Total Base Cations Research Articles

Mineral Components, Organic Matter Quality and Soil Enzymatic Activity under the Influence of Differentiated Farmyard Manure and Nitrogen Fertilisation

Research was carried out on the impact of long-term use of cattle manure (30 t ha−1 FYM) and various doses of N (0, 40, 60 and 120 t ha−1) in the form of ammonium nitrate on the following soil parameters: salinity, hydrolytic acidity, total exchangeable base cations, cation exchange capacity, degree of base saturation of the sorption complex, total organic carbon and total nitrogen content, dissolved organic matter, fractional composition of organic matter and content of bioavailable macroelements: phosphorus, potassium and magnesium in the soil of a multi-year static field experiment. The activities of dehydrogenases, catalase, alkaline and acid phosphatase and proteases were also tested. A significant effect of FYM and N fertilisation on the content of bioavailable macroelements was found. The application of manure at a dose of 30 t ha−1 mitigated the negative effects of the application of N at a dose of 120 kg ha−1. A higher content of total organic carbon (8.42 g kg−1) and humic acid fraction (1761 mg kg−1) and higher values of the CHA/CFA ratio (0.79; parameters that are indicators of soil quality) were found in the soil fertilised with manure compared to the soil without manure added (TOC—7.00 g kg−1; CHAs—1285 mg kg−1; CHAs/CFAs 0.66). The activity of the tested enzymes was also significantly determined by the applied fertilisation. Enzyme activity was highest in the soil to which manure had been applied. Nitrogen fertilisation varied in its impact on the activity of enzymes according to the specifics of each enzyme. The content of humic acids and CHA/CFA values correlated positively with the content of soil minerals and the activity of dehydrogenases, catalase, alkaline and acid phosphatase and GMea and TEI indices. Dehydrogenases and acid phosphatase can be considered enzymes that take part in transforming organic matter towards the formation of FAs.

Quantifying exchangeable base cations in permafrost: a reserve of nutrients about to thaw

Abstract. Permafrost ecosystems are limited in nutrients for vegetation development and constrain the biological activity to the active layer. Upon Arctic warming, permafrost thaw exposes large amounts of soil organic carbon (SOC) to decomposition and minerals to weathering but also releases organic and mineral soil material that may directly influence the soil exchange properties (cation exchange capacity, CEC, and base saturation, BS). The soil exchange properties are key for nutrient base cation supply (Ca2+, K+, Mg2+, and Na+) for vegetation growth and development. In this study, we investigate the distributions of soil exchange properties within Arctic tundra permafrost soils at Eight Mile Lake (Interior Alaska, USA) because they will dictate the potential reservoir of newly thawed nutrients and thereby influence soil biological activity and vegetation nutrient sources. Our results highlight much lower CEC density in surface horizons (∼9400 cmolc m−3) than in the mineral horizons of the active layer (∼16 000 cmolc m−3) or in permafrost soil horizons (∼12 000 cmolc m−3). Together, with the overall increase in CEC density with depth and the overall increase in BS (percentage of CEC occupied by exchangeable base cations Ca2+, K+, Mg2+, and Na+) with depth (from ∼19 % in organic surface horizons to 62 % in permafrost soil horizons), the total exchangeable base cation density (Ca2+, K+, Mg2+, and Na+ in g m−3) is up to 5 times higher in the permafrost than in the active layer. More specifically, the exchangeable base cation density in the 20 cm upper part of permafrost about to thaw is ∼850 g m−3 for Caexch, 45 g m−3 for Kexch, 200 g m−3 for Mgexch, and 150 g m−3 for Naexch. This estimate is needed for future ecosystem prediction models to provide constraints on the size of the reservoir in exchangeable nutrients (Ca, K, Mg, and Na) about to thaw. All data described in this paper are stored in Dataverse, the online repository of Université catholique de Louvain, and are accessible through the following DOI: https://doi.org/10.14428/DVN/FQVMEP (Mauclet et al., 2022b).

Intensity and Duration of Nitrogen Addition Jointly Alter Soil Nutrient Availability in a Temperate Grassland

AbstractIncreasing N input can alter soil nutrient availability and influence plant growth. Previous studies focused on N addition effects on N and P availability, while less on other mineral nutrients. Besides, how N addition duration affects nutrient availability has remained unclear. Based on a simulative N deposition experiment in a typical steppe with four N addition levels (0, 2, 10, and 50 g m−2 yr−1) under three N addition duration (2, 5, and 10 years), we determined contents of 10 mineral nutrients in surface soils. In the 0–10 cm soil, short‐term N addition (2‐year) significantly increased exchangeable Ca (+7.2%) and decreased exchangeable Mg (−22.5%) as compared with the control, while decreased available Fe, Cu, and Zn, but increased Mn remarkably (+80.4%). Medium‐term N addition (5‐year) significantly raised soil total N and available Fe, Mn and Cu, while decreased total P and exchangeable Ca, Na and Mg. The response patterns of these nutrients were largely similar in the 10–20 cm soil, but were weaker and significant only at high N inputs (50 g m−2 yr−1). Long‐term N addition (10‐year) significantly decreased contents of total base cations (K, Ca, Na, Mg) and micronutrients (Fe, Mn, Cu, Zn) by an average of 32.1% and 20.4%, respectively, across the two soil depths. Influences of pH and plant growth on micronutrients showed remarkable differences among different duration of N addition. These findings indicate that intensity and duration of N addition jointly alter soil nutrient availability and this should be considered in soil nutrient‐cycling modeling.

Net Geochemical Release of Base Cations From 25 Forested Watersheds in the Catskill Region of New York

Chemical weathering of minerals is the principal mechanism by which base cations (Ca2+, Mg2+, K+, and Na+) are released and acidity is neutralized in soils, bedrock, and drainage waters. Quantifying the release of base cations from watershed soils is therefore crucial for the calculation of “critical loads” of atmospheric acidity to forest ecosystems. We used a mass-balance approach to estimate the rate of release of base cations in 25 headwater catchments in the Catskill region of New York, an area historically subject to high inputs of acid deposition. In 2010–2013, total net base cation release via geochemical processes averaged 1,704 eq ha–1 yr–1 (range: 928–2,622). Calcium accounted for 58% of this total, averaging 498 mol ha–1 yr–1 (range: 209–815). Mass balance estimates of net geochemical release of base cations were most strongly driven by stream export and biomass uptake fluxes, with only minor contributions from precipitation. Documented rates of base cation depletion from soil exchange sites in the region were also small relative to the net geochemical release rates. We observed a significant influence of bedrock type on net base cation release rates (P = 0.002), and a weak but significant negative correlation with watershed elevation (r = −0.51). Relationships with other geographic factors such as aspect and watershed size were not significant. Net base cation release was 4.5 times higher than precipitation inputs of SO42– and NO3–, suggesting that sources of acidity internal to the watershed are now more important drivers of weathering than acid deposition. Our data suggest that release of base cations from most Catskill forest soils is sufficient to neutralize existing inputs of acidity.

Termite mound soil properties in West Bengal, India

Termites are ecosystem engineers, they play a major role in the biotransformation and modification of soil physicochemical and morphological properties. This study was conducted to evaluate the explored and compared physicochemical and morphological characteristics of soil between termite mounds and surrounding surface soil. Therefore, this study, especially emphasizes the impacts of the mound soil on the surrounding surface soil properties and also to find out the difference between the mound soil properties and surrounding surface soil properties at different soil depth, and characteristic of termite mounds. This study unveils that mound soil properties are directly proportional to the surrounding surface soil properties except for porosity and dispersion ratio. But mound soil properties are not significantly affecting all surface soil properties. The termites have a significant role to change soil physicochemical and morphological properties and there is a significant difference in soil physicochemical properties between mound and surrounding surface soil. However, relatively greater bulk density, clay content, soil pH, organic carbon, nitrogen, exchangeable calcium, exchangeable magnesium, exchangeable sodium, total exchangeable base cations and cation exchange capacity in mound soil than surrounding surface soil. But the relatively lesser value of porosity, dispersion ratio, exchangeable potassium, phosphorus, exchangeable acidity, and C: N ratio is found in mound soil than surrounding surface soil. Conical shaped mounds have greater nutrient concentration than surrounding surface soil. It also highlighted that most of the termite mound consists of trees and bushes containing 8–21 hole or chamber. The termite mounds have granular structure and particle shape are rounded to subrounded, which make them different from surrounding areas. This study suggests and statistically prove that termites have a significant effect on soil properties, they produce physicochemically more quality soil and have an influence on surrounding soil properties.

PH and exchangeable aluminum are major regulators of microbial energy flow and carbon use efficiency in soil microbial communities

The microbial partitioning of organic carbon (C) into either anabolic (i.e. growth) or catabolic (i.e. respiration) metabolic pathways represents a key process regulating the amount of added C that is retained in soil. The factors regulating C use efficiency (CUE) in agricultural soils, however, remain poorly understood. The aim of this study was to investigate substrate CUE from a wide range of soils (n = 970) and geographical area (200,000 km2) to determine which soil properties most influenced C retention within the microbial community. Using a 14C-labeling approach, we showed that the average CUE across all soils was 0.65 ± 0.003, but that the variation in CUE was relatively high within the sample population (CV 14.9%). Of the major properties measured in our soils, we found that pH and exchangeable aluminum (Al) were highly correlated with CUE. We identified a critical pH transition point at which CUE declined (pH 5.5). This coincided exactly with the point at which Al3+ started to become soluble. In contrast, other soil factors [e.g. total C and nitrogen (N), dissolved organic C (DOC), clay content, available calcium, phosphorus (P) and sulfur (S), total base cations] showed little or no relationship with CUE. We also found no evidence to suggest that nutrient stoichiometry (C:N, C:P and C:S ratios) influenced CUE in these soils. Based on current evidence, we postulate that the decline in microbial CUE at low pH and high Al reflects a greater channeling of C into energy intensive metabolic pathways involved in overcoming H+/Al3+ stress (e.g. cell repair and detoxification). The response may also be associated with shifts in microbial community structure, which are known to be tightly associated with soil pH. We conclude that maintaining agricultural soils above pH 5.5 maximizes microbial energy efficiency.

An approach at estimating present day base cation weathering rates: a case study for the Hermine watershed, Canada

A new methodological approach is described for estimating Ca, Mg and K fluxes from soil mineral weathering. This method combines Na flux in surface waters in the Hermine watershed with base cation (BC) concentrations to Na molar ratios from the soil weatherable pool obtained using sequential extraction method. Comparison of BC:Na molar ratios of the weatherable pool with those from other compartments of the watershed suggests possible accumulation of base cations in some areas of the watershed, while losses or minimal changes are observed in others. On average, present day Na weathering rates estimated using the watershed input–output budget method was 0.26 (range 0.16–0.36) kmolc ha−1 yearr−1, over the period of 1995–2006. For Ca, Mg and K, present day weathering rates estimated with the new methodological approach averaged 0.44 (range 0.27–0.60), 0.11 (range 0.07–0.15) and 0.02 (range 0.01–0.02) kmolc ha−1 year−1, respectively. These values are within the range of present day rates previously calculated for the same site and for forested soils from similar granitic environments using other methods. Candidate models for predicting BC weathering rates on individual annual observations were developed using Akaike’s information criterion. The best model includes the number of frost days (inverse relationship) and explained 51% of the variation in total BC weathering rates. The newly developed method may be applicable to other watersheds, providing yearly estimates of nutrient BC at the watershed scale.

Polycyclic Aromatic Hydrocarbons Content in Contaminated Forest Soils with Different Humus Types

The aim of the study was to determine polycyclic aromatic hydrocarbon (PAH) content in different forest humus types. The investigation was carried out in Chrzanów Forest District in southern Poland. Twenty research plots with different humus types (mor and mull) were selected. The samples for analysis were taken after litter horizons removing from a depth of 0–10 cm (from the Of- and Oh-horizon total or A-horizon). pH, organic carbon and total nitrogen content, base cations, acidity, and heavy metal content were determined. In the natural moisture state, the activity of dehydrogenase was determined. The study included the determination of PAH content. The conducted research confirms strong contamination of study soil by PAHs and heavy metals. Our experiment provided evidence that different forest humus types accumulate different PAH amounts. The highest content of PAHs and heavy metals was recorded in mor humus type. The content of PAHs in forest humus horizon depends on the content and quality of soil organic matter. Weaker degradation of hydrocarbons is associated with lower biological activity of soils. The mull humus type showed lower content of PAHs and at the same time the highest biological activity confirmed by high dehydrogenase activity.

Can highly saline irrigation water improve sodicity and alkalinity in sodic clayey subsoils?

The concept of irrigating crops with saline irrigation water is not new, but impacts of this practice on soil properties remain debatable, particularly the use of highly saline water. In this work, key soil chemical properties were assessed to a depth of 300 cm following 2.5 years of application of highly saline irrigation to a sodic texture-contrast soil (Brown Sodosol) in south-eastern Tasmania, Australia. Control plots (rainfall only) were compared to irrigation treatments of low (0.8 dS/m) and high salinity (16 dS/m) waters at application rates of both 200 and 800 mm/year. Whilst significant increases in both electrical conductivity and chloride concentration occurred throughout the soil profile in the high salinity treatment, these values were well below those of the irrigation water, indicating effective deep leaching. In the upper soil profile, 0–50 cm, of the high salinity treatments both the exchangeable Na+ and its ratio to total base cations (ESP) were significantly increased whilst the lower soil profile between 50 and 200 cm, was improved via both reduced alkalinity and sodicity. Leaching of the exchangeable base cations Ca2+, Mg2+ and K+ was significant in the upper soil profile (0–50 cm). As expected, the low salinity treatment (0.8 dS/m) had minimal impacts on soil chemical properties. The upper topsoil (0–10 cm) total organic carbon was significantly reduced in the high salinity plots and was negatively correlated with Cl− concentration. The data confirms the general concerns about application of saline irrigation, namely increased whole profile salinisation and upper soil profile (0–50 cm) sodicity, but they also show unexpected and desirable reductions in the lower soil profile (> 50 cm) alkalinity and sodicity. It appears the Na+ ions present in the saline waters led to differential leaching of base cations from the rooting zone, especially Ca2+ which then ameliorate the alkalinity and sodicity deeper in the soil profile (> 50 cm). Thus, surface application of gypsum may help sustain the application of highly saline waters; alternatively, subsurface irrigation above the sodic clayey subsoils could be trailed.

Aluminum Detoxification by Humic Substance Extracted from Compost of Organic Wastes

Aluminum Detoxification by Humic Substance Extracted from Compost of Organic Wastes (S Winarso, E Handayanto and A Taufiq): Humic substance could control the activity of metal as well as exchangeable aluminum (Alexch) on acid soil. The humic substance extracted from compost of agricultural waste is rarely conducted. The objective of research was to evaluate the effect of humic substance concentration and sources to pH and Al suspension. The research had been conducted in the Soil Laboratory of Agricultural Faculty of Jember University from April to July 2009. The humic substance used in these researches was extracted from compost of rice straw (RS), soybean straw (SS), cassava starch solid waste (CSSW), and empty bunch of oil palm tree (EBOPT). The humic substance concentration treatments were 0, 10, 20, 30, 40, 50, 75, 100, 150, 200, 250, and 300 ppm. Result of the analysis showed that characteristic of humic substance was difference depending on the source material used. The humic substance extracted from SS contain total base cations (K, Na, Ca, Mg) higher (1.17%) compared with CSSW (1.07%), OPT (0.87%), and RS (0.69%). While the humic substances extracted from RS contain total organic acid (Acetic, Fumeric, cetoglutamic, Sucsinic, Propionic, Butiric, Ocsalic, and sitric acid) higher (157 ppm) compared with EBOPT (129 ppm), SS (115%), and CSSW (108%). Among these organic acids, acetic acid was highest concentration (> 34.51% of total acid). The addition of humic substance increased pH and decreased aluminum concentration of the suspension. The higher pH increment and Al concentration reduction took placed in the suspension treated with humic substance from SS compost. The correlation between decreasing Al concentration with humic substance concentration which explained chelation was higher (r = 0.97) than decreasing Al concentration with increasing pH which explained precipitation (r = 0.93). Based on these research results, it can be concluded that humic substance extracted from agricultural waste have a good prospect as a soil ameliorant to increase soil pH, detoxify soil aluminum, and increase soil P availability on acid soil.

Evaluation of the addition of immobilizing agents on selected physicochemical properties of soil contaminated with heavy metals

This study was aimed at determining effects of increasing simultaneous contamination of soil with Pb and Zn at doses of 200, 400 and 800 mg·kg -1 and with Cd at doses of 5, 10 and 20 mg·kg -1 soil, after the addition of immobilizing agents (zeolite, diatomite, chalcedonite, dolomite, limestone, and activated carbon), on selected properties of soil. In the soil without the immobilizing agents, the highest doses of metals caused a decrease in pH value, total sorption capacity, total exchangeable base cations and saturation of the sorption complex with base cations as well as an increase in hydrolytic acidity and electrical conductivity of the soil. Among the agents applied, dolomite and activated carbon exerted a positive effect on the analyzed properties of soil, as they contributed to an increase in pH value, total exchangeable bases, and total sorption capacity, and to a decrease in hydrolytic acidity of the soil. The addition of zeolite caused soil electrical conductivity to decrease compared to the control pot, at all levels of soil contamination with Pb, Cd, and Zn.

The impact of restoration processes on the selected soil properties and organic matter transformation of mountain fens under Caltho-Alnetum community in the Babiog\xf3rski National Park in Outer Flysch Carpathians, Poland

PurposeThe objective of this study was to determine the impact of restoration processes on the selected soil properties and organic matter transformation of mountain fens under the Caltho-Alnetum community in the Babiogórski National Park in Outer Flysch Carpathians.Materials and methodsRestoration processes were conducted on three degraded mountain fens in the Babiogórski National Park in Outer Flysch Carpathians, Poland. The degradation degree of soils was the criterion for the selection of habitats for further studies. To determine the influence of restoration processes on mountain fen soil properties and organic matter transformation, samples were collected in 2011 and 2013. The soil samples were assayed for pH, base cation concentration, hydrolytic acidity, organic carbon and total nitrogen content, total exchangeable base cation concentration, cation exchange capacity, and base saturation. Organic matter fractions were extracted by IHSS method. Quantitative and qualitative study of organic matter was based on fraction composition analysis and the ratio of humic acid carbon to fulvic acid carbon. The research results were statistically verified.Results and discussionBased on morphological and chemical properties, the studied mountain fen soils can be classified as Sapric Dranic Eutric Histosols and Sapric Dranic Dystric Histosols according to WRB guidelines (2015). Before restoration processes, the mountain fen soils subjected to a different water regime showed various contents of total nitrogen and organic carbon. The decreasing of the groundwater level was reflected in pH, calcium ion content, exchangeable base cation concentration, and base saturation. The increase of the groundwater level had influence on chemical properties of mountain fen soils such as pH, total exchangeable base cation concentration, hydrolytic acidity, cation exchange capacity, and base saturation. Three-year restoration processes did not cause significant changes in the composition of humic substance fractions.ConclusionsMountain fens under Caltho-Alnetum community are priority habitats in Babiogórski National Park in Outer Flysch Carpathians, Poland. These habitats responded to restoration processes in varying degrees depending on the extent of their degradation. The least degraded mountain fen was characterized by a short response time on the restoration processes. The reaction of higher degraded habitats was weaker.

Influence of nitrogen fertilizer forms and crop straw biochars on soil exchange properties and maize growth on an acidic Ultisol

ABSTRACTEffects of repeated application of urea (UN) and calcium nitrate (CN) singly and together with crop straw biochars on soil acidity and maize growth were investigated with greenhouse pot experiments for two consecutive seasons. Canola straw biochar (CB), peanut straw biochar (PB) and wheat straw biochar (WB) were applied at 1% of dried soil weight in the first season. N fertilizers were applied at 200 mg N kg−1. In UN treatments, an initial rise in pH was subjected to proton consumption through urea hydrolysis, afterwards nitrification of NH4+ caused drastic reductions in pH as single UN had soil pH of 3.70, even lower than control (4.27) after the 2nd crop season. Post-harvest soil analyses indicated that soil pH, soil exchangeable acidity, NH4+, NO3− and total base cations showed highly significant variation under N and biochar types (P < 0.05). Articulated growth of plants under combined application with biochars was expressed by 22.7%, 22.5%, and 35.7% higher root and 25.6%, 23.8%, and 35.9% higher shoot biomass by CB, PB and WB combined with CN over UN, respectively. Therefore, CN combined with biochars is a better choice to correct soil acidity and improve maize growth than UN combined with biochars.

Impacts of long-term nitrogen fertilization on acid buffering rates and mechanisms of a slightly calcareous clay soil

Acidification of cropland soils is a serious problem in China that may cause long term pH decline, which threatens the sustainability of soil fertility and crop yields. The objective of this research was to investigate those rates and mechanisms for a slightly calcareous soil. The field data were based on selected treatments from a long-term (1991–2015) N fertilization experiment at a rice-wheat rotation on a slightly calcareous (pH7.7), young and hardly weathered clay soil (Regosol), including two plots with urea and NH4Cl fertilization and a control plot (no N fertilization). Urea and NH4Cl were applied at annual rates of 300kg (1991–1996) and 285kg (1997–2015) N ha−1. Soil pH and exchangeable Ca2+ and Mg2+ declined in the first 12years for the urea treatments, but remained constant thereafter. For the NH4Cl and control treatment, the exchangeable base cations showed an oscillating decrease over the 25years. Soil pH and exchangeable Ca2+, and Mg2+ levels were significantly (P<0.05) lower in the NH4Cl treatment plot than the control. After 25years, soil pH in the plots receiving urea and NH4Cl were 0.9 and 2.0 units lower than the control, respectively, while the total exchangeable base cations were about 10% and 16% lower, respectively. Carbonate dissolution, base cation exchange and mineral weathering were the main H+ buffer pathways of the Regosol. Long-term N fertilization favored the formation of smectite and vermiculite and accelerated the weathering of mica, potassium feldspar, and illite. This was more evident in the NH4Cl treatment than in the urea treatment. Consequently, the soil acid-buffering capacity was slightly enhanced after year 13 in the order of urea>control>NH4Cl. The increased weathering of soil primary minerals and clay minerals was the main reason that soil pH and exchangeable base cations stayed constant after about 12years.

Foliage Chemistry of Pinus baksiana in the Athabasca Oil Sands Region, Alberta, Canada

Industrial emissions in the Athabasca Oil Sands Region (AOSR), Alberta, Canada, have caused concerns about the effect of oil sands operations on the surrounding terrestrial environments, including jack pine (Pinus banksiana Lamb.) stands. We collected jack pine needles from 19 sites in the AOSR (13–128 km from main operations) for foliar chemical analyses to investigate the environmental impact on jack pine. Pine needles from three age classes, the current annual growth (CAG, 2011), one year and two year old pine needles, were collected. Samples were analyzed for total carbon (TC), nitrogen (TN), and sulfur (TS), inorganic S (SO4-S), base cations (Ca, Mg, Na), and other elements (B, Cu, Fe, Mn, P, Zn); CAG needles were also analyzed for their nitrogen and carbon isotopic compositions. Only TN, TS, Ca, B, Zn, and Fe contents showed weak but significant increases with proximity to the major oil sands operations. C and N isotopic compositions showed no trend with distance or TC and TN contents. Total S contents in CAG of pine foliage increased significantly with proximity to the main industrial operation while foliar inorganic S to organic S ratios (SO4-S/Sorg) ranged consistently between 0.13 and 0.32, indicating low to moderately high S loading. Hence, this study suggests some evidence of uptake of S emissions in close proximity to anthropogenic sources, although the reported values have not reached a level of environmental concern.

Evaluation of three methods for estimating the weathering rates of base cations in forested catchments

This paper investigates three techniques that are commonly used to generate estimates of base cation (BC) weathering rates, i.e. the profile mass balance (PEDON), the watershed input-output budget (WATERSHED) and the PROFILE model (MODEL). These methods were compared for their relative performance in estimating BC weathering rates for 21 watersheds located in southern Quebec that vary with respect to hydro-climatic conditions, soil properties and forest cover. Average total BC weathering rates for the 21 watersheds were 0.41±0.09 (±SE), 1.20±0.17 and 1.71±0.22kmolcha−1yr−1 for PEDON, WATERSHED and MODEL, respectively. Passing and Bablok regression analysis demonstrated good agreement between WATERSHED and MODEL {regression formula: WATERSHED=−0.08+0.74 MODEL, with 95% CI for intercept [−1.13; 0.25] and for slope [0.40; 1.43]}, while poorer agreements were observed between these two methods and PEDON. Contrary to the WATERSHED and the MODEL methods, BC weathering rates obtained with PEDON were not significantly associated with the spatial variation of the soil calcite content and of the size of the soil exchangeable BC pools. We hypothesized that in the calcite-containing watersheds, the performance of PEDON was negatively impacted by environmental conditions that favored the partial dissolution and leaching of the calcite contained in the initial parent material, including in the material situated at the base of the profile (C horizon).

The effect of biochar loading rates on soil fertility, soil biomass, potential nitrification, and soil community metabolic profiles in three different soils

Biochar is increasingly being used as a soil amendment to both increase soil carbon storage and improve soil chemical and biological properties. To better understand the shorter-term (10 months) impacts of biochar on selected soil parameters and biological process in three different textured soils, a wide range of loading rates was applied. Biochar derived from eucalypt green waste was mixed at 0, 2.5, 5, 10 % (wt/wt) with a reactive black clay loam (BCL), a non-reactive red loam (RL) and a brown sandy loam (BSL) and placed in pots exposed to the natural elements. After 10 months of incubation, analysis was performed to determine the impacts of the biochar rates on the different soil types. Also, microbial biomass was estimated by the total viable counts (TVC) and DNA extraction. Moreover, potential nitrification rate and community metabolic profiles were assayed to evaluate microbial function and biological process in biochar-amended soils. The results showed that biochar additions had a significant impact on NH4 and NO3, total C and N, pH, EC, and soil moisture content in both a soil type and loading-dependent manner. In the heavier and reactive BCL, no significant impact was observed on the available P and K levels, or the total exchangeable base cations (TEB) and CEC. However, in the other lighter soils, biochar addition had a significant effect on the exchangeable Al, Ca, Mg, and Na levels and CEC. There was a relatively limited effect on microbial biomass in amended soils; however, biochar additions and its interactions with different soils reduced the potential nitrification at the higher biochar rate in the two lighter soils. Community metabolic profile results showed that the effect of biochar on carbon substrate utilization was both soil type and loading dependent. The BCL and BSL showed reduced rates of substrate utilization as biochar loading levels increased while the opposite occurred for the RL. This research shows that biochar can improve soil carbon levels and raise pH but varies with soil type. High biochar loading rates may also influence nitrification and the function and activity of microbial community in lighter soils.

Historical Mining Signatures: Geochemical and Mineralogical Evaluation of Sediments in three Coastal–Estuarine Systems

The X-ray fluorescence (XRF) of the inter-tidal sediments in Hayle, Gannel and Camel estuaries in southwest England’s coasts are examined here to evaluate and compare the broad geochemistry of each of the three systems. The total base cation content (Na, Mg and K) of the samples in all of the estuaries is 5% while the Ca is ~>20%. In terms of sub-environment significance, the estuarine and inlet sediments of Hayle exhibit a high content of Ca than the coastal/beach samples while both the Gannel’s estuarine and beach samples exhibit ~25% of Ca composition. There is high variation in the dimension of Ca in the different sub-environments sampled in Camel estuary (outerestuary – 25-28%, mid-estuary - ~20%, inner – 30%). The Al and Fe contents in all of the sites are below 2% except in Camel where Al is around 3.5%. There clear difference in the percentage of composition of trace elements among the estuaries is also evident. Sn’s concentration in Hayle is higher than that of Camel and Gannel. Pb, Ba, Zr and Zn is significant in all of the estuaries at various degrees - Pb and Zn are abundant in Gannel, while Sn, W, Zr prominent in Camel. The significant effect of the release of the particulate mine waste are observed in the samples’ mineralogical composition despite the cessation of the mine activities in the 19th/early 20th Century, suggesting that these elements are still bio-available and bio-active for riverine processes to transport/migrate in the estuary–coast interaction.

Long-term tobacco plantation induces soil acidification and soil base cation loss.

Changes in soil exchangeable cations relative to soil acidification are less studied particularly under long-term cash crop plantation. This study investigated soil acidification in an Ali-Periudic Argosols after 10-year (2002-2012) long-term continuous tobacco plantation. Soils were respectively sampled at 1933 and 2143 sites in 2002 and 2012 (also 647 tobacco plants), from seven tobacco plantation counties in the Chongqing Municipal City, southwest China. After 10-year continuous tobacco plantation, a substantial acidification was evidenced by an average decrease of 0.20 soil pH unit with a substantial increase of soil sites toward the acidic status, especially those pH ranging from 4.5 to 5.5, whereas 1.93 kmol H(+) production ha(-1) year(-1) was mostly derived from nitrogen (N) fertilizer input and plant N uptake output. After 1 decade, an average decrease of 27.6 % total exchangeable base cations or of 0.20 pH unit occurred in all seven tobacco plantation counties. Meanwhile, for one unit pH decrease, 40.3 and 28.3 mmol base cations kg(-1) soil were consumed in 2002 and 2012, respectively. Furthermore, the aboveground tobacco biomass harvest removed 339.23 kg base cations ha(-1) year(-1) from soil, which was 7.57 times higher than the anions removal, leading to a 12.52 kmol H(+) production ha(-1) year(-1) as the main reason inducing soil acidification. Overall, our results showed that long-term tobacco plantation not only stimulated soil acidification but also decreased soil acid-buffering capacity, resulting in negative effects on sustainable soil uses. On the other hand, our results addressed the importance of a continuous monitoring of soil pH changes in tobacco plantation sites, which would enhance our understanding of soil fertility of health in this region.

Soils of temperate rainforests of the North American Pacific Coast

Temperate rainforests have high conservation and natural resource value, but the soils of this bioregion have not previously been studied as a unit. Here we examine the soils of North America's Pacific coastal temperate rainforests, utilizing databases from the United States Natural Resources Conservation Service and the Canadian Centre for Land and Biological Resources Research to (i) identify the soil taxa, (ii) evaluate the soil properties, and (iii) compare soils in temperate and tropical rainforests. There are strong climate gradients within these temperate rainforests, with the mean temperature declining from 11.7°C to 6.1°C and the mean annual precipitation increasing from 1500mm to around 3000mm from northern California (CA) to northwestern British Columbia (BC) and southeastern Alaska (AK). There is also high pedodiversity in this region, with soils representing 8 orders and 31 suborders, and, in the US portion, 65 great-groups, 142 subgroups, and 482 soil series. Twenty-six percent of described soil series are endemic to temperate rainforests in the US portion of the region, with the proportion declining with latitude. Dominant soil suborders vary along the latitudinal gradient from Humults–Udalfs/Ustalfs–Udepts–Udults in CA, to Udands–Udepts–Udands Humults in western Oregon (OR) and Washington (WA), to Orthods–Folists in BC and Cryods–Saprists in AK. The dominant diagnostic horizons are ochric/argillic (CA), umbric/cambic (OR, WA), and albic–histic/spodic (BC, AK). Whereas soils in CA, BC, and AK tend to have a mixed mineralogy, those in northern OR and WA commonly are derived from volcaniclastic materials and have a ferrihydritic or isotic mineralogy. Soils in this region are generally deep, hold abundant moisture, are not subject to deep-freezing, and are enriched in extractable Fe and Al. Organic C and total N contents are high overall, but also variable, with right-skewed distributions. Compared to tropical rainforest soils in the Pacific Basin, Pacific temperate rainforest have greater weatherable minerals, cation-exchange capacities, soil organic C, and total exchangeable base cations. However, soils of both bioregions tend to be deep, acidic Al-saturated, and can have large N reservoirs. This investigation provides a foundation for a more unified understanding of the soils of a globally significant bioregion.