DISTRIBUTION AND SEQUENTIAL EXTRACTION OF SOME HEAVY METALS FROM SOILS IRRIGATED WITH WASTEWATER FROM MEXICO CITY

A sequential extraction procedure was used to fractionate Cu, Cd, Pb and Zn in 4 soil profiles into the designated forms of water soluble + exchangeable, organically bound, carbonate and Mn oxides bound. Soil profiles were obtained from the Rural Development District 063, State of Hidalgo, which have been irrigated with wastewater coming out of the basin of Mexico. The total heavy metal contents range as follows: Cu, 8.9 to 86.5 mg kg^-1 Cd, 0.86 to 5.07 mg kg^-1 Pb, 18.1 to 131.7 mg kg^-1 and Zn, 101 to 235.5 mg kg^-1. The highest concentrations of total heavy metals were found in the surface layers at all soil profiles. Sequential chemical fractionation indicated that the four metals were predominantly associated with the organic fraction at most soil samples. The contents in all fractions of the four metals showed a decrease with depth which has been explained by the variations in the organic matter and CaCO₃ contents in the different layers of soils. These soil properties were also the most important variables in the biological availability of the metals in these soils.     

Influence of Lime and Gypsum on Yield and Yield Components of Soybean and Changes in Soil Chemical Properties

Soybean is one of the most important legume crops in the world. Two greenhouse experiments were conducted to determine the influence of liming and gypsum application on yield and yield components of soybean and changes in soil chemical properties of an Oxisol. Lime rates used were 0, 0.71, 1.42, 2.14, 2.85, and 4.28 g kg^?1 soil. Gypsum rates applied were 0, 0.28, 0.57, 1.14, 1.71, and 2.28 g kg^?1 soil. Lime as well as gypsum significantly increased grain yield in a quadratic fashion. Maximum grain yield was achieved with the application of 1.57 g lime per kg soil, whereas the gypsum requirement for maximum grain yield was 1.43 g per kg of soil. Lime significantly improved soil pH, exchangeable soil calcium (Ca) and magnesium (Mg) contents, base saturation, and effective cation exchange capacity (ECEC). However, lime application significantly decreased total acidity [hydrogen (H) + aluminum (Al)], zinc (Zn), and iron (Fe) contents of the soil. The decrease in these soil properties was associated with increase in soil pH. Gypsum application significantly increased exchangeable soil Ca, base saturation, and ECEC. However, gypsum did not change pH and total acidity (H + Al) significantly. Adequate soil acidity indices established for maximum grain yield with the application of lime were pH 5.5, Ca 1.8 cmol_c kg^?1, Mg 0.66 cmol_c kg^?1, base saturation 53%, Ca saturation 35%, and Mg saturation 13%. Soybean plants tolerated acidity (H + Al) up to 2.26 cmol_c kg^?1 soil. In the case of gypsum, maximum grain yield was obtained at exchangeable Ca content of 2.12 cmol_c kg^?1, base saturation of 56%, and Ca saturation of 41%.     

Changes in soil properties and soil solution nutrients due to conservation versus conventional tillage in Vertisols

Understanding of tillage effects on soil chemical properties and cations in soil solution dynamics is essential for making appropriate land-management decisions. Measurements were made after more than 25 years of different tillage treatments: conventional tillage (CT) and conservation tillage, which includes no-till (NT) and minimum tillage (MT). pH and bulk density did not show important changes but exchangeable cations and cations in soil solution were affected by depth and different tillage. The highest concentration of exchangeable Ca²⁺ and Mg²⁺ was found in NT, decreased in MT and the lowest concentration was found in CT (mean values were 26.0, 24.4 and 23.3 cmol_c kg^?1 for exchangeable Ca²⁺ and 4.2, 3.7 and 3.3 cmol_c kg^?1 for exchangeable Mg²⁺ in NT, MT and CT, respectively). In addition, the highest concentration of exchangeable Na⁺ was found in NT, decreased in CT and the lowest concentration was found in MT. However, the highest concentration of exchangeable K⁺ was found in MT. A significant depth effect was observed for cations in soil solution: Na⁺ increased with depth whereas K⁺ and Ca²⁺ decreased with depth. This study aims to demonstrate the effect of tillage on the distribution and concentration of certain chemical soil properties.     

Distribution of Forms of Copper and their Association with Soil Properties and Uptake in Major Soil Orders in Semi-arid Soils of Punjab,India

Profiles of semi-arid-zone soils in Punjab, northwestern India, were investigated for different forms of copper (Cu), including total Cu, diethylenetriaminepentaacetic acid (DTPA)–extractable Cu, soil solution plus exchangeable Cu, Cu adsorbed onto inorganic sites, Cu bound by organic sites, and Cu adsorbed onto oxide surfaces. When all soils were considered, total Cu content ranged from 7 to 37 mg kg^?1, while DTPA-extractable and soil solution plus exchangeable Cu contents ranged from 0.30 to 3.26 mg kg^?1 and from 0.02 to 0.43 mg kg^?1, respectively. Copper adsorbed onto inorganic sites ranged from 0.62 to 2.6 mg kg^?1 and that onto oxide surfaces ranged from 2.0 to 13.2 mg kg^?1. The Cu bound by organic sites ranged from 1.2 to 12.2 mg kg^?1. The magnitudes of different forms of Cu in soils did not exhibit any consistent pattern of distribution. Organic matter and size fractions (clay and silt) had a strong influence on the distribution of different forms of Cu. The content of all forms of Cu was generally greater in the fine-textured Alfisols and Inceptisols than coarse-textured Entisols. Soil solution plus exchangeable Cu, Cu held onto organic sites, and and Cu adsorbed onto inorganic sites (crystalline) had significant positive correlations with organic carbon and silt contents.The DTPA Cu was positively correlated with organic carbon, silt, and clay contents. Total Cu content strongly correlated with silt and clay contents of soils. Among the forms, Cu held on the organic site, water soluble + exchangeable Cu, and Cu adsorbed onto oxide surface were positively correlated with DTPA-extractable Cu. The DTPA-extractable Cu and soil solution plus exchangeable Cu seems to be good indices of Cu availability in soils and can be used for correction of Cu deficiency in the soils of the region. The uptake of Cu was greater in fine-textured Inceptisols and Alfisols than coarse-textured Entisols. Among the different forms only DTPA-extractable Cu was positively correlated with total uptake of Cu.     

Nutrient Element Contents and Cation Exchange Capacity in Fine Fractions of Southeastern Nigerian Soils in Relation to Their Stability

Abstract

Soils collected from 15 locations from SE Nigeria at the 0‐ to 20‐cm depth were studied for the nutrient elements of fine fractions and their role in the stability of the soils. The objective was to understand the role of these elements in the stability of the aggregates. The fine fractions were clay and silt, and elements measured in the fine fractions were exchangeable sodium (Na⁺), potassium (K⁺), calcium (Ca²⁺), magnesium (Mg²⁺), exchangeable acidity (EA), cation exchange capacity (CEC), and available phosphorus (P). The aggregate stability was measured at the microlevel with clay dispersible indices and water‐stable aggregate (WSA) <0.25 mm, and at macrolevel with other WSA indices and mean‐weight diameter (MWD). Soils varied from loamy sand to sandy clay. There were more exchangeable cations, CEC, EA, and available P in clay than in the silt fraction. Whereas EA values ranged from 2.8 to 10.4 cmol kg^?1, they were between 1.6 and 9.2 cmol kg^?1 in silt. The CEC in the clay fraction was from 7.4 to 70 cmol kg^?1 and between 4.0 and 32.8 cmol kg^?1 in the silt fraction. The WDC were from 50 to 310 g kg^?1 while the average dispersion ratio (DR) was generally higher than the corresponding clay‐dispersion ratio (CDR), and the MWD ranged from 0.45 to 2.68 mm. Soils with WSA skewed mostly to higher WSA (>2–1.00 mm) had a higher MWD. Exchangeable Ca²⁺ in clay correlated significantly with CDR and WSA sizes 1.0–0.5 mm and 0.5–0.25 mm (r=0.45,* 0.51,* and 0.60*), respectively, but negatively correlated with clay flocculation index (CFI) (r=?0.45*). Also, available P in clay correlated respectively with CDR and CFI (r=0.45*, ?0.45*), whereas K⁺ in silt correlated significantly with WDSi (r=0.64*), CFI (r=0.62*), and CDR (r=?0.65*). Principal component analysis revealed that elemental contents in the silt fraction can play very significant roles in the microaggregate stability.     

Effects of Different Rates of Ca2+ Addition on Respiration and Sorption of Water-Extractable Organic C to a Vertisol Subsoil

It is well known that calcium (Ca²⁺) plays an important role in binding organic matter to clay. However, most previous studies were conducted with either topsoil or pure aluminosilicates. Less is known about the effect of Ca²⁺ on binding of organic matter to clay-rich subsoils, which have lower organic-matter contents than topsoils, and their clays are more strongly weathered than pure aluminosilicates. Two experiments were conducted with a Vertisol subsoil (69% clay): a laboratory incubation and a batch sorption. The mineral substrate in the incubation experiment was pure sand alone or sand amended with 300 g clay kg^?1. Powdered calcium sulfate (CaSO₄) at rates of 0, 5, 10, and 15 g Ca kg^?1 and mature wheat residue at a rate of 20 g kg^?1 were added to this mineral substrate and the water content was adjusted to 70% of water-holding capacity. Carbon dioxide release was measured for 28 days. Cumulative respiration per g soil organic carbon (C) (SOC from clay and residues) was increased by clay addition. Increasing Ca²⁺ addition rate decreased cumulative respiration in the sand with clay but had no effect on respiration in the pure sand. Clay and Ca²⁺ addition had no significant effect on microbial biomass carbon (MBC) per g SOC but clay addition reduced the concentration of potassium sulfate (K₂SO₄)–extractable C per g SOC. For the batch sorption experiment, the subsoil was mixed with 0 to 15 g Ca kg^?1 and water-extractable organic C (WEOC) derived from mature wheat straw was added at 0, 1485, 3267, and 5099 mg WEOC kg^?1. Increasing Ca²⁺ addition rate increased sorption of WEOC, particularly at the greatest concentration of WEOC added, and decreased desorption. This study confirmed the importance of Ca²⁺ in binding organic matter to clay and suggests that Ca²⁺ addition to clay-rich subsoils could be used to increase their organic C sequestration.     

Upper and lower levels of boron for cotton and wheat as influenced by calcium carbonate

Abstract

Pot studies were conducted to study effect of the boron (B) levels (0, 0.12, 0.25, 0.50, 0.75, 1.0, 2.0 3.0, 4.0, 5.0 and 10?mg?B?kg^?1) and calcium carbonate (CaCO₃) (0, 1.25, 2.5 and 5.0%) on cotton and wheat crops in cropping system. In absence of CaCO_3, reduced growth of cotton and wheat were observed when B was applied @ 2.0?mg?kg^?1 soil. Necrosis of leaves in cotton and purple coloration of plumule in wheat was observed @ 10.0?mg?B?kg^?1. Irrespective of CaCO₃, 0.57 and 7.67?mg?kg^?1 Hot Water Soluble B (HWS-B), 62 and 940?mg?kg^?1 B dry matter (DM) of leaves, 45 and 210?mg?B?kg^?1 DM of petioles and 20 and 51?mg?B?kg^?1 DM of sticks, produced 90 and 50%of the maximum dry matter yield (DMY) of cotton, respectively. The values for wheat were 0.66 and 6.71?mg HWS-B kg^?1, 7.94 and 27.0?mg?B?kg^?1 grain and 15.3 and 170?mg?B?kg^?1 straw, respectively.     

Zinc adsorption characteristics of selected calcareous soils of Iran and their relationship with soil properties

Abstract

The apparent recovery of applied zinc (Zn) by plants is very low in calcareous soils of Iran because most of it is retained by the soil solids. Subsamples of 24 surface soil (clay 130–530 g kg^‐1; pH 7.7–8.4; electrical conductivity 0.63–3.10 dS m^‐1; organic matter 6.0–22.0 g kg^‐1; cation exchange capacity 8–20 cmol kg^‐1; calcium carbonate (CaCO₃) equivalent 180–460 g kg^‐1) representing 13 soil series in three taxonomic orders were equilibrated with zinc sulphate (ZnSO₄) solutions and the amount of Zn disappeared from solution after a 24‐h shaking period was taken as that adsorbed (retained) by the soil solids. The adsorption data were fitted to Freundlich (X=AC^B) and Langmuir [X=(K‐bC)/(1+K#lbC)] adsorption isotherms. Backward stepwiseprocedure was used to obtain regression equations with isotherms coefficients as dependent and soil properties as independent variables. Freundlich A and Langmuir K were found to be highly significantly related to pH and clay and increasing as these soil properties increased. But Langmuir b was related only to clay and Freundlich B showed no significant relationship with any of the properties studied. The distribution coefficient (also called maximum buffering capacity), calculated as the product of Langmuir K and b, was also found to be highly significantly related to pH and clay. It is concluded that pH and clay content of calcareous soils are the most influential soil properties in retention of Zn.     

Response of Corn Growth in Salt‐Affected Soils of Northeast China to Flue‐Gas Desulfurization By‐product

Abstract

In semiarid and arid regions, plant growth is limited by high pH, salinity, and poor physical properties of salt‐affected soils. A field experiment was conducted in the semiarid region of Kangping in northeast China (42°70′ N, 123°50′ E) to evaluate a soil‐management system that utilized a by‐product of flue‐gas desulfurization (FGD). Soil was treated with 23,100 kg ha^?1 of the by‐product. Results of corn growth were grouped into three grades (GD) according to stages of corn growth: GD1, seeds did not germinate; GD2, seeds germinated but corn was not harvested; and GD3, plants grew well and corn was harvested. The pH, electrical conductivity (EC), bicarbonate (HCO₃ ^?), carbonate (CO₃ ^2?), exchangeable and soluble calcium (Ca²⁺), chloride (Cl), and sulfate (SO₄ ^2?) in surface soils of the three grades (>20 cm) was measured to assess the correlation between corn growth and soil properties. Vertical differences in subsoil properties (0‐100 cm) between GD1 and GD3 were compared to known benchmark soil profiles. The FGD by‐product significantly increased EC, exchangeable and soluble Ca²⁺, and SO₄ ^2? and decreased CO₃ ^2?, exchangeable sodium (Na⁺), and soluble Na⁺. pH, EC, HCO₃ ^?, CO₃ ^2?, and Cl^? were higher in surface soils of GD1 than GD3. Soil hardness, soil moisture content, Cl^?, and calcium carbonate (CaCO₃) were higher in GD1 than in GD3, whereas the amount of available P was lower in GD1. Interestingly, the concentration of Cl^?, a toxic element for plant growth, was 2.5 and 1.5 times higher in GD1 than in GD3 and control soil, respectively. In the comparison study of subsoils, GD1 and GD3 were classified as having typical characteristics of saline‐alkali soil (pH>8.5; exchangeable‐sodium‐percentage [ESP]>15; EC>4.0) and alkali soil (pH>8.5; ESP>15; EC<4.0), respectively.     

Forms and Uptake of Manganese in Relation to Soil Taxonomic Orders in Alluvial Soils of Punjab,India

Different forms of manganese (Mn) were investigated, including total, diethylenetriamine penta-acetic acid (DTPA) extractable, soil solution plus exchangeable (Mn), Mn adsorbed onto inorganic sites, Mn bound by organic sites, and Mn adsorbed onto oxide surfaces, from four soil taxonomic orders in northwestern India. The total Mn content was 200–950 mg kg^?1, DTPA-extractable Mn content was 0.60–5.80 mg kg^?1, soil solution plus exchangeable Mn content was 0.02–0.80 mg kg^?1, Mn adsorbed onto inorganic sites was 2.46–90 mg kg^?1, and Mc adsorbed onto oxide surfaces was 6.0–225.0 mg kg^?1. Irrespective of the different fractions of Mn their content was generally greater in the fine-textured Alfisols and Inceptisols than in coarse-textured Entisols and Aridisols. The proportion of the Mn fractions extracted from the soil was in the order as follows: Adsorbed onto oxide surfaces > adsorbed onto inorganic site > organically bound > DTPA > soil solution + exchangeable. Based on coefficient of correlation, the soil solution plus exchangeable Mn, held onto organic site and oxide surface (amorphous) and DTPA-extractable Mn, increased with increase in organic carbon of the soil. The two forms, adsorbed onto inorganic site (crystalline) and DTPA extractable, along with organic carbon, increased with increase in clay content of the soil. DTPA-Mn and Mn adsorbed onto oxide surfaces and held on organic site decreased with increased with an increase in calcium carbonate and pH. Total Mn was strongly correlated with organic carbon and clay content of soil. Among the forms, Mn held on the organic site, water soluble + exchangeable and adsorbed onto oxide surface were positively correlated with DTPA-extractable Mn. DTPA-extractable Mn seems to be a good index of Mn availability in soils and this form is helpful for correction of Mn deficiency in the soils of the region. The uptake of Mn was greater in fine-textured Inceptisols and Alfisols than in coarse-textured Entisols and Aridisols. Among the different forms only DTPA-extractable Mn was positively correlated with total uptake of Mn. Among soil properties Mn uptake was only significantly affected by pH of the soil.     

RELATIONSHIP OF SOIL EXTRACTABLE AND FERTILIZER BORON TO SOME SOIL PROPERTIES,CROP YIELDS,AND TOTAL BORON IN COTTON AND WHEAT PLANTS ON SELECTED SOILS OF PUNJAB,PAKISTAN

Boron (B) is an essential microelement, which is necessary for reproductive organs including pollen tube formation in wheat (Triticum aestivum L.), and flowering and boll formation in cotton (Gossypium hirsutum L.) The study was associated with wheat-cotton rotation in 80 farm fields, belonging to different soil series, in four districts of cotton belt of Punjab, Pakistan to assess concentrations of extractable B in soils [0.05 M hydrochloric acid (HCl) extractable B], and added fertilizer B and their relationship to some soil physico-chemical properties [pH, organic matter (OM), calcium carbonate (CaCO₃) and clay content], yields and total B concentrations in wheat and cotton plants. All soils had alkaline pH (7.45 to 8.55), high CaCO₃ content (2.14 to 8.65%), less than 1.0% OM (0.33 to 0.99%), low plant available-P (Olsen P less than 8 mg kg^?1 soil) and medium ammonium acetate extractable potassium (K) (< 200 mg K kg^?1 soil). Of the 80 soil samples, 65 samples (81%) were low in available B (<0.45 mg B kg^?1, ranging from 0.11 to 0.43 mg B kg^?1) Of the corresponding 80 plant samples, leaves B concentrations were below critical levels (<10 mg B kg^?1 for wheat; <30 mg B kg^?1 for cotton) for all the tested samples for wheat and cotton. The regression analysis between plant total B concentrations and soil extractable B concentrations showed strong linear positive relationships for both wheat (R² = 0.509***, significant at P <0.001) and cotton (R² = 0.525***, significant at P <0.001). Further regression analysis between extractable soil B and wheat grain yield as well as between wheat leaves total B and wheat grain yield also depicted strong linear relationships (R² = 0.76 and 0.42, respectively). Boron fertilizer demonstration plots laid out at farmers’ fields low in extractable B, in each district not only enhanced grain yields of wheat crop but also contributed a significant increase towards seed cotton yield of succeeding cotton crop through residual B effect. In conclusion, the findings suggest that many soils in the cotton belt of Punjab may be low in extractable B for wheat and cotton, especially when these crops are grown on low OM soils with high CaCO₃ content.     

Soil Depletion of Ca, Mg and K Due to Vicinal Intensive Hog Farming Operation Located in East Mediterranean

One of the main environmental impacts of concentrated animal feeding operations is soil degradation in the vicinity of the livestock breeding facilities due to substances such as ammonia emitted from the various stages of the process. In this research, the soil degradation effects of an intensive hog farming operation (IHFO) located at a Mediterranean limestone soil coastal area have been investigated. Soil samples of the upper mineral soil were taken in various distances and directions from the IHFO boundaries. Thirteen experimental cycles were carried out in the duration of 1.5?years starting in March 2009 until October 2010. The soil samples were analysed on total, exchangeable and water-soluble Ca, Mg and K as well as water-soluble ammonium concentrations. Significantly lower concentrations of the exchangeable and water-soluble base cations were observed on soil samples at increasing proximity downwind from the farm (south). Southern soil average concentrations of exchangeable base cations ranged between 78.6 and 128.52?mmol Ca²⁺?kg^?1 soil, 8.42?C21.39?mmol?Mg²⁺?kg^?1 soil and 4.25?C8.1?mmol?K⁺?kg^?1 soil, respectively. Southern soil average concentrations of water-soluble base cations ranged between 0.57 and 2.17?mmol Ca²⁺?kg^?1 soil, 0.16?C0.89?mmol?Mg²⁺?kg^?1 soil and 0.48?C0.95?mmol?K⁺?kg^?1 soil, respectively.     

Genese und Klassifikation von Organomarschen der Wesermarsch

Formation and classification of humus-rich marshland soils of the Weser marshland, Germany The formation and classification of marshland soils are still controversial. To improve the knowledge on the formation of humus-rich marshland soils 11 soil profiles have been investigated. The soils mostly showed Phragmitis in the subsoil. The Gr-horizons began at low depths (40–60 cm). The clay content was often about 60% and the C_org content up to 480 g kg^?1. The amount of total sulfur was up to 29.6 g kg^?1, that of exchangeable sulfate up to 4608 mg kg^?1 and that of sulfate in the saturation extract 51.2 mg l^?1. With pH (H₂O) values between 2.0 and 7.4, Carbonate/S ratios < 3 and total sulfur contents > 7.5 g kg^?1 some soils showed “Actual Acid Sulfate Soil” (AASS) properties. The pH(per) values varied between 2.4 and 7.1, thus some profiles showed “Potential Acid Sulfate Soils” (PASS) properties. Brakish as well as marine environments with an intensive sulfur dynamics and carbonate leaching are likely within the geogenetic phase of soil development. Via the control of the water regime the pedogenetic phase is mainly of anthropogenic influence. We propose to classify humus-rich marshland soils into “Organomarsch” and “Thiomarsch” on the soil type level of the German systematics.     

Soil physicochemical properties in a high-quality tea production area of Thai Nguyen province in northern region,Vietnam

This study investigated general physicochemical properties of tea garden soils at the alluvial plain of Cong River in Tan Cuong commune, Vietnam. Four gardens were selected as study sites on three transect lines established perpendicularly to the river. Soil samples were collected from the surface (0–10 cm) and subsurface (20–30 cm). Soil texture classes varied from sandy loam to light clay, which was affected by different terrains along the transect lines as well as severe disturbance such as terracing and earth excavation. The levels of total C and total N were correlated with increasing garden age, suggesting the replenishment of soil organic matter pool by the addition of plant residue and manure. Meanwhile, the soils showed strongly acidic nature with the average pH(H₂O) of 3.7 at the surface and 3.9 at the subsurface. The effective cation exchange capacity (ECEC) was low at 4.7 and 4.9 cmol_c kg^?1, respectively, and dominated by exchangeable Al³⁺. Soil acidification was exacerbated with increasing garden age. However, a relatively large saturation of exchangeable calcium (Ca²⁺), potassium (K⁺), and magnesium (Mg²⁺) on the ECEC was found in the surface soils. The levels of available P were high, occasionally exceeding 1000 and 500 mg kg^?1 at the surface and subsurface, respectively. In spite of strongly acidic condition, ammonium (NH₄-N) applied as fertilizer was converted to nitrate (NO₃-N) to move down to deeper layers. The levels of the bases, P, and mineral N seem to be principally determined by management practices. Significant portion of these nutrients was likely to exist in water soluble forms without adsorption onto soils. It should be required to develop proper schemes and to educate the owners for adequate fertilizer managements.     

Extractability and Transformation of Copper and Zinc Added to Tropical Savanna Soil under Long-Term Pasture

The extractability and slow reactions of copper (Cu) and zinc (Zn) in a weathered savanna soil under Brachiaria decumbens, Digitaria smutsii, and Stylosanthes guianensis pastures were determined in a laboratory incubation study using a sequential extraction to remove operationally defined fractions of the metals, consisting of exchangeable, organically bound, precipitate [occluded in aluminum (Al) and iron (Fe) oxides], and residual metal fractions. The soils from the pasture fields were spiked with 100 mg Cu kg^–1 soil and 200 mg Zn kg^–1 soil for 24 weeks. Copper and Zn extractable with 1 N potassium nitrate (KNO₃) solution decreased exponentially with time but reached a steady state after 2–3 weeks. The concentrations of Cu and Zn exchangeable with potassium (K) were greater in the Digitaria smutsii field soil than Brachiaria decumbens and Stylosanthes guianensis field soils. The exchangeability of added Cu and Zn (indexed Mⁿ⁺ _(exch)) with time was described by a simple exponential decay equation: Mⁿ⁺ _(exch) = αe^βt, where α is a constant, β is a coefficient that defines the rate of transformation of added Cu and Zn from the exchangeable to nonexchangeable pools, and t is time. The β values for Cu (0.040–0.076 mg kg^–1 d^–1) were almost 10 times greater than those of Zn (0.005–0.007 mg kg^–1 d^–1). Sequential extraction of added Cu and Zn indicated that between 26 and 30% of the total Cu and between 19 and 30% of the total Zn were associated with organic matter. Similarly, between 35 and 38% of total Cu and between 47 and 60% of total Zn were associated with Fe, Al, and manganese (Mn) oxides. The differential capacity of the pasture fields to transform added Cu and Zn from exchangeable and labile form to nonlabile and nonexchangeable form appears to be governed by organic matter (OM), pH, and active Fe ratio in the pasture field soils.     

Soil Nutrient Status and Leaf Nutrient Norms in Oil Palm (Elaeis Guineensis Jacq.) Plantations Grown in the West Coastal Area of India

Oil palm (Elaeis guineensis Jacq.) is a heavy feeder of nutrients and requires balanced and adequate supply of nutrients for optimum growth and yield. Information regarding soil nutrient status and leaf nutrient concentration is very much required for proper fertilizer application. Therefore, a survey was conducted for assessment of soil nutrient status and leaf nutrient concentration in 64 oil palm plantations in the state of Goa lying in the west coastal region of India. Soil pH, electrical conductivity (EC), organic carbon (OC), available potassium (K) (ammonium acetate-extractable K) (NH₄OAc-K), available phosphorus (P) (Bray’s-P), exchangeable calcium (Ca) (Exch. Ca) and magnesium (Mg) (Exch. Mg), available sulphur (S) (calcium chloride-extractable S) (CaCl₂-S), and hot water soluble boron (B) (HWB) in surface (0–20 cm depth) soil layers ranged from 4.25 to 6.77, 0.05 to 1.06 dS m^–1, 5.07 to 48.4 g kg^–1, 58.1 to 1167 mg kg^–1, 1.80 to 415 mg kg^–1, 200 to 2997 mg kg^–1, 36.0 to 744 mg kg^–1, 3.00 to 87.7 mg kg^–1 and 0.09 to 2.10 mg kg^–1, respectively. Diagnosis and Recommendation Integrated System (DRIS) norms were established for different nutrient expressions and were used to compute DRIS indices. As per DRIS indices, the order of requirement of nutrients in the region was found to be P > Mg > K > nitrogen (N) > B. Optimum leaf nutrient ranges as per DRIS norms varied from 1.64 to 2.79%, 0.36 to 0.52%, 0.37 to 0.75%, 0.89 to 1.97%, 0.35 to 0.63%, 0.89 to 1.50%, 3.10 to 13.9 mg kg^?1, 7.50 to 32.2 mg kg^?1, 35.0 to 91.1 mg kg^?1, 206 to 948 mg kg^?1, and 895 to 2075 mg kg^?1 for N, P, K, Ca, Mg, S, B, copper (Cu), zinc (Zn), manganese (Mn), and iron (Fe) respectively. On the basis of DRIS-derived sufficiency ranges, 14, 5, 11, 6, 6, 6, 8, 2, 3, 6, and 16% of leaf samples had less than optimum concentrations of N, P, K, Ca, Mg, S, B, Cu, Zn, Mn, and Fe respectively. The optimum ranges developed can be used as a guide for routine diagnostic and advisory purpose for balanced utilization of fertilizers.     

Microbial Biomass and Tolerance of Microbial Community on an Aged Heavy Metal Polluted Floodplain in Japan

The objective of the present study was to increase understanding of the effects of heavy metal pollution and soil properties on microorganisms in relation to the biomass and microbial functional community. Soil samples were collected from aged polluted and reference sites on a floodplain. The soil Cu, Zn and Pb total concentrations were much higher at the polluted sites (average 231.6–309.9 mg kg^?1, 195.7–233.0 mg kg^?1, and 72.4–86.0 mg kg^?1, respectively) than at the reference site (average 33.3–44.0 mg kg^?1, 76.7–98.0 mg kg^?1, and 30.8–41.6 mg kg^?1, respectively), while the available heavy metal concentrations in CaCl₂ extraction were similar in all sites. Small seasonal variations in the size of microbial biomass were observed. Ambient soil properties (e.g. total C, N, pH, moisture content, and CEC) affected the soil microbial biomass more than the heavy metal pollution. However, the aged pollution tended to impact on the composition of the microbial community. PICT (pollution-induced community tolerance) test using BIOLOG Ecoplates showed enhanced tolerance of the microbial community to Cu stress in the polluted site. In non polluted but low nutrient, low pH and low moisture soil, the microbial biomass was lower and the microbial community was more vulnerable to Cu stress. In spite of the low heavy metal availability due to ageing, the BIOLOG technique provided sensitive detection of microbial community level changes in PICT analysis.     

Potassium Status in Maize Rhizosphere of Smectitic Soils

This study has been taken up to generate information on potassium status in maize rhizosphere soils differing in their clay content at different levels of added potassium. Soils with larger amounts of clay showed greater amounts of water soluble and ammonium acetate extractable K (NH₄OAc K) in both the rhizosphere as well as non-rhizosphere. In the absence of added K (control), non-rhizosphere samples showed higher water soluble and NH₄OAc K ranging from 8.0 to 28.9 mg kg^?1 and from 132.5 to 294.0 mg kg^?1, respectively compared to rhizosphere samples where water soluble K varied between 6.0 and 26.5 mg kg^?1 and NH₄OAc K from 125.0 to 262.5 mg kg^?1. The difference in K content between rhizosphere and non-rhizosphere which could have been resulted from plant K uptake was significantly related with clay content (r = 0.98**) in control whereas at 150 mg kg^?1 K addition this relationship was found to be non significant (r = 0.64^NS). Electro ultra filtration (EUF) fractions also showed similar differences in K contents in soil between rhizosphere and non-rhizosphere.     

Changes in Chemical Properties of an Oxisol Due to Gypsum Application

The increasing demand for fertilizers and the fact that the world reserves of phosphorus (P) and potassium (K) are depletable make appropriate soil management a critical factor in agriculture. Techniques for the fertilizer use and soil acidity corrective are becoming increasingly necessary to minimize the cost of yield and increase the nutrient efficiency. In view of the aforementioned, the present study aimed to assess the effects of gypsum application on the leaching of cations in the soil profile. A completely randomized design in a 5 × 4 factorial arrangement, with five replicates, was used. The treatments corresponded to five gypsum rates (0, 1, 2, 4, and 8 magnesium (Mg) ha^?1) applied on broadcast of soil and at four depth sampled (0–5, 6–10, 11–15, and 16–20 cm). Gypsum application increased the fertility in depth, with the leaching of cations. There was an increase in soil pH, exchangeable K⁺ and calcium (Ca²⁺), sulfur (S–SO₄^2?), P, boron (B), and manganese (Mn) concentration, cation exchange capacity (CEC), K⁺ and Ca²⁺ saturation, Ca²⁺/Mg²⁺, Ca²⁺/K⁺, and K⁺/(Ca²⁺ + Mg²⁺) ratios, and electrical conductivity in soil depth. On the other hand, there was a decrease in exchangeable Mg²⁺ and potential acidity hydrogen and aluminum (H⁺ + Al³⁺), available silicon (Si), Mg²⁺ saturation, and Ca²⁺/K⁺ and Mg²⁺/K⁺ ratio. These results demonstrate that the gypsum application in an Oxisol with 690 g kg^?1 of clay improves the root system with a significant increase in the soil fertility in the profile.