Effect Of Soil pH Research Articles

Bovine urine inhibits microbial function and increases urea turnover in dairy grazed soils

Effects of bovine urine on microbial functional attributes within the carbon (C) cycle have not previously been investigated. The magnitude of urine effects on microbial populations may be mediated by the ability of a soil to buffer changes to pH and electrical conductivity (EC) in response to urine. We examined changes in the metabolism of C substrates by microbial communities subsequent to treatment with dairy cow urine in 27 dairy grazed soils across four soil orders. Untreated soils (baseline) and soil treated with urine or water were incubated (25°C) for 21 days then assessed for microbial function using MicroResp™. Urine addition decreased functional capacity, microbial diversity, and microbial biomass C at 21 days after urine addition, but did not affect basal respiration, compared with the water control. Urine addition also led to a shift in community-level physiological profiles. There were no indirect effects of soil pH or EC buffering capacity on the functional microbial parameters measured. Urine addition increased the utilisation of urea and may be a factor in losses of fertiliser nitrogen in dairy systems. The length of time that urine depresses catabolic function could have important implications for long-term soil organic matter cycling under urine patches.

The influence of climatic legacies on the distribution of dryland biocrust communities.

Predicting the distribution of biocrust species, mosses, lichens and liverworts associated with surface soils is difficult, but climatic legacies (changes in climate over the last 20k years) can improve our prediction of the distribution of biocrust species. To provide empirical support for this hypothesis, we used a combination of network analyses and structural equation modelling to identify the role of climatic legacies in predicting the distribution of ecological clusters formed by species of mosses, lichens and liverworts using data from 282 large sites distributed across 0.6 million km2 of eastern Australia. Two ecological clusters contained 87% of the 120 moss, lichen and liverwort species. Both clusters contained lichen, moss and liverwort species, but were dominated by different families. Sites where the air temperature increased the most over 20kyears (positive temperature legacies) were associated with reductions in the relative abundance of species from the lichen (Peltulaceae and Teloschistaceae) and moss (Bryaceae) families (Cluster A species), greater groundstorey plant cover and lower soil pH. Sites where precipitation has increased over the past 20kyears (positive precipitation legacy) were associated with increases in the relative abundance of lichen (Cladoniaceae, Lecideaceae and Thelotremataceae) and moss (Pottiaceae) families (Cluster B species) and lower levels of soil pH. Sites where temperatures have increased the most in the past 20kyears suppressed the negative effects of plant cover on Cluster B by reducing plant cover. Increased intensity of grazing suppressed the negative effect of soil pH and the positive effect of soil carbon, on the relative abundance of Cluster B taxa. Finally, increasing temperature and precipitation legacies reduced the negative effect of soil pH on Cluster B. Understanding of the importance of climatic legacies improves our ability to predict how biocrust assemblies might respond to ongoing global environmental change associated with increasing land use intensification, increasing temperature and reduced rainfall.

Inoculation of soybean seeds coated with osmoprotector in diferents soil pH's

Inoculation with nitrogen-fixing bacteria ( Bradyrhizobium ) is an indispensable technology to increase the productivity of the soybean crop. The objective of this study was to evaluate the viability of the inoculation with Bradyrizobium bacteria associated with the osmoprotector coating on different pre-sowing days and the effect of different soil pH on the components of yield, nodulation and grain yield of soybean. Two soybean cultivars were used, sown in two seasons and submitted to soil pH of 5.3 and 6.5. The seeds were inoculated at different pre-sowin periods with Bradyrizobium bacteria in the presence or absence of osmoprotectants. In the cultivar NA 5909RG (pH 5.3), the seeds inoculated with Bradyrhizobium and osmoprotector, at four and seven days of pre-sowing, presented an increase of 10.8% and 8.3% of productivity, in relation to those without osmoprotector. The osmoprotector and the inoculation of Bradyrhizobium increases the number and dry mass of nodules in soil with more acidic pH. The soil of lower acidity is responsible for higher grain yield, compared to the higher acidity, when both were not inoculated. The variable with the greatest explanatory power and contribution in the variability in the data of the experiment is the grain yield.

Soil biological and physiochemical factors limiting the growth potential of tomato planted in waterlogged volcanic soil

Many vegetable growers in Japan practice a unique waterlogged cultivation method with ample nitrogen (N) supply and microbial supplements, reporting vigorous plant growth, no soilborne diseases, and high yields. We simulated waterlogged soil conditions in greenhouse experiments to examine effects of soil pH and redox potential (Eh) as well as microbial influence on the growth of tomato seedlings. Soil pasteurization enhanced seedling growth whether the acidic, volcanic soil was waterlogged or well-drained. Among various antimicrobials, only soil treatment with polymyxin B improved shoot growth in nonpasteurized soil. The seedlings grew best in pasteurized acidic, waterlogged soil fertilized with ample potassium nitrate (KNO3), which maintained soil Eh above zero. In nonpasteurized soil, growth was severely stunted by raising soil pH progressively to 8.5 while Eh dropped to –194 mV. The results suggested that heat-sensitive Gram-negative soil bacteria and low soil Eh were key factors limiting the growth potential of tomato plants in waterlogged soils.

Effects of soil pH on the root growth of passion fruit and the mechanism of mineral uptake

Acidic soil has recently been reported to be rather preferable for passion fruit growth, although the mechanisms underlying these observations are not known. For these reasons, in the present study the effects of soil pH on the root growth and mineral uptake were examined. The vines and roots of passion fruit plants were pruned in half before transplanting them to 10-L pots filled with soils adjusted to four different pH levels (3.5, 4.5, 5.5, and 6.5). Soil exchangeable cations, leaf and root mineral contents, root length density, vegetative growth, photosynthetic rate, stomatal conductance, and leaf water potential were measured. Soil exchangeable aluminium (Al) as well as Al saturation were higher at the lower pH (pH 3.5, 4.5) than at higher pH (pH 5.5, 6.5), whereas negative effects of neither root elongation nor mineral uptake were observed. On the contrary, the root growth was even the highest of all the treatments at pH 3.5. The root Al content at pH 3.5 was similar to the other treatments, and the leaf Al content was lower than the average concentrations detected in other herbaceous plants. Accordingly, the passion fruit root system seems to use an Al exclusion mechanism, thus resulting tolerant to Al toxicity. Vegetative growth, photosynthetic rate, stomatal conductance, and leaf water potential were lowered at higher pH values of the soils. Insufficient root growth at higher pH caused water deficit in leaves, and the water stress might lead to stomatal closure, which might cause depression of photosynthetic rate. At acidic soil such as pH 3.5, on the contrary, a larger root volume is considered to be advantageous to keep higher leaf water potential and resulted in higher photosynthetic rate with strong vegetative growth.

Effect of soil properties and environmental factors on chemical compositions of forest soils in the Russian Far East

Forest ecosystem acts as a significant sink and source of elements; however, the dynamics of trace elements (TEs) in soils of boreal zone are still poorly characterized. Data on relationships of TEs, major elements (MEs), soil properties, and parent rock geochemistry in boreal forest of Northeast Asia are scarce. Therefore, the objectives of this study were to evaluate the origination of TEs in forest soils and identify soil properties and ecosystem processes controlling accumulation and profile distribution of TEs. Dystric Cambisols and underlying parent rocks have been sampled within hilly landscape covered by Gmelin larch (Larix gmelinii (Rupr.) Rupr.) forests in Amur region (Russia). This paper considers 10-selected soil characteristics, total concentrations of 19 TEs, and 10 MEs measured by ICP-MS and RFA analysis. Factor analysis has been employed to highlight underlying relationships hidden in a complex data of element concentration and soil characteristics. Origination of TEs was assessed by using an enrichment factor (EF) considering concentration of TEs in soil in comparison to underlying parent rocks using Ti as a reference element. A group of biophile Zn, Mo, Sn, and Pb were enriched in the upper soil horizon, and depleted in mineral compared to parent rocks. Beryllium, Sc, Cr, Cu, Ga, Ge, Ta, Th, and U were depleted in both horizons. Ni and Cs show highest enrichment in both studied soil horizons. Frequently occurring forest fires affect soil characteristics and TEs dynamic only in the upper part of soil profile. Factor analysis revealed potential effect of exchangeable Na and soil pH on accumulation of the elements in the upper horizon, as a result of ash deposition by fire. The studied TEs primarily originate from underlying parent rocks. Accumulation versus leaching of TEs in Dystric Cambisols might be element specific and affected by fire-derived ash. Our work shows that the upper horizon of forest soils could act as a significant sink of group of TEs. Therefore, long-term observations of TEs dynamic in soil profiles are needed to elucidate biogeochemical cycles in frequently burned forests of Northeast Asia. The present study for the first time has established an important wide data set of TEs concentration in Dystric Cambisols of natural boreal forests in the Russian Far East.

Effect of Soil pH on the Growth, Reproductive Investment and Pollen Allergenicity of Ambrosia artemisiifolia L.

Despite the importance of soil reaction for alien plant establishment, few and incomplete studies have included this key factor so far. In this study, we investigated the effects of soil pH on the germination, growth (plant height, width, dry weight, etc.) and reproductive investment (inflorescence size and n° of flowers) of Ambrosia artemisiifolia (common ragweed), an allergenic species that is highly invasive and alien in Europe, through a replicated experiment in controlled conditions. In addition, we determined if soil pH has an effect on the total pollen allergenicity of the species. After preliminary germination tests on agar at different pH (from pH4 to pH8), plants were grown in natural soils with pH values of 5 (acid), 6 (sub-acid) and 7 (neutral) obtained by modifying a natural soil by liming methods (calcium hydroxide solution). Results showed that plants grown at pH7 were shorter and developed leaves at a slower rate than those grown at pH5 and pH6; plants grown at pH7 did not produce flowers and pollen. We also observed that, at pH5 and pH6, larger plants (as assessed by the dry weight of the aerial biomass) had both larger and more numerous inflorescences and emitted pollen earlier. Finally, the IgE-binding signal was higher in pollen samples collected from plants grown at pH5 (Integrated Optical Density, IOD, range: 1.12–1.25) than in those grown at pH6 (IOD range: 0.86 −1.03). Although we acknowledge the limitations of only testing the effects of pH in controlled conditions, this study suggests that soil pH greatly affects the growth and development of A. artemisiifolia and indicates that it may have a role in limiting the distribution and hazardousness of this plant. Future field tests should therefore assess the effectiveness of liming in the management and control of ragweed and other alien species.

Utilization of manure of buffalo and goats on growth of Kelor plants in Pangururan District Samosir Regency

The need for livestock feed is crucial in Pangururan subdistrict of Samosir Regency. Therefore, it is worthed planting various alternative feed plants such as Kelor (Moringa oleifera). Goat and buffalo feces can be utilized by the community as solid manure. This study aims to utilize the manure density of goat and buffalo againts growth of Kelor (Moringa oleifera). This research was conducted in Pangururan Subdistrict of Samosir Regency of North Sumatera starting from March to May 2018. The research design used in this research was Complete Randomized Design (RAL) with 4 treatments of 5 replications. The treatments consisted of P0 (100% top soil), P1 (50% top soil + 50% Buffalo manure), P2 (50% top Soil + 50% Goat Manure), and P3 (50% top soil + 25% buffalo Manure + 25% Goat Manure). The parameters observed were the effect of treatments on soil pH, leaf width, number of tertier branch. The results showed that 50% top soil + 25% buffalo manure and 25% Goat Manure was better than 100% top soil +50% top soil + 25% Cow Manure + 25% Goat Manure significantly (P <0.05) better than 50% top soil + 50% Cow Manure Buffalow and 50% top soil + 50% Goat Manure to the effect of soil Ph on buffalo and goat manure, leaf width, number of branch children of Moringa oleifera.

Experimental study of the effects of soil pH and ionic species on the electro-osmotic consolidation of kaolin.

The application of an electric field on soil mass induces both electro-osmotic flow and electro-migration, which has been used for the dewatering of soft soils and remediation of contaminated soils. The physical and chemical properties of soft soils are influenced by the soil pH as well as ionic species and their concentrations, which subsequently influence the dewatering and remediation efficiency. In the present study, one-dimensional column experiments were conducted to investigate the influence of soil pH and ionic species on the electro-osmotic consolidation process of kaolin. The initial drainage rate, total volume of the discharged water and the voltage loss near the anode increased with the increase in the initial soil pH. After electro-osmosis, the water content was lower near the anode and higher near the cathode for sample with higher initial soil pH. The addition of copper ions reduced the dewatering efficiency while the addition of sodium ions increased the drainage rate and total volume of discharged water. Moreover, the precipitation of copper ions increased the voltage loss near the cathode.

Effect of soil pH on efficiency of mycorrhizal symbiosis on Salvia miltiorrhiza

By comparing the effects of soil pH on the efficiency of mycorrhizal symbiosis on Salvia miltiorrhiza， the study is aimed to provide guidance for the use of mycorrhiza in the cultivation of S. miltiorrhiza. In this experiment, the inoculant treated and the non-inoculant treated control were grown in different soil pH. The data was collected after 60 days of cultivation including rate of mycorrhizal infection, biomass, and three chemical constituents with known medicinal action. The results showed that Glomus versiforme was more apt to infect S. miltiorrhiza (F>94.00%; M>69.45%; m>73.66%) and promote the growth of S. miltiorrhiza under pH 5-9 soil. The mycorrhizal contribution to the growth of S. miltiorrhiza was the highest when grown in pH 8 soil. Plants grown with mycorrhiza in pH 8 soil had above-ground biomass more than 2 times and root biomass more than 5 times. The uninoculated plants grew better under acidic and neutral conditions, but the inoculated plants grew better under alkaline (pH 8) conditions. This result showed mycorrhiza can play a role in the adaptability of S. miltiorrhiza to the environment. Inoculation of mycorrhiza significantly increased the accumulation of rosmarinic acid, salvianolic acid B, and dihydrotanshinone by 6.59,5.03 and 2.20-folds. Based on our results alkaline soil (pH 8) is most suitable for the cultivation of S. miltiorrhiza by inoculation with the mycorrhiza G. versiforme.

Understanding the electrochemical processes at the interface of cathodically protected steel pipeline and soil during anodic transients

ABSTRACTThe steel/soil interface on cathodically protected pipeline steel has been investigated using electrochemical polarisation measurements and electrochemical impedance spectroscopy, to add more insights into the electrochemical processes occurring at the interface. A critical electrode potential (CEP) was found that divides the steel corrosion reaction kinetics into two regions. When the electrode potential is below this critical value, the steel surface has a large impedance value, indicating much slower corrosion kinetics than when the electrode potential is more positive than the CEP value. This critical value is found to be related to pitting potential determined by potentiodynamic polarisation measurements. The CEP could be affected by the CP condition and environmental, including the CP potential and the soil moisture content. At a more negative CP potential, the CEP was found to be nobler; while at the same CP potential but in the soil with a higher moisture content, the CEP became more negative. The impact of the CP potential and soil moisture level on the CEP value is explained by local soil pH effects on steel passivity.

Soil pH effects on the toxicity of zinc oxide nanoparticles to soil microbial community.

We conducted an experiment with two agricultural soils with acidic and alkaline pH levels to assess the effects of zinc oxide nanoparticles (nZnO) on the bacterial community. The effect of the nZnO concentrations (0, 0.1, 1, 10, 100, 1000mgZn/kg soil) and contact time between nanoparticles and soil (180days) was considered. We measured the microbial respiration rate, nitrogen transformation, enzymatic activities (dehydrogenase (DH), acidic phosphatase (ACP), and alkaline phosphatase (ALP)), and the community-level physiological profile (CLPP) soil parameters. Respiration potential and nitrogen transformation were negatively affected only at the highest nZnO concentration. The changes in enzymatic activities were very variable with time and between both soils. A stimulating effect of the nanoparticles on microbial activity was clearly shown at 30days after the nZnO application in both soils, except for the 1000mg/kg in calcareous soil, after which time in the latter, the functional richness of the bacterial community was reduced to virtually zero. However, values of the enzymatic activities demonstrated that there was self-adaptation of microbial communities over the study period (180days). The nZnO 1000mg/kg dose produced an increase in bacterial growth in the acidic soil, without apparent changes in their metabolic profiles over time. A good correlation was found between microbial respiration rates (calcareous and acidic soils) and microbial metabolic activity (acidic soil) based on extracted Zn concentrations. Our findings suggest the necessity of additional studies to examine the effects of nZnO in natural microorganism populations in soil with different pH levels for extended periods of time.

Effect of Soil pH on Composition and Abundance of Nitrite-oxidising Bacteria

Nitrification, the microbial oxidation of ammonia to nitrate (NO3-) via nitrite (NO2-) is a vital process in the biogeochemical nitrogen cycle and is performed by two distinct functional groups; ammonia oxidisers [comprised of ammonia oxidising bacteria (AOB) and ammonia oxidising archaea (AOA)] and nitrite oxidising bacteria. Autotrophic nitrification is said to occur in acidic soils, even though most laboratory cultures of isolated ammonia and nitrite oxidising bacteria fail to grow below neutral pH. Published studies revealed that soil pH is a major driver for determining the distribution and abundance of AOB and AOA. To determine whether distinct populations of nitrite oxidising bacteria within the lineages of Nitrospira and Nitrobacter are adapted to a particular range of pH as observed in ammonia oxidising organisms, the community structure of Nitrospira-like and Nitrobacter-like NOB were determined across a pH gradient (4.5 – 7.5) by amplifying nitrite oxidoreductase (nxrA) and 16S rRNA genes followed by denaturing gradient gel electrophoresis (DGGE). The community structure of both Nitrospira and Nitrobacter changed with soil pH, with distinct populations observed in acidic and neutral soils. The abundance of Nitrospira-like 16S rRNA and Nitrobacter-like nxrA gene copies contrasted across the pH gradient. Nitrobacter-like nxrA gene abundance decreased with increasing soil pH, whereas Nitrospira-like 16S rRNA gene abundance increased with increasing pH. Nitrification activity of both Nitrospira-like and Nitrobacter-like NOB in acidic and neutral pH soil was investigated in a microcosm experiment incubated at 30 oC for 21 days, with high rates of nitrification observed in both soils. Findings indicated that abundance and distributions of soil NOB is influence by soil pH.

Faktor – Faktor yang Mempengaruhi Bioavailabilitas Besi bagi Tumbuhan

Besi berperan penting dalam metabolisme tumbuhan, yang mana salah satunya adalah sebagai pembentuk kloroplas. Besi dibutuhkan dalam jumlah sedikit tetapi defisiensi besi dapat menyebabkan muncul bercak-bercak kuning pada daun, yang menandakan gagalnya pembentukan klorofil atau yang dikenal dengan klorosis. Oleh karena itu, besi menjadi unsur esensial atau unsur hara mikro yang keberadaannya mutlak harus dipenuhi oleh tumbuhan. Besi sangat melimpah di alam yang dijumpai dalam bentuk mineralnya. Namun, ketersediaan besi bagi tumbuhan sangat rendah. Ketersediaan besi berkaitan dengan kelarutan besi dalam larutan tanah atau air di alam. Tulisan ini akan mereview faktor - faktor yang mempengaruhi ketersedian besi bagi tumbuhan meliputi pengaruh pH air dan tanah, peran bakteri, material organik tanah dan potensial reduksi tanah atau air. Faktor-faktor ini berinteraksi menghasilkan nilai pH dan potensial reduksi(E) tertentu di air maupun di tanah. Spesi besi yang dihasilkan berdasarkan korelasi antara nilai pH dan nilai reaksi redoks lingkungan dapat diprediksi menggunakan diagram pourbaix Fe dalam air dan tanah.

The response of metabolically active Clostridium community to initial pH shift is closely correlated with microbial Fe(III) reduction in flooded paddy soils

Soil pH could be greatly affected by agriculture practices in paddy soils, in which microbial Fe(III) reduction is a prevalent and important biogeochemical process. There is increasing evidence that microbial fermentative processes can play an important role in Fe(III) reduction. In this study, the response of metabolically active Clostridium community to initial pH adjustment was investigated to elucidate the mechanism of the effects of soil pH on microbial Fe(III) reduction through fermentative microbes. Two paddy soils with different original pH were incubated anaerobically for 40 days. The initial pH of alkaline paddy soil (Baodi district; pH 7.89) was adjusted to acidic levels (approximately pH 5.2), and the initial pH of acidic paddy soil (Nanchang county; pH 5.17) was adjusted to alkaline levels (approximately pH 7.9). The abundance and the structure of metabolically active Clostridium community were measured on days 0, 1, 5, 10, 20, and 40 during anaerobic incubation. Decreasing the initial pH of alkaline paddy soil decreased the Clostridium abundance by 3.77 × 104 to 1.30 × 107 copies g−1 soil, while increasing the initial pH of acidic paddy soil decreased the Clostridium abundance by 1.25 × 108 to 1.80 × 1010 copies g−1 soil within the first 20 days. Decreased initial pH stimulated the growth of H2-producing Clostridium species, while increased initial pH was conducive to the growth of Fe(III)-reducing Clostridium species. The dynamics of the abundance and structure of Clostridium community were closely correlated with processes of hydrogen production and Fe(III) reduction. Decreased pH could inhibit Fe(III) reduction by reducing the abundance and changing the structure of Clostridium community. However, the effects of increased pH on Fe(III) reduction were not obvious as a result of stimulation of the growth of Fe(III)-reducing Clostridium species and H2 utilization ability. Decreasing the initial pH of alkaline paddy soil and increasing the initial pH of acidic paddy soil led to significant decreases in the abundances and great differences in the structures of metabolically active Clostridium community. This study further demonstrated that fermentative microbes could play an important role in Fe(III) reduction via direct and indirect effects, and their optimum pH for growth was closely related to the inherent soil pH.

The contrasting effects of N-(n-butyl) thiophosphoric triamide (NBPT) on N2O emissions in arable soils differing in pH are underlain by complex microbial mechanisms

The urease inhibitor, N-(n-butyl) thiophosphoric triamide (NBPT), has been proposed to reduce synthetic fertilizer-N losses, including nitrous oxide (N2O) emissions from agricultural soils. However, the response of N2O emission to NBPT amendment is inconsistent across soils and associated microbial mechanisms remain largely unknown. Here we performed a meta-analysis of the effects of NBPT on N2O emissions and found NBPT significantly reduced N2O emissions in alkaline soils whereas no obvious effects exhibited in acid soils. Based on the finding of meta-analysis that pH was a key modifier in regulating the effect of NBPT on N2O emissions, we selected two arable soils differing in pH and conducted a microcosm study. In conjunction with measurement of N2O emission, community structure and abundance of functional guilds were assessed using T-RFLP and qPCR. Our results showed NBPT retarded urea hydrolysis and inhibited nitrification, but stimulated N2O emission in alkaline soil, whereas it exhibited no remarkable effects in acid soil, thereby only partly confirming the results of meta-analysis. Abundances of AOB and ureC-containing bacteria decreased, while abundance of AOA increased in both soils with NBPT addition. For acid soil, N2O emissions were significantly correlated with both abundances and community structures of AOA and ureC-containing bacteria, as well as abundance of AOB; for alkaline soil, abundances and community structures of AOB were correlated with N2O emission, as well as community structures of ureC-containing bacteria and archaea, indicating an inconsistent response pattern of community traits of N2O emissions-related functional guilds to NBPT between alkaline soil and acid soil. Our findings suggest that (i) efficacy of NBPT in N2O emission was mainly influenced by soil pH and (ii) variable effects of NBPT on N2O emission might originate not only from the direct effect of NBPT on community traits of urease-positive microbes, but from the indirect effect on ammonia oxidizers.

Effect of biochar origin and soil pH on greenhouse gas emissions from sandy and clay soils

Emissions of greenhouse gases (GHGs), such as carbon dioxide (CO2) and nitrous oxide (N2O) have great impact on global warming and atmospheric chemistry. Biochar addition is a potential option for reducing GHGs emissions through carbon (C) sequestration and N2O mitigation. However, the influences of biochar on C and nitrogen (N) transformations in soil are still unclear, resulting in a poor understanding of the mechanisms of N2O mitigation effects of biochar. Here we carried out two soil incubation experiments to investigate the influence of two common biochars addition (corn cob and olive pulp) with ammonium sulfate on CO2 and N2O emissions from two contrasting soil types (acidic sandy and alkaline clay soil). Furthermore, four extracellular enzymes activities that related to C and N cycling, i.e. cellobiohydrolase, chitinase, xylanase and β-glucosidase, were analyzed to gain insights into the underlying mechanisms of biochar’s effects on CO2 and N2O evolutions. Contrasting effects of two biochars on CO2 and N2O emissions were observed in the two different soils. The corn biochar addition had no significant effect on CO2 and N2O emissions in the alkaline clay soil, but significantly decreased CO2 emissions by 11.8% and N2O emissions by 26.9% in the acidic sandy soil compared to N-fertilizer only treatment. In contrast, olive biochar addition showed no significant effect on CO2 emissions but decreased N2O emissions by 34.3% in the alkaline clay soil, while in the acidic sandy soil addition of olive biochar triggered about a twofold higher maximum CO2 emission rate and decreased N2O emissions by 68.4%. Up to 50–130% higher specific CO2 emissions (per unit of C-related enzyme activity: cellobiohydrolase, chitinases and β-glucosidase) were observed after addition of olive biochar compared to corn biochar addition in the acidic sandy soil. We concluded that biochar’s effects on N2O and CO2 emissions are more pronounced in acidic soils. Alkaline biochar’s N2O mitigation potential in acidic soils seems to be dependent on soil NO3− content as drastically higher N2O emissions were measured in early phase of the experiment (where soil NO3− was high) and significantly lower N2O fluxes were obtained in later phases (with lower soil NO3− content).

Nitrogen additions inhibit nitrification in acidic soils in a subtropical pine plantation: effects of soil pH and compositional shifts in microbial groups

Plantation forests play a pivotal role in carbon sequestration in terrestrial ecosystems, but enhanced nitrogen (N) deposition in these forests may affect plantation productivity by altering soil N cycling. Hence, understanding how simulated N deposition affects the rate and direction of soil N transformation is critically important in predicting responses of plantation productivity in the context of N loading. This study reports the effects of N addition rate (0, 40, and 120 kg N ha−1 a−1) and form (NH4Cl vs. NaNO3) on net N mineralization and nitrification estimated by in situ soil core incubation and on-soil microbial biomass determined by the phospholipid fatty acid (PLFA) method in a subtropical pine plantation. N additions had no influences on net N mineralization throughout the year. Net nitrification rate was significantly reduced by additions of both NH4Cl (71.5) and NaNO3 (47.1%) during the active growing season, with the stronger inhibitory effect at high N rates. Soil pH was markedly decreased by 0.16 units by NH4Cl additions. N inputs significantly decreased the ratio of fungal-to-bacterial PLFAs on average by 0.28 (49.1%) in November. Under NH4Cl additions, nitrification was positively related with fungal biomass and soil pH. Under NaNO3 additions, nitrification was positively related with all microbial groups except for bacterial biomass. We conclude that simulated N deposition inhibited net nitrification in the acidic soils of a subtropical plantation forest in China, primarily due to accelerated soil acidification and compositional shifts in microbial functional groups. These findings may facilitate a better mechanistic understanding of soil N cycling in the context of N loading.

Managing the interactions between soil abiotic factors to alleviate the effect of Fusarium wilt in bananas

Soil management offers various options to alleviate the effects of Fusarium wilt caused by Fusarium oxysporum f. sp. cubense (Foc) in bananas. Nevertheless, it receives little attention as a strategy in Fusarium wilt management. Literature provides ample evidence linking soil conditions such as soil texture and fertility to the spread and severity of plant diseases. However, the inconsistency of results between case studies limits the attention of soil management in crop disease management. The present study aimed at unravelling the role of soil abiotic factors on nutrient concentrations in plant tissue, biomass production and the incidence of Fusarium wilt (Foc race 1) in bananas ('Gros Michel', AAA) under field conditions. A large field trial was established in which the effects of soil pH and nutrients (N, Ca, Mg and Mn) were studied. Around 30% of the plants showed symptoms of Fusarium wilt at flowering in the first season. However, Fusarium wilt incidence did not vary between treatments. Soil pH showed significant interactions with soil N and Mn concentrations resulting in a lower bunch weight and increased micronutrient concentrations in the pseudostem. With a higher pH, bunch weight increased, although higher Mn concentrations suppressed this positive effect. Interactions between a high soil pH and Ca and Mg resulted in a higher bunch weight and lower micronutrient concentrations in the pseudostem. The results can be used to develop soil management strategies for improving banana productivity in infected plantations.

Tebuthiuron leaching in three Brazilian soils as affected by soil pH

Underground contamination water by herbicides depends on the interactions between their molecules with physical and chemical soil characteristics and climatic conditions. Studies with columns can estimate the leaching potential of herbicides in soils. This study aimed to determine the effect of soil pH on tebuthiuron leaching, and capacity of bioindicators to detect tebuthiuron residues in three Brazilian soils. Cucumber plants (Cucumis sativus) were more negatively affected when grown in soils with lower amounts of organic matter and clay, and in these soils, the tebuthiuron levels reached greater depths in the column. There was a positive correlation between tebuthiuron concentration and cucumber intoxication, and a negative correlation between tebuthiuron concentration and dry matter cucumber in all soils. The tebuthiuron leached up to 50 cm depth even in soils with higher organic matter and clay content. The increasing of soil pH can affect the leaching of nonionic herbicides, and liming practice may elevate the environmental contamination risk by tebuthiuron. The bioindicator method using Cucumis sativus is viable and can be recommended to detect tebuthiuron concentrations above 0.2 mg kg−1.