Base Cation Saturation Research Articles

Cation imbalance and heavy metal content of seven Indonesian soils as affected by elemental compositions of parent rocks

Elemental composition of various fresh parent rocks has received little attention in relation to cation imbalance and potential for high concentrations of heavy metals in soils. The objective of the study was to assess elemental composition of fresh parent rocks and its effect on cation imbalance and natural heavy metal occurrence in soils. Seven fresh rocks consisting of basalt, gabbro, basaltic andesite, volcanic tuff, volcanic ash, mica schist, and serpentinite and their corresponding overlying soil profiles were sampled for various chemical analyses. The elemental composition of finely ground individual fresh rock was determined by X-ray fluorescence (XRF). Exchangeable cations and heavy metals of soils were extracted by NH4OAc and by a mixture of concentrated HNO3 and HClO4, respectively. Results showed that major elements of fresh rocks, referred to as a source of ‘potential exchangeable cations’, were different among the rock types. The order of parent rocks in decreasing potential cations was gabbro>basaltic andesite>basalt>volcanic ash>volcanic tuff>serpentinite>mica schist for Ca, serpentinite≫gabbro>basalt>basaltic andesite>mica schist~volcanic ash>volcanic tuff for Mg, volcanic tuff>mica schist>volcanic ash>basaltic andesite>basalt>serpentinite>gabbro for K, and volcanic tuff>basaltic andesite>basalt>volcanic ash>gabbro>mica schist>serpentinite for Na. Based on base cation saturation ratio (BCSR) of Ca:Mg:K=6.5:1:0.5, none of the seven soils overlying different fresh rocks met the “ideal soil” suggesting cation imbalance. The critical cation deficiency status (CCDS) showed all soils (except MA5) were insufficient in K accompanied either by insufficient or high content of either Ca, Mg, or Na. The heavy metals of Pb, Cd, and Hg were not detected in all fresh rocks, while Cr and Ni were present in different amounts. In soils overlying fresh rocks, the order of magnitude of natural Cr agreed well with its order in fresh rocks, while Ni disagreed. This indicated that Cr in soils was mainly dictated by Cr content in parent rocks, while Ni depended on soil forming processes in addition to parent rocks. Cr and Ni have exceeded threshold limits in soils developed from serpentinite and gabbro, respectively, while soils developed from mica schist, volcanic tuff, basaltic andesite and volcanic ash parent rocks were below the threshold limit, viz., Cr and Ni contents were less than 11ppm each. Implications for the study are the risk of Cr and Ni toxicity that should be taken into account when selecting crops to be grown (e.g. non-food crops) on soils derived from serpentinite and gabbro respectively, to avoid heavy metal risk for human health. The content of heavy metals in soils derived from various rocks in the present study may be used as baseline data if no information is available under tropical conditions.

Influence of liquid manure and NPK on selected sorption properties of soil

The aim of the experiment was to assess the effect of long-term fertilization with liquid manure applied annually and biennially and with mineral fertilizers on selected sorption properties of soil, i.e. the content of exchangeable magnesium, potassium, calcium, sodium and as well as the value of hydrolytic acidity, sorption capacity and base cation saturation ratio. It was found that fertilization with liquid manure, in contrast to NPK application (N as NH4NO3, P as triple super phosphate, K as KCl), led to a significant rise in the content of exchangeable magnesium in soil, whereas application of liquid manure or mineral fertilizers contributed to a significant increase in the potassium content in soil. Application of liquid manure did not cause significant changes in the value of hydrolytic acidity between the lowest and the highest dose used, while mineral fertilization contributed to an increase in the value of hydrolytic acidity. Application of liquid manure reduced the value of hydrolytic acidity as deep as the third layer of the soil profile. Fertilization with liquid manure and mineral fertilizers did not affect the content of exchangeable calcium in the whole soil profile, although the calcium content in the soil profile increased to the 51-75 cm layer. Application of liquid manure and NPK did not alter significantly the content of exchangeable sodium in soil. Upon application of both liquid manure and NPK, no significant changes were observed in the total base exchangeable cations in soil (S) or in the sorption complex saturation (V). However, S and V significantly increased along the depth of sampling. It was found that fertilization with both liquid manure and mineral fertilizers did not induce substantial changes in the soil sorption capacity, although there was an increase in the total sorption capacity in two layers (51-75 cm and 76-100 cm) of the soil profile.

Soil Acidification of Alfisols as Influenced by Tea Cultivation in Eastern China

Soil acidification is an important process in land degradation around the world as well as in China. Acidification of Alfisols was investigated in the tea gardens with various years of tea cultivation in the eastern China. Cultivation of tea plants caused soil acidification and soil acidity increased with the increase of tea cultivation period. Soil pH of composite samples from cultivated layers decreased by 1.37, 1.62 and 1.85, respectively, after 13, 34 and 54 years of tea plantation, as compared to the surface soil obtained from the unused land. Soil acidification rates at early stages of tea cultivation were found to be higher than those at the later stages. The acidification rate for the period of 0–13 years was as high as 4.40 kmol H + ha −1 year −1 for the cultivated layer samples. Soil acidification induced the decrease of soil exchangeable base cations and base cation saturation and thus increased the soil exchangeable acidity. Soil acidification also caused the decrease of soil cation exchange capacity, especially for the 54-year-old tea garden. Soil acidification induced by tea plantation also led to the increase of soil exchangeable Al and soluble Al, which was responsible for the Al toxicity to plants.

Use of agricultural by‐products to study the pH effects in an acid tea garden soil

AbstractThe amelioration of an acid Alfisol from a tea garden was studied by incorporating various plant materials: canola straw, wheat straw, rice straw, corn straw, soybean straw, peanut straw, faba bean straw, Chinese milk vetch shoot and pea straw prior to incubation for a maximum of 65 days. Soil pH increased after incubation with all the incorporated materials with the legumes causing the largest increases. The final soil pH was correlated with ash alkalinity (r2 = 0.73), base cations (r2 = 0.74) and N content (r2 = 0.93) of the applied materials. It was assumed that the incubation released the base cations in plant materials as they decomposed which ultimately increased the base cation saturation of the soil. Similarly, soil exchangeable Al was also decreased with the incorporation of the legume plant materials and corn straw and rice straw. Our investigation demonstrated that legumes are the preferred choice for controlling the soil acidity and also for reducing the toxicity of Al in acid soils.

Cation exchange in forest soils: the need for a new perspective

SummaryThe long‐term sustainability of forest soils may be affected by the retention of exchangeable nutrient cations such as Ca2+ and the availability of potentially toxic cations such as Al3+. Many of our current concepts of cation exchange and base cation saturation are largely unchanged since the beginnings of soil chemistry over a century ago. Many of the same methods are still in use even though they were developed in a period when exchangeable aluminium (Al) and variable charge were not generally recognized. These concepts and methods are not easily applicable to acid, highly organic forest soils. The source of charge in these soils is primarily derived from organic matter (OM) but the retention of cations, especially Al species, cannot be described by simple exchange phenomena. In this review, we trace the development of modern cation exchange definitions and procedures, and focus on how these are challenged by recent research on the behaviour of acid forest soils. Although the effective cation exchange capacity (CECe) in an individual forest soil sample can be easily shown to vary with the addition of strong base or acid, it is difficult to find a pH effect in a population of different acid forest soil samples. In the very acidic pH range below ca 4.5, soils will generally have smaller concentrations of adsorbed Al3+. This can be ascribed to a reduced availability of weatherable Al‐containing minerals and a large amount of weak, organic acidity. Base cation saturation calculations in this pH range do not provide a useful metric and, in fact, pH is modelled better if Al3+ is considered to be a base cation. Measurement of exchangeable Al3+ with a neutral salt represents an ill‐defined but repeatable portion of organically complexed Al, affected by the pH of the extractant. Cation exchange in these soils can be modelled if assumptions are made as to the proportion of individual cations that are non‐specifically bound by soil OM. Future research should recognize these challenges and focus on redefining our concepts of cation retention in these important soils.

The forms of aluminium in Stagnosols in Serbia

The interactive relations of Al forms and the most important characteristics of Stagnosols were researched to diagnose which factors are the best to control the content of phytotoxic Al forms. The values of exchangeable Al (Al<sub>KCl</sub>) range from 0.0 to 560.7 mg/kg and increase with depth. The variation of exchangeable Al is high and it depends on the changes of all forms of soil acidity and the degree of base cation saturation. Their relation is best described by a non-linear function. The contents of total Al and Al extracted by ammonium oxalate in dark (Al amorphous, Al<sub>oxa</sub>) increase with depth, together with the increase of the content of clay particles. The values of Al extracted by sodium citrate/dithionite (Al crystalline, Al<sub>dit</sub>), 0.5M CuCl<sub>2</sub> (Al<sub>Cu</sub>) and 0.25M EDTA (Al<sub>EDTA</sub>) are in good correlation and they predominantly depend on the parameters of soil acidity. The value of Al<sub>Cu</sub>-Al<sub>KCl</sub> (in eluvial horizons) is best represented by organically bound Al. Effects of the reserves of aluminium Al<sub>dit</sub>, Al<sub>Cu</sub> and Al<sub>EDTA</sub> on the changes of exchangeable Al are higher (medium and high correlation), while the effects of the total Al and Al<sub>oxa</sub> are lower.

Is soil degradation unrelated to deforestation? Examining soil parameters of land use systems in upland Central Sulawesi, Indonesia

It is generally assumed that declining soil fertility during cultivation forces farmers to clear forest. We wanted to test this for a rainforest margin area in Central Sulawesi, Indonesia. We compared soil characteristics in different land-use systems and after different length of cultivation. 66 sites with four major land-use systems (maize, agroforestry, forest fallow and natural forest) were sampled. Soils were generally fertile, with high base cation saturation, high cation exchange capacity, moderate pH-values and moderate to high stocks of total nitrogen. Organic matter stocks were highest in natural forest, intermediate in forest fallow and lowest in maize and agroforestry sites. In maize fields soil organic matter decreased during continuous cultivation, whereas in agroforestry it was stable or had the tendency to increase in time. The effective cation exchange capacity (ECEC) was highest in natural forest and lowest in maize fields. Base cations saturation of ECEC did not change significantly during cultivation both maize and agroforestry, whereas the contribution of K cations decreased in maize and showed no changes in agroforestry sites. Our results indicate that maize cultivation tends to reduce soil fertility but agroforestry systems are able to stop this decline of soil fertility or even improve it. As most areas in this rain forest margin are converted into agroforestry systems it is unlikely that soil degradation causes deforestation in this case. On the contrary, the relatively high soil fertility may actually attract new immigrants who contribute to deforestation and start agriculture as smallholders.

The impact of climate on the biogeochemical functioning of volcanic soils

Rainfall and the amount of water available to leach ions from soil are among the most important features determining mineral weathering, secondary mineral synthesis and soil chemical properties. Along an arid to humid climosequence on Kohala Mountain, Hawaii, we sampled 16 soil profiles and found that weathering and soil properties change in a nonlinear fashion with increased rainfall. The lavas are influenced by a strong rain shadow with mean annual precipitation (MAP) averaging 160 mm near the coast and rising to >3000 mm near the summit. A temperature decline from 24 to 15 °C with increasing elevation is matched by lower potential evapotranspiration (ET). A water balance model (monthly precipitation minus monthly ET) defines three broad climate zones along the sampling transect: an arid zone with moisture deficit in every month, an intermediate zone with moisture deficit during low-rainfall summer months and moisture surplus during high-rainfall winter months, and a humid zone with moisture surplus during every month. The annualized water balance can be ratioed with the integrated porosity of the top meter of soil to provide a leaching index. The index reaches 1 (total filling of the pore space on an annual basis) at about 1400 mm MAP. Index values >1 imply intense leaching conditions because of pore water replacement. In these 170 ka soils, leaching losses of soluble base cations and Si are nearly complete at index values >1, whereas only 60% of Al has been lost. At index values <1 leaching losses are progressively lower with the lowest rainfall sites having lost 10–20% of the original base cations and Si and none of the Al. At all sites, the secondary clay mineral assemblage is dominated by metastable noncrystalline weathering products; humid soil profiles contain very few crystalline minerals whereas the arid profiles contain halloysite, hematite, gibbsite and small amounts of carbonates. Soil surface exchange properties are influenced strongly by climatic conditions and show a dramatic threshold in base cation saturation, pH and effective cation exchange capacity (ECEC) at leaching index of 1 (1400 mm MAP). Soils with leaching index of <1 have high base cation saturation, near-neutral pH and high ECEC. At MAP >1400 mm, soil buffering capacity has been totally exhausted leading to low pH and low ECEC. The nonlinear decline in ECEC is irreversible under natural conditions; base cation depleted soils will remain so even if the climate shifts to drier conditions. In contrast, a climate shift to wetter conditions can drastically modify surface chemical properties existing in the drier soils as weathering depletes primary minerals, elements are lost to leaching, and surface chemistry is modified. There is a time-dimension implied in climate gradient studies; soils forming in recently rejuvenated landscapes contain more primary minerals and should experience loss of buffering capacity at higher rainfall. Loss of buffering capacity means that biological acidity will move more deeply into the vadose zone or into the aquatic system. The details of this transfer depend on present and past climate, and the age and erosional stability of landscapes.

Radial variations in cation exchange capacity and base saturation rate in the wood of pedunculate oak and European beech

In a mixed forest stand on an ochreous brown earth in the Belgian Ardennes, pedunculate oak (Quercus robur L.) and European beech (Fagus sylvatica L.) have outwardly decreasing cation concentration profiles in wood. To test if these profiles can be ascribed to endogenous factors or to decreased availability of cations in the soil, radial profiles of water-soluble, exchangeable, and total cations and of cation exchange capacity (CEC) of wood were determined. In both species, [Formula: see text]75% of K is in the water-soluble form so is of little use for dendrochemical monitoring. About 80% of Mg is adsorbed on wood exchange sites. For Ca, 30 (beech) to 60% (oak) of total content cannot be extracted by SrCl2 and is, thus, relatively immobile in wood. Wood CEC decreases from pith to bark in European beech and from pith to outer heartwood in pedunculate oak. Decreasing profiles of exchangeable Ca and Mg in pedunculate oak and exchangeable Ca in European beech are strongly constrained by CEC and, thus, are not related to environmental change. Base cation saturation rate shows no consistent radial change in either species. European beech maintained much higher base cation saturation rate than pedunculate oak, although both species had similar CEC. In conclusion, the results do not provide convincing evidence for a significant change in nutritional status of pedunculate oak and European beech in the Belgian Ardennes due to atmospheric pollution.

Site classification in a mixed hardwood forest (Hallerbos, Belgium) with a homogeneous ground vegetation dominated by Hyacinthoides non-scripta (L.) Chouard ex. Rothm.

The forest of Halle (560 ha), situated 20 km south of Brussels is covered by a beech (Fagus sylvatica) forest, locally mixed with secundary species (Tilia, Fraxinus, Acer, Quercus,... ). In almost all stands, herbal vegetation is dominated by bluebell (Hyacinthoides non-scripta). The research intended to classify 36 plots of different tree species composition according to their site quality. Three classification methods were compared: the first one based on the indicator value of the understorey vegetation, a second one on the humus morphology and a last one on some quantitative soil characteristics. According to the plant sociological site classification, the plots have the same site quality. However, humus forms differ apparently and significant differences were found in pH value and base cation saturation of the soil, abundance and biomass of earthworms and biomass of the ectorganic horizon. Tree species proved to be the main cause of these differences. The results illustrate that the herbal vegetation is not always a reliable indicator of site quality. In the case of a homogeneous vegetation dominated by one or more indifferent species, classification on humus morphology or soil analysis are more appropriate. In the forest of Halle, the tree species is probably the main cause of the observed differences in site quality.

The effects of limestone and of limestone plus NPK fertilization on the soil and mass balance of a spruce stand ( Picea abies (L.) Karst.) in the Vosges mountains

Calcareous amendment and/or fertilization trials were carried out in a declining 66-year-old Norway spruce ( Picea abies (L.) Karst.) stand in the Vosges mountains (northeast France, altitude 1100 m) in 1985. The aim was to test tree response to nutritional deficiencies (Ca + Mg) and to alleviate soil acidity. In 1988, experimental equipment was set up to collect atmospheric input (bulk precipitation, throughfall) and soil seepage water. The soils are podzolic (‘ocre-podzolique’), derived from an acid-poor granitic bedrock (‘granite du Valtin’). The soils are coarsely textured, hence very porous. They are very acid (pH 3.4 in the A 1 horizon, and pH 4.1 in the Bs horizon). The cation exchange capacity (CEC) is highly saturated in exchangeable acidity: 86% in the A 1 horizon. Ca 2+ + Mg 2+ saturation is very low (<10% in A 1 and <1% in the subsoil). Liming and fertilization significantly increase soil pH, base cation saturation and decrease soil acidity, especially in the surface horizons. Bulk precipitation is dilute and acidic (pH 4.5); ion concentration of the precipitation greatly increases after passing through the tree canopy. Dry deposition is moderate and has values in the lower range reported for Europe. Nitrification produced large amounts of NO 3 −-N and H + ions in the O layer and organo-mineral horizons. Nitrate and aluminium dominate the chemical composition of the soil see-page water. Liming induces a considerable rise in the soil solution pH and the base cations (Ca 2+ + Mg 2+) and decreases nitrate and aluminium substantially. Liming alone seems to lower the rate of nitrification. Addition of fertilizers increases the deep drainage of base cations which could reduce the long term efficiency of liming. Improvement of tree health-status accords with the positive effects of liming and/or fertilization on the soil's solid phase and solution.