Evaluation of Mercury,Lead, Arsenic,and Cadmium in Some Species of Fish in the Atrato River Delta,Gulf of Urabá, Colombian Caribbean

The concentrations of mercury, lead, cadmium, and arsenic were evaluated in 96 samples, 12 by each one of the following eight fish species: snook (Centropomus undecimalis), crevalle jack (Caranx hippos), Serra Spanish mackerel (Scomberomorus brasiliensis), southern red snapper (Lutjanus purpureus), blue runner (Caranx crysos), Atlantic tarpon (Megalops atlanticus), ladyfish (Elops saurus), and Atlantic goliath grouper (Epinephelus itajara), which were collected during 1 year in the Atrato River Delta in the Gulf of Urabá, Colombian Caribbean. Three fish were caught from each of the following sites the community usually uses to catch them (known as fishing grounds): Bahía Candelaria, Bahía Marirrío, Bocas del Roto, and Bocas del Atrato. The quantification of metals was performed by microwave-induced plasma-optical emission spectrometry. The Pb concentration fluctuated from 0.672 to 3.110 mg kg^?1, surpassing the maximum permissible limit (MPL?=?0.3 mg kg^?1) for human consumption for all species. The Hg concentration ranged between < Limit of detection and 6.303 mg kg^?1, and in the crevalle jack and Atlantic tarpon, concentrations exceeded the MPL (0.5 mg kg^?1). The levels of Cd and As were not significant in the studied species and did not exceed the MPL (0.05 mg kg^?1).     

Effect of calcium sprays,time of harvest,cold storage,and ripeness on fruit quality of ‘anjou’ pears 1

Calcium chloride (CaCl₂), increased Ca concentrations in fruit cortex and peel of ‘Anjou’ pears (Pyrus communis L.). Calcium sprays reduced the fruit disorders: brown core, cork spot and superficial scald. Fruit size (weight) increased while fruit Ca concentrations decreased with fruit at the later harvest dates. The earliest harvest date was associated with a lower incidence of fruit disorders. Superficial scald increased in fruit held longer in cold storage and in ripened fruit. Shelf‐life and fruit quality of Ca‐sprayed fruit was improved due to higher Ca concentrations in fruit peel and cortex resulting in overall enhancement of fruit appearance, and in improvement in the control of the incidences of cork spot, scald, brown core, and external and internal rots, and in amelioration of fruit juiciness and fruit color.     

Distribution of Total and DTPA‐Extractable Zinc,Copper, Manganese,and Iron in Vertisols of India

Abstract

Vertisols of India are developed over isohyets of 600 to 1500 mm, and their chemical cycles are set by drainage, landforms, and particle size, which results in variable pedogenic development within the otherwise homogeneous soils. The purpose of this study was to identify pedogenic processes in the distribution of total and DTPA‐extractable zinc (Zn), copper (Cu), manganese (Mn), and iron (Fe). The soils are developed over basaltic parent material of Cretaceous age. Soil samples were drawn from genetic horizons of the 13 benchmark profiles and analyzed by using HF–HClO₄ acid for total and DTPA extraction. Correlation coefficients were calculated taking all samples together. The total concentration varied from 24 to 102 mg kg^?1 for Zn, 21 to 148 mg kg^?1 for Cu, 387 to 1396 mg kg^?1 for Mn, and 2.36 to 9.50% for Fe. Their variability was proisotropic and haplodized, and their concentrations increased with advancing isohyets. Within the isohyets, hindrance in drainage caused retention of Zn and Cu but loss of Fe. The piedmont soils had more Fe than alluvium soils. The spatial distribution of total contents of Zn, Cu, and Fe was influenced by the pedogenic processes associated with Haplusterts but not with provenance materials. Surface concentrations of the elements by biotic lifting and/or harvest removal were negated by the pedoturbation that further contributed to the irregular distribution of the elements in the profiles. Total Zn and total Cu had positive coefficients of correlations with coarse clay, whereas total Mn and total Fe were positively correlated with fine clay. The DTPA‐extractable forms were functions of isohyets and drainage and showed association with organic carbon content and coarse clay.     

Influence of trenching,soil amendments,and mulching on the mineral content,growth, yield,and quality of “Italian” prunes

Abstract

Yields were evaluated three years after applied treatments to determine if responses that were not evident during earlier years eventually occurred. Potassium sulfate was applied to established, non‐irrigated, K deficient trees on fine textured soil by banding, placing in augered holes, adding to the backfilled trenches, and by injecting into the soil. Trenches were dug in the fall beside trees to break roots and ammended during backfilling with K₂SO₄, dolomite lime or combinations of the two. Additional trees received a heavy compost mulch in the early fall. Trenching treatments were generally detrimental. Trenching alone reduced yield and leaf Ca but increased fruit soluble solids content. Trenching plus K₂SO₄, trenching and lime, all soil amendments, and mushroom compost elevated leaf K from deficient or below normal to the normal range, but decreased leaf Mg. Most K application techniques eventually increased yield, but simple surface applications of K₂SO₄ in a narrow band were as effective as other more costly procedures. Mulching treatments appear to be as effective as K additions and produce quicker yield responses. Mushroom composts and alfalfa increased leaf N and yield in two years. Mushroom compost doubled yield even three years after a single application.     

Impact of Supplemental Calcium Chloride on Yield,Quality, Nutrient Status,and Postharvest Attributes of Tomato

Little is known regarding the impact of calcium chloride applications during growth and development on tomato postharvest quality. This trial investigated supplemental calcium chloride applications on yield, nutrient content, texture, and postharvest quality of tomato fruit. Calcium (Ca) nutrient solution concentrations were: 60, 180, and 360 mg·L^?1 calcium, while foliar applications were (0, 1, and 2% calcium chloride w/v). Plants grown with 60 mg·L^?1 Ca had a high incidence of blossom end rot, which was not affected by calcium chloride sprays. Fruit nutrient concentrations were affected by calcium delivered through the nutrient solution. As fruit cluster position increased, fruit nutrient concentrations significantly decreased. Foliar calcium chloride sprays affected fruit soluble solids content and dry weight, but did not affect texture. Pericarp elasticity increased concomitantly with calcium in the nutrient solution. Postharvest disease incidence was not affected by calcium treatment, though weight loss during storage was negatively affected by calcium chloride sprays.     

Influence of olive storage period on oil quality of three Portuguese cultivars of Olea europea,Cobrançosa,Madural, and Verdeal Transmontana

Olives (Olea europaea cv. Cobran?osa, Madural, and Verdeal Transmontana) used for oil production were stored, in plastic containers, at 5 +/- 2 degrees C (70% relative humidity) for three different periods before oil extraction: 0, 7, and 14 days (T(0), T(7), and T(14), respectively). In the crop year 1997/1998 this procedure was done only for cv. Cobran?osa and in 1998/1999 for the three cultivars. After storage, the oils were extracted from the fruits, and the acidity, peroxide value, coefficients of specific extinction at 232 and 270 nm, stability, color, p-anisidine value, fatty acids, and tocopherols compositions were determined. The results confirm that storage of fruits produces losses in the olive oil quality. Acidity and stability to oxidation indicate a progressive deterioration of oil quality as fruit is stored. The storage time affects the total tocopherols contents, namely, alpha-tocopherol, which clearly decreased during fruit storage. The oil quality of the Verdeal Transmontana cultivar deteriorated more rapidly than that of Cobran?osa and Madural cultivars. This study also shows that cv. Cobran?osa, the main cultivar in the region, is a good choice in terms of final olive oil quality.     

Comparison of mehlich 3, mehlich 1, ammonium bicarbonate‐DTPA, 1.0M ammonium acetate,and 0.2M ammonium chloride for extraction of calcium,magnesium, phosphorus,and potassium for a wide range of soils

Abstract

Extractants employed for routine soil analysis vary from one laboratory to another. Lack of a universal soil extractant is a serious limitation for interpretation of analytical results from various laboratories on nutritional status of a given soil. This limitation can be overcome by developing functional relationships for concentrations of a given nutrient extractable by various extradants. In this study, extractability of Ca, Mg, P, and K in a wide range of soils (0–15 cm) from citrus groves in Florida representing 21 soil series, with varying cultural operations, were compared using Mehlich 3 (M3), Mehlich 1 (M1), ammonium acetate (NH₄AOc), pH = 7.0 (AA), 0.2M ammonium chloride (NH₄Cl), and ammonium bicarbonate‐DTPA (AB‐DTPA) extractants. Soil pH (0.01M CaCl₂) varied from 3.57 to 7.28. The concentrations of Ca or Mg extractable by M3, M1, AA, and NH₄Cl were strongly correlated with soil pH (r² = 0.381–0.482). Weak but significant correlations were also found between AB‐DTPA extractable Ca or Mg and soil pH (r² = 0.235–0.278). Soil pH relationships with extractable K were rather weak (r² = < 0.131) for M1 and NH₄Cl but non‐significant for M3, AB‐DTPA, and AA. Concentrations of Ca, Mg, and K extractable by M3 were significantly correlated with those by either M1, AA, or NH₄Cl extractants. Mehlich 3‐P was significantly correlated with P extractable by M1 extractant only. Mehlich 3 versus AB‐DTPA relationship was strong for K (r² = 0.964), weaker for Mg and P (r² = 0.180–0.319), and non‐significant for Ca. With the increasing emphasis on possible use of M3 as an universal soil extractant, data from this study support the hypothesis that M3 can be adapted as a suitable extractant for routine soil analysis.     

Influence of different calcium materials and spray timing on mineral composition,yield, fruit quality,and control of fruit disorders of ‘anjou’ pears

During a six‐year period (1980, 1985–1989), 20 different calcium (Ca) materials were sprayed at an early (3X; June to July), late (3X; July to August), and an early plus late (5X; June to August) timing on 25‐year‐old ‘Anjou’ pear (Pyrus communis L.) trees. Calcium chloride (CaCl₂) sprays increased fruit Ca in the cortex by an average of 10.5% greater than in unsprayed controls and cork spot was reduced by an average of six‐fold. Yield from trees sprayed with Ca materials averaged greater than 13% more crop load than the unsprayed control trees. Leaf and fruit injury from CaCl₂ sprays in 1980 were near borderline acceptability, but injury was reduced slightly by halving the spray concentration rate to 681 g CaCl₂ per 379 liters of water in 1985 to 1989. Due to temperatures above 26°C, leaf and fruit injury from Ca sprays, particularly calcium nitrate [Ca(NO₃)₂], were more severe for the late or early plus late sprays than for the early sprays. Fruit size was slightly larger on trees sprayed only three times (early or late sprays) versus trees sprayed five times during the season (early plus late sprays). Best control of cork spot occurred with early plus late sprays. Best control of alfalfa greening and black end occurred with late or early plus late sprays. The importance of fruit Ca for controlling cork spot is illustrated when triiodobenzoic acid (TIBA) was sprayed on trees which resulted in reduced fruit Ca and increased incidence of fruit disorders, alfalfa greening, black end, and cork spot. Sprays containing nitrates or sulfates were frequently associated with a higher incidence of fruit disorders. Although fruit quality was not significantly influenced by Ca treatments or spray time, it was related to Ca in fruit peel or cortex due to annual variations in Ca concentrations.     

Distribution of Chemical Forms for Co, Cr, Ni and V in Typical Soils of China

Co,Ni,Cr and V in 25 typical soils of China were fractionated into exchangeable,carbonate bound (calcareous soils),Mn oxide bound,organically bound,amorphous Fe oxide bound,crystalline Fe oxide bound and residual forms using a seven-step sequential extraction procedure,so as to study the distribution of chemical forms of these metals as well as the effects of soil proiperties on the distribution.The results showed that most of soil Co,Ni,Cr and V were present in residual forms,and the distribution ratio averaged 48.2% for Co,53.0% for Ni,81.5% for Cr and 68.7% for V.The speciation of heavy metals was greatly influenced by soil physico-chemical properties and the chemistry of elements.The results also indicated that the recovery of metal elements by the sequential extraction procedure was satisfactory,with the relative difference between the sum of seven forms and the total content in soils averaging 9.5% for Co,12.8% for Ni,6.6% for Cr and 7.2% for V.     

Effects of Biomethanated Spentwash on Soil Properties,Nutrient Availability,Uptake, and Yield of Soybean–Wheat Sequence on Inceptisol

The research aimed to study the effect of presown application of primary biomethanated spentwash (PBSW) on soil properties, nutrient availability, uptake and yield of soybean–wheat sequence on Inceptisol. The field experiment with randomised block design was initiated during 2007–8 and present observation was recorded during 2009–10 and 2010–11.The five treatments were, recommended dose (RD) of NPK (T₁), 100% RD of N through PBSW without (T₂) and with P chemical fertilizer (T₃), 50 and 25% RD of N through PBSW + remaining N and P through chemical fertilizers (T₄,T₅), respectively. The results revealed that the soil physical properties and microbial populations were improved in T₂ and T₃. The lowest soil pH and pHs were observed in T₂. The soil electrical conductivity, organic carbon, exchangeable sodium percentage and sodium adsorption ratio of soil extracts and available K were increased with the increase in PBSW as compared to RD-NPK. The soil available N and P were decreased as PBSW increased at all the soil depths. The greatest yields and total N,P,K uptake of soybean and wheat were observed in T₅.     

Effect of calcium spray materials,rate, time of spray application,and rootstocks on fruit quality of ‘red’ and ‘golden delicious’ apples

Calcium (Ca) spray materials improved fruit quality as measured by control of bitter pit, fruit finish (appearance), increased red skin color, reduced incidence of scald, increased juiciness, texture, and fruit firmness of ‘Red’ and ‘Golden Delicious’ apples (Malus domestica, Borkh.). Concentrations of Ca in leaf and fruit tissues were increased by Ca sprays, especially calcium chloride (CaCl₂)‐containing spray materials. Improved fruit firmness and control of bitter pit occurred for either standard recommended or high rates of Ca spray materials. At high rates of application, the only significant difference that occurred between early and late applications of Ca spray materials was that less leaf injury occurred with the early applications. Unsprayed ‘Red Delicious’ fruit from M.7 rootstocks had greater fruit peel Ca concentrations and a lower incidence of bitter pit but smaller fruit than fruit from trees on M.26 rootstocks. The above information is strong evidence that Ca sprays are important for the improvement of apple quality.     

Reconstruction of Climate,Soils, and Vegetation in the Turan–Uyuk Basin of South Siberia at the Beginning of the Subatlantic Period of the Holocene

Four Scythian kurgans of the burial site Beloe Lake-3 were studied in the Turan–Uyuk Depression in the Republic of Tyva. They were constructed about 2565–2390 calendar years ago (calibrated with deviation 1 σ). Soil formation after 2500 yrs of the construction of the kurgans was examined in the interkurgan area. The properties of the background surface and ancient buried soils have much in common, and the difference between the soils of the four kurgans is small. This attests to the fact that the paleoclimatic conditions in the period of the necropolis construction remained stable and were similar to the modern climatic conditions. According to palynological data, the climate at the stage of the construction of the first two kurgans was a little more humid in comparison with the modern climate; it became somewhat drier after 95 years, during the construction of the third kurgan (2425 cal. BP) and again tended to humidification at the final stage of the necropolis creation. These changes in the paleoclimatic conditions are indicated by variations in the structure and composition of associations of xerophytes, mesophytes, hydrophytes, and ruderal plants. At the Uyuk stage, the area was mainly occupied by steppe phytocenoses with a predominance of xerophytes over mesophytes, and hydrophilous vegetation was allocated to moistened habitats near water reservoirs. Larch forests grew near water bodies. The variable anthropogenic impact on the landscape was stronger at the initial and final stages of the construction of the Uyuk culture necropolis.     

Cultivation of potato – use of plastic mulch and row covers on soil temperature,growth, nutrient status,and yield

Potato is one of the most important crops in the world because of its high nutritional value; however, traditional cultivation in bare soil may render low yields and poor quality. Crop production efficiency can be increased by using plastic mulching and row covers to modify root zone temperature and plant growth, in addition to reduction in pest damage and enhance production in cultivated plants. However, there is little information demonstrating the effect of row covers in combination with plastic mulch on potato. The aim of this study was to assess the change in root zone temperature and its effect on growth, leaf nutrient, and yield of potato using plastic mulch of different colors, in combination with row covers. Seed of cultivar Mondial was planted in May 2012. The study included four plastic films: black, white/black, silver/black, aluminum/black, and a control with bare soil, which were evaluated alone and in combination with row covers removed at 30 days after sowing in a split-plot design. Higher yields were obtained when no row cover (43.2 t ha^?1) and the white/black film (42.2 t ha^?1) were used. Leaf nitrogen, sulfur, and manganese concentration were higher in plants when row cover was used; in contrast, no–row cover plants were higher in Fe and Zn. Mulched plants were higher in Mn concentration than control plants. There was a quadratic relationship between mean soil temperature and total yield (R² = 0.94), and between plant biomass and total yield (R² = 0.98), between leaf area with total yield (R² = 0.98).     

Evaluation of rice–legume–rice cropping system on grain yield,nutrient uptake,nitrogen fixation,and chemical,physical, and biological properties of soil

To achieve higher yields and better soil quality under rice–legume–rice (RLR) rotation in a rainfed production system, we formulated integrated nutrient management (INM) comprised of Azospirillum (Azo), Rhizobium (Rh), and phosphate-solubilizing bacteria (PSB) with phosphate rock (PR), compost, and muriate of potash (MOP). Performance of bacterial bioinoculants was evaluated by determining grain yield, nitrogenase activity, uptake and balance of N, P, and Zn, changes in water stability and distribution of soil aggregates, soil organic C and pH, fungal/bacterial biomass C ratio, casting activities of earthworms, and bacterial community composition using denaturing gradient gel electrophoresis (DGGE) fingerprinting. The performance comparison was made against the prevailing farmers’ nutrient management practices [N/P₂O₅/K₂O at 40:20:20 kg ha⁻¹ for rice and 20:30:20 kg ha⁻¹ for legume as urea/single super-phosphate/MOP (urea/SSP/MOP)]. Cumulative grain yields of crops increased by 7–16% per RLR rotation and removal of N and P by six crops of 2 years rotation increased significantly (P < 0.05) in bacterial bioinoculants-based INM plots over that in compost alone or urea/SSP/MOP plots. Apparent loss of soil total N and P at 0–15 cm soil depth was minimum and apparent N gain at 15–30 cm depth was maximum in Azo/Rh plus PSB dual INM plots. Zinc uptake by rice crop and diethylenetriaminepentaacetate-extractable Zn content in soil increased significantly (P < 0.05) in bacterial bioinoculants-based INM plots compared to other nutrient management plots. Total organic C content in soil declined at 0–15 cm depth and increased at 15–30 cm depth in all nutrient management plots after a 2-year crop cycle; however, bacterial bioinoculants-based INM plots showed minimum loss and maximum gain of total organic C content in the corresponding soil depths. Water-stable aggregation and distribution of soil aggregates in 53–250- and 250–2,000 μm classes increased significantly (P < 0.05) in bacterial bioinoculants-based INM plots compared to other nutrient management plots. Fungal/bacterial biomass C ratio seems to be a more reliable indicator of C and N dynamics in acidic soils than total microbial biomass C. Compost alone or Azo/Rh plus PSB dual INM plots showed significantly (P < 0.05) higher numbers of earthworms’ casts compared to urea/SSP/MOP alone and bacterial bioinoculants with urea or SSP-applied plots. Hierarchical cluster analysis based on similarity matrix of DGGE profiles revealed changes in bacterial community composition in soils due to differences in nutrient management, and these changes were seen to occur according to the states of C and N dynamics in acidic soil under RLR rotation.     

Effects of supplemental nitrogen on nitrogen‐assimilation enzymes,free amino nitrogen,soluble sugars,and crude protein of rice

Abstract

An upland rice variety IAC‐47 was grown in a greenhouse to determine the effect of foliar nitrogen (N) supplementation during grain development on the activity of the N assimilation enzymes, nitrate reductase (NR) and glutamine synthetase (GS), on free amino‐N content and leaf soluble sugars, and on grain crude protein content. At 10 and 20 days after anthesis (DAA), the leaves were fertilized with a liquid fertilizer containing 32% N as 12.8% urea, 9.6% ammonium (NH₄), and 9.6% nitrate (NO₃) in increasing rates corresponding to 0,20+20, 40+40, and 60+60 kg N ha^‐1. Leaves were collected twice (at 12 DAA and 14 DAA for GS activity, sugar and amino‐N content, and at 11 and 13 DAA for NRA) after each application of leaf N. The late foliar application of N increased significantly grain crude protein without a corresponding decrease in grain weight. The NR activity (NRA) increased after the foliar application of N. In the flag leaf, 60+60 kg N ha^‐1 (21 DAA) resulted in higher NRA (20x over the control), while GS activity was smaller than the control. At 22 DAA there was an increase in GS activity in the flag leaf at 20+20 N level. However, the GS activity decreased as applied N levels increased. Also at the 20+20 level, there were increases in free amino‐N in the flag leaf and second leaf at the final harvest. Throughout the experiment, plants at the 60+60 N level had the lowest levels of soluble sugars. Increases in crude protein were highest at 40+40 N level (27.9%), followed by 60+60 (18.7%).     

Accumulation and potential sources of heavy metals in soils of the Hetao area,Inner Mongolia,China

Soil contamination by heavy metals is a problem in agricultural irrigation systems.To assess the accumulation and sources of heavy metals in the Yongji irrigation district of the Hetao area,Inner Mongolia,China,195 soil samples from 39 sites(0–100 cm)were collected,and Zn,Cu,Pb,Cr,and Cd concentrations were analyzed.The mean concentrations were 107.17,32.48,12.31,53.53,and 0.22 mg kg-1,respectively,with no significant differences between soil depths(P>0.05).Concentrations of Zn,Cu,and Cd were higher than the background levels,with moderate accumulation;the contamination factor(CF)values were 1.9,1.7,and 1.9,respectively,and the geoaccumulation index(Igeo)was>0.Concentrations of Pb and Cr were lower than,or close to,the background levels(CF<1,Igeo<0),indicating that they originated from a natural source.The monomial potential ecological risk index(Eri)for Zn,Cu,Pb,and Cr was low;Eri for Cd was 55.73,implying a moderate risk.The grade of potential ecological risk index of the five heavy metals(RI)was low,declining from south to north.The studied soils were contaminated with Zn,Cu,and Cd;principal component(PC)analysis implicated the enrichment of Cd and partial Cu(high loading in PC 2)was related to agricultural activities;Zn and partial Cu,closely associated with PC 3,may have originated from irrigation water from the Yellow River.Future agricultural development should focus on fertilizer and pesticide application and the quality of irrigation water.     

Effect of Molybdenum Foliar Sprays on Yield,Berry Size,Seed Formation,and Petiolar Nutrient Composition of “Merlot” Grapevines

Abstract

Field experiments with irrigated “Merlot” vines were carried out at 3 sites in the Mount Lofty Ranges of South Australia over 3 years to examine the effects of molybdenum (Mo) foliar sprays on bunch yield, berry size, and nutrient composition of petioles. Bunches were divided into different size grades for black and green berries. Basal petioles were sampled at flowering and veraison for nutrient analyses. In year 3, seed number per berry was assessed at sites 2 and 3. Two Mo foliar sprays (each spray contained 118 g Mo as sodium molybdate/ha in 410–800 L/ha of water) applied before flowering increased yield per vine and bunch weight in all experiments in year 2 and at site 3 in year 3. Yield responses ranged from 221% at site 1 to 750% at site 2 in year 2 and 70% for site 3, year 3. Average bunch weight increased from 243% at site 2 to 425% at site 1 for year 2 and by 69% at site 3 in year 3, and was the main yield component affected by Mo application. In year 1, the application of Mo did not affect yield or bunch weight at any site. In year 2, the application of Mo increased the yield of 5–15 mm colored berries by 301, 499, and 258% at sites 1, 2, and 3, respectively, and by 70% at site 3, year 3. Mo application increased the percent of berries, which had one or more functional seeds (when assessed at sites 2 and 3 in year 3). Molybdenum concentrations in petioles sampled at flowering and veraison increased in response to applied Mo in all years. Petiolar Mo concentrations in unsprayed vines were consistently higher in year 1 compared with other years. The effect of applied Mo on the concentration of other nutrients in basal petioles sampled at flowering and veraison were small and of little practical importance. Nitrate-N did not accumulate in the petioles of unsprayed plants in any year. Changes in petiolar Mo concentrations between flowering and veraison were dependent on supply. Nitrate-N, total-N, and phosphorus (P) concentrations declined with time, while calcium (Ca), manganese (Mn), and iron (Fe) tended to increase. At flowering, Mo concentrations in basal petioles of 0.05–0.09 mg/kg were associated with significant bunch yield response to applied Mo. Molybdenum deficiency can be a major factor in the occurrence of berry development disorders such as shot berry formation and hens and chickens (millerandage) in “Merlot” grapevines. The increased percent of colored berries with one or more functional seeds and the decrease in the proportion of green berries suggests that Mo application affected pollination and/or fertilization, and thereafter berry development.     

Adsorption of Copper,Zinc, and Cadmium on Goethite,Aluminum‐Substituted Goethite,and a System of Kaolinite–Goethite: Surface Complexation Modeling

Abstract

Goethite, aluminum‐(Al)‐substituted goethite (GA2), and a system of kaolinite–goethite were examined for their ability to adsorb copper (Cu), zinc (Zn), and cadmium (Cd) as a function of pH, in two ionic strengths and two different metal concentrations. Specific surface area was determined by BET‐N₂, whereas the charge development on the solid surface was studied in the pH range ～3.5 to ～10.0 by potentiometric titration under continuous flow of argon.

Constant capacitance (CCM) and the double‐layer model (DLM) were used to fit the titration and adsorption data with the help of the least‐square optimization program FITEQL32. In both models, surface site density was fixed at Ns=2.31 sites nm^?2, whereas for CCM capacitance density was set at C=1.06. Alternatively, bibliographic suggestions for these two parameters were examined.

Aluminum‐substituted goethite exhibited higher specific surface area and adsorbed all three metals in lower pH values than the other solids. Moreover, GA2 exhibited point of zero salt effect (PZSE) higher than goethite, approaching that corresponding to Al₂O₃, possibly due to Al‐substitution, and the system exhibited PZSE values much higher than kaolinite, approaching that corresponding to goethite. The adsorption order for all three solids was Cu>Zn>Cd in any case, thus more Cu is adsorbed at a certain pH than Zn and even more than Cd, whereas the increase of metal concentration shifts the adsorption curve toward higher pH values.

Constant capacitance described the titration data satisfactorily, but by altering the Ns and C values, the fit became worse. Adsorption data are described by CCM, by emphasizing the formation of monodentate surface complex. Bidentate complex, in most of the cases, was of no importance in describing the data despite the evidence of its presence in recent spectroscopic studies for Cu and Cd on goethite. Alteration of Ns and C values worsened the fit in any case, and bidentate complex vanished. The DLM exhibited the worse fit in any case.     

Seasonal variation of selenium,crude protein,and in vitro organic matter digestibility of Brachiaria humidicola from marajó island,brazil

Abstract

Nutritional content of Brachiaria humidicola grass in relation to crude protein (CP), in vitro organic matter digestibility (IVOMD), and selenium (Se) as related to wet and dry seasons in the Amazon region of Marajó Island, Brazil, was determined. Twenty‐four samples, 12 from the dry and 12 from the wet season, were analyzed. Grass selenium concentrations were not influenced by season and the means were above the minimal requirement for beef cattle in both seasons (0.14 or 0.15 ppm). Factors other than rainfall may be involved. Crude protein concentrations were lower (P<.05) in the dry (3.5%) than in the rainy season (4.8%) and in both seasons were lower than the critical level for cattle (<7.0%). The IVOMD means were extremely low, 33.5% in the wet season and 33.6% in the dry season. These analytical values indicate that Brachiaria humidicola grown at Marajó Island has nutritional limitations for grazing buffalo and cattle production.