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This study describes iron (Fe) pipestems formed around and within root channels during the development of a homogeneous unripe sulfidic sediment into a ripe soil where redox‐ or pH‐active elements segregate. Pipestems and adjacent soil material samples were characterised by chemical and mineralogical analyses and scanning electron microscopy (SEM) associated with energy dispersive spectroscopy (EDS). Pipestems occurred at 60–190 cm and at 30–130 cm in a young Finnish soil and a more mature Australian soil, respectively, while sulfidic materials were found below 170–180 cm. The pipestems consisted of mineral grains cemented together by Fe precipitate. There was an up to 24‐fold enrichment of Fe and an up to 13‐fold enrichment of sulfur (S) in the Finnish pipestems compared to the adjacent soil material, whereas the corresponding enrichment in the Australian soil was up to 27‐fold for Fe and up to 8‐fold for S. In the Australian pipestem matrices, the Fe concentration was as high as 40% compared to 14% in the Finnish ones. It was estimated that about 70 ton ha−1 S had been mobilised from the sulfidic material in the Finnish soil at the depth of 50–150 cm. Part of S has leached out but a substantial amount remained in the soil constituting the stock of retained acidity. Almost all pipestems contained a new solid phase precipitated within the former cortex cells of the plant roots. In the Finnish samples, this precipitate consisted of jarosite and schwertmannite. After oxidative exhaustion of sulfidic material in the surrounding soil, these metastable minerals are gradually hydrolysed, associated with leaching of S. In the mature Australian soil, most of these minerals had already been transformed to goethite. Pipestems formed after roots in unripe soil are sites for synthesis and hydrolysis of minerals and serve as routes for atmospheric oxygen into the reduced subsoil and for soluble reaction products to exit the soil. Pipestems have an important role in the ripening of the soil profile. [ABSTRACT FROM AUTHOR]

Fluazinam, a widely used pesticide in conventional potato cultivation, is effective against epidemics of the fungal disease late blight. To assess fluazinam persistence in soil, laboratory experiments were conducted with fluazinam added to soil as a pure chemical or contained in the commercial product Shirlan®. In a follow-up experiment, the persistence was monitored under constant temperature and water content conditions during a maximum period of 1 year. In an annual climatic rotation experiment, fluazinam added to soil was exposed to the year-round temperature and water content conditions occurring in the boreal zone. A third experiment was undertaken to clarify the effect of soil organic matter (SOM) on the recovery of fluazinam. In the follow-up and annual climatic rotation experiments, more than half of the added fluazinam was recovered after 1 year of incubation. The estimated half-life of fluazinam ranged between 355 and 833 days. The degradation of fluazinam was enhanced by an abundance of SOM, a warm temperature, and wetness. Additionally, in over half of soil samples collected from fields where potato had been intensively cultivated for many years, varying concentrations of fluazinam were detected. Fluazinam can carry over to the next growing season in professional potato production. [ABSTRACT FROM AUTHOR]

Abstract: Accumulation and depletion of soil phosphorus (P) was studied in a long‐term (37 y) field experiment in Southern Finland. The loam soil had a high pH (7.5–7.7) due to an earlier liming. Spring barley, spring wheat, oat, and ryegrass, grown in rotation, were annually fertilized with 0, 32, or 67 kg P ha−1 y−1 (P0, P1, and P2K) and sufficient N. The average dry matter grain yield 2,600 kg ha−1 of the P0 plots increased by about 500 kg ha−1 at P1 treatment and another 600 kg ha−1 by P2K. Soil samples were collected in 1978 (beginning), 1995, 2005, and 2015. According to the Chang and Jackson sequential extraction, the P2K and P1 treatments increased the inorganic soil P by 732 and 32 kg P ha −1 in 37 years, respectively, while the P0 plots were depleted by –459 kg P ha −1. The P2K treatment increased all four P fractions, extracted with NH4Cl (easily soluble), NH4F (Al‐P), NaOH (Fe‐P), and H2SO4 (Ca‐P). Continuous depletion (P0) decreased the NH4Cl‐P and NH4F‐P pools, NaOH‐P and H2SO4‐P pools remaining stable. None of the P pools changed significantly at P1. The remarkable gap between the measured change and the balance for the P2K and P1 treatments cannot be explained solely by lateral soil movement, meaning that a significant proportion of the applied P was lost either in surface runoff or transported below the investigated depth of 40 cm. Despite large P applications, the degree of P saturation reached only 20% in the P2K topsoil, assuming a 50% reactivity of Fe and Al oxides. As derived from sorption isotherms, a high EPC0 (i.e., equilibrium P concentration at zero net P sorption or desorption) of 1.30 mg L−1 had been built up in the P2K treatment, while in the P1 treatment EPC0 (0.33 mg L−1) had remained unchanged and P depletion (P0) had caused a decrease to 0.12 mg L−1. These results demonstrate that P sorption and desorption properties respond strongly to both P fertilization and null fertilization treatments and that in a long‐term field experiment only a low proportion of the residual fertilizer P can be recovered from soil. [ABSTRACT FROM AUTHOR]

Soil carbon (C) represents the largest terrestrial carbon stock and is key for soil productivity. Major fractions of soil C consist of organic C, carbonates and black C. The turnover rate of black C is lower than that of organic C, and black C abundance decreases the vulnerablility of soil C stock to decomposition under climate change. The aim of this study was to determine the distribution of soil C in different pools and impact of agricultural management on the abundance of different species. Soil C fractions were quantified in the topsoils (0–15 cm) of 23 sites in the tropical highlands of Ethiopia. The sites in central Ethiopia represented paired plots of agroforestry and adjacent control plots where cereal crops were traditionally grown in clayey soils. In the sandy loam and loam soils of northern Ethiopia, the pairs represented restrained grazing with adjacent control plots with free grazing, and terracing with cereal-based cropping with adjacent control plots without terracing. Soil C contained in carbonates, organic matter and black C along with total C was determined. The total C median was 1.5% (range 0.3–3.6%). The median proportion of organic C was 85% (range 53–94%), 6% (0–41%) for carbonate C and 6% (4–21%) for black C. An increase was observed in the organic C and black C fractions attributable to agroforestry and restrained grazing. The very low concentration of the relatively stable black C fraction and the dominance of organic C in these Ethiopian soils suggest vulnerability to degradation and the necessity for cultivation practices maintaining the C stock. [ABSTRACT FROM AUTHOR]

Little has been studied on genesis and properties of soils in Western Ethiopia. This study was conducted to understand the pedogenesis, and to classify benchmark soils in Didessa watershed along a toposequence. The six soil profiles are representative of low, mid and highland positions within an elevation range from 1273 to 2700 m above sea level along a 53-km long transect. Their pedological processes, soil properties and classification are discussed in context of soil forming factors and sustainable soil use. Melanization, cheluviation (chelation) of organo-mineral substances, oxidation of iron and leaching of iron compounds and basic cations, clay translocation, de-alkalization, and acidification were major pedological processes at the upland soils while erosion took place at shoulder positions. Calcification and pedoturbation (vertization) were major pedological processes in the lowland and melanization was also observed there. The surface horizons of these very deep soils had loam a loamy texture while the subsurface horizons were clayey. Leaching of basic cations increased with elevation. The U.S. Soil Taxonomy classification identified a soil sequence consisting of Typic Hapludults, Typic Ferrudalfs, Typic Rhodudalfs and Typic Hapluderts while the World Reference Base classified the corresponding soils as Ferric Rhodic Alisols, Ferric Rhodic Luvisols, Ferric Chromic Luvisols, and Calcic Pellic Vertisols. Numerical hierarchical cluster analysis identified similar and dissimilar horizons in the soil catena. Ultisols were developed on tertiary basalt at midland, Alfisols were developed on tertiary basalts and granitic gneisses at midland and highland, and Vertisols were developed on alluvium and colluvium at lowland. The relief characteristics, lithologic units, agro-ecology and land use covered by the current study are typical of much of the Western and Southwestern Ethiopia. The study indicated that Didessa toposequence has three soil orders (reference groups) that need different management requirements for sustainable soil use. Thus, the transect serves as a model of soil development and soil management in humid Western Ethiopia. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Rotation with dicotyledonous crops to break cereal monoculture has proven to be beneficial to successive cereals. In two fields where the soil had been subjected to prolonged, continuous cereal production, two 3-year rotation trials were established. In the first year, faba bean, turnip rape and barley were grown, as first crops, in large blocks and their residues tilled into the soil after harvest. In the following year, barley, buckwheat, caraway, faba bean, hemp and white lupin were sown, as second crops, in each block and incorporated either at flowering stage (except barley) or after harvest. In the third year, barley was grown in all plots and its yield and grain protein concentration were determined. Mineral N in the plough layer was determined two months after incorporation of crops and again before sowing barley in the following year. The effect of faba bean and turnip rape on improving barley yields and grain protein concentration was still detectable two years after they were grown. The yield response of barley was not sensitive to the growth stage of second crops when they were incorporated, but was to different second crops, showing clear benefits averaging 6-7% after white lupin, faba bean and hemp but no benefit from caraway or buckwheat. The effect of increased N in the plough layer derived from rotation crops on barley yields was minor. Incorporation of plants at flowering stage slightly increased third-year barley grain protein concentration but posed a great potential for N loss compared with incorporation of crop residues after harvest, showing the value of either delayed incorporation or using catch crops. [ABSTRACT FROM AUTHOR]

Leaching of nitrogen fertilizers such as nitrates from agricultural systems causes watershed eutrophication and is an economic loss for the farmer. This issue may be solved by including a catch crop in a crop rotation. For instance, winter turnip rape is a potential N catch crop for cold climates. Here, we studied winter turnip rape as a catch crop from 2009 to 2011 in Finland. Winter turnip rape was either undersown with barley in May or sown after harvesting barley in late July. In two reference treatments, the barley stubble was either left over the winter or ploughed into the soil in autumn. We collected samples from topsoil, 0-20 cm, and subsoil, 30-50 cm, in early autumn, before snowfall and in the following spring. We measured soil ammonium-N and nitrate-N, and the N content of winter turnip rape plants. Results show that undersown winter turnip rape did not change the yield and quality of barley. Winter turnip rape decreased nitrate-N in the subsoil by 83 % in 2009 and by 61 % in 2010, compared to ploughed barley. By the end of October 2009, winter turnip rape undersown in May took up 74 kg N/ha, whereas the crop sown after barley in July took up 57 kg N/ha. We conclude that winter turnip rape, either undersown with barley or sown after barley, is effective in depleting subsoil nitrates. Even though numerous reports describe the efficiency of different crucifers as catch crops under temperate climate, this is the first article concerning winter turnip rape as a catch crop under cold and humid climate. [ABSTRACT FROM AUTHOR]

In soil, adsorption of selenium (Se) onto mineral surfaces is accompanied by poorly known retention via organic matter. The effects of these components on the availability of Se were examined in two pot experiments. Spring wheat was grown with increasing amounts of selenate (SeO42–) in one sand and three peat soils, and ryegrass with selenate and selenite (SeO32–) in sphagnum peat manipulated by iron (Fe) hydroxide. Selenate persisted in soluble form, whereas selenite was fixed in the soil. In wheat, 5–50% of the selenate addition was recovered in the plant, the proportion increasing with increasing Se. In ryegrass, 30–40% of the added selenate but less than 2% of the selenite was found within the leaves. The Fe hydroxide enrichment enhanced the selenite uptake. Phosphate buffer desorbed a minor proportion of the added selenite, except in peat amply enriched with Fe hydroxide. The results suggest that the retention mechanism of selenite was changed due to the hydroxide amendment. [ABSTRACT FROM AUTHOR]

Discharge from acid sulfate soils (a.s. soils) poses a threat to the living organisms of about 30 rivers in western Finland. Most agricultural a.s. soils in the country are well drained with subsurface piping at a depth of 1 m, resulting in oxidation of the sulfidic materials. Consequently, acidic solutes, hazardous to fish and other aquatic organisms, are effectively leached to watercourses. Many of the soils are not recognised as a.s. soils by international classification systems, such as the FAO–UNESCO system, Soil Taxonomy and the World Reference Base for Soil Resources (WRB), because the acidic horizon and sulfidic materials are too deep to be diagnostic. The purpose of this study was to (1) investigate the influence of sulfidic materials on the quality of drainage water where these materials are below the depth of the drainage pipes, (2) test the effectiveness of controlled drainage as a means to decrease the production of acidic solutes and (3) assess the criteria for a.s. soils in international classification systems against the actual characteristics of well-drained a.s. soils of Finland.Quality of drainage waters was monitored in 1998–2000 in two soils, which had sulfidic materials (total S 0.7–1.2%) below 110 cm (Mustasaari soil) and below 150–200 cm (Ilmajoki soil). The soils had been pipe-drained for 30 and 70 years, respectively. According to Soil Taxonomy, both soils were Sulfic Cryaquepts. In the FAO–UNESCO system, the Mustasaari soil was a Thionic Gleysol and the Ilmajoki soil was a Dystric Gleysol. The a.s. characteristics were not expressed in any of the classifications of the WRB system. The average acidity of drainage waters from the fields was 11.5 and 3.5 mmol l−1 at Mustasaari and Ilmajoki, respectively. In the Mustasaari discharge, the pH was always <4.0 and in the Ilmajoki discharge mostly <4.5. Controlled drainage, applied at Ilmajoki, slightly improved the quality of the drainage water. Discharge from these soils contributes substantially to the acidification of river water, where acidity >0.3 mmol l−1 and pH<5.5 are considered critical for fish survival. In well-drained soils, sulfidic materials, at least above depths of 200 cm, have a detrimental effect on the quality of discharge. Diagnostic criteria for a.s. soils, particularly in the WRB system, should be revised to include this kind of soil among the thionic taxa. [Copyright &y& Elsevier]

A total of 75 bacterial isolates were obtained from nodules of beans cultivated across 10 sites in six agro-ecological zones in Uganda. Using recA gene sequence analysis, 66 isolates were identified as members of the genus Rhizobium , while 9 were related to Agrobacterium species. In the recA gene tree, most Rhizobium strains were classified into five recognized species. Phylogenetic analysis based on six concatenated sequences (r ecA–rpoB–dnaK–glnII–gyrB–atpD) placed 32 representative strains into five distinct Rhizobium species, consistent with the species groups observed in the recA gene tree: R. phaseoli, R. etli, R. hidalgonense, R. ecuadorense , and R. sophoriradicis , with the first three being the predominant. The rhizobial strains grouped into three nodC subclades within the symbiovar phaseoli clade, encompassing strains from distinct phylogenetic groups. This pattern reflects the conservation of symbiotic genes, likely acquired through horizontal gene transfer among diverse rhizobial species. The 32 representative strains formed symbiotic relationships with host beans, while the Agrobacterium strains did not form nodules and lacked symbiotic genes. Multivariate analysis revealed that species distribution was influenced by the environmental factors of the sampling sites, emphasizing the need to consider these factors in future effectiveness studies to identify effective nitrogen-fixing strains for specific locations. [ABSTRACT FROM AUTHOR]

A total of 102 bacterial strains isolated from nodules of three Bambara groundnut and one soybean cultivars grown in nineteen soil samples collected from northern Ghana were characterized using multilocus gene sequence analysis. Based on a concatenated sequence analysis (glnII-rpoB-recA-gyrB-atpD - dnaK), 54 representative strains were distributed in 12 distinct lineages, many of which were placed mainly in the Bradyrhizobium japonicum and Bradyrhizobium elkanii supergroups. Twenty-four of the 54 representative strains belonged to seven putative novel species, while 30 were conspecific with four recognized Bradyrhizobium species. The nodA phylogeny placed all the representative strains in the cosmopolitan nodA clade III. The strains were further separated in seven nodA subclusters with reference strains mainly of African origin. The nifH phylogeny was somewhat congruent with the nodA phylogeny, but both symbiotic genes were mostly incongruent with the core housekeeping gene phylogeny indicating that the strains acquired their symbiotic genes horizontally from distantly related Bradyrhizobium species. Using redundancy analysis, the distribution of genospecies was found to be influenced by the edaphic factors of the respective sampling sites. In general, these results mainly underscore the high genetic diversity of Bambara groundnut-nodulating bradyrhizobia in Ghanaian soils and suggest a possible vast resource of adapted inoculant strains. [ABSTRACT FROM AUTHOR]

A correction to the article "Winter Turnip Rape as a Soil N Scavenging Catch Crop in a Cool Humid Climate" that was published in the June 27, 2014 issue of the journal is presented.

Acid sulfate soil leachates deteriorate the aquatic ecosystems of their recipient waters around the world. In Finland, AS soils are located mainly on the coast of the Baltic Sea, where rivers and estuaries suffer from acid leachates and waters do not meet with the criteria of good water quality set by the EU. Field drainage of cultivated AS soils is attributable to leaching of acidity, but regardless of various mitigation measures, the acidity of discharge water in these areas has not decreased significantly. In order to better understand the pathways involved in the formation of acidity, the redox status of 56 Finnish AS soil fields was examined using redox potential and pH data measured down to 2 m. The findings indicated that the oxidation of soils has occurred at depths below the drainage pipes, with the median being at a depth of 1.6 m. In fields cultivated for a long time, soil texture had a stronger effect on the depth of the redox interface than the drainage method; open ditch drainage and subsurface drainage; oxidation being faster in sandy and silty soils than in clayey soils. The isostatic land uplift also seems to affect the depth of the redox interface in the long run. Most of the studied fields had been cultivated for at least 30 years prior to the study. However, the pH values of the soils were still very low, probably due to actual and retained acidity. The prevention of oxidation of sulfidic materials in subsoils is important, but measures for neutralizing the acidity are needed. Without them it seems that the leaching of acidity will continue and may decrease only slowly. However, severe droughts during summers and the reclamation of unripe AS soils for any purpose will increase the leaching of acidity. [ABSTRACT FROM AUTHOR]

Established international soil classification systems have not properly accommodated acid sulfate soils (ASS) and soil materials in Finland and Sweden because: (1) in these soils some diagnostic ASS properties are too deep to meet the depth requirements, and (2) there is a lack of defined diagnostic soil classification criteria for acidic and potentially acidic soil materials that do not completely fulfill the diagnostic pH-criterion of pH < 4.0. In this paper, two new ASS materials are introduced with the prefix "para" for parasulfuric material (oxidized material) and parahypersulfidic material (reduced material). These materials have diagnostic pH-criteria of pH 4.0-4.5 and 3.0-3.5 (field-pH for parasulfuric material and incubation-pH for parahypersulfidic material) for mineral and organic soil materials (here defined as > 20% organic matter; peat and gyttja), respectively. The term "para-acid sulfate soil (para-ASS) material" is introduced for soil materials which may have a considerable environmental impact due to mobilization of acidity and dissolved metals. Because organic acids may lower pH to values below the established pH-value of < 4.0 for ASS materials, a pH of < 3.0 is used in the Finnish-Swedish ASS classification for organic soil materials. These changes and new additions to existing diagnostic ASS materials have consequently also led to a slight modification of the required field-pH values of the existing terms "hypersulfidic material" and "sulfuric material". The Finnish-Swedish ASS classification further includes a systematic way for classification of the entire soil profile and no depth requirements for diagnostic ASS materials are present; what matters is the current or potential environmental impact that the soil has or may have. It is proposed that the Finnish-Swedish ASS classification may serve as a framework for establishing a unified ASS classification globally and that the new diagnostic ASS materials are included in relevant international soil classification systems. [ABSTRACT FROM AUTHOR]

Acid sulfate soils (ASS) cause big problems worldwide due to their potential to form sulfuric acid during oxidation of sulfidic materials, resulting in very acid soil (pH <4.0). Impacts include acidification of soil and water, leaching of metals, decreased nutrient supply, deterioration of water fauna and flora, and corrosion of infrastructure. These soils also exhibit poor geotechnical properties. Finland has the largest occurrences of ASS in Europe, mainly along the coast of the Baltic Sea. The EU Water Framework Directive brought about wide co-operation to reduce the harmful impacts of ASS in Finland. One urgent step was to localize and characterize the occurrences of ASS The more than 10 year-long programme, led by the Geological Survey of Finland (GTK), started in 2009 and field work was completed in 2021. During the programme observations, measurements, sampling and analyses were made at 23 000 sites in an area of 5 010 000 ha. Traditionally ASS in Finland have been considered to comprise fine-grained sulfidic sediments and/or their oxidized layers, occurring on agricultural land along the coast below the highest shoreline of the Littorina Sea transgression. This study recognized and classified significant occurrences of other types of potentially harmful ASS materials: (1) coarse-grained ASS (sand), (2) organic ASS (peat) and (3) unsorted ASS (till material). The methods, definition and classification of Finnish ASS have been revised. We calculated the extent of ASS along the coast to be about 1000 000 ha corresponding to 21% of the area covered in the past by the Littorina Sea. and three to six times more than earlier estimates. In addition, some occurrences of ASS were recognized inland, mainly related to black shales and sulfidic ores. The mapping data can be accessed via the GTK map service (www.gtk.fi) providing information about the distribution and properties of ASS. [ABSTRACT FROM AUTHOR]

More than half of the cultivation-induced carbon loss from agricultural soils could be restored through improved management. To incentivise carbon sequestration, the potential of improved practices needs to be verified. To date, there is sparse empirical evidence of carbon sequestration through improved practices in East-Africa. Here, we show that agroforestry and restrained grazing had a greater stock of soil carbon than their bordering pair-matched controls, but the difference was less obvious with terracing. The controls were treeless cultivated fields for agroforestry, on slopes not terraced for terracing, and permanent pasture for restrained grazing, representing traditionally managed agricultural practices dominant in the case regions. The gain by the improved management depended on the carbon stocks in the control plots. Agroforestry for 6-20 years led to 11.4 Mg ha−1 and restrained grazing for 6-17 years to 9.6 Mg ha−1 greater median soil carbon stock compared with the traditional management. The empirical estimates are higher than previous process-model-based estimates and indicate that Ethiopian agriculture has greater potential to sequester carbon in soil than previously estimated. [ABSTRACT FROM AUTHOR]

Constructed wetlands and ponds (CWs) are installed to trap suspended material and particulate phosphorus (P) in agricultural runoff. This study investigated whether the P speciation and P sorption capacity of source soils differ from those of CW sediments and whether drying of dredged sediment changes its characteristics. Samples collected from five agricultural CW sites in south-west Finland, two with chemical-aided (aluminium chloride and ferric sulphate) P precipitation and all representing fine-textured mineral soils, were analysed for various P plant availability indices. Clay contents of the CW sediments were much higher than in catchment soils, likely because of selective erosion. All CW sediments were characterised by similar total P content but clearly higher content of anion exchange resin-extractable P in fresh sediments than the source soils. In general, sediment content of NH 4 F-extractable (aluminium (Al)-associated) P was significantly lower and NaOH-extractable (iron (Fe)-associated) significantly higher than in source soils. Reduced conditions, conducive to mobilisation of Fe-associated P, were observed in all CWs. Accumulation of sulphur (S) in sediments and a pH decline of up to two units upon drying suggested presence of Fe sulphides. Drying also increased oxalate-extractable Al and Fe (hydr)oxide content by 9–47%, resulting in lower degree of P saturation. These results indicate that dredged CW sediments differ greatly in their P retention characteristics from their parent soils. Returning CW sediments to fields is likely to decrease the amount of readily available P for crop uptake. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate whether ground reed canary grass ( Phalaris arundinacea ) straw (RC) could be used to replace peat for short production cycle greenhouse crops. Characteristics of RC, peat, mixture of RC + peat (50% + 50%), and coir were determined and the performance of strawberry ( Fragaria × ananassa cv. Elsanta) on these substrates was evaluated. Water holding capacity of RC was low in comparison to peat and coir, but could probably be improved by decreasing its particle size in processing. The buffering capacity of RC was similar to coir, but clearly lower than in peat. Because of similar reactions to addition of base, liming recommendation of RC would probably be approximately the same as for peat. The C-to-N ratio was 60 in coir, 41 in peat, 23 in RC, and 29 in the mixture of RC + peat. High concentration of inorganic N in RC was rapidly consumed by the microbial activity in the incubation experiment. Vegetative growth of the strawberry plants was the most vigorous in peat, but the total yield, berry size, and sugar to acid ratio in berries were similar in all the substrates. In conclusion, ground reed canary grass may be used to replace peat or coir in soilless culture of strawberry. However, due to its low water holding capacity, irrigation regime has to be adjusted accordingly. [ABSTRACT FROM AUTHOR]

Fluazinam is a widely used pesticide employed against the fungal disease late blight in potato cultivation. A specific, repeatable, and rapid high-performance liquid chromatography (HPLC) method utilizing a diode array detector (DAD) was developed to determine the presence of fluazinam in soil. The method consists of acetonitrile (ACN) extraction, clean-up with solid-phase extraction (SPE), and separation using a mobile phase consisting of 70% ACN and 30% water (v/v), including 0.02% acetic acid. HPLC was performed with a C18 column and the detection wavelength was 240 nm. The method was successfully applied to an incubation experiment and to soil samples taken from potato fields where fluazinam had been applied two to three times during the on-going growing season. In the 90-day incubation experiment, analytical standard fluazinam and the commercial fungicide Shirlan®were added to soil samples that had never been treated with fluazinam, and were then extracted with ACN and 0.01 M calcium chloride (CaCl2). Fluazinam was not extractable with CaCl2, indicating that it does not leach to watercourses in the dissolved form. Recovery with ACN extraction for sandy soils was 72–95% immediately after application and 53–73% after 90 days of incubation. Out of the eight potato field soil samples, fluazinam was found in two samples at concentrations of 2.1 mg kg−1and 1.9 mg kg−1, well above the limit of quantification (0.1 mg kg−1). [ABSTRACT FROM AUTHOR]

Abstract: Selenium (Se) has been added to fertilizers in Finland since 1984, but the fate of the annual selenate addition not removed by the crops is unclear. Residual Se is assumed to be reduced from soluble selenate into insoluble species, which accumulate in the soil, but this has not been verified by soil analyses. In order to develop an appropriate extraction method for tracing the fate of fertilizer Se, Se reserves of two mineral soils were characterized with two sequential extraction procedures. In addition, we compared the efficiency of single extractions with hot water, phosphate-buffer solutions, acid ammonium oxalate, and aqua regia. As for the sequential extractions, approximately 1% of soil Se was soluble in a salt solution, 15–20% was adsorbed on oxide surfaces, and 50% was associated with organic matter, 10% being elemental and 20% in recalcitrant forms. About 50% of Se extractable with aqua regia was recovered with a single extraction with oxalate. The extraction efficiency of phosphate buffers strongly depended on the pH and phosphate concentration of the buffer, which enabled differentiation of Se by sorption strength. A 0.1M buffer at pH 4.4 extracted only 5–10% of the aqua regia extractable Se, whereas with neutral, 1M buffer 30% was recovered. Hot water proved to be an inefficient extractant that removed only 5–10% of soil Se. Due to the low level of readily soluble Se in Finnish soils, extraction methods directed at releasing adsorbed Se are needed. Therefore, phosphate buffers and oxalate seemed to be the most promising extractants for routine monitoring purposes of our soils. [Copyright &y& Elsevier]

Abstract: This article explores long-term land improvements (lime and phosphorus application) under land tenure insecurity on leased land. The dynamic optimisation problem is solved by a stochastic dynamic programming routine with known parameters for one-period returns and transition equations. The model parameters represent Finnish soil quality and production conditions. The decision rules are solved for alternative likelihood scenarios over the continuation of the fixed term lease contract. The results suggest that, as the probability for non-renewal of the lease contract increases, farmers quickly decrease investments in irreversible land improvements and, thereafter, yields decline gradually. The simulations highlight the observed trends of decreasing land improvements on land parcels that are cultivated under lease contracts. [Copyright &y& Elsevier]

Abstract: Destroyed soil structure can increase surface runoff water, with adverse environmental impacts. The effects of trampling by cattle on physical parameters of a heavy clay (a Typic Cryaquept) were studied at the followings four Site types of a pasture after grazing for three seasons: (1) grass with no visible trampling; (2) pasture with some trampling; (3) vicinity of a drinking site with some signs of penetrated hooves, and; (4) a drinking site with totally homogenized surface soil and destroyed vegetation. Additionally, Site types 1 and 4 were studied on sandy loam (an Aquic Cryothent) derived from glacial till after one grazing season. Steady state infiltration rates were reached after 15–35min of infiltration, depending on the degree of trampling and soil texture. On the sandy loam the infiltration rate at the drinking site was only 20% of that under natural pasture with no visible trampling. When the trampling occurred for longer periods in a soil with higher clay content, the infiltration rate of drinking site was only 10–15% of that in non-trampled pastures. These findings could be explained by a reduced porosity for both soils. In heavy clay at the depth of 10–15cm, macropores (Ø>30μm) decreased from 5 to 1.5% (v/v) by the most severe trampling and mechanical strength was lost near the soil surface (cohesion≈1kPa). Deeper at 10–13cm, cohesion (at water potential of −6kPa) was near 30kPa at the drinking site but around 20kPa in non-trampled sites. At the 20–23cm depth of Site 4, the angle of internal friction value (35) for smaller stresses (&#60;150kPa) was reduced to smaller values (9) at greater strengths (150–300kPa) due to a stress dependent aggregate strength and the conversion of a structured soil system to a mostly texture dependent one. The data showed that even a low intensity of grazing will reduce infiltration and hence increase susceptibility to erosion at the drinking sites. [Copyright &y& Elsevier]

The distribution of plant species, the species compositions of different sites, and the factors that affect them in tropical rain forests are not well understood. The main hypotheses are that species composition is either (i) uniform over large areas, (ii) random but spatially autocorrelated because of dispersal limitation, or (iii) patchy and environmentally determined. Here we test these hypotheses, using a large data set from western Amazonia. The uniformity hypothesis gains no support, but the other hypotheses do. Environmental determinism explains a larger proportion of the variation in floristic differences between sites than does dispersal limitation; together, these processes explain 70 to 75% of the variation. Consequently, it is important that management planning for conservation and resource use take into account both habitat heterogeneity and biogeographic differences. [ABSTRACT FROM AUTHOR]

While pulses are staple food-legumes in Ethiopia, their productivity is low due to low soil fertility. Elite rhizobial strains that significantly increased shoot dry weight and nitrogen (N) contents of common beans and soybeans in greenhouse were selected for two-year field trials to evaluate their effect on yields of the pulses in the field. Each pulse had six treatments, namely four rhizobial inoculants, uninoculated control, and synthetic N fertilizer. In the drought-affected year 2015, inoculated pulses tolerated moisture stress better than non-inoculated controls. Inoculation was conducive to higher or equivalent yields compared to synthetic N fertilizer. At Halaba, bean inoculated with strain HAMBI3562 gave the highest grain yield (1500 ± 81 kg ha−1; mean±SE) while the control yielded only 653 ± 22 kg ha−1. At Boricha, HAMBI3570 gave a grain yield (640 ± 35 kg ha−1) comparable to synthetic N. When rainfall was optimal in 2016, inoculation with HAMBI3562 and HAMBI3570 gave grain yields (around 4300 kg ha−1) equivalent to synthetic N. With soybean, strain HAMBI3513 produced consistently higher or comparable biomass and grain yields compared to synthetic N. In conclusion, HAMBI3562 and HAMBI3570 for beans and HAMBI3513 for soybeans can serve as inoculants for areas having similar conditions as the test areas. [ABSTRACT FROM AUTHOR]

Agricultural constructed wetlands (CWs) are intended to retain sediment and phosphorus (P) carried off with runoff and drainage water. The accumulated sediment, with adsorbed P, is often advised to be recycled to agricultural land, but little is known about the fertilizer value of sediment-associated P. This study examined the effects on P adsorption characteristics and P plant availability of mixing CW sediment into soil. Although the total P content in the sediment was approximately equal to that in catchment soil and the NaOH-extractable P content was higher to that in catchment soil, in adsorption-desorption tests sediment P solubility decreased and affinity for P increased with increasing addition rate of CW sediment to soil. Already the lowest sediment addition rate (12.5% of dry weight) decreased the equilibrium P concentration (EPC0') by 60% on average compared to unamended catchment soil. In a greenhouse pot experiment, Italian ryegrass ( Lolium multiflorum L.) yield was largely unaffected by CW sediment application, but P uptake systematically decreased when the rate of sediment application to soil increased. When 12.5% dry weight of sediment was added, plant P uptake decreased by 6-50% in P-unfertilized pots and by 6-17% in P-fertilized pots (150 mg P kg−1) compared with P uptake of ryegrass grown in unamended field soil. Our other results suggest that the plant availability of P in CW sediments is very low due to high clay content and high concentrations of aluminium (Al) and iron (Fe) (hydr)oxides in the sediment. Thus, if applied to agricultural fields in large quantities, dredged CW sediment may impair crop P supply. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: 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 (5.66μgCg−1 h−1, as compared to 2.71μgCg−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. 8.6ngNg−1d−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. [Copyright &y& Elsevier]

Highlights: [•] Monolithic lysimeters are feasible tools to study environmental hazards in AS soil. [•] Water management-dependent processes could be simulated with lysimeters in AS soil. [•] Continuously monitored E h varied according to the water management practice. [•] Crop root growth had a significant impact on soil reduction in lysimeters. [Copyright &y& Elsevier]

Abstract: 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 (>50μm) 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 300μm 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. [Copyright &y& Elsevier]

Abstract: The largest areas of acid sulphate (AS) soils in Europe are located in Finland, where 67,000–130,000ha 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 (110MgCorg ha−1 and 15MgNtot ha−1) as well as high substrate induced respiration (33μgCO2–Cg−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. [Copyright &y& Elsevier]

Abstract: Nine filter beds have been constructed in the Nordic countries, Denmark, Finland, Norway and Sweden. Filter beds consist of a septic tank followed by an aerobic pre-treatment biofilter and a subsequent saturated flow grass-covered filter. Thus, filter beds are similar to subsurface flow constructed wetlands with pre-treatment biofilters, but do not have wetland plants with roots submerged into the saturated filter. All saturated filters contain Filtralite®P, a light-weight expanded clay aggregate possessing high phosphorus sorption capacity. The filter bed systems showed stable and consistent performance during the testing period of 3 years. Removal of organic matter measured as biochemical oxygen demand (BOD) was >80%, total phosphorus (TP) >94% and total nitrogen (TN) ranged from 32 to 66%. Effluent concentrations of fecal indicator bacteria met the European bathing water quality criteria in all systems. One system was investigated for virus removal and somatic viruses were not detected in the effluent. The investigations revealed that the majority of the BOD and nitrogen removal occurred in the pre-treatment filters and the phosphorus and bacteria removal was more prominent in the saturated filters. The saturated filters could be built substantially smaller than the current design guidelines without sacrificing treatment performance. The used filter material met the Norwegian regulations for reuse in agriculture with respect to heavy metals, bacteria and parasites. When saturated with phosphorus, the light-weight aggregate, Filtralite®P used in the saturated bed is a suitable phosphorus fertilizer and additionally has a liming effect. [ABSTRACT FROM AUTHOR]

Summary 1 Unravelling which factors affect where tropical trees grow is an important goal for ecologists and conservationists. At the landscape scale, debate is mostly focused on the degree to which the distributions of tree species are determined by soil conditions or by neutral, distance-dependent processes. Problems with spatial autocorrelation, sparse soil sampling, inclusion of species-poor sites with extreme edaphic conditions, and the difficulty of obtaining sufficient sample sizes have all complicated assessments for high diversity tropical forests. 2 We evaluated the extent and pervasiveness of habitat association of trees within a 10 000 km[sup 2] species-rich lowland landscape of uniform climate in south-west Amazonia. Forests growing on two non-flooded landscape units were inventoried using 88 floristic plots and detailed soil analyses, sampling up to 849 tree species. We applied single-species and community-level analytical techniques (frequency-distributions of presence records, association analysis, indicator species analysis, ordination, Mantel correlations, and multiple regression of distance matrices) to quantify soil/floristic relationships while controlling for spatial autocorrelation. 3 Obligate habitat-restriction is very rare: among 230 tree species recorded in ≥ 10 localities only five (2.2%) were always restricted to one landscape unit or the other. 4 However, many species show a significant tendency to habitat association. For example, using Monte Carlo randomization tests, of the 34 most dominant species across the landscape the distributions of 26 (76.5%) are significantly related to habitat. We applied density-independent and frequency-independent estimates of habitat association and found that rarer species tend to score higher, suggesting that our full community estimates of habitat association are still underestimated due to the inadequate sampling of rarer species. 5 Community-level floristic variation across the whole landscape is related to the variation in 14 of 16 measured soil variables, and to the geographical distances between samples. 6 Multiple regression of distance matrices shows that 10% of the floristic variation can be attributed to spatial autocorrelation, but even after accounting for this at least 40% is attributable to measured environmental variation. 7 Our results suggest that substrate-mediated local processes play a much more important role than distance-dependent processes in structuring forest composition in Amazonian landscapes. [ABSTRACT FROM AUTHOR]

• In black schist AS soils, the respiration profile differs from coastal AS soils. • Peat horizons dominate oxic CO 2 and N 2 O production over mineral subsoil. • Oxic GHG production in subsoil is little affected by NH 4 +, glucose or temperature. • Anoxic denitrification is limited by nitrate in all but topsoil H1 horizon. • Anoxic denitrification is not limited by available C in any but subsoil Cr horizon. Factors limiting the production of the greenhouse gases nitrous oxide (N 2 O) and carbon dioxide (CO 2) were investigated in three incubation experiments conducted with soil from top- and subsoil horizons of a peatland which had an acid sulphate mineral subsoil derived from black schists. The effect of moisture was investigated by equilibrating undisturbed soil samples from three horizons (H2, Cg and Cr) at −10, −60 or −100 cm matric potential and measuring the gas production. In the second experiment, the effects of temperature and various substrates were studied by incubating disturbed soil samples in aerobic conditions at 5 or 20 °C, and measuring basal respiration and N 2 O production before and after adding water, glucose or ammonium into the soil. In the third experiment, the effects of added glucose and/or nitrate on the denitrification in soil samples from four horizons (H1, H2, Cg and Cr were investigated by acetylene inhibition and monitoring of N 2 O production during a 48-h anaerobic incubation. The production of CO 2 in the topmost peat horizon was largest at −10 cm matric potential, and it was larger than those in the mineral subsoil also at −60 and −100 cm potentials. In contrast, drainage seemed to increase N 2 O production, whereas in the wettest condition the production of N 2 O in the mineral subsoil was small and the peat horizon was a sink of N 2 O. Lowering of temperature (from 20 °C to 5 °C) decreased CO 2 production, as expected, but it had almost no role in the production of N 2 O in aerobic conditions. Glucose addition increased the aerobic production of CO 2 in peat, but it had a minor effect in the mineral horizons. Lack of C source (glucose) was limiting anaerobic N 2 O production in the uppermost peat horizon, while in all other horizons, nitrate proved to be the most limiting factor. It is concluded that peatlands with black schist derived acid sulphate subsoil horizons, such as in this study, have high microbial activity in the peaty topsoil horizons but little microbial activity in the mineral subsoil. These findings are contrary to previous results obtained in sediment-derived acid sulphate soils. [ABSTRACT FROM AUTHOR]