Soil Exchange Complex Research Articles

Nitrogen additions (NaNO 3 and NH 4NO 3) at Aber forest, Wales: I. Response of throughfall and soil water chemistry

Nitrogen was sprayed weekly onto the forest floor of a Sitka spruce stand for 2.5 years in a replicated block design experiment to investigate the impacts of chronic atmospheric nitrogen deposition, in both oxidised and reduced form, on these ecosystems. The nitrogen was applied as sodium nitrate at 35 or 75 kg N ha −1 year −1 and as ammonium nitrate at 35 kg N ha −1 year −1, and the response of the throughfall and soil water chemistry determined. The response to increased water availability was also determined in a zero-N treatment. Increased water availability resulted in decreased concentrations of ammonium and phosphate and increased hydrogen ion concentration in the throughfall above the height of the spray, indicating tree growth is limited by water at this site. No effect of increased nitrogen availability on throughfall or stemflow chemistry above that of the water response was observed. Ambient nitrogen inputs in throughfall plus stemflow were 17 kg N ha −1 year −1 of which 11 kg N ha −1 year −1 was leached. Retention capacity of additional nitrogen applied to the forest floor was found to differ for nitrate-N and ammonium-N. There was no retention capacity for incoming nitrate-N but 100% retention capacity for applied ammonium-N. Nitrate leaching losses increased in parallel with nitrate inputs and were independent of ammonium addition. There was no apparent transformation of ammonium to nitrate in the ammonium nitrate treatment. Total dissolved nitrogen losses were therefore lower in the ammonium nitrate 35 kg N ha −1 year −1 treatment relative to the sodium nitrate 35 kg N ha −1 year −1. As the soil exchange complex is dominated by aluminium, the increase in salt loading and lack of nitrate retention in both treatments was associated with increased soil water aluminium concentrations due to ion exchange between the incoming sodium or ammonium ions and aluminium on the soil exchange complex. No increase in soil water concentrations of any other cation, with exception of sodium in the sodium nitrate treatments, was observed. These findings suggest that any increase in nitrate deposition will result in increased nitrate and aluminium leaching at this site which can perhaps best be described as ‘nitrate saturated’. Elevated ammonium deposition will also result in increased aluminium leaching if accompanied by a mobile anion. More long term monitoring is required to evaluate these changes in soil water chemistry on tree vitality and the internal nitrogen cycle.

The recycling of Linz-Donawitz (LD) converter slag by use as a liming agent on pasture land

Slag is a major by-product of the basic oxygen steelmaking converter process (BOS). Methods are being developed to make use of this by-product and large quantities are now employed in agriculture and in the production of aggregates in several European Community (EC) countries. However, a great deal of slag is still either simply discarded or discharged in landfills. This paper reports the effects over a 3-year period on both soil and crops, of the application of Linz-Donawitz (LD) converter slag on pasture land. Comparative studies were performed using different quantities of low phosphorus LD converter slag and fertilizer on land sown with Dactylis glomerata, Trifolium repens and Lolium perenne. The results showed an increase in soil pH and in the availability of Ca and Mg in the soil exchange complex. Aluminium content was reduced. When LD converter slag and fertilizer were applied together, plants were seen to contain the greatest concentrations of nutrients and greater yields were obtained.

The effect of spruce (Picea abies Karst.) on soil development: an analytical and experimental approach

SummaryChanges in soil and biogeochemical processes following the replacement, 60 years ago, of part of a deciduous forest by a coniferous stand were evaluated by (i) a balance‐sheet approach using soil and biomass element content analyses and the mineral flux, and (ii) the inclusion of test‐mineral and resin bags in an integrative experimental approach.The comparison of soils under different stands shows that the change to spruce is inducing physical, chemical and biological modifications in soil properties. Changes in the humus layers lead to a reduction in mineralization and the mobilization of active organic acids in the system. Under spruce, the soil structural stability is reduced as fine clay is dispersed. Soil acidification is increased, linked to a decrease in soil pH and desaturation of the soil exchange complex. Soil mineralogy also indicates this tendency, particularly with an increase in the stability of Al intergrades. The biogeochemical cycle is modified especially for N, S and Al. with large changes in the internal fluxes between the ecosystem components, but the modification of the input‐output balance due to spruce introduction is large only for S.The acidification is partly due to a change in litter quality, which inhibits biological activity, and partly because, during the dormant season, evergreen species intercept ‘dry and occult’ depositions from the atmosphere containing acidic or potentially acidic components.Use of test‐mineral bags improves understanding and interpretation of the current soil mechanisms. The test mineral, a vermiculite, introduced into the soil or placed in the lysimeter flux very quickly undergoes measurable transformation characterized by desaturation and fixation of non‐exchangeable Al in the interlayer zone, easily identified by Al speciation. The acidifying effect of spruce is clearly demonstrated by the experimental approach used, including the characterization of soil solutions by resin bags.All the techniques are complementary and could be used together or individually, depending on the aim of the study.

Effects of silicate weathering on water chemistry in forested, upland, felsic terrane of the USA

We use data from the US EPA National Surface Water Survey (NSWS), the USGS Bench-Mark Station monitoring program, and the National Acid Deposition Program (NADP) to evaluate the role of weathering in supplying base cations to surface waters in forested, upland, felsic terrane of the northeastern, northcentral, and northwestern (Idaho batholith) United States. Multivariate regression reveals differential effects of discharge on individual base cations and silica, but no secular trend in the Ca Na denudation rate over 24 yr (1965–1988) for the Wild River catchment in the White Mountains. Because the turn-over time for Na in the soil-exchange complex is only ca. 1.5 yr, the long-term behavior of the ratios Ca Na and Si Na in waters leaving this catchment indicates that weathering is compensating for base cation export. In every subregion, Ca and Mg concentrations in lakes are statistically linked to nonmarine Na, but the median Ca Na ratio is greater than the ratio in local plagioclase. We attribute this inequality to nonstoichiometric weathering of calcium in juvenile (formerly glaciated) terrane, not to leaching of exchangeable cations by SO 4, because intraregional and cross-regional statistical analysis reveals no effect of atmospherically derived sulfate ion. The median base cation denudation rates (meq m −2 yr −1) for these American lake regions are: Maine granites (108); western Adirondack felsic gneiss (85); Vermilion batholith (42); Idaho batholith (52). The regional rates are high enough to compensate for present wet deposition of acidifying anions except in some vulnerable lake watersheds in the western Adirondacks.

The Importance of Hydrological Source Areas in Terrestrial Liming

AbstractTerrestrial liming experiments have been carried out in the Welsh uplands at Llyn Brianne, 30 km northwest of Brecon. Limestone has been applied to an entire moorland catchment and to the hydrological source areas of a moorland catchment. The hydrological source areas were derived from topographic data. Blanket liming and source area liming proved successful in (a) raising the pH value of the stream, (b) increasing the calcium concentration, and (c) decreasing the aluminium concentration. The response to the source area liming proved to be more successful, resulting in a higher calcium concentration. Neither site showed any signs of long‐term exhaustion, although the initial response in stream chemistry indicated the importance of the soil exchange complex in determining optimum application rates. Source area liming has economic and environmental advantages over blanket liming, and its increased effectiveness suggests that it is the most viable technique for ameliorating acidification in upland areas.

Acidification Induced by Different Nitrogen Sources in Columns of Selected Tropical Soils

AbstractSustainability in agriculture is a rising concern in the tropics where fertilizers are introduced to meet increasing food demands. The adverse effects of long‐term fertilizer use were monitored through changes in the soil exchange complex in packed columns of an Oxic Paleustalf, a Typic Paleudult, and a Tropeptic Haplustox. Following each application of N at rates of 0, 50, or 100 kg ha−1 as urea, ammonium sulfate (AS), or calcium ammonium nitrate (CAN), the soils were flushed with distilled water, representing the water draining from these soils in their respective tropical environments during a growing season. The procedure was repeated 30 times during 2 yr with 6‐wk rest periods after each five cycles. The rate of acidification reflected the rate of application and acid‐producing capacity of the N source. In the Oxisol and Ultisol, further acidification resulted in an increase in exchangeable Al and Mn, which were eventually found in the effluent, suggesting mineral dissolution. In the Alfisol, acidification resulted in a loss of cation‐exchange sites and the increasing predominance of Al and Mn. This acid‐consuming process caused the development of a descending acidification front, in which soil pH dropped from 6.7 to 5.0. Leachates remained neutral until the acidification front reached the bottom of the soil column. Applied N was quantitatively recovered in the leachates of all soils. Although plant growth would moderate these processes, the results show that indiscriminate N use on such fragile soils may eventually cause soil degradation and groundwater pollution.

Factors Determining Differences in Soil pH in Adjacent Conifer and Alder‐Conifer Stands

AbstractTree species may differ in their influence on biogeochemical cycles, leading to differing rates of soil acidification. Over time, quantitative and qualitative changes develop in the characteristics of the soil exchange complex. Three such characteristics regulate soil pH: (i) the quantity of acids present, which can be represented as the total cation‐exchange capacity (CEC); (ii) the degree of dissociation of the acids, commonly called base saturation; and (iii) the affinity of the acids for H+, or acid strength, which represents the composite pKa (negative log of the acid ionization constant) of the exchange complex. We examined the importance of these three factors in explaining the differences in soil pH between adjacent stands of conifers [primarily Douglas fir, Pseudotsuga menziesii (Mirbel) Franco] and conifers mixed with N‐fixing red alder (Alnus rubra Bong.). At a low‐productivity site (Wind River, WA), the pH of 0 to 0.15 m of soil from both alder‐conifer and conifer stands averaged 4.3 in 0.01 M CaCl2. The pH values were the same, however, only because higher base saturation in the alder‐conifer stand was offset by greater acid strength. At a more productive site (Cascade Head, OR), soil pH (in 0.01 M CaCl2) averaged 3.7 in the alder‐conifer stand but 4.4 in the conifer stand. The difference in pH resulted primarily from greater acid strength of soil organic matter under alder, and secondarily from lower base saturation of the exchange complex. These results underscore the importance of considering qualitative changes in soil organic matter as factors driving changes in soil pH and other parameters.

Aluminium mobilization in soil and stream waters at three Norwegian catchments with different acid deposition and site characteristics

Streamwater, soil water, and soil chemistry data are collated for three small (18–41 ha) Norwegian headwater catchments and intercomparisons are made to allow assessment of the effects of acid deposition on aluminium mobilization. Two of the sites (Birkenes I and II), situated in the most heavily impacted area of southern Norway, show pronounced differences in streamwater chemistry, especially at highflow. The pH and inorganic monomeric aluminium (Al i) at Birkenes I reach 4.2 and 20 μM respectively, compared with pH 5-4.6 and 3 μM Al i at Birkenes II. The third catchment (Ingabekken) is in a pristine area in mid-Norway where streamwater pH changes from 7.2 at baseflow to ∼ 5 at highflow; in this case, Al i is generally < 1 μM. The differences in streamwater chemistry are mirrored in the soil solution composition at the three sites. Major differences also occur in the compositions of exchangeable ions, even though cation exchange capacities are similar. In the pristine area, exchangeable aluminium is low, with the exchange complex being dominated by H +; this contrasts with the impacted sites where exchangeable aluminium is much more predominant, especially at Birkenes I. It is concluded that one of the main changes observed during acidification is the conversion of the soil exchange complex from a hydrogen-dominated form to one where aluminium plays an increasingly important role. Such a transformation is not included in most acidification models and should therefore be a focus for further model development.

Evaluation of the role of sea salt inputs in the long-term acidification of coastal New England lakes

Input of neutral salt (NaCl) from sea spray, followed by Na{sup +}-H{sup +} exchange within the soil exchange complex, has been proposed as an important factor in surface water acidification of coastal areas. This hypothesis was tested on a regional basis by comparing the Na:Cl ratio of lake water with that of precipitation for the coastal lakes included in the US Environmental Protection Agency Eastern Lake Survey-I in New England. The precipitation Na:Cl ratio closely approximated that of seawater at monitoring stations located within approximately 20 km of the coast. Few lakes in this coastal region exhibited a Na:Cl ratio less than that observed in precipitation. Those lakes that were acidic (ANC {<=} 0) showed no tendency toward a lowered Na:Cl ratio. Sodium contribution from, rather than retention by, watershed soils was suggested by the data from these lakes. Although episodic acidification of runoff due to NaCl deposition may occur, there is little support for the neutral salt effect being an important long-term acidifying process in Northeastern lakes.

Nutrient Retention by Savanna Ecosystems: II. Retention After Fire

(1) The daily patterns of precipitation, soil water movement, and the concentration of nutrient elements in soil solutions at five depths were examined beneath three types of savanna in Belize, Central America, after burning. (2) Large increases in the concentration of some elements were recorded in the rooting zones in all types, but these disappeared within 1 week. Despite much percolation, no comparably large increases were recorded in solution concentrations deeper in the soil. (3) A comparison of the mean element concentrations after this post-fire peak with concentrations before the burn, and during an equivalent period 1 year earlier. showed many significant increases in concentration in the topsoil, but few increases in deeper soil. Ca and P appear to have been most effectively retained, Mg and K less so, and Na the least. (4) The results confirm the resistance of the three savanna types to acute losses of nutrients due to leaching after fire, and it is suggested that greater losses are likely to result from surface run-off during rainstorms. However, repeated burning has not significantly reduced the fertility of the surface soil, but has significantlv increased the amounts of Ca and Mg in the soil exchange complex.

Spatial and temporal variations in concentrations of three ions in solutions extracted from a woodland soil

Concentrations of Cl, Mg and K in soil solutions extracted from a gleyic brown earth under mixed oak woodland were measured at weekly intervals over a 1 year period. Spatial variability of ion concentrations was large, with coefficients of variation of 30–90% in a 0.1 ha plot. Seasonal variability in Mg and K was effectively buffered by the soil exchange complex, but Cl displayed a distinct pattern with a maximum concentration in late autumn. Flushing of Cl during soil rewetting is the most probable explanation.

Acid rain and soil.

A summary of important chemical properties of soil is given and the way in which acid rain may affect these properties is discussed. Acid rain may suppress microbiological decomposition and nitrification processes, thus influencing the nutrient status of soils. It has also been found that soil organic matter is less soluble in more acid solutions. Changed nutrient availability patterns are predicted in a low pH environment and enhanced leaching of essential elements from the soil exchange complex has been observed. Increased solubility of potentially toxic elements such as aluminium may also occur from soils which have been exposed to acidified rainfall.

Spatial and temporal variations in concentrations of three ions in solutions extracted from a woodland soil

Concentrations of Cl, Mg and K in soil solutions extracted from a gleyic brown earth under mixed oak woodland were measured at weekly intervals over a 1 year period. Spatial variability of ion concentrations was large, with coefficients of variation of 30–90% in a 0.1 ha plot. Seasonal variability in Mg and K was effectively buffered by the soil exchange complex, but Cl displayed a distinct pattern with a maximum concentration in late autumn. Flushing of Cl during soil rewetting is the most probable explanation.

PRECIPITATION OF CARBONATES IN SOILS IN CONTACT WITH WATERS UNDERSATURATED OR OVERSATURATED IN RESPECT TO CALCITE*

SummaryUnder transient conditions, the precipitation of carbonates in a calcareous and a non‐calcareous soil was influenced by calcium, magnesium and bicarbonate ions from soil sources. These sources were: the soil solution, the soil exchange complex and the dissolution of aluminosilicates. There was no significant difference between the amount of carbonates which precipitated in the two soils when in contact with the same water. It was found that for small portions of water in contact with the two soils, precipitation of carbonates took place both from under‐saturated and the over‐saturated waters. As the cumulative amounts of water in contact with the soils increased, the amount of ions contributed by the residual soil solutions and the exchange complexes decreased, and the amount of precipitating carbonates decreased also. At very large cumulative amounts of water, the precipitation of carbonates in the soils was controlled by both the water and the ions released from the soils.

Chemistry of bulk precipitation throughfall, soil water and stream water in a small catchment in Devon, England

Monthly mean concentrations of potassium, calcium, sodium, magnesium chloride and nitrate-nitrogen were determined from samples of bulk precipitation, throughfall, soil water and streamflow collected weekly between April 1975 and September 1977 in a small catchment in Devon, England. Soil water concentrations are compared with the analysis of exchange capacity in composite soil samples. Rain contributed much sodium and chloride to total catchment output, and potassium was selectively enriched in throughfall. Calcium and magnesium concentrations were high in soil water samples and on the soil exchange complex.

Transient Changes in the Soil‐water System from Irrigation with Saline Water: I. Theory

AbstractTransient soil solution concentrations and salt precipitation rates in the root zone are shown to be influenced by the ion composition and concentration of the applied water and soil exchange complex as well as by the water uptake distribution and infiltration rate. Calculations are performed on three kinds of infiltration water to estimate the ionic composition of the soil solution, the rate of gypsum and CaCO3 precipitation, and the time to reach steady state for a given irrigation management. Solution concentrations adjusted for exchange interactions were shown to precipitate twice the quantity of salt in a given time, resulting in lowered solution concentration and altered composition of Ca2+, Mg2+, Na2+, and SO42‐ ion concentrations in the solution phase, with up to 1,600 days required to reach steady state through the top 150 cm for a leaching fraction of 0.05. The extent of precipitation is also found to depend strongly on the concentration of sulfate and degree of saturation with gypsum in the irrigation water. Diffusion and dispersion are also shown to influence the duration of the transient phase.

The geobiology of calcium

Abstract Calcium is present in igneous rocks to the extent of about 3.6 per cent. The exchange complex of most soils carries comparatively large quantities of calcium but the geologic trend at present is a net movement of calcium from the continental shields to the continental shelves, and hemipelagic and pelagic sediments. There is a continual return by oceanic circulation to shelf and hemipelagic zones and a small return to land by oceanic spray generated aerosols. A universal requirement of plants and animals for calcium figures strongly in oceanic cycling and the influence of plants and microorganisms on the carbonic acid‐carbonate system modulates its terrestrial mobility.

EFFECT OF NITROGEN ON CESIUM-137 IN SOILS AND ITS UPTAKE BY OAT PLANTS

In an experiment designed to show the effects of time of addition of NH4 relative to Cs-137 and of NH, compared with NO3, the results showed conclusively that NH4 caused higher Cs-137 concentrations in oats than did the NO3 form of N at low soil K contents. The results were less conclusive for soils to which K had been applied. When NH4 was applied before Cs-137, in most instances the Cs-137 concentration was higher than when Cs was applied before NH4 without added K. When K was added, however, the trends were for the most part the reverse. Thus NH4, K and Cs-137 in the soil interact for sites on the soil exchange complex and the amount of Cs-137 taken up by the plant is a function of this interaction.Liming of one acid soil consistently increased the Cs-137 concentration and uptake, whereas in another acid soil the effects of liming were less consistent.

Reactions of Surfactants with Montmorillonitic Soils

AbstractTwo montmorillonitic soils were treated with each of eight surfactants at three treatment rates: 1%, 0.1%, and 0.01% by weight. The effects of the treatments on certain important physical properties of the soils were investigated by means of aggregate stability analysis, capillary rise measurements, and modulus of rupture.The surfactants included three anionic, three cationic, and two nonionic compounds. The anionics were not strongly adsorbed by the soils. When the soils were dried in contact with them, they were weakly held and readily released to the liquid phase upon rewetting. Their effects on soil physical properties were directly related to the lowering of surface tension of the liquid phase, and the magnitude of the effect was strongly dependent on treatment rate.The cationics were strongly adsorbed by the soil exchange complex and not readily released upon rewetting. Their effects on soil physical properties were directly related to the degree of hydrophobicity imparted, which increased with alkyl chain length and amount of material added to the soil.The nonionics were adsorbed by hydrogen‐bonding to clay and other oxygen‐rich mineral surfaces. Their sorption energy was somewhat greater than that of water, and they displaced water from the surfaces. Their effects on soil physical properties were small and in proportion to the amount of chemical added. Those effects were related to reduced hydration of surfaces and the hydrophilic centers associated with the nonionic compounds.

Prediction of the Concentration of Solutes in Soil Solutions For Soil Systems Containing Gypsum and Exchangeable Ca and Mg

AbstractThe equilibrium relationships for the solubility of CaSO4 in solution and the exchange of Ca++ and Mg++ between solution and the soil exchange complex may be used in conjunction with the Debye‐Hückel theory to predict the equilibrium concentrations of the ions in solution and ions adsorbed by the exchanger when distilled water or a solution of Ca++ and/or Mg++ salts is used to wet a Ca‐Mg‐soil which contains an excess of CaSO4.The equilibrium concentration of the solution and adsorbed ions have been calculated for mixtures of CaSO4, Yolo soils, containing different ratios of Ca++ to Mg++, and distilled water or 0.05 M MgCl2. The ionic concentration of the equilibrium solution was also determined experimentally for these same mixtures. The theoretical and measured concentrations of the ions in the equilibrium solution are compared.