Interactions between anthropogenic sulphate and marine salts in the Bs horizons of acidic soils in Scotland

In laboratory adsorption experiments, the comparison of podzol Bs horizons from coastal and inland moderately-impacted catchments with those from a severely-acidified inland region has demonstrated the effect of marine inputs on SO₄ ^2– -retention. Moderate sea-salt inputs and low acid deposition leads to the retention of most of the SO₄ ^2– and the release of soluble Mg²⁺; increasing the marine salt loading causes the development of a selectivity towards retention of acidic SO₄ ^2– and the retention of Mg²⁺. In the highly-impacted soil, the marine input caused a decrease in SO₄ ^2– retention in open moorland soils. The opposite occurred under forest, due to the ion-exchange of marine Mg²⁺ for soil Al³⁺, increasing soil acidity towards the pH₀ (Gillman and Uehara, 1980), which is depressed below that of its moorland equivalent.     

Effectiveness of crop straws,and swine manure in ameliorating acidic red soils: a laboratory study

Purpose

Crop straws and animal manure have the potential to ameliorate acidic soils, but their effectiveness and the mechanisms involved are not fully understood. The aim of this study was to evaluate the effectiveness of two crop (maize and soybean) straws, swine manure, and their application rates on acidity changes in acidic red soils (Ferralic Cambisol) differing in initial pH.

Materials and methods

Two red soils were collected after 21 years of the (1) no fertilization history (CK soil, pH 5.46) and (2) receiving annual chemical nitrogen (N) fertilization (N soil, pH 4.18). The soils were incubated for 105 days at 25 °C after amending the crop straws or manure at 0, 5, 10, 20, and 40 g kg^?1 (w/w), and examined for changes in pH, exchangeable acidity, N mineralization, and speciation in 2 M KCl extract as ammonium (NH₄⁺) and nitrate plus nitrite (NO₃^??+?NO₂^?).

Results and discussion

All three organic materials significantly decreased soil acidity (dominated by aluminum) as the application rate increased. Soybean straw was as effective (sometimes more effective) as swine manure in raising pH in both soils. Soybean straw and swine manure both significantly reduced exchangeable acidity at amendment rate as low as 10 g kg^?1 in the highly acidic N soil, but swine manure was more effective in reducing the total acidity especially exchangeable aluminum (e.g., in the N soil from initial 5.79 to 0.50 cmol₍₊₎ kg^?1 compared to 2.82 and 4.19 cmol₍₊₎ kg^?1 by soybean straw and maize straw, respectively). Maize straw was less effective than soybean straw in affecting soil pH and the acidity. The exchangeable aluminum decreased at a rate of 4.48 cmol₍₊₎ kg^?1 per pH unit increase for both straws compared to 6.25 cmol₍₊₎ kg^?1 per pH unit from the manure. The NO₃^??+?NO₂^? concentration in soil increased significantly for swine manure amendment, but decreased markedly for straw treatments. The high C/N ratio in the straws led to N immobilization and pH increase.

Conclusions

While swine manure continues to be effective for ameliorating soil acidity, crop straw amendment has also shown a good potential to ameliorate the acidity of the red soil. Thus, after harvest, straws should preferably not be removed from the field, but mixed with the soil to decelerate acidification. The long-term effect of straw return on soil acidity management warrants further determination under field conditions.

     

Influence of sea salts on the soil metabolism

Abstract

Microbial metabolism in reduction process of waterlogged paddy soils has been studied by Takai, Koyama, and Kamura (1, 2, 3, 4, 5, 6), Koyama (7, 8, 9, 10, 11, 12), and others. The results indicated that microbial metabolism in waterlogged soils takes place according to the following steps: (1) In the early stage of the incubation period, dissolved O₂, is consumed and the redox potential drops rapidly. (2) NO₂? and NO₂? are reduced to N₂. (3) Mn⁴⁺ is reduced to Mn²⁺. (4) Fe³⁺ is reduced to Fe²⁺. (5) SO₄ ²? is reduced to S^2?. (6) H₂ and CH₄ are produced. Takai and Chiang (13) reported that NH₄₊ and PO₄ ³⁺ in waterlogged paddy soils increase with the incubation period. Chiang and Takai (14) indicated that carbohydrates in the soil solutions almost remain constant throughout the incubation period, however, organic acids change similarly to those reported previously (5, 6).     

Band-applied elemental sulfur to enhance the phytoavailability of phosphorus in alkaline calcareous soils

Summary Applications of elemental sulfur (S°) increase the phytoavailability of P in alkaline high-Ca soils through the production of H₂SO₄ which is induced by microbial oxidation of S. Concentrated S bands, allowing time release acidity, may aid in maintaining the phytoavailability of both residual and fertilizer P. Greenhouse and field studies were therefore conducted to determine the effectiveness of band-applied S° for increasing the phytoavailability of residual and fertilizer P for spring wheat (Triticum aestivum L.) and corn (Zea mays L.). We also used inoculation of S° with Thiobacillus thioparus to determine whether it is necessary or helpful in alkaline soils to initiate acidification. Treatments were inoculation, S°, S° + inoculation, triple superphosphate, triple superphosphate + S°, triple superphosphate + inoculation, and triple superphosphate + S° + inoculation applied to three alkaline soils: Typic Argiborolls, Borollic Calciorthids, and Ustollic Haplargids. P availability was determined by plant uptake of P, NaHCO₃-extractable P, dry-matter yield, grain yield and grain-protein production, and on available-P index (NaHCO₃-extractable P, post-harvest, + plant uptake of P). Application of S° with triple superphosphate gave a significantly higher available-P index than triple superphosphate alone on all three soils. Inoculation of S° with T. thioparus increased soil acidity; however, in some cases this treatment eliminated the beneficial effect of S°. Grain yields of wheat increased with S° applications at one of two field sites. These results suggest that applying S° with triple superphosphate may be an effective means of increasing soil P availability and the efficiency of superphosphate fertilizers on alkaline high-Ca soils.     

Acidification and salinization of soils with different initial pH under greenhouse vegetable cultivation

Purpose

Field survey and sampling of vegetable greenhouse soils were conducted in Shouguang, Shandong Province, and Ningbo, Zhejiang Province to study the acidification and salinization characteristics of soils with different initial soil pH values and greenhouse cultivation time.

Materials and methods

The pH, electrical conductivity (EC), and ion composition of 74 composite soil samples were analyzed to evaluate their relation to soil acidification and salinization.

Results and discussion

Compared with their corresponding open-field soils, acidification and salinization of the greenhouse soils occurred in both 0-20 cm and 20-40 cm soil layers for the Shouguang and Ningbo soils. The soil pH decreased gradually at different rates as greenhouse cultivation time increased in the two surveyed regions, but the opposite trend was observed for soil EC. For the Shouguang soils, while the percentages of K⁺ and NO₃ ^? increased dramatically and Ca²⁺ and HCO₃ ^- decreased significantly after the soils were converted to greenhouse use, the correlation between soil pH and EC was significant, and the stepwise multiple regression analysis further showed that there was a significant correlation between pH and the percent of Ca²⁺ and HCO₃ ^?.

Conclusions

Soil acidification and salinization are common in greenhouse soils with different initial soil pH. Soil acidification in the Shouguang soils is a result of decrease in the percent of Ca²⁺, HCO₃ ^? due to over application of N and K fertilizers. Future research should be devoted to understanding the relevant mechanisms in greenhouse soils with lower initial soil pH values to assess if there are correlations between soil acidification and salinization under greenhouse cultivation.     

Acidic precipitation at a site within the northeastern conurbation

Rain and snow were collected in plastic beakers either manually or with a Wong sampler during 58 precipitation events in 1974 at Yonkers, New York approximately 24 km north of the center of New York City. Determinations were made of total dissolved ionic species, free H ions, total H ions, sulfate, nitrate, chloride, and fluoride. Conductivity measurements ranged from 6.8 to 162 gmhos, pH from 3.4 to 4.9, total acidity from 36 to 557 μeq 1^?1 sulfate from less than 1 to 20 mg 1^?1, nitrate from less than 1 to 14 mg 1^?1, and chloride from less than 1 to 7 mg 1^?1. All fluoride concentrations were less than 0.1 mg 1^?1. The results indicate that precipitation at this suburban location adjacent to New York City is consistently acidic and contains concentrations of sulfate, nitrate, and chloride which are similar to values found for other locations in the northeastern United States. Positive correlations were found between nitrate and sulfate concentrations and acidity suggesting that the atmospheric contaminants, SO₂, and NO₂ are causally-related to the occurrence of acidic precipitation. Further research will be necessary to clarify the relative influence of natural and man-made sources of N and S compounds and the contributions of gaseous and particulate contaminants in the atmosphere to the acidity of precipitation at this location.     

Exploring the effect of organic matter on the interactions between mineral particles and cations with Wien effect measurements

Purpose

Understanding of the interactions between cations, mineral particles, and organic matter (OM) in soils is of paramount importance in plant nutrition and environmental science, and thus, these phenomena have been studied extensively. At present, an effective and simple tool to investigate these interactions does not exist. Based on previous studies of Wien effect in suspensions, the interactions of cations with soil mineral particles, complicated by the presence of organic matter, can be easily determined by means of Wien effect measurements, which was the objective of this study.

Materials and methods

A paddy soil originating from a yellow-brown soil, rich in organic matter, served as a test sample, from which the clay fraction of less than 2 μm in diameter was separated. Organic matter of aliquots of the clay fraction was removed by the oxidation with hot H₂O₂, and the natural and OM-free samples were saturated with various cations: Na⁺, K⁺, Ca²⁺, and Cd²⁺. The effects of OM present in the paddy soil on the interactions between the cations and the soil mineral particles were investigated by measuring the suspension Wien effect with a homemade apparatus, SHP-2.

Results and discussion

The weak electrical field electrical conductivities (EC₀) of suspensions of the natural soils saturated with various cations were higher than those of the OM-free soils. The rate of increase in electrical conductivity of suspensions of the OM-free soil, except that of suspensions saturated with Na⁺, at electrical field strengths >50～100 kV?cm^?1 was higher than those of the natural soil suspensions. The presence of OM increased the mean free binding energies of cations other than Na⁺. The increasing binding energies for K⁺ and Ca²⁺ were 0.56 and 0.57 kJ?mol^?1, respectively, which were significantly larger than the increase for Cd²⁺ as only 0.03 kJ?mol^?1. The binding energies of various cations on both natural and OM-free soils were all in the order: Na⁺?<?K⁺?<?Ca²⁺≈Cd²⁺. As opposed to its effect on the binding energies, the presence of OM reduced the mean free adsorption energies of the cations. Except for Na⁺, the adsorption energies of K⁺, Ca²⁺, and Cd²⁺ at field strengths >50 kV?cm^?1 were lower in the natural soil as compared with the OM-free soil, and the differences between the adsorption energies became larger with increasing field strengths. The presence of OM made the zeta potential of the soil particles saturated with Na⁺ and K⁺ positive, and the particles saturated with Ca²⁺ and Cd²⁺ negative.

Conclusions

Organic matter affected the interactions of cations with soil mineral particles significantly. Binding and adsorption energies, which were quantitative measures of the interactions between cations and soil particles, could be determined by Wien effect measurements in suspensions. The binding energies on natural soils were larger than those on the corresponding OM-free soils, and the adsorption energies on the natural soils were lower than those on OM-free soils.     

Effect of low energy-consuming biochars in combination with nitrate fertilizer on soil acidity amelioration and maize growth

Purpose

We evaluated the ameliorative effects of crop straw biochars either alone or in combination with nitrate fertilizer on soil acidity and maize growth.

Materials and methods

Low energy-consuming biochars were prepared from canola and peanut straws at 400 °C for 2 h. Incubation experiment was conducted to determine application rate of biochars. Afterward, maize crop was grown in pots for 85 days to investigate the effects of 1 % biochars combined with nitrate fertilizer on soil pH, exchangeable acidity, and maize growth in an Ultisol collected from Guangdong Province, China.

Results and discussion

Application of 0.5, 1.0, and 1.5 % either canola straw biochar (CSB) or peanut straw biochar (PSB) increased soil pH by 0.15, 0.27, 0.34, and 0.30, 0.58, 0.83 U, respectively, after 65-day incubation. Soil pH was increased by 0.49, 0.72, 0.78, and 0.88 U when 1 % CSB or PSB was applied in combination with 100 and 200 mg N/kg of nitrate, respectively, after maize harvest in greenhouse pot experiment. These low-cost biochars when applied alone or in combination with nitrate not only reduced soil exchangeable acidity, but also increased Ca²⁺, Mg²⁺, K⁺, Na⁺, and base saturation degree of the soil. A total of 49.91 and 80.58 % decreases in exchangeable acidity were observed when 1 % CSB and PSB were incubated with the soil for 65 days, compared to pot experiment where 71.35, 78.64, 80.2, and 81.77 % reductions of exchangeable acidity were observed when 1 % CSB and PSB were applied in combination with 100 and 200 mg N/kg of nitrate, respectively. The higher contents of base cations (Ca²⁺, Mg²⁺, K⁺, Na⁺) in biochars also influenced the plant growth. The higher biomass in CSB-treated pots was attributed to the higher K content compared to PSB. The higher percent reduction in exchangeable Al³⁺ by applying 1 % CSB combined with 200 mg N/kg of nitrate consistently produced maximum biomass (129.65 g/pot) compared to 100 mg N/kg of nitrate and 1 % PSB combined with 100 and 200 mg N/kg of nitrate. The exchangeable Al³⁺ mainly responsible for exchangeable acidity was decreased with the application of biochars and nitrate fertilizer. A highly significant negative relationship was observed between soil exchangeable Al³⁺ and plant biomass (r ²?=?0.88, P?<?0.05).

Conclusions

The biochars in combination with nitrate fertilizer are cost-effective options to effectively reduce soil acidity and improve crop growth on sustainable basis.

     

A method for evaluation of acidic sulfate and nitrate in precipitation

A simple method is presented and used to estimate the portions of SO _inf4 ^sup2? and NO _inf? ^sup3 that contribute to the strong acidity in weekly precipitation samples collected at three NADP sites in the eastern United States. The method assumes that, in general, the difference between SO _inf4 ^sup2? and NH _inf+ ^sup4 represents acidic sulfate and the difference between NO _inf? ^sup3 and soil-derived materials (the sum of Ca²⁺, Mg²⁺, and K⁺) represents acidic nitrate. Acidic sulfate and nitrate are considered to be the predominant source of H⁺ (determined from laboratory pH) in the weekly precipitation samples. Most of the acidity for all three sites was attributed to acidic sulfate. The highest fraction of acidic SO _inf4 ^sup2? to H⁺ wet deposition values was for the east-central Tennessee site (0.95) and the northeastern Illinois site (0.90), and the lowest fraction occurred at the central Pennsylvania site (0.75). The Tennessee site had the greatest acidic fraction of sulfate (0.84) and the Pennsylvania site had the greatest acidic fraction of nitrate (0.59).     

Influence of Different Forms of Iron and Aluminum on the Nature of Soil Acidity of Some Inceptisols,Alfisols, and Ultisols

Abstract

Fifteen acid soils of Mizoram representing Ultisols and Inceptisols, and Madhya Pradesh, representing Alfisols, were studied to characterize the nature of acidity in relation to different forms of iron (Fe) and aluminum (Al). The mean contents of Fe and Al were extracted by various extracting reagents and were found to be in descending order as followed: dithionite>oxalate>pyrophosphate>ammonium acetate>KCl. The electrostatically bonded EB‐H⁺ and EB‐Al³⁺ acidity comprised 28.3 and 71.7% of exchangeable acidity whereas EB‐H⁺, EB‐Al³⁺, exchangeable, and pH‐dependent acidities comprised 9.8, 30.7, 40.5, and 59.5% of total potential acidity. All forms, of acidity showed significant correlation with pH_k and organic carbon. Among the different forms, Fe and Al caused most of the variations in different forms of soil acidity but the effect of different forms of Al are more active and directly participate in the formation of EB‐H⁺, EB‐Al³⁺, and exchangeable acidity.     

Nutrient Fluxes in Planted Norway Spruce Stands of Different Age in Southern Poland

The fluxes of N–NO ₃ ^? , N–NH ₄ ⁺ , S–SO ₄ ^2? , Na⁺, K⁺, Ca²⁺ and Mg²⁺ from bulk precipitation to throughfall, stemflow and soil water surface flows were studied during 1999–2003 in planted Norway spruce forest stands of different ages (11, 24, 91 and 116 years in 1999). Also, runoff from the corresponding Potok Dupniański Catchment in the Silesian Beskid Mts was studied. N deposition was above the critical load for coniferous trees. The interception increased with stand age as well as leaf area index and so did the leaching from the canopy of almost all the analysed elements, but especially S–SO ₄ ^2? , H⁺ and K⁺. The nutrient fluxes varied with age of the spruce stands. Throughfall showed a high amount of S and of the strong acids (S–SO ₄ ^2? and N–NO ₃ ^? ) deposited to the soil, especially in older spruce age classes. Decomposition of organic matter caused a rise in water acidity and an increase in the concentrations of all the analysed ions; the leaching of minerals, however, was low (under 1%). The horizontal soil water flow showed an increase in the amount of water and amount of ions and contributed to a further decrease of pH at the soil depth of 20 cm. Element concentrations and their amounts increased with water penetrating vertically and horizontally on the slopes. Considerable amounts of ions, especially S and alkaline cations, were carried beyond the reach of the root system and then left the catchment. In the long term, these mineral losses will adversely affect health and growth of the spruce stands, and the increased acidity with stand age will presumably have negative effects on the runoff water ecosystem.     

Impacts of continuous excessive fertilization on soil potential nitrification activity and nitrifying microbial community dynamics in greenhouse system

Purpose

Sampling and analysis of greenhouse soils were conducted in Shouguang, China, to study continuous excessive fertilization effect on nitrifying microbial community dynamics in greenhouse environment.

Materials and methods

Potential nitrification activity (PNA), abundance, and structure of nitrifying microbial communities as well as the correlations with soil properties were investigated.

Results and discussion

Short-term excessive fertilization increased soil nutrient contents and the diversity of nitrifying microbial communities under greenhouse cultivation. However, the abundance and diversity of nitrifying communities decreased greatly due to the increase of soil acidity and salinity after 14 years of high fertilization in greenhouse. There was a significant positive correlation between soil PNA and the abundance of ammonia-oxidizing bacteria (AOB) but not that of ammonia-oxidizing archaea (AOA) in topsoil (0–20 cm) when pH ≥7. Soil PNA and AOB were strongly influenced by soil pH. The groups of Nitrososphaeraceae, Nitrosomonadaceae, and Nitrospiraceae were predominant in the AOA, AOB, and nitrite-oxidizing bacteria (NOB) communities, respectively. Nitrifying community structure was significantly correlated with soil electrical salinity (EC), organic carbon (OC), and nitrate nitrogen (NO₃ ^?–N) content by redundancy analysis (RDA).

Conclusions

Nitrification was predominated by AOB in greenhouse topsoil with high fertilizer loads. Soil salinity, OC, NO₃ ^?–N content, and pH affected by continuous excessive fertilization were the major edaphic factors in shaping nitrifying community structure in greenhouse soils.

     

Evaluating the fraction of electrically associated cations on surfaces of soil particles by extrapolation of strong-field Wien effect measurements in dilute suspensions

Purpose

For agricultural production and environment protection, it is cations loosely bound to the soil particles that have a great significance in short-term processes of adsorption–desorption, exchange, and transport. It is beneficial to be able to evaluate the fractions of these cations in order to correctly predict potential pollution of soils by heavy metals and availability of plant nutrients.

Materials and methods

The homionic suspensions of yellow-brown soil (YB) and black soil I (BI) saturated with Na⁺ and Ca²⁺ and three subsamples of black soil II (BII) saturated with Ca²⁺ and Cd²⁺ were prepared to determine the electrical conductivity (EC) of the suspensions. On the basis of electrical conductivity vs. field strength (EC-E) curve, the fraction of electrically associated cations on surfaces of soil particles was evaluated by extrapolation of strong-field Wien effect measurements in dilute suspensions.

Results and discussion

The maximum dissociation degree (α _max) of Na⁺ adsorbed on surfaces of yellow-brown soil and black soil I was about 0.21, which is approximately twice as much as those of Ca²⁺ (0.07–0.10) adsorbed on surfaces of two soils. The soil type was not the main factor in evaluating α _max, and the valence of the cations was. For divalent cations, α _max of Ca²⁺ and Cd²⁺ adsorbed on soil particles with different contents of organic matter descended in the order: top black soil II?>?bottom black soil II?>?OM-free bottom black soil II.

Conclusions

The relatively small fractions of electrically adsorbed cations—about 0.2 for Na⁺ and 0.1 for Ca²⁺ on yellow-brown and black soils particles indicated that even for the more loosely adsorbed Na⁺ ions, most of the cations in the double layers of soil particles were adsorbed strongly by other, more specific mechanisms and cannot be stripped off into the solution, which would increase its electrical conductivity in a strong applied field.

     

Temporal variation in aluminum speciation and concentration during snowmelt

Precipitation samples in Alberta were collected and analyzed monthly from six Alberta Environment stations. Samples were collected with Sangamo samplers and analyzed for the major ions, pH and acidity. The data were tabulated and analyzed for spatial distribution, seasonal variation, temporal trends, ionic character and wet sulphate deposition. The major ionic species in Alberta precipitation are Ca²⁺, SO _inf4 ^sup2? , NH _inf4 ^sup+ and N0 _inf3 ^sup? . The spatial distribution shows a slight decrease in pH from southern Alberta (pH 6.0) to northern Alberta (pH 5.4). The seasonal variation shows higher hydrogen ion content in the summer months (pH 5.4 in summer and pH 5.8 in winter). Temporal trends are not apparent over the five year period investigated. The five year average wet sulphate deposition rate in Alberta is 9.1 kg ha^?1 yr^?1.     

华南红壤的交换性碱和交换性酸

本文提出了一个同时测定土壤的交换性酸和交换性碱的简易方法。将土壤的交换性酸和交换性碱区分为:Na-交换性酸、Ba-交换性酸和SO₄-交换性碱、F-交换性碱。用推荐的方法,在野外对华南地区由不同母质发育的砖红壤、赤红壤、红壤等10个剖面进行了测定。结果表明,红壤类土壤含有相当量的交换性碱,但其数量比交换性酸少。酸性母质发育的土壤的交换性酸和交换性碱量大于由基性岩发育的土壤者。红壤的交换性酸和碱的量随电性盐浓度的增高而增大,浓度大于0.1N后,数量基本不变。     

胀果甘草原生境土壤盐分特征分析

 通过野外调查采样和土样化学测定,分析胀果甘草原生境下土壤盐分的特征。结果表明:研究区土壤盐分普遍较高且表聚作用明显,土壤表层0～10 cm土层盐分均值高达32+.08g/kg,属典型的强度盐渍化土;土壤盐分组成中,含阳离子Ca2+、Na+、Mg2+、K+和阴离子Cl-、SO24、HCO-3,不含CO2-3,土壤盐分的特征因子为Ca2+、C1-、SO2-4、NaCa+,其盐渍类型主要为硫酸盐-氯化物型,重碳酸盐是土壤盐分的次要成分;该生境土壤中在整个垂直剖面上Ca2+的含量丰富,属典型钙质土。     

Biotic and abiotic processes controlling water chemistry during snowmelt at rabbit ears pass,Rocky Mountains,Colorado, U.S.A.

The chemical composition of snowmelt, groundwater, and streamwater was monitored during the spring of 1991 and 1992 in a 200-ha subalpine catchment on the western flank of the Rocky Mountains near Steamboat Springs, Colorado. Most of the snowmelt occurred during a one-month period annually that began in mid-May 1991 and mid-April 1992. The average water quality characteristics of individual sampling sites (meltwater, streamwater, and groundwater) were similar in 1991 and 1992. The major ions in meltwater were differentially eluted from the snowpack, and meltwater was dominated by Ca²⁺, SO ₄ ^2? , and NO ₃ ^? . Groundwater and streamwater were dominated by weathering products, including Ca²⁺, HCO ₃ ^? (measured as alkalinity), and SiO₂, and their concentrations decreased as snowmelt progressed. One well had extremely high NO ₃ ^? . concentrations, which were balanced by Ca²⁺ concentrations. For this well, hydrogen ion was hypothesized to be generated from nitrification in overlying soils, and subsequently exchanged with other cations, particularly Ca²⁺. Solute concentrations in streamwater also decreased as snowmelt progressed. Variations in groundwater levels and solute concentrations indicate that most of the meltwater traveled through the surficial materials. A mass balance for 1992 indicated that the watershed retained H⁺, NH ₄ ⁺ , NO ₃ ^? , SO ₄ ^2? and Cl^? and was the primary source of base cations and other weathering products. Proportionally more SO ₄ ^2? was deposited with the unusually high summer rainfall in 1992 compared to that released from snowmelt, whereas NO ₃ ^? was higher in snowmelt and Cl^? was the same. The sum of snowmelt and rainfall could account for greater than 90% of the H⁺ and NH ₄ ⁺ retained by the watershed and greater than 50% of the NO ₃ ^? .     

Yield,Nutrient Uptake,and Changes in Soil Chemical Properties as Influenced by Liming and Iron Application in Common Bean in a No-Tillage System

Soil acidity is the principal limiting factor in crop production in Oxisols, and deficiency of micronutrients has increased in recent years because of intensive cropping. A field experiment was conducted over three consecutive years to assess response of common bean (Phaseolus vulgaris L.) to lime and iron (Fe) applications on an Oxisol in a no-tillage system. Changes in selected soil chemical properties in the soil profile (0- to 10- and 10- to 20-cm depths) with liming were also determined. Lime rates used were 0, 12, and 24 Mg ha^–1, and Fe application rates were 0, 50, 100, 150 200, and 400 kg ha^–1. Both lime and Fe were applied as broadcast and incorporated in the soil. Grain yields of common bean were significantly increased with the application of lime. Iron application, however, did not influence bean yield. There were significant changes in soil profile (0- to 10-cm and 10- to 20-cm depths) in pH, calcium (Ca²⁺), magnesium (Mg²⁺), hydrogen + aluminum (H⁺ + Al³⁺), base saturation, acidity saturation, cation exchange capacity (CEC), Ca²⁺ saturation, Mg²⁺ saturation, potassium (K⁺) saturation, and ratios of Ca/Mg, Ca/K, and Mg/K. These soil chemical properties had significant positive association with common bean grain yield. Averaged across two depths and three crops, common bean produced maximum grain yield at pH_w 6.3, Ca²⁺ 3.8 cmol_c kg^–1, Mg²⁺ 1.1 cmol_c kg^–1, 3.5 H⁺ + Al³⁺ cmol_c kg^–1, acidity saturation 41.8%, CEC 7.5 cmol_c kg^–1, base saturation 57.4%, Ca saturation 45.2%, Mg saturation 14.2%, K saturation 9.1%, Ca/Mg ratio 3.1, Ca/K ratio 22.6, and Mg/K ratio 6.7.     

Response of Physic Nut Trees to Liming of Acidic Soils

The physic nut tree (Jatropha curcas) is an oilseed species with potential for biodiesel production. We evaluated the effect of soil acidity indices on nutrient uptake for optimal growth in physic nut plants grown on acidic soils under greenhouse conditions. Two soils were used in the experiment. Maximum growth was obtained with the application of 1.05 g lime kg^-1 for both soils. Maximum growth of the physic nut plants occurred under the following conditions: pH of water = 6.1, calcium (Ca²⁺) = 17.0 mmol_c kg^?1, magnesium (Mg²⁺) = 5.7 mmol_c kg^?1, acidity saturation = 10.3%, base saturation = 52.3%, Ca saturation = 36.0%, Mg saturation = 12.0% and potassium (K) saturation = 3.8%. Furthermore, the nitrogen (N) requirement of physic nut trees was shown to be high, and to a lesser degree, Ca and Mg requirements were also high, suggesting that liming is very important in crop cultivation of this species.     

Some impacts of urban waste landfills on Mediterranean soils

Seventy soil samples around and under urban waste landfills in central Spain were studied for 28 physical and chemical properties. In the unaffected surroundings of landfills there is always a higher proportion of coarse and fine gravel. Chlorides, sulphates and nitrates increase noticeably in all the soils affected by landfills as do Na⁺, B³⁺ and Zn²⁺. Multivariate analyses show that higher or lower water retention in the surface layer plays a main role in the organization of both acid and sandier soils as well as of basic soils and those with a higher proportion of silt and clay. Depending on the acidity or basicity, however, the other main factors reveal different hierarchical levels in the soil variables with regard to the organization of these systems. Thus, in acid soils, Zn²⁺ and B³⁺ contribute most noticeably to the second hierarchical level in the edaphic organization. In basic soil without gypsum, the second important gradient of variation is the stoniness (gravel)–fine sand (<2 mm fraction) while the importance of the K⁺, B³⁺ and SO₄⁼ is relegated to the third factor. In the basic soils with gypsum, not only sulphate, but also Na⁺, Cl⁻ and Zn²⁺ plays an essential role in the first factor and the coarse surface elements are also important. The principal components analysis made it possible to establish the main factors involved in the degradation caused by leachates from landfills. Consequently, greater attention could be given to these factors with a view to rehabilitation of degraded soils. © 1998 John Wiley & Sons, Ltd.