Application of organic and mineral fertilizers improves crop productivity and availability of plant nutrients. Further investigation into their integral application is crucial to obtaining optimum crop productivity. A field experiment was conducted during 2020–21 and 2021–22 at experimental field station in Benshangul Gumuz, Assosa University, Assosa, Ethiopia to investigate the response of maize (Zea mays L.) yield to lime, blended NPSZnB fertilizer and vermicompost. Two lime levels, three vermicompost levels, and three blended fertilizer levels were factorially combined and laid out in a randomized complete block design (RCBD). The integral application of organic fertilizer with blended fertilizer with lime significantly affected the agronomic parameters. Grain yield, number of grains per cob, 1000-seed weights, plant height, and days to 50% tasseling were parameters most affected by the amendments. Integral application of 50% of the recommended rate of blended fertilizer and vermicompost with lime improved maize yield by 53%, while the application of NPSZnB and vermicompost individually improved maize yield by 34% and 22% over the control treatment. One tonne of vermicompost and lime could substitute 38 kg and 23 kg of blended fertilizer, respectively. In conclusion, the integrated application of NPSZnB and vermicompost with the recommended amount of lime was the best soil fertility management option. In terms of grain yield and net benefit, 4 t/ha lime, 2.5 t/ha vermicompost and 100 kg/ha blended fertilizers were recommended for optimum maize production in the Assosa area and similar agroecologies.

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 (recA-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.

Cultivated peatlands are important for grass production in Northern Europe, but the potential impact of nutrients leaching to surface waters is a major concern. Due to a lack of data on nitrogen (N), phosphorus (P) and organic carbon leaching, a monitoring programme was established at Ruukki (Siikajoki, Finland), an agricultural, subsurface drained peat site with a peat thickness of 20-80 cm. Concentrations and loading of N, P, and total organic carbon (TOC) were monitored, along with other water quality parameters for the field discharge, in 2018-2021. We observed N leaching from subsurface discharge to be 25 kg N ha-1 year-1 (range 11-40 kg N ha-1 year-1, 74 % as nitrate NO3-N). The least N leaching was recorded from plots of thinner peat topsoil and those with grass cover, while the majority of N leaching originated from thicker peat plots (bare or under barley) in spring. Leaching of N strongly decreased during periods of thick grass cover. Significant N leaching also occurred during the mild winter of 2019-2020, characterized by alternating freeze and thaw periods. Annual P loading from subsurface drainage was 0.30 kg P ha-1 (0.20-0.43 kg P ha-1), low compared to that of average cultivated soils in Finland. It was estimated that 13 % of the total N leaching and 50 % of the total P leaching occurred in surface runoff. Leaching of TOC was significant at 87 kg ha-1 year-1 (31-137 kg ha-1 year-1). Leaching of dissolved P and TOC increased with peat thickness. Abundant loading of sulfur and acidity indicates the oxidation of sulfidic material in the subsoil. Leaching concentrations correlated with discharge quantity, suggesting that mobilization processes during the dry periods resulted in leaching during high discharge periods. The results show the importance of avoiding bare peat soil for NO3-N leaching reduction, even during wintertime in cultivated peatlands.

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.

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 1 000 000 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.

To use peatlands for agriculture or forestry, they need to be drained. Lowered water table and increased oxygen concentration in the soil profile alter soil biogeochemistry, enhancing peat decomposition and mineralization processes. After the drainage, peatland changes from carbon sink to carbon source into the atmosphere and watercourses. The drainage affects the greenhouse gas (GHG) fluxes and runoff water quality depending on soil nutrient status and the new water table depth. Usually, carbon dioxide ad nitrous oxide fluxes increase, and methane fluxes decrease.In Finland, approximately 10% of cultivated fields are on organic soils but they are responsible for a larger share of agricultural GHG emissions. Finland has set a challenging goal for carbon neutrality by 2035, thus the pressure to mitigate GHG emissions from cultivated peatlands is high. However, if the cultivation of drained peatlands was heavily restricted, their local importance creates socio-economic challenges, due to their uneven distribution in Finland. At the same time, recent global and economic circumstances as well as the increased occurrence of extreme weather events have underlined the importance of national food security. During dry growing seasons, cultivated peatlands produce decent crop yields more reliably than mineral soils.NorPeat research platform (26 ha) located at Ruukki, Finland (64.68°N, 25.11°E) and governed by Natural Resources Institute Finland (Luke) is a cultivated peatland under normal silage grass rotation for beef cattle feed production. The platform was established in 2017 to study various environmental effects of cultivated peatlands monitoring year-round GHG fluxes, as well as flow and the quality of subsurface drainage water and overflow. The field is divided into 8 plots and the peat depth varies from 15 to 75 cm. Water storage reservoir (0.7 ha) located next to the field is connected to the subsurface drainage system and it allows subsurface irrigation and manipulation of the water table level in the individual plots. Environmental conditions are monitored with multiple sensors to supplement the datasets of GHG emissions and leaching. Along with field experiments, we are running column experiments in controlled conditions in the laboratory to study environmental impacts in more detail. In addition, the technical usability of sub-irrigation systems as a tool for GHG mitigation via water table control is studied in the field and laboratory. These are carried out with the aim to add automated features to the system to optimize the operation of the sub-irrigation.

Field application of gypsum (CaSO4 × 2H2O) is a tool to decrease phosphorus (P) load to watercourses. Effects of gypsum application (4 tons ha-1) on soil and crop composition were monitored up to four years after the treatment in the Savijoki catchment, southwestern Finland. Eleven amended fields and 17 control fields were analyzed for easily soluble P, Ca, Mg, K, S, pH(H2O), electrical conductivity (EC) and loss-on-ignition. Plant samples were analyzed for most nutrients and Se. Downward S transport was monitored in two fields. In the first spring after gypsum application, but not later, S concentrations and EC were substantially but not harmfully elevated in the plough layer, with no other significant effects on soil composition. Sulfur leached out slightly less rapidly from clay than from the coarse mineral soil. Plant S concentration increased for the first and the second year. In conclusion, gypsum application did not have adverse effects on soil or crop chemical composition in this survey of predominantly clay soils.

The off-site effects of agricultural organic soils include the leaching of N, P, and organic carbon (OC) to watercourses and CO2, CH4, and N2O emissions into the atmosphere. The aim of this study was to quantify how the thickness of organic layers affects these loads. A 19.56-ha experimental field drained by subsurface pipes was established in Ruukki, northwestern Finland. Three plots had a 60-80 cm-thick sedge peat layer and three others had a thickness of 20 cm or less. The drainage pipes lie in mineral soil that, in this field, contains sulfidicmaterial. This study documents the experimental settings and reports on the leaching of substances in the first two years, as well as CO2, CH4 and N2O emissions during eight weeks in one summer. Total N (TN) and OC loads were higher from the thicker peat plots. The mean TN loads during a hydrological year were 15.4 and 9.2 kg ha(-1) from the thicker and thinner peat plots, respectively, with organic N representing 36% of TN load. Total P (TP) load averaged 0.27 kg ha(-1) yr(-1). Dissolved P load represented 63 and 36% of TP in the thicker peat area and only 23 and 13% in the thinner peat area, and was thus increased upon peat thickness. These N and P loads through the subsurface drainage system represented roughly 83% of TN and 64% of TP loads from this field. There were no clear differences in greenhouse gas emissions among the plots during the eight-week monitoring period. Slowly oxidizing sulfide in the subsoil resulted in annual leaching of 147 kg S ha(-1), almost ten times that of non-sulfidic soils. Our first results emphasize the effect of the peat thickness on the leaching of substances and warn about considering all organic soils as a single group in environmental assessments. (C) 2021 The Authors. Published by Elsevier B.V.

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.

Acid sulfate (AS) soils contain sulfidic compounds formed in anaerobic conditions. In aerobic conditions, they will oxidize to sulfuric acid, which commonly lowers the pH to 3 – 4. These soils cover approximately 10,000 km2 in Finland, mainly on the western coast, and over 170,000 km2 globally. Acidity and the metals dissolved from the soil matrix and leached out of the soil are serious threats to aquatic biota. Initially, AS soils were regarded as an exclusively agricultural problem, but since the 1970s nearly all studies of AS soils have been environmentally motivated. Awareness of these soils has also risen in forestry, peat mining, and in engineering projects. Liming and water management are the key methods toward the sustainable use of these soils.

Factors limiting the production of the greenhouse gases nitrous oxide (N2O) and carbon dioxide (CO2) 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 (H-2, 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 degrees C, and measuring basal respiration and N2O 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 N2O production during a 48-h anaerobic incubation. The production of CO2 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 N2O production, whereas in the wettest condition the production of N2O in the mineral subsoil was small and the peat horizon was a sink of N2O. Lowering of temperature (from 20 degrees C to 5 degrees C) decreased CO2 production, as expected, but it had almost no role in the production of N2O in aerobic conditions. Glucose addition increased the aerobic production of CO2 in peat, but it had a minor effect in the mineral horizons. Lack of C source (glucose) was limiting anaerobic N2O 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.

Clay content and the ability to reversibly retain cations affect many essential chemical and physical properties of soil, such as pH buffering and carbon sequestration. Cation exchange capacity (CEC) and base saturation are also commonly used as criteria in soil classification. However, determination of CEC and particle-size distribution is laborious and not included in routine soil testing. In this study, pedotransfer functions including soil test cations (STCat; Ca2+ + Mg2+ + K+), pH and soil organic carbon (SOC, %) as explanatory variables were developed for estimating CEC, titratable acidity (TA; H+ + Al3+) and clay content (clay, %). In addition, reference values for potential CEC and its components were determined for Finnish mineral and organic soils. The mean of potential CEC extracted by 1 M ammonium acetate at pH 7.0 ranged from 14 (range 6.4−25) in coarse soils to 33 (21−45) cmol(+) kg-1 in heavy clay soils, and from 42 (24−82) in mull soils to 77 (25−138) cmol(+) kg-1 in peat soils. The average CEC of clay and SOC were 27 and 160 cmol(+) kg-1, respectively. Titratable acidity occupied 53% and around 40% of the CEC sites in organic and mineral soils, respectively, evidencing that it is a prominent component of the potential CEC in these predominantly acidic soils. STCat, pH and SOC explained 96% of the variation in potential CEC. STCat and pH can be used in estimating the clay content especially for soils containing over 30% clay. In coarse textured soils, in contrast, SOC hampers the STCat based estimation of clay content.

The productivity of the faba bean has declined in Ethiopia, owing to poor management practices, such as blanket fertilisation. In 2018, a field experiment was conducted in a Nitisol soil during the main cropping season in Northwestern Ethiopia, to determine the amount of chemical fertiliser and Rhizobium inoculant to be used for the optimum yield within economic feasibility. The experiment consisted of a factorial combination of five rates of blended NPSZnB fertiliser (0, 60, 121, 180 and 240 kg ha−1) and three rates of inoculant (0, 500 and 750 g ha−1). Sole chemical fertilisation, as well as inoculation, individually produced a seed yield of 2.3–2.5 t ha−1, about 1.0–1.2 t ha−1 more than the control. However, the maximum seed yield (3.3 t ha−1) was recorded from the combined application of both the chemical fertiliser and the inoculant. The seed yield correlated closely with the number of active nodules (R2 = 0.78 **), suggesting a substantial contribution of symbiotic N2 fixation. Inoculation increased the N content of the seed yield by at least 30 kg ha−1. Chemical fertilisation, containing at least 44 kg ha−1 of mineral N does not appear to have an adverse effect on N2 fixation. The combined use of 180 kg ha−1 blended fertiliser with 750 g ha−1 inoculant, producing a maximum net profit of 72,918 birr ha−1 (EUR 2232), is recommended for the study area. This study emphasises that (1) inoculation alone can produce as much seed as the maximum rate of chemical fertilisation, but (2) the maximum yield was produced with a combined use of inoculant and chemical fertiliser, by promoting the vigour of the nodules and N2 fixation.

Background There is scarcity of scientific information on stocks and retention rate of soil organic carbon (SOC) among mixed farming systems in humid Western Ethiopia. The objectives of study were to determine the SOC stocks and retention rates along a 53-km long toposequence of Didessa watershed. The study was conducted in mixed farming systems (annual arable cropping, grazing, fallow, grassland, coffee agroforestry, eucalyptus agroforestry and mechanized irrigated sugarcane production) within an elevation range of 1273 to 2543 m above sea level. Results The results revealed that land use types greatly affected SOC stocks and retention rates in the upper 20 cm soil depth. The SOC stocks ranged from 9.27 to 13.5 Mg C ha −1 (0–20 cm) while the retention rates were 0.11, 0.20, 0.28, 0.31 and 1.14 Mg C ha −1 year −1 for coffee agroforestry, fallow, grazing, eucalyptus agroforestry and irrigated sugarcane production systems, respectively. Conclusion The retention rates demonstrated that the different farming systems are potential source of C sinks. The study indicated that the farming systems are efficient in sequestering SOC and their benefits can be further adopted for their economic values, social significance, restoration of degraded land, and sequestration of carbon (C) in humid tropical Western Ethiopia.

Besides causing acidification, acid sulfate (AS) soils contain large nitrogen (N) stocks and are a potential source of N loading to waters and nitrous oxide (N2O) emissions. We quantified the stocks and flows of N, including crop yields, N leaching, and N2O emissions, in a cultivated AS soil in western Finland. We also investigated whether controlled drainage (CD) and sub-irrigation (CDI) to keep the sulfidic horizons inundated can alleviate N losses. Total N stock at 0–100 cm (19.5 Mg ha−1) was smaller than at 100–200 cm (26.6 Mg ha−1), and the mineral N stock was largest below 170 cm. Annual N leaching (31–91 kg N ha−1) plus N in harvested grain (74–122 kg N ha−1) was 148% (range 118–189%) of N applied in fertilizers (90–125 kg N ha−1) in 2011–2017, suggesting substantial N supply from soil reserves. Annual emissions of N2O measured during 2 years were 8–28 kg N ha−1. The most probable reasons for high N2O emission rates in AS soils are concomitant large mineral N pools with fluctuating redox conditions and low pH in the oxidized subsoil, all favoring formation of N2O in nitrification and denitrification. Although the groundwater level was higher in CD and CDI than in conventional drainage, N load and crop offtake did not differ between the drainage methods, but there were differences in emissions. Nitrogen flows to the atmosphere and drainage water were clearly larger than those in non-AS mineral soils indicating that AS soils are potential hotspots of environmental impacts.

Clogging of subsurface pipe drainage systems by rust precipitates is a problem in many cultivated areas and especially on the coast of Ostrobothnia, northwestern Finland. The subsurface drainage pipes need to be flushed every few years to remove the rust, which causes additional maintenance costs. These problems are particularly common in acid sulphate (AS) soils that have peat horizons on top of sulfidic materials. These soils are often wet, and the drainage water contains high dissolved iron concentration, commonly above 20 mg l-1. Reducing conditions prevail in certain horizons and oxidation of sulfidic minerals and low pH are typical of the horizons above, all resulting in mobilization of several elements. Upon entering the aerobic drainage pipe dissolved iron is oxidized and readily precipitates as rust. In dry summers, the precipitate is typically hardened and the whole pipe drainage system can be blocked. Minerals containing sulphur (S) may also be precipitated in the pipes. The fresh precipitates can adsorb heavy metals that occur in substantial concentrations in AS drainage waters. In this study, 10 rust samples were collected from ditches and wells. All sites, except one, had a 20-70 cm peaty topsoil. A comprehensive chemical analysis was carried out and the precipitates were investigated with a scanning electron microscope (SEM). Colours of the samples were strong brown or reddish yellow (Munsell notation 7.5YR 5/6-6/8). Silicon content was only 0.3-0.9%, indicating the absence of actual soil material in the precipitates. The material contained 27-49% organic matter (1.9 x C), co-precipitated from the humic substances of drainage water. Iron was by far the most abundant element. If all Fe is contained in ferrihydrite (66% Fe), this mineral constituted 35-63% (mean 46%) of the precipitate while aluminium hydroxide (34% Al) constituted 0.7-9% (mean 5%). Even though most drainage waters were rich in S (commonly above 40 mg l-1, the maximum S concentration of the precipitates was only 1.9% and the mean at 0.7%. Sulphur-containing minerals jarosite and schwertmannite were not detected in the SEM images, either, suggesting that these minerals are not precipitated from AS drainage waters. Dissolved heavy metals are leached from AS soils but they were not markedly co-precipitated in our samples. The mean concentration of Cd was only 1 mg kg-1 and Ni 12 mg kg-1, Cr 33 mg kg-1, Cu and Zn 32 mg kg-1 while Mn was more abundant, 355 mg kg-1. In our peaty AS soils there is thus substantial mobilization of Fe and a flux out of the soil and a new solid phase is formed in the drainage pipes and ditches constituting mostly of iron hydroxide and humic substances. If dredged, application of this material onto the fields seems not to pose major environmental hazards.

Liming improve the properties of acidic soils and commenly increases crop productivity. The experiment to evaluate the effect of lime, manure and kitchen ash application on yield and yield components of faba bean was conducted at Yebokla kebele in Gozamin district of Amhara Region in 2017 season. The factorial combination of 0, 1.5 and 3 t/ha lime, 0, 2.5 and 5 t/ha manure and 0, 0.5 and 1 t/ha kitchen ash treatments were replicated three times and laid out in randomized complete block design. The results show shortened days to maturity was recorded from plot receiving 1.5 t lime, 2.5 t manure and 1 t/ha kitchen ash. The numbers of effective nodule was significantly higher at 1.5 t.lime and 2.5 t/ha manure while higher plant height was recorded from 1.5 t/ha lime and 5 t/ha manure treatments. Number of pods per plant increased by combined application of 2.5 t manure and 1 t/ha kitchen ash while maximum number of seeds per pod observed at 5 t/ha manure. The highest seed yield (2.59 t/ha) obtained from combined used of 1.5 t lime, 5 t manure and 0.5 t/ha kitchen ash meanwhile maximum straw yield was recorded from 5 t/ha manure rate. The economic analysis revealed that combined used of 1.5 t lime, 0.5 t kitchen ash and 5 t/ha manure gave a net profit of 26,533 Birr/ha with acceptable MRR (98%), thus this treatment is found optimum to increase crop yield on acidic soils of Gozamin district.

In total 196 bacterial isolates were obtained from root nodules of lentil (Lens culinaris) and faba bean (Vicia faba) grown on soil samples collected from 10 different sites in central and southern parts of Ethiopia. All isolates were identified as members of the genus Rhizobium by using recA gene sequence analysis. In the recA phylogenetic tree 195 rhizobial strains were classified into nine genospecies. The phylogeny of symbiotic genes nodC and nifH revealed five and six distinct groups respectively, largely dominated by symbiovar viciae. A multivariate analysis showed that environmental variables of the sampling sites considered in this study had more effect on the distribution and composition of the genospecies than the host legumes of the strains. Twenty representative strains, selected based on their isolation site, host plant and nodC group, were able to nodulate all lentil, faba bean, field pea (Pisum abyssinicum) and grass pea (Lathyrus sativus) plants in a greenhouse test in axenic conditions. The majority of the rhizobial strains were effective nitrogen-fixing symbionts for all tested legumes, indicating their potential to serve as broad host-range inoculants in agriculture. The present work suggests the presence of taxonomically and symbiotically diverse rhizobial species for legumes in the Viciae tribe in Ethiopia.

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 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.