Soil‐solution speciation by MINEQL+4.6 model and plant uptake of Cd and Zn by barley (Hordeum vulgare L.) after application of different phosphate fertilizers

A greenhouse experiment was conducted to investigate the immediate effect of application of mono‐ammonium phosphate (MAP), single superphosphate (SSP), and triple superphosphate (TSP) fertilizers containing varying concentrations of Cd on (1) chemical speciation of Cd and Zn in soil solution by chemical‐equilibrium calculations (MINEQL+4.6 model), (2) growth of barley plants, (3) concentrations of Cd, P, and Zn in soil solution and plant tissue, as well as total plant accumulation of Cd, P, and Zn, and (4) monitoring pH and element changes during incubation periods following phosphate application. Results show that, in general, the pH of soil solution increased during the first 40 d of incubation, then declined. Also, at the end of incubation period, pH of soil solution was affected by fertilization source and fertilization rate. The concentration of Cd in soil solution changed with time. Phosphate fertilization (p < 0.05) or fertilizer source (p < 0.05) showed consistent effects. Also, the application of phosphate fertilizers with three rates significantly increased Zn concentrations in soil solution during the first half (0–30 d) of incubation period and then decreased but still more than in the control. In general, application of different sources of phosphate at 100 g kg^–1 did not change the dominant forms of Cd in soil solution during all incubation time intervals. Speciation of Zn in the control after 30 d of incubation had changed, in comparison to 10 d of incubation, and the dominant forms were Zn²⁺, ZnOH⁺, ZnHCO₃, ZnCO₃(aq), and Zn(OH)₂(aq). Adding phosphate fertilizer significantly increased both shoot and root dry weight compared to control, indicating P was a growth‐limiting factor in the control plants. The Zn concentrations in shoot and root were lower in the TSP‐ and SSP‐fertilizers treatment than those in the MAP and fertilizer treatments at all rates of fertilization. Adding phosphate increased the Cd : Zn and P : Zn ratios in the shoot and root tissue, with the effect being greater with increasing fertilization rate. Phosphate fertilization greatly increased the total accumulation of Cd of barley compared with the control plants (p < 0.001), with the effect being greater with increasing fertilization rate. Source and rate of fertilizers, and their interactions had significant effect (p < 0.05) on Cd accumulation in the whole plant.     

Effects of Forms and Rates of Zinc Fertilizers on Cadmium Concentrations in Two Cultivars of Maize

Abstract

A pot experiment was conducted to investigate the effects of three soluble zinc (Zn) fertilizers on cadmium (Cd) concentrations in two genotypes of maize (Zea mays): Jidan 209 and Changdan 374. Zinc fertilizers were added to soil at four levels: 0, 80, 160, and 240 mg kg^?1 soil as nitrate [Zn(NO₃)₂], chloride (ZnCl₂), and sulfate (ZnSO₄). Cadmium nitrate [Cd(NO₃)₂] was added to all the treatments at a uniform rate equivalent to 10 mg kg^?1 soil. The biomass of maize plants was increased with the application of three zinc fertilizers, of which Zn(NO₃)₂ yielded more than others. Under ZnCl₂ treatment, plant growth was promoted at the lower level and depressed at the higher one. All the three fertilizers decreased Cd concentration in shoots in comparison with treatments without Zn, but there were variations with different forms, especially in plants treated with Zn(NO₃)₂, which had the minimal value. The orders of average Cd concentration in shoots with different zinc fertilizers were ZnSO₄>ZnCl₂>Zn(NO₃)₂ for Jidan 209 and ZnCl₂>ZnSO₄>Zn(NO₃)₂ for Changdan 374, respectively (P<0.001). There was no significant difference between ZnSO₄ and ZnCl₂ treatments. The lowest Cd concentration in shoots was found in the 80‐mg‐kg^?1 soil or 160‐mg‐kg^?1 soil treatment. Cadmium concentration in roots in the presence of ZnCl₂ was the lowest and under ZnSO₄ the highest. The mechanism involved needs to be studied to elucidate the characteristics of complexation of Cl^? and SO₄ ^2? with Cd in plants and their influence on transfer from roots to shoots.     

The effect of long-term fertilization with organic or inorganic fertilizers on mycorrhiza-mediated phosphorus uptake in subterranean clover

 A pot experiment was conducted with soil from a long-term (74-year) fertilization field experiment to compare the effects of organic and mineral fertilizers on mycorrhiza formation in clover, and mycorrhiza-mediated plant P uptake. Five treatments were selected from the field experiment representing different forms and levels of P. Mycorrhizal effects on plant growth and P uptake were estimated by comparing plants grown in untreated soil containing indigenous arbuscular mycorrhizal (AM) fungi, with plants grown in pasteurized soil. Short-term versus residual effects of fertilizer/manure were also measured by comparing treatments with or without fertilizers added at the start of the pot experiment. Mycorrhiza formation was greatest in soil that had received no P for 74 years, followed by soil having received 30 or 60 Mg ha^–1 farmyard manure (FYM), and soil having received 25 or 44 kg P ha^–1 in NPK fertilizers. Plant growth and P uptake were severely reduced in the absence of AM fungi for all mineral fertilizer treatments. In contrast, plants growing in soil that had received FYM grew equally well or better when non-mycorrhizal. Recent additions of NK fertilizer and FYM had no effect on mycorrhiza formation, while additions of NPK led to reduced colonization. It thus seems that moderate quantities of FYM have less adverse effects on AM than equivalent amounts of nutrients in NPK fertilizers, a phenomenon that is most likely due to a temporal difference in P availability and its gradual release that balance plant demand. Received: 4 November 1999     

Long‐term application of biowaste compost versus mineral fertilization: Effects on the nutrient and heavy metal contents of soil and plants

In recent years the use of biowaste compost (BC) as a soil amendment is of increasing interest. The aim of the experiment was to investigate the influence of different fertilization systems: biowaste compost, annual average of 32 Mg ha^—1 BC (fresh matter) and mineral fertilizer (83:52:95 kg ha^—1 NPK fertilizer) on the nutrient and heavy metal contents of soil and plants. Soil samples (1997) and harvest products (1996—1998) from a field trial (initiated 1992) were analyzed for K, Mg, P, Cu, Mn, Mo, Zn, Cd, Ni, and Pb. The five‐year fertilization with composted biowaste did not influence the total contents of Cd, Mn, Mo, and Ni in soil. The total soil contents of Zn and Pb were significantly higher in soils of the BC treatment than in the unfertilized control. Both fertilized plots tended to have higher Cu and Zn contents in harvest products than the unfertilized control. The mineral fertilization inhibited the Mo uptake by plants. In 1998 the mineral fertilization led to higher, and the biowaste compost application to lower, Cd contents in potato tubers as compared to the control.     

Accumulation of cadmium,fluorine, magnesium,and zinc in soil after application of phosphate fertilizer for 31 years in a grazing trial

Phosphate fertilizers are recognized as a potential source of elements that could contribute to soil pollution. The objective of this study was to determine the extent to which use of phosphate fertilizer in the past had resulted in an increase in heavy‐metal content in Irish soils. Samples were taken from a long‐term replicated (six replicates of 0.18 ha each) plot experiment with grazing cattle. Phosphate as superphosphate had been applied at two rates, 0 and 930 kg ha^–1 total P, over a 31 y period. Phosphorus, pH, soil organic matter, Cd, F, Mg, and Zn were measured in 0–10 and 10–20 cm soil layers in addition to extractable P and Mg (Morgan's solution) and Zn (0.5M EDTA). Increases in the phosphate‐enriched soil were significant at p < 0.05 except for F at both soil layers and for Cd at the 10–20 cm layer (p < 0.1) Recoveries for P, Cd, and F were in fair agreement with application. High recoveries of total Mg and Zn were encountered which could not readily be explained. These increases were paralleled by increases in extractable‐soil‐test values for these elements. Accumulation in soil of P over the period was such as to now necessitate little application of this element to soil for the near future. At the same time, increase in soil Cd was small, little more than 0.05 mg kg^–1 in soil, although it amounted to a sizable proportion of Cd in the soil. Similarly, increases in other elements, although real, would not lead to major concerns at the present time.     

Cadmium Uptake by Lettuce from Soil Amended with Phosphorus and Trace Element Fertilizers

Some phosphorus and trace element fertilizers may contain elevatedamounts of toxic metals such as cadmium (Cd) and repeated uses of the fertilizers at high rates over time may increase Cd uptake by plants. This greenhouse study investigated the availability to leaf lettuce (Lactuca sativa L.) (Royal Green) of Cd in a western phosphate rock (PR), and a zinc (G-Zn) and an iron (IR) fertilizers that are by products of industrial wastes. The water-soluble CdCl₂ was included in the study for comparison. Applications of Cd from the fertilizers orCdCl₂ up to 16 times the Canadian Standards for maximum annual Cd loading limit increased soil total Cd. This was true also for the labileCd extractable by DTPA (diethylenetriaminepentaacetic acid) or 0.05 M CaCl₂ for all Cd sources except IR. Lime and Cd source and rate allaffected Cd availability in the soil and accumulation by the plant. Theadded Cd from CdCl₂ was more labile and readily available to the plant than the added Cd from the PR or G-Zn. Lettuce-Cd was best describedby CaCl₂-Cd (r² = 0.782), followed by DTPA-Cd (r² = 0.686), with soil total Cd being least effective in predicting lettuce-Cd (r² = 0.186). If soil total Cd has to be used in describing Cd accumulation bythe plant, it should be included with pH in a stepwise multiple regression. The Cd transfer coefficient for the fertilizers should be measured based on labile Cd extractable by CaCl₂ or DPTA, instead of soil total Cd. The labile-based Cd transfer coefficient could improve the assessment ofthe risk of human exposure to the metal in the fertilizers through consumption of the food crop.     

Influence of water solubility of granular zinc fertilizers on plant uptake and growth

Abstract

Zinc (Zn) fertilizer application has increased during the past three decades. This increase has created the need for more information regarding the availability and agronomic effectiveness of Zn containing fertilizers because differences of opinions exist relating the relationships between Zn water solubility and plant availability. Plant availability of eight commercialized Zn fertilizer materials having different water solubilities was measured under greenhouse conditions. Corn (Zea mays L.) plants were grown for 40 days in a soil (loamy, mixed, mesic arenic Ustollic Haplargid) amended with lime to two pH's: 6.3 and 7.4. To evaluate the effect of pH, some Zn fertilizers were used at both soil pH levels while all Zn fertilizers were used in the pH 7.4 soil. The experimental design was a factorial combination of pH, Zn fertilizers, and Zn rates of 0,2.1,4.2,8.4 mg Zn kg^?1 soil. Dry matter production and Zn uptake increased significantly when the soil pH decreased from 7.4 to 6.3. The highest dry matter production was obtained with ZnSO₄ (ZnSO₄ H₂O, 99.9% total water soluble Zn), Zn20 (Zn oxysulfate, 98.3% total water soluble Zn), and Zn27 (Zn oxysulfate, 66.4% total water soluble Zn). While ZnFe (Zn iron ferrite, 0.3% total water soluble Zn), ZnK (Zn oxide, KO61, 1% total water soluble Zn), and ZnOS (Zn oxysulfate, 0.7% total water soluble Zn) were less effective followed by Zn40 (Zn oxysulfate, 26.5% total water soluble Zn) and ZnOxS (Zn oxysulfate, 11% total water soluble Zn). The same trend was observed for Zn concentration and uptake. Regression correlations showed that the higher the water solubility, the more effective the Zn fertilizer in increasing dry matter production. Assuming that 5 to 10 kg Zn ha^?1 are the rates commonly recommended, about 50% water soluble Zn is required to adequately supply the crop's needs. Lower fertilizer rates were needed as Zn solubility increased. The cadmium (Cd) and lead (Pb) concentrations and uptakes in corn forage were not significant for any of the sources and rates.     

Cadmium and zinc additions to wisconsin soils by commercial fertilizers and wastewater sludge application

Cadmium and Zn concentrations were determined on 21 commercial fertilizer samples by atomic absorption. The Cd concentration ranged from 1.5 to 9.7 mg kg^?1, the median being 4.3 mg kg^?1. Zinc showed a much wider range. The Cd added to soil by commercial fertilizers may be as much as 2150 kg annually in Wisconsin, compared to a potential of 1700 kg if wastewater sludges from all municipal sewage treatment plants in the state were disposed of on land. However, because of the higher application rates, sludge Cd on a soil concentration basis is a much more concentrated source of Cd than that from phosphate fertilizers.     

Responses of wheat to zinc sulfate fertilizer and plant growth‐promoting rhizobacteria under cadmium stress in soil

Cadmium (Cd) is a major pollutant in soils as a result of extensive use of fertilizers, mining and industrial discharges. Zinc (Zn) and certain bacterial species have been known to alleviate Cd toxicity in plants. In this study, the individual and combined effects of the application of Zn and Pseudomonas species with the aim of reducing Cd stress in wheat cultivars were investigated. Plants (durum wheat and bread wheat) were exposed to different concentrations of Cd and Zn, and either P. putida or P. fluorescens in a growth chamber. Concentrations of Zn, Cd, chlorophyll (Chl), carotenoid, hydrogen peroxide (H₂O₂), and malondialdehyde (MDA), as well as antioxidant enzyme activities were assayed. The addition of Zn in soils reduced the toxicity of Cd in durum wheat more than in bread wheat even though there was more uptake of Zn in bread wheat. Analysis of variance showed that by using Zn fertilizer and Pseudomonas species the amounts of peroxidase (POD), polyphenoloxidase (PPO), MDA, and H₂O₂ were reduced at three growth stages. Surprisingly, with increasing Zn concentration, Cd concentration in plant tissue was slightly increased, which suggests that adding Zn to soil could facilitate Cd desorption from soil particles. Application of Pseudomonas and Zn could be a promising solution to reduce detrimental effects of Cd, especially in durum wheat.     

二种钾肥对海泡石钝化修复镉污染土壤效应影响的研究

为了揭示钾肥对Cd污染土壤钝化修复效果的影响,为土壤钝化修复过程中合理施钾肥提供理论依据。本文选取不同剂量(含量以K2O计算,分别为0.1 g·kg~(-1)、0.2 g·kg~(-1)和0.3 g·kg~(-1))的KCl和K_2SO_4作为典型钾肥,以海泡石(10 g·kg~(-1))作为钝化材料,通过油菜盆栽试验,研究了两种钾肥在海泡石钝化条件下对Cd污染土壤修复效应的影响。结果表明:K_2SO_4显著增加了油菜的生物量,其增幅为6.06%~10.05%。与单施海泡石钝化相比,在海泡石钝化时施用KCl和K_2SO_4两种钾肥,油菜地上部茎叶Cd含量分别增加16.38%~60.73%和15.62%~25.19%;施用KCl和K_2SO_4对土壤p H未产生显著性影响,却显著地增加了土壤有效态Cd含量,其增幅分别为25.51%~34.65%和18.5%~24.96%。添加海泡石可使土壤的Zeta电位向负值方向移动,提高土壤对Cd的负载能力;但添加海泡石下施用KCl和K_2SO_4均能提高土壤的Zeta电位,降低土壤对Cd的负载能力。等温吸附试验同样表明,添加KCl和K_2SO_4均能降低海泡石对Cd的吸附量,在水溶液中海泡石对Cd的最大吸附量为5.30 mg·kg~(-1),添加KCl和K_2SO_4后吸附量分别降低至2.87 mg·g~(-1)和4.92 mg·g~(-1)。KCl和K_2SO_4显著改善了土壤中K、Mn、Cu和Zn等营养元素的有效态含量。从上述结果可以发现,在海泡石钝化修复Cd污染土壤过程中,施K_2SO_4对钝化效果的影响小于施KCl。     

A Laboratory Study on Revegetation and Metal Uptake in Native Plant Species from Neutral Mine Tailings

Lygeum spartum, Zygophyllum fabago and Piptatherum miliaceum are typical plant species that grow in mine tailings in semiarid Mediterranean areas. The aim of this work was to investigate metal uptake of these species growing on neutral mine tailings under controlled conditions and their response to fertilizer additions. A neutral mine tailing (pH of soil solution of 7.1–7.2) with high total metal concentrations (9,100 and 5,200 mg kg^?1 Zn and Pb, respectively) from Southern Spain was used. Soluble Zn and Pb were low (0.5 and <0.1 mg l^?1, respectively) but the major cations and anions reached relatively high levels (e.g. 2,600 and 1,400 mg l^?1 Cl and Na). Fertilization caused a significant increase of the plant weight for the three species and decreased metal accumulation with the exception of Cd. Roots accumulated much higher metal concentrations for the three plants than shoots, except Cd in L. spartum. Shoot concentrations for the three plants were 3–14 mg kg^?1 Cd, 150–300 mg kg^?1 Zn, 4–11 mg kg^?1 Cu, and 1–10 mg kg^?1 As, and 6–110 mg kg^?1 Pb. The results indicate that neutral pH mine tailings present a suitable substrate for establishment of these native plants species and fertilizer favors this establishment. Metal accumulation in plants is relatively low despite high total soil concentrations.     

Long-term fertilization and residue return affect soil stoichiometry characteristics and labile soil organic matter fractions

Ecological stoichiometry provides the possibility for linking microbial dynamics with soil carbon (C), nitrogen (N), and phosphorus (P) metabolisms in response to agricultural nutrient management. To determine the roles of fertilization and residue return with respect to ecological stoichiometry, we collected soil samples from a 30-year field experiment on residue return (maize straw) at rates of 0, 2.5, and 5.0 Mg ha^-1 in combination with 8 fertilization treatments:no fertilizer (F0), N fertilizer, P fertilizer, potassium (K) fertilizer, N and P (NP) fertilizers, N and K (NK) fertilizers, P and K (PK) fertilizers, and N, P, and K (NPK) fertilizers. We measured soil organic C (SOC), total N and P, microbial biomass C, N, and P, water-soluble organic C and N, KMnO₄-oxidizable C (KMnO₄-C), and carbon management index (CMI). Compared with the control (F0 treatment without residue return), fertilization and residue return significantly increased the KMnO₄-C content and CMI. Furthermore, compared with the control, residue return significantly increased the SOC content. Moreover, the NPK treatment with residue return at 5.0 Mg ha^-1 significantly enhanced the C:N, C:P, and N:P ratios in the soil, whereas it significantly decreased the C:N and C:P ratios in soil microbial biomass. Therefore, NPK fertilizer application combined with residue return at 5.0 Mg ha^-1 could enhance the SOC content through the stoichiometric plasticity of microorganisms. Residue return and fertilization increased the soil C pools by directly modifying the microbial stoichiometry of the biomass that was C limited.     

Development of annual xylem rings and shoot growth of young beech (Fagus sylvatica L.) grown in soil with various Cd and Zn levels

In a pot culture experiment two-year-old beech (Fagus sylvatica L.) were planted in soil amended with different concentrations of Cd and Zn or combinations of both. Concentrations ranged up to ca 180 μmol Cd and 7500μmol Zn kg^?1 soil dry weight (1 M ammonium acetate extracts). After 2 seasons of growth plants were harvested. Annual xylem growth rings in stems were significantly smaller at 50 μmol Cd kg^?1 and 1000 μmol Zn kg^?1 as compared to controls. Elongation of apical shoots was significantly reduced at 180 μmol Cd kg^?1 and 1000 μmol Zn kg^?1. The lowest treatment of 50 μmol Zn kg^?1 caused no significant growth depressions of stem diameter and shoot elongation. In the second year of treatment growth reductions were generally more pronounced than in the first season. Uptake and translocation of Cd and Zn into stem wood and leaves were marked and were correlated with substrate concentrations. The observed growth reductions are discussed with respect to possible adverse effects of trace elements on forest trees under field conditions.     

Availability of Cadmium in some Phosphorus Fertilizers to Field-Grown Lettuce

Although evaluations of the availability of cadmium (Cd) contaminants in phosphate fertilizers have been made, few have examined the transfer efficiency of Cd from fertilizers to plants, especially under field conditions. This 2-year field study determined the transfer of added Cd to lettuce (Lactuca sativa L.) (Royal Green) from a western phosphate rock (PR) and a triple superphosphate (TSP) as affected by liming and rate of fertilizer (or Cd) input. A readily soluble Cd salt, CdCl₂, was included in the study for comparison. The cumulative amounts of Cd added from the fertilizers and CdCl₂ over the 2-year period ranged from 0 to 1440 g ha^–1. Lettuce yield increased with increasing TSP rates, but was unaffected by PR. Significant (P < 0.01) effects of Cd source and rate, lime, and year were found on Cd accumulation by lettuce. The transfer of the added Cd was consistently higher for CdCl₂ than for the fertilizers regardless of lime rate. A contrasting year effect was also found between the two P fertilizers. In the second year of application, the Cd transfer efficiency increased in the soil treated with the PR, but decreased in the soil treated with the TSP. The Cd transfer efficiency for the plant was better measured with DTPA–Cd (r ²= 0.78 – 0.80) or CaCl₂–Cd (r ²= 0.57 – 0.76) than with soil total Cd (r ²= 0.39 to 0.54) across all Cd sources and lime rates. This is because DTPA–Cd or CaCl₂–Cd reflected the influences of the amount of Cd added, Cd source, and lime rate on Cd accumulation by the plant better than did the soil total Cd. Of the amount of Cd added from the fertilizers an average of 1.0% or less was accumulated in the harvested lettuce tissue. Applications of the fertilizers at high rates could result in increased Cd accumulation in the soil over time.     

Influence of potassium and magnesium fertilizer application on the yield and nutrient accumulation of maize genotypes under field conditions

The use of maize (Zea mays L.) genotypes that are able to utilize nutrients efficiently is an important strategy in the management of plant nutritional status; it is of particular importance with regard to potassium (K) and magnesium (Mg), due to their high requirement and influence on plant growth. The influence of K and Mg fertilizers on certain growth parameters of maize genotypes TM.815 and KL.72.AA, including length, seed in ear, seed weight growth, and nutrient concentration, was determined under field conditions over two successive years. The aim of the experiment was to study the effect of different rates of K and Mg fertilizers on maize genotype plant growth parameters, grain yield, and nutrient accumulation under field conditions.

A split plot design with three replicates was used and each block contained three treatments of 0, 100, and 200 kg ha^?1 of K₂O and 0, 10, and 20 kg ha^?1 of Mg; K₂SO₄ was used to supply K, and MgSO₄ was used for Mg.

Plants that responded to the K fertilizer had an increase in height, yield, and the concentration of K in the leaves and seeds. The addition of K fertilizer increased the concentration of nitrogen (N), iron (Fe), zinc (Zn), manganese (Mn), and K in the plant leaves and increased seed K concentration. Mg fertilizer increased the concentration of N, Fe, copper, and Mn in the leaves; however, it exerted no significant influence on K concentration. The KL.72.AA maize genotype had a higher mean plant height, number of seeds in ear, yield, and N, K, Fe, and Zn concentrations compared to the TM.815 maize genotype. In the experiment, the K fertilizer exerted a statistically significant effect on the leaf and seed K concentration; however, on a statistical basis, the Mg fertilizer did not affect the Mg concentration.     

Phytoavailability of Toxic Heavy Metals and Productivity in Wheat Cultivated Under Residual Effect of Fertilization in Soybean Culture

Achieving high productivity in agriculture is increasingly needed and requested; however, this activity should be performed in a sustainable and rational way. The use of micronutrients in the fertilization of the most diverse cultures is becoming a common practice on farms, but it is important to conduct studies in relation to fertilizers used for this supplement, including raw materials with which they are produced. Therefore, this study aimed to evaluate the phytoavailability of nutrients and toxic heavy metals Cd, Pb, and Cr; productivity; and yield components in wheat sown in soil with residue of N/P₂O₅/K₂O?+?Zn-based fertilizer applied in previous crop. Treatments consisted of residual fertilization of five forms arranged in two doses (D1?=?300 kg ha^?1 and D2?=?600 kg ha^?1). The five types of fertilization were composed of formulated N/P₂O₅/K₂O and the variation of different Zn sources. In the assessment of phytoavailability were determined levels of K, Ca, Mg, Cu, Mn, Zn, Fe, Cd, Pb, and Cr in wheat leaves. The results show that the residual effect of fertilization was not enough for there being difference between treatments at both doses used; however, it was found that the fertilizers used to Zn supply provided residual effect, providing significant levels of Pb and Cr for wheat plants.     

Metal uptake in plants from a birch forest area near a copper smelter in Norway

Uptake of Ca, Mg, K, Mn, Fe, Al, Rb, Ph, Cu, Zn, and Cd in vascular plants from a birch forest area near a Cu smelter in northern Norway was investigated. The primary objective was to study metal uptake in plants growing in a strong local acidification gradient. Decreased levels of Mn, Mg, and Ca found in Betula pubescens, Vaccinum myrtillus, and Deschampsia flexuosa near the smelter corresponded to a decrease in base saturation of the soil. This suggests that appreciable soil acidification has taken place. The level of Rb in Vaccinum myrtillus and Sorbus aucuparia increased significantly towards the smelter, probably due to the higher soil acidity. Elevated levels of Cu, Zn, Ph, and Cd in surface soil were found with values up to 2500 mg kg^?1 Cu within 1 km from the smelter. These concentrations decreased significantly with distance, but metal contamination was detectable up to 27 km from the smelter along the prevailing wind direction. A corresponding decrease was detected for Cu in the four plant species analyzed. Elevated levels of Zn, Ph, Fe, and Al were found in some, but not all, species.     

Long‐term fertilization impacts on corn yields and soil organic matter on a clay‐loam soil in Northeast China

A long‐term fertilization experiment with monoculture corn (Zea mays L.) was established in 1980 on a clay‐loam soil (Black Soil in Chinese Soil Classification and Typic Halpudoll in USDA Soil Taxonomy) at Gongzhuling, Jilin Province, China. The experiment aimed to study the sustainability of grain‐corn production on this soil type with eight different nitrogen (N)‐, phosphorus (P)‐, and potassium (K)–mineral fertilizer combinations and three levels (0, 30, and 60 Mg ha^–1 y^–1) of farmyard manure (FYM). On average, FYM additions produced higher grain yields (7.78 and 8.03 Mg ha^–1) compared to the FYM0 (no farmyard application) treatments (5.67 Mg ha^–1). The application of N fertilizer (solely or in various combinations with P and K) in the FYM0 treatment resulted in substantial grain‐yield increases compared to the FYM0 control treatment (3.56 Mg ha^–1). However, the use of NP or NK did not yield in any significant additional effect on the corn yield compared to the use of N alone. The treatments involving P, K, and PK fertilizers resulted in an average 24% increase in yield over the FYM0 control. Over all FYM treatments, the effect of fertilization on corn yield was NPK > NP = NK = N > PK = P > K = control. Farmyard‐manure additions for 25 y increased soil organic‐matter (SOM) content by 3.8 g kg^–1 (13.6%) in the FYM1 treatments and by 7.8 g kg^–1 (27.8%) in the FYM2 treatments, compared to a 3.2 g kg^–1 decrease (11.4%) in the FYM0 treatments. Overall, the results suggest that mineral fertilizers can maintain high yields, but a combination of mineral fertilizers plus farmyard manure are needed to enhance soil organic‐matter levels in this soil type.     

Effects of Soil Amended with Cadmium and Lead on Growth,Yield, and Metal Accumulation and Distribution in Parsley

A greenhouse experiment was designed to determine the cadmium (Cd) and lead (Pb) distribution and accumulation in parsley plants grown on soil amended with Cd and Pb. The soil was amended with 0, 5, 10 20, 40, 60, 80, and 100 mg Cd kg^?1 in the form of cadmium nitrate [Cd(NO₃)₂] and 0, 5, 10, 50 and 100 mg Pb kg^?1 in the form of lead nitrate [Pb(NO₃)₂]. The main soil properties; concentrations of the diethylenetriaminepentaacetic acid (DTPA)–extractable metals lead (Pb), Cd, copper (Cu), iron (Fe), zinc (Zn), and manganese (Mn) in soil; plant growth; and total contents of metals in shoots and roots were measured. The DTPA-extractable Cd was increased significantly by the addition of Cd. Despite the fact that Pb was not applied, its availability was significantly greater in treatments 40–100 mg Cd kg^?1 compared with the control. Fresh biomass was increased significantly in treatments of 5 and 10 mg Cd kg^?1 as compared to the control. Further addition of Cd reduced fresh weight but not significantly, although Cd concentration in shoots reached 26.5 mg kg^?1. Although Pb was not applied with Cd, its concentration in parsley increased significantly in treatments with 60, 80, and 100 mg Cd g^?1 compared with the others. Available soil Pb was increased significantly with Pb levels; nevertheless, the increase was small compared to the additions of Pb to soil. There were no significant differences in shoot and root fresh weights between treatments, although metal contents reached 20.0 mg Pb kg^?1 and 16.4 mg Pb kg^?1 respectively. Lead accumulation was enhanced by Pb treatments, but the positive effect on its uptake was not relative to the increase of Pb rates. Cadmium was not applied, and yet considerable uptake of Cd by control plants was evident. The interactive effects of Pb and Cd on their availability in soil and plants and their relation to other metals are also discussed.