Available potassium in volcanic soils of Kamchatka

The distribution of available potassium in the profiles of synlithogenic volcanic soils of Kamchatka has been studied. Most of the soils in the Central Kamchatka Depression and the Western Kamchatka Lowland are characterized by a medium content of nonexchangeable potassium and a high content of exchangeable potassium. The soils of the east coast are less rich in potassium. The reserves of available potassium in the root layer of the virgin and cultivated soils of Kamchatka have been calculated. It is shown that differences in the reserves of potassium are related to different degrees of the soil tolerance toward the depletion of potassium and to the uneven application of potassium fertilizers. In most cases, soil cultivation is accompanied by a general rise in the reserves of available potassium with an increase in the portion of exchangeable potassium relative to its nonexchangeable forms.     

Geochemical specificity of volcanic soils of Kamchatka

The microelemental composition of volcanic soils of Kamchatka is specified by the composition of the volcanic ashes from which these soils are developed. It is found that the soils developing from acid and intermediate ashes are characterized by low contents of most of the studied microelements as compared with their clarke values in soils of the world. The background concentrations of microelements in the soils developed from intermediate ashes of Kamchatka are higher than those in the soils developed from acid pyroclastic deposits. Differences in the microelemental composition of the soils developed from different ashes are seen against the regional background specificity of the volcanic soils of Kamchatka. These soils are enriched in the elements typical of mafic magnetic rocks. In particular, this concerns Cu, Mn, Sc, V, and Ag; the concentrations of these elements in the soils of Kamchatka are higher than their average concentrations in soils of the world. This is related to the common geochemical properties of volcanic ashes in Kamchatka, whose composition reflects the geochemical specificity of the multistage volcanism on this peninsula.     

Differential potassium buffer behavior of individual soils related to potassium corrective treatments

Abstract

Although the basic chemistry and behavior of potassium in the soil is well understood, little of this knowledge is used in soil testing and practical soil fertility mangement. In this study the K buffer behavior of three individual soils (Hagerstown silt loam (Typic Hapludalf), Gatesburg sand (Entic Haplorthod) and Gilpin channery silt loam (Typic Hapludult)) was investigated. The buffer relationships determined indicated very different K behavior for these soils even though exchangeable K soil tests indicated similar K levels. It was also determined that for these soils the buffer relationship was apparently independent of previous K management, indicating that the K buffer behavior could be included as part of soil characterization data.

The role of nonexchangeable K in determining K buffer behavior was also investigated. It was found that the levels of solution K where the release of nonexchangeable K becomes measurable (0.27 ‐ 0.83 × 10^‐4 M) are similar to solution K levels reportedly required for crop growth (0.02 ‐ 0.95 × 10^‐4 M). It was also found that these soils were capable of maintaining a relatively high level of exchangeable K even after extraction of significant amounts of nonexchangeable K with sodium tetraphenyl boron.

It was concluded that K buffering behavior of individual soils could and should be included in K management decisions involving corrective soil treatments and/or crop removal estimation. Otherwise, based on current soil tests, soils with very different K buffer behavior will be treated similarly.     

Specific features of the morphology of volcanic soils in the altitudinal zones of Kamchatka

Under conditions of active volcanism, the soils on different geomorphic positions (from high-mountain landscapes to river valleys) are formed under the impact of periodic ashfalls. The exogenous processes affect the redistribution of volcanic ashes by the elements of the relief, so that the soils of different altitudinal zones have their own morphological specificity. It is suggested that two additional types of volcanic soils should be included in the new Russian soil classification: the type of alluvial volcanic soils in the order of volcanic soils and the type of volcanic lithozems in the order of lithozems. These soils can be considered intergrades between volcanic and alluvial soils and between volcanic soils and lithozems, respectively.     

Radiogeochemistry of Kamchatka soils

Background concentrations of Th and U in volcanic soils (Andosols) of Kamchatka are much lower than their clarkes in continental soils. The dose rate of gamma radiation above the soil surface (10–11.5 µR/h in the south and 8–9.5 [m]R/h in the north of Kamchatka Peninsula) is lower than the natural level of this index for the mountainous areas in the boreal zone of Russia. The natural radiogeochemical background of Kamchatka soils is controlled by the petrochemical composition of volcanic ash composing the mineral basis of Kamchatka soils. It is higher in the southern soil province, where soils develop from acidic ashes, in comparison with the northern province, with a predominance of soils developing from ashes of basic and intermediate composition. This agrees with Th and U clarkes for the corresponding types of volcanic rocks and explains the natural origin of the elevated radiogeochemical background in the southern part of Kamchatka as compared with its northern part. The soils of the northern province developing from relatively fresh volcanic ashes show a lower Th/U ratio as compared to the soils of southern Kamchatka because of higher uranium content in the newly deposited ashes.     

Chemical composition of soils in the areas of volcanic ashfalls around active volcanoes in Kamchatka

The geochemical features of volcanic soils (Andosols) in the northern soil province of Kamchatka are identified. The background regional concentrations (Cb_r) of most of chemical elements in the studied soils are lower than their average concentrations in soils of the world and in the European volcanic soils. Only Na, Ca, and Mg are present in elevated concentrations in all the studied soils in the north of Kamchatka. Regional background concentrations of elements are exceeded by 1.6 times in the area of active ashfalls of the Tolbachik volcano and by 1.3 times in the area of active ashfalls of the Shiveluch volcano. The concentrations of mobile forms of elements in these areas exceed their regional background concentrations by 2.1 and 2.6 times, respectively.     

Potential mineralization and nitrification in volcanic grassland soils in Chile

Abstract

A proportion of the nitrogen (N) applied to grasslands as organic or inorganic fertilizers can be lost to water courses as nitrate and to the atmosphere as nitrous and nitric oxides. Volcanic soils from Chile are not generally prone to leaching, possibly due to net immobilization of nitrate and/or ammonium, and/or due to inhibition of nitrification by either chemical or physical processes. In laboratory studies we found large mineralization potentials in soils from three different Chilean soils after 17 weeks of incubation, totalling 215 and 254 mg kg^?1 dry soil for two Andisols and 127 mg kg^?1 dry soil in an Ultisol. Nitrification occurred after a short period, and was lowest in the Ultisol. In addition, microbial analysis showed nitrifiers to be present in all three soils. Adsorption of ammonium was two-fold stronger than for nitrate, ranging from 29 to 180 kg N ha^?1. The highest potential for N adsorption in the 0–60 cm soil profile was with the Ultisol (398 kg N ha^?1), but was similar in both Andisols (193 and 172 kg N ha^?1, respectively). The combination of ammonium retention together with delayed nitrification could account for the low leaching rates in these soils.     

Development of buffer methods and evaluation of pedotransfer functions to estimate pH buffer capacity of highly weathered soils

The pH buffer capacity of a soil (pHBC) determines the amount of lime required to raise the pH of the soil layer from its initial acid condition to an optimal pH for plant growth and the time available under current net acid addition rate (NAAR) until the soil layer acidifies to a critical pH leading to likely production losses. Accurate values of pHBC can also be used to calculate NAAR from observed changes in soil pH. In spite of its importance, there is a critical shortage of pHBC data, likely due to the long period of time needed for its direct measurement. This work aimed to develop quick, simple and reliable methods of pHBC measurement and to test these methods against a slow (7‐day) titration used as benchmark. The method developed here calculates pHBC directly from the pH buffer capacity of the buffer solution and the increase in soil pH and corresponding decrease in pH of the buffer solution following mixing and equilibration. The pHBC values calculated using Adams and Evans or modified Woodruff buffers were in accord with those measured by slow titration. Buffer methods are easily deployed in commercial and research laboratories as well as in the field. The advantage of using buffer solutions to calculate pHBC instead of lime requirement is the broad application of this soil property. The pHBC of a soil is an intrinsic property that would not be expected to need remeasurement over periods of less than decades. Recurring lime requirement can be calculated from the soil's pHBC, initial and target pH values. A large proportion of the variability in pHBC was explained by the soil organic carbon content. This relationship between pHBC and soil organic carbon content allowed us to develop local pedotransfer functions to estimate pHBC for different regions of Australia.     

Influence of applied p on the cation exchange capacity of volcanic ash soils

Abstract

The CEC of volcanic ash derived soils in Guatemala was measured following equilibration with 1.5 and 6.0 me P/100 g soil supplied through KH₂PO₄ solutions. An increase in CEC resulted due to P reaction and the increase was substantial after removal of soluble Al from P reacted soils. The average ratios of increase in CEC to P retained were 0.49 and 1.63 in the former and later, respectively. P apparently neutralized positive charges on the surface of amorphous component and those internally in the soil particles resulting in a net increase in negative charge (CEC).     

Measuring and simulating pH buffer capacity of calcareous soils using empirical and mechanistic models

ABSTRACT

We studied (i) the pH buffer capacity (pHBC) of calcareous soils varied widely in calcite and texture, (ii) the contribution of soil properties to pHBC and (iii) the significance of using a model based on calcite dissolution to estimate the pHBC of calcareous soils. The pHBC of soils was measured by adding several rates of HCl to soils (100–6500 mM H⁺ kg^–1), in a 0.01 M CaCl₂ background and an equilibration time of 24 h. The pHBC (mM H⁺ kg^–1 pH^?1) varied from 55 to 3383, with the mean of 1073. The pHBC of the soils was strongly correlated with soil CaCO₃ equivalent (calcite) (r = 0.94), sand (r = ?0.72), silt (r = 0.60), EC (r = 0.63), pH (r = 0.55), and weakly (r = 0.37) but significantly with clay content. The attained pHBC values indicated that calcite was probably the main buffer system in these soils. The chemical equilibrium model successfully predicted pH titration curves based on calcite dissolution, indicating buffering of acid inputs in the calcareous soils is dominated by calcite dissolution. The model can be used to simulate acidification of calcareous soils and to provide information for making environmental management decisions.     

The acid buffer capacity of some finnish forest soils: Results of acid addition laboratory experiments

Batch acid addition experiments were carried out to determine the acid buffer capacities (amount of acid required to lower soil pH by one unit) of forest soils. Samples of O, E, B (or BC), and C horizons taken from 29 podzolic profiles in southern Finland were used in the experiments. Subsamples of soil were equilibrated for 24 h with NaCl solution containing additions of HCl acid. Cation exchange, mineral dissolution (weathering), and the protonation of organic matter all appeared to have been involved in the buffering of the acid additions. For the O horizon samples, most of the cations released in response to the acid additions were base cations. For the mineral soil samples, most of the cations released were Al³⁺ ions. With the exception of a few samples, the added acid was not fully neutralised and pH was lowered even with the lowest addition treatment. However, the acid addition treatments corresponded to many times the regional annual acid deposition load (1.6–2.0 cmol(c) m^?2). Calculated acid buffer capacities (cmol(c) kg^?1 pH^?1) ranged from 9.8 to 40.8 for O horizon soil samples and from 0.1 (C horizon) to 5.2 (E horizon) for the mineral soil samples. Total acid buffer capacities for a profile (to a depth of 50 cm) ranged from 500 to 2349, with a mean value of 1091 cmol(c) m^?2 pH^?1. It is concluded that, in addition to CEC and base saturation, acid buffer capacity is a useful measure to describe the ecological effects of acid deposition on soil.     

Use of intensity and capacity measurements to assess the potassium supplying power of soils

Abstract

For depletions of soil exchangeable potassium of between 15 and 50%, potassium concentrations in ryegrass and strawberry leaf were linearly related to pAR^O _K√BC^O where AR^O _K is the equilibrium potassium activity ratio and BC^O is the slope, measured at AR^O _K of the curve relating the quantity of labile potassium and the activity ratio. Potassium supplying power as measured by pAR^O _K√BC^O could also be expressed as a function of the equilibrium activity ratio and the mineral component of the cation exchange capacity of the soil.     

Shrinkage potential and pore shrinkage capacity of differently developed volcanic ash soils under pastures in southern Chile

The drying process of volcanic ash soils often results in the formation of shrinkage cracks with consequences for their physical properties (i.e., decrease of water retention capacity) and land use management. This study presents the soil water characteristics and shrinkage behaviour (shrinkage phases in terms of void and moisture ratio), the shrinkage potential (COLE index), and the pore shrinkage capacity (PSI) for 5 and 20 cm depth of a Haplic Arenosol (tephric) and two Silandic Andosols under pasture management along a soil gradient from the Andean mountains to the coastal range in southern Chile. The main focus of the presented study is on the effect of soil development in conjunction with the weathering of volcanic ash soils on the shrinkage properties. The water retention and shrinkage curves were continuously determined for undisturbed soil samples (100 cm³) during a drying process under laboratory conditions. In addition, the shrinkage curve data were modelled to distinguish different shrinkage zones. The results suggest that the investigated soil properties vary depending on soil development. The more developed Andosols had higher total porosities (up to 70 cm³ cm^?3) than the less developed Arenosol. The shrinkage behaviour of the Haplic Arenosol showed a wide structural shrinkage phase, whereas the Silandic Andosols revealed a more pronounced proportional shrinkage phase, which is related to the pore size distribution. In addition, wide and narrow coarse pores of the Haplic Arenosol and medium and fine pores of the Silandic Andosols determine the shrinkage potential (COLE) and the pore shrinkage capacity, respectively. The finer‐grained and organic matter‐rich Andosols indicate a higher COLE index (> 0.03–0.09) compared to the Arenosol (≤ 0.03). The pore shrinkage index (PSI) of the total pores (TP) varied significantly (P < 0.05) with values of 0.042–0.149 in 5 cm depth and 0.04–0.091 in 20 cm depth of sites 1–3, respectively.In summary, the shrinkage potential and pore shrinkage capacity are positively correlated to the organic carbon content and decrease with increasing dry bulk density. The study points out a higher risk of soil degradation due to irreversible drying processes for the more clayey and allophane containing Andosols than the Arenosol.     

Assessment of potassium in soils

Abstract

Potassium in soils from selected plots of the Broadbalk Experiment at Rothamsted, and Rotation I experiment at Saxmundham, U.K. was measured by five methods: the boiling nitric acid extractions of Haylock and Maclean, electro‐ultrafiltration, release to Ca‐saturated ion exchange resin, and a new procedure using extraction by HCl under reflux. All. the methods showed clearly the Gifferences between the two soil types, and between the differently fertilized plots on the basis of amounts, and 1n some cases rates of release, of different categories of soil K (exchangeable, fixed and native). The quantity of exchangeable K measured by each method, except that by Ca‐resin, gave significant correlations with the K balance of the soils, and yield and/or K offtake of winter wheat grown on the plots. The new HCl ‐reflux method gave the closest correlations. The amount and rate of release of fixed (available but not exchangeable) K estimated by HCl‐reflux was also correlated with yield and offtake.     

Soil formation on acid and basic volcanic ashes of different ages in Kamchatka

The use of tephrochronological data on the ages of volcanic eruptions and the corresponding ash layers buried in the profiles of forest soils in Kamchatka makes it possible to distinguish between two groups of volcanic soils related to different stages of the volcanic activity. In the Holocene, the southern group of volcanoes was characterized by the ejection of acid pyroclasts typical of the mature stage of volcanism (the stage of caldera formation). The northern group of volcanoes ejected basic pyroclasts typical of the early (basaltic) stage of volcanism. Thus, the effect of the full cycle of volcanism on the soil formation can be traced in the soil profiles. It is shown that soil formation in volcanic areas depends on the frequency and intensity of ash falls and on the composition of the pyroclastic material.     

Potential role of phosphate buffering capacity of soils in fertilizer management strategies fitted to environmental goals

Sorption behavior and buffering of phosphorus (P) are important, both from an agricultural and an environmental point of view. The objectives of this study were to investigate: (1) the kinetics of the transfer of P from soil to soil solution and assessing P buffering capacity of soils (PBC), as a function of soil solution P; (2) the effect of PBC on soil P status fitted to environmental targets for water quality; (3) the effect of PBC on crop response. PBC was derived from the non‐linear Q‐I curve describing the time‐dependent relationship between plant‐available reserve of soil P (Q) versus soil solution P (I). The Q‐I curve was determined in soil suspension using sorption and isotopic dilution methods for soil samples from French, Swedish, and Dutch field trials. Soils with low PBC values were more sensitive to the loss of P to the environment, required higher critical value in soil solution P to comply with P demand of maize, and had higher change in soil solution P per unit of P budget. In different soils, both the critical soil solution P for maize and the change in soil solution P per unit of P balance varied inversely with PBC. It is concluded that (1) PBC plays a key role in determining the agronomic and environmental threshold levels of available P content in the soils, and (2) PBC is a prerequisite for the development of more environmentally oriented fertilization recommendation systems.     

水旱轮作条件下不同类型土壤供钾能力及钾素动态变化研究

采用盆栽试验,研究了黑麦草-水稻轮作条件下不同类型土壤供钾能力及钾素动态变化,以期为土壤供钾机制研究及合理的钾素调控提供依据。结果表明：不施钾条件下（NP处理）,潮土上种植作物的生物量和吸钾量最高,黄褐土次之,红壤最低;施钾条件下（NPK处理）,3种土壤上种植作物的生物量无显著差异,作物吸钾量为黄褐土>潮土>红壤。整个轮作期,红壤、黄褐土和潮土NPK处理的作物生物量较NP处理分别增加55.6%、45.2%和23.2%,作物吸钾量分别增加368.8%、166.8%和74.5%。轮作前季（黑麦草季）,NP处理的3种土壤水溶性钾含量和交换性钾含量均降低,潮土非交换性钾含量明显降低,红壤和黄褐土非交换性钾含量在前期变化不大,中期有升高的趋势,后期显著降低;NPK处理的土壤钾含量均高于NP处理,且各种形态钾含量的变化趋势与NP处理基本相同。轮作后季（水稻季）,NP处理的3种土壤水溶性钾含量变化不大,交换性钾含量呈先降低后升高的趋势,非交换性钾含量呈先升高后降低的趋势;NPK处理的土壤交换性钾含量在水稻生长前期明显升高,中期下降,后期有略微上升,水溶性钾和非交换性钾含量有先升高后降低的变化趋势。综上所述,在不施钾条件下,轮作期内各土壤钾素消耗量较大,水溶性钾和交换性钾含量降低,并促进了非交换性钾的释放;施钾能提高土壤水溶性钾和交换性钾含量,并向非交换性钾方向转化,施钾对黑麦草和水稻有显著增产效果,可以有效地提高土壤供钾水平。     

土壤非交换态钾与结构态钾能够区分吗？

Nonexchangeable K (NEK) is the major portion of the reserve of available K in soil and a primary factor in determining soil K fertility. The questions of how much NEK is in soils and how to quantify total NEK in soils are so far still unclear due to the complicated effects of various minerals on K fixation. In this study, the NEK in 9 soils was extracted with sodium tetraphenylboron (NaBPh₄) for various time periods longer than 1 d. The results showed that the NEK extracted by NaBPh₄ gradually increased with time, but showed no more increase after the duration of extraction exceeded 10--20 d. As the temperature increased from 25 to 45 ^oC, the duration to obtain the maximum extraction of NEK was reduced from 20 to 10 d, and the maximum values of NEK released at both temperatures was almost the same for each soil. The maximum NEK (MNEK) of the 9 soils extracted by NaBPh4 varied from 3 074 to 10 081 mg kg^-1, accounting for 21%--56% of the total soil K. There was no significant correlation between MNEK released by NaBPh₄ and other forms of K, such as NH₄OAc-extracted K, HNO₃-extracted K and total K in soils, which indicates that NEK is a special form of K that has no inevitable relationship to the other forms of K in soils. The MNEK extraction by NaBPh₄ in this study indicated that the total NEK in the soils could be differentiated from soil structural K and quantified with the modified NaBPh₄ method. The high MNEK in soils made NEK much more important in the role of the plant-available K pool. How to fractionate NEK into different fractions and establish the methods to quantify each NEK fraction according to their bioavailability is of great importance for future research.     

The acid-base buffer capacity of podzolic soils and its changes under the impact of treatment with the Mehra-Jackson and Tamm reagents

The acid-base buffer capacity before and after the treatment with the Mehra-Jackson and Tamm reagents was assessed by continuous potentiometric titration for the main genetic horizons of two profiles of podzolic soils in the Central Forest State Reserve. The total buffer capacity was calculated in the pH range from the initial titration point (ITP) to 3 for the acid titration and from the ITP to 10 for the base titration, as well as the buffer capacities in the pH intervals of 0.25. It was found that both treatments abruptly decreased the base buffer capacity, which reached 70–90% in the E horizons. The high direct linear correlation of the difference between the total base buffer capacities before and after each treatment with the content of Fe in the Tamm extract was revealed. From the results obtained, a conclusion was drawn that finely dispersed Fe hydroxides were the main solid-phase constituents ensuring the base buffer capacity, and the deprotonation of hydroxyl groups on the surface of Fe hydroxides was the essential buffer reaction during the base titration.