LWC, 70 cm below soil surface, considered normal for acid sulphate soils) were considered and there were 4 replicates. Tiller height, net photosynthesis, and above ground biomass at harvest were measured and Al, Fe, K, Si and S were analysed using ICP-OES. Tillers in HWC lysimeters were 30 and 23% taller than those in LWC lysimeters (P = 0.003, P = 0.002) in September 2009 and 2010 respectively. Net photosynthesis was higher in LWC grasses, although the margin was significant only in year 2009 (P = 0.04). Spring 2009, dry matter yields were almost the same in both treatments, but in 2010 and 2011, HWC grasses yielded 43% and 37 % more than LWC (P = 0.001 in both years), respectively. Dry matter harvested in spring of both 2010 and 2011 contained more Al, K, S and Si in the LWC treatment than in HWC treatment, whereas the concentration of Fe was higher in HWC treatment in 2009 and 2010. It was concluded that reed canary grass, an established bioenergy crop, grows well in acid sulphate soils and can perform better when the water table is raised to reduce acidity and prevent environmental hazards. This could serve as management option and a solution to the problems cause by acid sulphate soils and same time reduce the controversy about the use of bioenergy crops on arable land.

The largest areas of acid sulphate (AS) soils in Europe are located in Finland, where 67,000–130,000 ha of AS soils are in agricultural use. In addition to their acidifying effects on waters, AS soils might be a significant source of greenhouse gases. In this pilot research, carbon and nitrogen content and microbial activity were studied in an AS and a non-AS soil. Large carbon and nitrogen stocks (110 Mg Corg ha−1 and 15 Mg Ntot ha−1) as well as high substrate induced respiration (33 μg CO2–C g−1h−1) were found in the C horizons of the AS soil but not in the non-AS soil. High microbial activity in these horizons of the AS soil was further confirmed by the measurement of dehydrogenase activity, basal respiration, the numbers of culturable bacterial cells, and the ratio of culturable to total numbers of cells. Still, the denitrifying enzyme activity was very low in the anaerobic horizons of the AS soil, indicating the prevalence of microbes other than denitrifiers. We suspect that the microbial community originated with the genesis of AS soil and has been supported by the large stocks of accumulated carbon and mineral nitrogen in the C horizons. If these permanently water-saturated subsoils are exposed to oxygen and their microbial activity consequently increases, large carbon and nitrogen stocks are likely to be mobilised, resulting in increased emission of greenhouse gases. Additional studies of boreal AS soils are needed to assess their potential contribution to increases in greenhouse gas fluxes at the local, regional, and global scales.

Happamilta sulfaattimailta purkautuva valumavesi on hapanta ja se sisältää haitallisen korkeita alumiini- ja raskasmetallipitoisuuksia. Nämä valumavedet ovat huonontaneet purkuvesistöjensä veden laatua. Veden happamuuteen ovat syynä maassa olevien sulfidien hapettumisessa vapautuvat protonit. Runsas protonien määrä edistää mineraalien rapautumista ja vapauttaa niissä olevia metalleja, jotka happamissa oloissa pysyvät liukoisina ja huuhtoutuvat vesistöön. Eräs ratkaisu valumaveden laadun parantamiseen on estää sulfidien hapettuminen pitämällä niitä sisältävät maakerrokset pohjaveden pinnan alla. Pohjaveden korkeuden vaikutusta happamien sulfaattimaiden huokosveden laatuun tutkitaan Helsingin yliopistossa kesällä 2008 aloitetussa vuoden 2010 loppuun kestävässä lysimetrikokeessa. Kokeessa selvitetään maan kyllästymisen aiheuttamia muutoksia happamalta sulfaattimaalta otettujen maamonoliittien eri kerroksissa. Kokeessa pohjavettä pidetään joko korkealla (pohjavesi 20 cm syvyydellä) tai matalalla (pohjavesi 65 cm syvyydellä). Matalalla pohjavedellä simuloidaan normaalia kuivatusta ja korkealla pohjavedellä keinotekoisesti lähelle maan pintaa nostettua pohjavettä. Kymmenestä lysimetristä kahdeksassa kasvatetaan kosteita oloja sietävää ruokohelpiä ja kaksi on kasvitonta. Kokeen ensimmäisenä vuonna korkea pohjavesi vähensi kasvillisen maan happamuutta horisonteissa B ja BC, kun veden alle joutuneet kerrokset pelkistyivät. Kun pohjavesi pidettiin matalalla, nämä kerrokset pysyivät hapettuneina. Veden kyllästämien kerrosten huokosveden alumiinipitoisuudet olivat alle kymmenesosa hapettuneiden kerrosten pitoisuuksista. Kun pohjavesi oli korkealla, raskasmetallien (Ni-, Co- ja Zn) pitoisuudet BC-kerroksessa olivat pienempiä kuin pohjaveden ollessa matalalla. Matalan pohjaveden koejäsenessä huokosveden alumiinipitoisuudet (150 mg l-1) ja Ni-, Co- ja Zn–pitoisuudet olivat yli viisinkertaisia salaoja- tai jokivesissä mitattuihin pitoisuuksiin verrattuna. Korkean pohjaveden aiheuttaman pelkistymisen seurauksena huokosveden raudan pitoisuudet kohosivat B-kerroksessa suuriksi (450 mg l-1). Vastaavaa raudan määrän lisääntymistä huokosvedessä ei todettu kasvittomissa lysimetreissä. Syynä kasvillisen maan huokosveden suuriin rautapitoisuuksiin olivat todennäköisesti ruokohelven juuriston huokosveteen tuottamat orgaaniset hiiliyhdisteet, jotka toimivat rautaa pelkistävien mikrobien substraattina ja muodostivat liuenneen raudan kanssa orgaanisia yhdisteitä. Kokeen tulosten perusteella laskettiin huokosveden orgaanisten rautayhdisteiden osuudeksi yli puolet huokosveden kokonaisraudasta tässä kerroksessa.

Intensification of mechanical agriculture has increased the risk for soil compaction and deformation. Simultaneously, reduced tillage practices have become popular due to energy saving and environmental concerns, as they may strengthen and improve the functioning of structured soil pore system. Soil aeration is affected by both compaction and reduced tillage through changes in soil structure and in the distribution of easily decomposable organic matter. We investigated whether a single wheeling by a 35 000 kg sugar-beet harvester in a Stagnic Luvisol derived from loess near Göttingen, Germany, influenced the gas transport properties (air permeability, gaseous macro- and microdiffusivities, oxygen diffusion rate) in the topsoil and subsoil samples, and whether the effects were different between long-term reduced tillage and mouldboard ploughing. Poor structure in the topsoil resulted in slow macro- and microscale gas transport at moisture contents near field capacity. The macrodiffusivities in the topsoil under conventional tillage were slower compared with those under conservation treatment, and soil compaction reduced the diffusivities by about half at the soil depths studied. This shows that even one pass with heavy machinery near field capacity impairs soil structure deep into the profile, and supports the view that reduced tillage improves soil structure and aeration compared with ploughing, especially in the topsoil., Maatalouden koneellistuminen ja tehostuminen ovatlisänneet viljelymaiden tiivistymisen riskiä. Samanaikaisesti pyrkimykset energian säästämiseen, ympäristönäkökohtien huomioimiseen sekä kestävään ja hyvin toimivaan maan huokosrakenteeseen ovat johtaneet kevennettyjen maanmuokkaustapojen yleistymiseen. Tiivistäminen ja muokkaus vaikuttavat maan ilmavuuteen muuttamalla maan rakennetta ja helposti hajoavan eloperäisen aineksen määrää ja jakaantumaa. Maan kevennetyn muokkauksen ja perinteisen kynnön vaikutuksia kaasun liikkumiseen maan eri syvyyksillä tutkittiin 12 v jatkuneessa maanmuokkauskokeessa (Sokerijuurikkaan tutkimuslaitos IfZ, Göttingen, Saksa) kentällä, jonka maannos (Stagnic Luvisol) osoitti siinä ilmenevän ajoittaista hapenpuutetta. Lisäksi tutkittiin 35 000 kg painavan sokerijuurikkaankorjuukoneen yksittäisen ajokerran aiheuttaman maan tiivistymisen vaikutuksia näissä muokkauskäsittelyissä. Tarkoitusta varten otettiin syksyllä 2003 pintamaasta (12 cm syvyydeltä), kyntöanturasta (35 cm syvyydeltä) ja syvältä pohjamaasta (60 cm) rakennenäytteitä, joista mitattiin ilmatilan määrä, hapen makro- ja mikrodiffuusiokerroin, hapen diffuusionopeus ja ilmanläpäisevyys eri tavoitekosteuksissa. Huonon rakenteen vuoksi pintamaan ilmatila oli pieni ja sen hapen makro- ja mikrodiffuusio hidasta lähellä kenttäkapasiteettia olevissa kosteuksissa. Kevennetysti muokatussa maassa hapen makrodiffuusio pintamaassa oli nopeampaa kuin kynnetyssä maassa. Maan tiivistäminen hidasti hapen diffuusiota noin puoleen tiivistämättömän maan arvoista kaikissa tutkituissa maan syvyyksissä. Tulokset osoittavat, että jo yksi ajokerta nykyaikaisella raskaalla korjuukoneella tiivistää maan rakennetta ja heikentää kaasun liikkumista sekä pintamaassa että syvällä pohjamaassa. Tulokset tukevat myös käsitystä kevennetyn muokkauksen edullisista vaikutuksista maan rakenteeseen ja ilmavuuteen, erityisesti maan pintakerroksissa. Aiheesta tarvitaan lisätutkimusta, jossa kiinnitetään erityishuomiota rakenteen kehittymiseen eri maalajeilla.

Soil contamination by petroleum hydrocarbons is a global problem. Phytoremediation by plants and their associated microorganisms is a cost-effective strategy to degrade soil contaminants. In boreal regions the cool climate limits the efficiency of phytoremediation. The planting of oil-tolerant perennial crops, especially legumes, in oil-contaminated soil holds promise for great economic benefits for bioenergy and bio-fertilizer production while accelerating the oil degradation process. We established a multi-year field experiment to study the ecological and agronomic feasibility of phytoremediation by a legume (fodder galega) and a grass (smooth brome) in a boreal climate. In 40 months, soil oil content decreased by 73%–92%, depending on the crop type. The oil degradation followed first-order kinetics with the reduction rates decreasing as follows: bare fallow > galega–brome grass mixture > brome grass > galega. Surprisingly, the presence of oil enhanced crop dry matter and nitrogen yield, particularly in the fourth year. The unfertilized galega–brome grass mixture out-yielded the N-fertilized pure grass swards over years by an average of 33%. Thus, a perennial legume–grass mixture is both ecologically and agronomically sustainable as a cropping system to alleviate soil contamination in the boreal zone, with considerable potential for bioenergy and bio-fertilizer production. Soil contamination by petroleum hydrocarbons is a global problem. Phytoremediation by plants and their associated microorganisms is a cost-effective strategy to degrade soil contaminants. In boreal regions the cool climate limits the efficiency of phytoremediation. The planting of oil-tolerant perennial crops, especially legumes, in oil-contaminated soil holds promise for great economic benefits for bioenergy and bio-fertilizer production while accelerating the oil degradation process. We established a multi-year field experiment to study the ecological and agronomic feasibility of phytoremediation by a legume (fodder galega) and a grass (smooth brome) in a boreal climate. In 40 months, soil oil content decreased by 73% - 92%, depending on the crop type. The oil degradation followed first-order kinetics with the reduction rates decreasing as follows: bare fallow > galega-brome grass mixture > brome grass > galega. Surprisingly, the presence of oil enhanced crop dry matter and nitrogen yield, particularly in the fourth year. The unfertilized galega-brome grass mixture out-yielded the N-fertilized pure grass swards over years by an average of 33%. Thus, a perennial legume-grass mixture is both ecologically and agronomically sustainable as a cropping system to alleviate soil contamination in the boreal zone, with considerable potential for bioenergy and bio-fertilizer production.

Agricultural soils are a significant source of nitrous oxide (N2O). Since mitigation of greenhouse gas emissions is needed in all sectors of society, it is important to identify the processes producing N2O and the factors affecting the production rates in agricultural soils. This study aimed to elucidate the N2O production in peat, clay and loamy sand at four different soil moisture conditions (40, 60, 80 and 100% Water Filled Pore Space). The ace­tylene inhibition technique was used to evaluate the contribution of nitrification to N2O production. Nitrous oxide production responded markedly to soil moisture in all three soils. The highest N2O production, measured at the wettest soils (100% WFPS), was up to four orders of magnitude higher than that at the dry soils (40% WFPS). In dry conditions N2O production decreased in the order of peat > clay > loamy sand, while in wet conditions the highest N2O production was measured in loamy sand, then in peat, and the lowest in clay soils. Nitrification was the dominant N2O producing process in all the soils at 60% WFPS. In the sandy soil 70% of the total N2O production originated from nitrification, while in the peat soil most of the total N2O production originated from denitrification. Data on processes producing N2O in agricultural soils are needed to develop process-based models that could reduce the uncertainty of the emission estimates in greenhouse gas inventories.

Allocation of selenium (Se) in lettuce and its impact on root morphology were studied to better understand the growth responses of plants to added Se. Lettuce was grown in vermiculite under controlled growing conditions for seven weeks, and the allocation in the shoots and roots of selenate added in increasing dosages (0, 1, 10, 100, 500 and 1000 µg Se per 3.5-litre pot) as well as morphological variables of the roots were determined. The intermediate additions of 100 and 500 µg Se per pot seemed to produce the highest biomasses, although this was nearly masked by large scatter in the data. The Se contents both in roots and shoots increased roughly proportionally to the amount of Se added. However, at small additions Se was preferentially allocated to roots, whereas at larger additions the contents in roots and shoots (mg kg-1 dry matter) were roughly equal. Se treatments did not change the morphology of hypocotyls. On the contrary, the specific length and area of basal and lateral roots were smallest at intermediate Se additions, whereas the specific volume was largest at the largest Se addition. These effects of Se on root morphology were, however, not unambiguously related to plant growth. As the Se contents in roots increased, the roots grew thicker and the specific volume of lateral roots increased in agreement with a hypothesis of increased endogenous ethylene production., Seleeni on eläimille ja ihmisille välttämätön alkuaine,jota lisätään Suomessa moniravinteisiin lannoitteisiin. Lisäyksen tarkoituksena on parantaa peltokasvien seleenin ottoa ja taata ihmisille riittävä seleenin saanti ruoasta. Kasvihuoneviljelyssä seleenilannoitus ei kuitenkaan ole vielä sallittua, osittain koska kasvien seleenin otto ja jakautuminen kasvissa sekä siihen liittyvä myrkytysvaara tunnetaan puutteellisesti. Seleenin jakautumista versoihin ja juuriin sekä vaikutusta juurten morfologiaan tutkittiin kokeessa, jossa salaattia kasvatettiin vermikuliitissa kontrolloiduissa oloissa seitsemän viikon ajan nousevilla selenaattilisäyksillä (0, 1, 10, 100, 500 ja 1000 µg Se 3,5 litran astiassa). Suurin biomassa saatiin keskisuurilla lisäyksillä (100 tai 500 µg seleeniä astiaa kohti), joskin aineistossa oli paljon satunnaisvaihtelua. Juurten ja verso- SELOSTUS Seleenin jakautuminen salaatin versoihin ja vaikutus juuriin Asko Simojoki, Tailin Xue, Kaarina Lukkari, Arja Pennanen ja Helinä Hartikainen Helsingin yliopisto, Kiinan tiedeakatemia ja Merentutkimuslaitos jen seleenipitoisuudet nousivat seleenimäärää lisätessä lähes verrannollisesti lisättyyn määrään. Pienillä lisäyksillä seleenipitoisuudet olivat suurempia juurissa kuin versoissa, kun taas suurilla määrillä juurten ja versojen seleenipitoisuuksissa ei ollut eroa. Seleenikäsittelyt eivät muuttaneet juurenniskan morfologiaa. Sitä vastoin basaali- ja lateraalijuurten pienimmät ominaispituudet ja ominaispinta-alat saatiin keskisuurilla seleenilisäyksillä (100 tai 500 µg Se per astia), ja suurin ominaistilavuus suurimmalla seleenilisäyksellä. Seleenin vaikutuksia juurten morfologiaan ei kuitenkaan voitu kytkeä yksiselitteisesti kasvin kasvuun. Lateraalijuurten paksuus ja ominaistilavuus kasvavat juuren seleenipitoisuuden noustessa, mikä tukee hypoteesia, että seleenilisä indusoi endogeenista etyleenin tuotantoa.

Compaction of subsoil is a hidden but persistent damage that impairs a range of soil functions and ecosystem services. We analyzed the soil compaction issue in the Driver-Pressure-State-Impact-Response (DPSIR) context. The driving force (DPSIR-D) is the farmers' efforts to sustain economic viability. This entails a steady increase in the size and weight of the agricultural machinery (DPSIR-P) exerting the specific pressures on the soil system. Simulations using historical data for agricultural machinery show significant increases in the mechanical stresses exerted on the soil profile during the last five decades. Surveys and comparative measurements (DPSIR-S) in the literature indicate that much of the European subsoil is compacted to critical levels for cropping. This calls for changes in agricultural management (DPSIR-R). Mechanical stresses impact the soil (DPSIR-I) by reducing the volume, dimensions, and interconnections of soil pores. Subsequent impacts on ecosystem services (subtle DPSIR-I aspects) include a decrease in crop production, an impaired soil filtering of pollutants, and the risk of higher greenhouse gas emissions. The natural ability of compacted subsoil to recover is poor. We highlight the need to expand the DPSIR concept to include a risk assessment methodology to identify sustainable management systems. Risk assessment involves the evaluation of the mechanistic cause–effect chain of the compaction process. Measured data as well as modeling indicate that contemporary tires are not able to carry the loads frequently inflicted on wet soil without exerting critical stresses on deep subsoil layers. We suggest the use of online modeling tools that combine existing knowledge. Such tools may also create maps of vulnerable areas from the field to the continent scale. Groups of stakeholders including researchers, farmers and their consultants, and policy-makers need to identify sustainable traffic systems that secure both presently focused ecosystem services as well as nonuse soil values (the bequest for future generations).

Most of the nitrous oxide (N 2 O) in the atmosphere, thought to be involved in global warming, is emitted from soil. Although the main factors controlling the production of N 2 O in soil are well known, we need more quantitative data on the interactions of soil and the environment in the soil that affect the emission. We therefore studied the effects of irrigation, cropping (fallow, barley with grass undersown) and N fertilization (unfertilized, 103 kg N ha -1 ) on the composition of soil air and direct N 2 O emission from soil (using the closed chamber method) in a factorial field experiment on a well-structured loamy clay soil during 1 June-22 October 1993. The measurements were made weekly during the growing season and three times after harvesting. The composition of the soil air did not indicate severe anoxia in any treatment or combination of treatments, but the accumulation of N 2 O in the soil air indicated that hypoxia was common. At the start of the irrigation the emissions were small, even though there was much ammonium and nitrate in the soil and therefore a potential for emission of N 2 O produced by both nitrification and denitrification. Larger emissions occurred later. The largest emissions were found when 60-90% of the soil pore space was filled with water. Irrigation and fertilization with N both roughly doubled the cumulative N 2 O emission. Growing a crop decreased it by a factor of 3-7. Most N 2 O was lost from the irrigated fertilized soil under fallow (3.5 kg N ha -1 ), and least from the unirrigated unfertilized soil under barley (0.1 kg N ha -1 ).

Methodological tests with dark metal wires and barley roots showed that selecting proper scanner brightness adjustment is crucial when calibrating a desktop scanner for digital image analysis of root morphology. At high brightness the digitization of roots was incomplete, and thus the real length and width of the roots were underestimated. Lowering of the brightness improved the digitization, whereas stronger staining of the roots alone was not effective. Inaccurate results were produced also, if the size of the scanned sample was too large. The variation caused by the scanning and image analysis itself was minimal. A small amount of dry matter was lost from the roots during the preservation in the ethanol solution for several months before scanning. If absolute data on root masses are required, this loss cannot be neglected. Subsampling is strongly recommended to reduce the time required for the procedure., Testit tummilla metallilangoilla ja ohran juurilla osoittivat, että oikea valotussäätö on ensiarvoisen tärkeä kalibroitaessa tasoskanneria juurten morfologisten ominaisuuksien digitaalista kuva-analyysia varten. Jos valotus oli liian kirkas, juurten digitoituminen oli epätäydellistä, minkä vuoksi kuva-analyysi antoi juurille todellista pienemmän pituuden ja leveyden. Valotuksen himmentäminen paransi digitoitumista, kun taasjuurten värjääminen neljä kertaa tavallista suuremmalla värimäärällä ei sitä tehnyt. Tulokset olivat epätarkkoja myös, jos kerralla skannattiin liian suuri näyte. Itse skannaus ja kuva-analyysi aiheuttivat tuloksiin vain vähän vaihtelua. Hieman kuiva-ainetta hävisi juurista, kun niitä säilytettiin monen kuukauden ajan 15 % etanoliliuoksessa ennen skannausta. Vaikka määrä oli pieni, sitä ei voi kuitenkaan jättää ottamatta huomioon, jos tarkka tieto juurten massasta on tarpeen. Osanäytteen ottoa suositellaan käytettäväksi lyhentämään analyysimenetelmän eri vaiheiden vaatimaa aikaa.

Environmental hazards caused by acid sulphate (AS) soils are of worldwide concern. Among various mitigation measures, waterlogging has mainly been studied in subtropical and tropical conditions. To assess the environmental relevance of waterlogging as a mitigation option in boreal AS soils, we arranged a 2.5-year experiment with monolithic lysimeters to monitor changes in the soil redox potential, pH and the concentrations of aluminium (Al), iron (Fe) and sulphur (S) in pore water in response to low and high groundwater levels in four AS soil horizons. The monoliths consisted of acidic oxidized B horizons and a reduced C horizon containing sulphidic material. Eight lysimeters were cropped (reed canary grass, Phalaris arundinacea) and two were bare without a crop. Waterlogging was conducive to reduction reactions causing a slight rise in pH, a substantial increase in Fe (Fepw) and a decrease in Al (Alpw) in the pore water. The increase in Fepw was decisively higher in the cropped waterlogged lysimeters than in the bare ones, which was attributable to the microbiologically catalysed reductive dissolution of poorly ordered iron oxides and secondary minerals. In contrast to warmer climates, Fepw concentrations remained high throughout the experiment, indicating that the reduction was poised in the iron range, while sulphate was not reduced to sulphide. Therefore, the precipitation of iron sulphide was negligible in the environment with a low pH and abundant with poorly ordered Fe oxides. Increased Fe in pore water counteracts the positive effects of waterlogging, when water is flushed from fields to watercourses, where re-oxidation of Fe causes acidity and oxygen depletion. However, waterlogging prevented further oxidation of sulphidic materials and decreased Alpw to one-tenth of the initial concentrations, and even to one-hundredth of the levels in the low water table lysimeters.

Acid sulphate (AS) soils along the Baltic coasts contain significant amounts of organic carbon and nitrogen in their subsoils. The abundance, composition, and activity of microbial communities throughout the AS soil profile were analysed. The data from a drained AS soil were compared with those from a drained non-AS soil and a pristine wetland soil from the same region. Moreover, the potential production of methane, carbon dioxide, and nitrous oxide from the soils was determined under laboratory conditions. Direct microscopic counting, glucose-induced respiration (GIR), whole cell hybridisation, and extended phospholipid fatty acid (PLFA) analysis confirmed the presence of abundant microbial communities in the topsoil and also in the deepest Cg2 horizon of the AS soil. The patterns of microbial counts, biomass and activity in the profile of the AS soil and partly also in the non-AS soil therefore differed from the general tendency of gradual decreases in soil profiles. High respiration in the deepest Cg2 horizon of the AS soil (5.66 μg Cg(-1)h(-1), as compared to 2.71 μg Cg(-1)h(-1) in a top Ap horizon) is unusual but reasonable given the large amount of organic carbon in this horizon. Nitrous oxide production peaked in the BCgc horizon of the AS and in the BC horizon of the non-AS soil, but the peak value was ten-fold higher in the AS soil than in the non-AS soil (82.3 vs. 8.6 ng Ng(-1)d(-1)). The data suggest that boreal AS soils on the Baltic coast contain high microbial abundance and activity. This, together with the abundant carbon and total and mineral nitrogen in the deep layers of AS soils, may result in substantial gas production. Consequently, high GHG emissions could occur, for example, when the generally high water table is lowered because of arable farming.

Arrangements of elementary soil particles during soil deposition and subsequent biological and physical processes in long-term pedogenesis are expected to lead to anisotropy of the non-tilled subsoil pore system. Soil compaction by agricultural machinery is known to affect soil pore characteristics, but few studies have addressed the effect on soil pore anisotropy. This study was conducted within two long-term field experiments on soil compaction, established in 1981 on a claysoil in Finland (60º49N, 23º23'E) and in 1995 on a sandy clay loam in Sweden (55º49'N, 13º11'E). In 2009/2010, soil cores were sampled in vertical and horizontal directions from 0.3, 0.5, 0.7 and 0.9 m depth (the two lower depths only in Sweden). In the laboratory, water retention, air permeability (ka) and gas diffusivity (Ds/D0) were determined. For the sandy clay loam, morphological characteristics of pores (effective pore diameter, dB; tortuosity, τ; the number of effective pores per unit area, nB) were calculated using a tortuous tube model at -100 hPa matric potential and blocked air-filled porosity (εb) and pore continuity index (N) were estimated from the relationship between ka and air-filled porosity(εa) for a range of matric potentials. Factor of anisotropy (FA) was determined as the ratio of a given property measured in the horizontal direction to that in the vertical direction. For both soils, ka was anisotropic at some depths (FAinterpreted this as a minor effect of biological activities and physical processes in the C-horizon (0.9 m depth), which is likely to exhibit intrinsic isotropic pore characteristics because of its origin (glacial till soil). Compaction generally reduced ka, Ds/D0 and pore morphology indices for both sampling directions. Compaction had an effect on anisotropy of ka and dB only in the sandy clay loam at 0.3 m depth, where it reduced the anisotropy of the pore system due to lower reduction in these parameters in the horizontal than in the vertical direction. Compaction reduced anisotropy for the N parameter, indicating soil pore continuity at macropore scale, while it increased the anisotropy for εb. Our datathus indicate that soil compaction affects anisotropy, especially that of macropores.

Antibiotics are routinely used to improve livestock health and growth. However, this practice may have unintended environmental impacts mediated by interactions among the wide range of micro- and macroorganisms found in agroecosystems. For example, antibiotics may alter microbial emissions of greenhouse gases by affecting livestock gut microbiota. Furthermore, antibiotics may affect the microbiota of non-target animals that rely on dung, such as dung beetles, and the ecosystem services they provide. To examine these interactions, we treated cattle with a commonly used broad-spectrum antibiotic and assessed downstream effects on microbiota in dung and dung beetles, greenhouse gas fluxes from dung, and beetle size, survival and reproduction. We found that antibiotic treatment restructured microbiota in dung beetles, which harboured a microbial community distinct from those in the dung they were consuming. The antibiotic effect on beetle microbiota was not associated with smaller size or lower numbers. Unexpectedly, antibiotic treatment raised methane fluxes from dung, possibly by altering the interactions between methanogenic archaea and bacteria in rumen and dung environments. Our findings that antibiotics restructure dung beetle microbiota and modify greenhouse gas emissions from dung indicate that antibiotic treatment may have unintended, cascading ecological effects that extend beyond the target animal.

The metabolic and physical processes result in concentration, pressure and temperature differences that generate fluxes within ecosystems and between ecosystems and their surroundings. We apply the same approach combining metabolic and physical processes with transport in the analysis of very different phenomena from water and sugar transport within trees to the fluxes of carbon and nutrients in the forest ecosystem.

Effects of cropping (bare fallow, grass), heavy irrigation and N fertilization (0, 100 kg ha-1) on soil air (at depths of 15 and 30 cm) and N2O emission were studied in a factorial two-year field experiment in southern Finland. The responses of soil mineral N, dry-matter yield and uptake of N were also determined. Irrigation was performed during two periods in 1993 and one period in 1994. During sampling periods, the soil moisture ranged from 11% to 45% (v/v) and soil temperature from 0°C to 21°C. Unirrigated bare fallow contained 14-21% O2, 0.1-2% CO2 and 0.2-100 µl l-1 N2O (1993 maximum 27 µl l-1) in the soil air. Cropping and irrigation lowered O2 (minimum 3-7%) and raised CO2 (maximum 9%) in soil air, but fertilization had no effect. Irrigation raised N2O in the soil air if nitrate was present abundantly. Consequently, fertilization increased N2O especially in the irrigated bare soil, which still contained plenty of nitrate in autumn 1993. Cropping decreased N2O. The variation in soil air composition was partly explained by that in soil air-space. The average daily N2O-N emission amounted to 0-40 g ha-1 (mean 7 g ha-1) and correlated positively with N2O concentration in the soil air., Kaksivuotinen kenttäkoe tehtiin hiuemaalla Etelä-Suomessa. Faktorikokeen koetekijöinä olivat rankka kastelu ja typpilannoitus. Osa ruuduista oli kasvittomia, osalla kasvoi heinää. Maan ilman koostumusta 15 ja 30 cm syvyydessä seurattiin yhden tai kahden viikon välein otetuista näytteistä. Myös maan kosteutta (TDR) ja lämpötilaa mitattiin säännöllisesti. Kasvittoman, kastelemattoman ja lannoittamattoman maan ilmassa oli 14-21 % happea, 0,1-2 % hiilidioksidia ja 0,2-100 µl l-1 dityppioksidia.Lukuunottamatta toisen vuoden toukokuun kaikkein suurimpia dityppioksidipitoisuuksia, suurin pitoisuus oli 27 µl l-1. Maan kosteus vaihteli välillä 11-45 % ja lämpötila 15 cm syvyydessä välillä 0-21 °C. Kasvipeite ja kastelu vähensivät happipitoisuutta ja lisäsivät hiilidioksidipitoisuutta. Happipitoisuus muuttui selvästi enemmän syvemmällä maassa (30 cm) kuin matalammassa (15 cm), sen sijaan hiilidioksidipitoisuuden muutos oli syvyydestä riippumaton. Kasvipeitteisen ja kastellun maan pienimmät happipitoisuudet olivat 7 % (15 cm syvyydessä) ja 3 % (30 cm syvyydessä). Suurimmat hiilidioksidipitoisuudet olivat 9 %. Typpilannoitus ei vaikuttanut merkitsevästi maan ilman happi- ja hiilidioksidipitoisuuksiin. Kastelu lisäsi maan ilman dityppioksidipitoisuutta silloin kun maassa oli runsaasti nitraattia. Kasvittomassa maassa oli runsaasti nitraattia jäljellä vielä elokuussa. Typpilannoitus nosti maan ilman dityppioksidipitoisuutta erityisesti kastellussa kasvittomassa maassa. Kasvipeite vähensi dityppioksidipitoisuutta. Maan ilman koostumuksen vaihtelua voitiin osittain selittää arvioidun ilmahuokoisuuden avulla. Muutamalta ruudulta suljetun kammion menetelmällä mitattu koekentän dityppioksidiemissio vaihteli välillä 0-40 g N ha-1 d-1. Kaikkien mittausten keskiarvo oli 7 g N ha-1 d-1. Emissio korreloi 15 cm syvyydestä mitatun dityppioksidipitoisuuden kanssa (r=0,80 n=234) ja 30 cm syvyydestä mitatun pitoisuuden kanssa (r=0,65, n=234).

Peltoviljelyssä olevista happamista sulfaattimaista purkautuu vesistöihin ajoittain hyvin hapanta ja runsaasti metalleja sisältävää kuivatusvettä. Vähäistä kuivatussyvyyttä vaativan ruokohelven viljely bioenergiatuotantoon saatttaisi olla yksi ratkaisu tähän ongelmaan näillä alueilla. Tutkimus kuivatussyvyyden vaikutuksesta ruokohelven tuotantoon happamilla sulfaattimailla sekä kuivatussyvyyden ja kasvin vaikutuksesta valumaveden laatuun aloitettiin kesällä 2007 osana maatalousmetsätieteellisen tiedekunnan yhteistutkimushanketta "Peltobioenergiaketjut raaka-aineen tuotanto ympäristöllisesti ja taloudellisesti kestävällä tavalla" esikokeilla, joissa selvitettiin, voidaanko happamilta sulfaattimailta otettuja suuria maanäytelieriöitä käyttää pelto-olojen simulointiin. Esikokeissa pyrittiin luomaan toimiva mittausjärjestelmä ennen laajemman kokeen aloittamista ja kasvullisten jäsenten mukaanottamista. Käytännön toteutukseen kehitettiin häiriintymättömien suurten maapatsaiden ottamisen tekniikka, vedensäätöjärjestelmä ja jatkuvatoimisten mittausten instrumentointi kahden suuren maanäytelieriön avulla. Isot maalieriöt otettiin Viikin koetilan pellolta, joka on hapanta sulfaattimaata. Samalle peltolohkolle asennettiin pohjavesiputkia pohjaveden laadun ja korkeuden seuraamiseksi. Pohjaveden korkeuden vaihtelun aiheuttamia muutoksia maanäytelieriöissä verrattiin kasvukauden aikana pellolta mitattuihin pohjaveden laadun muutoksiin. Maanäytelieriöistä mitattiin maan redox-potentiaalia sekä vesipitoisuutta, lämpötilaa ja sähkönjohtavuutta jatkuvatoimisesti 10 minuutin välein muokkauskerroksesta, hapettuneesta kerroksesta ja pelkistyneestä kerroksesta. Aineiston keräämiseen käytettiin dataloggereita (Agilent 34980A) ja (Degacon Em50), josta tulokset siirrettiin tietokoneelle. Maan pH-arvoa ja huokosveden koostumusta seurattiin määräajoin. Redox-mittausten toteutus käyttämen suolasillan avulla toteuttua yhteistä referenssielektrodia kaikille Pt-elektrodeille antoi luotettavia tuloksia. Jatkuvatoimisen ja manuaalisen redox-mittauksen keskimääräinen ero oli pienin pelkistyneessä kerroksessa (38 mV) ja hapettuneissa kerroksissa hieman isompi (100 mV). Pohjaveden pH:n, sähkönjohtavuuden ja redox-potentiaalin muutokset pohjaveden korkeuden funktiona pellolla ja maanäytelieriöissä olivat samansuuntaisia. Pohjaveden pinnan nousu laski redox-potentiaalia ja sähkönjohtavuutta ja nosti veden/maan pH-arvoa molemmissa. Esikokeesta saadut alustavat tulokset viittaavat siihen, että maanäytelieriöllä voidaan simuloida pellolla tapahtuvia pohjaveden muutoksia ja seurata pohjaveden korkeuden vaikutusta maan ominaisuuksiin. Pohjaveden nostolla oli esitutkimuksessa pH-arvoa nostava vaikutus, kuten aiemmissa happamilla sulfaattimailla tehdyissä tutkimuksissa on havaittu. Ruokohelven kasvu pohjaveden pinnan ollessa korkealla ja kasvin vaikutus maan ominaisuuksiin ja valumaveden laatuun on tutkimuksen seuraava vaihe.

Nitrous oxide (N 2 O) and carbon dioxide (CO 2 ) fluxes were measured in a boreal forest during two growing seasons with soil gradient and chamber methods. N 2 O fluxes obtained by these two techniques varied from small emission to small uptake. N 2 O fluxes were of the same order of magnitude, however, the fluxes measured by the soil gradient method were higher and more variable than the fluxes measured with chambers. The highest soil gradient N 2 O fluxes were measured in the late summer and the lowest in the autumn and spring. In the autumn, litter fall induced a peak in N 2 O concentration in the organic O-horizon, whereas in the spring N 2 O was consumed in the O-horizon. Overall, the uppermost soil layer was responsible for most of the N 2 O production and consumption. Soil gradient and chamber methods agreed well with CO 2 fluxes. Due to the very small N 2 O fluxes and the sensitivity of the flux to small concentration difference between the soil and the ambient air, the flux calculations from the O-horizon to the atmosphere were considered unreliable. N 2 O fluxes calculated between the soil A- and O-horizons agreed relatively well with the chamber measurements. DOI: 10.1111/j.1600-0889.2007.00278.x