Evaluation of chemical methods for estimating available zinc and response of green gram (Phaseolus aureus roxb) to applied zinc in non-calcareous soils

Summary Studies were conducted in 22 non-calcareous soils (India) to evaluate various extractants,viz. (6N HCl, 0.1N HCl, EDTA (NH₄)₂CO₃, EDTA NH₄OAc, DTPA+CaCl₂ and 1M MgCl₂) to find critical levels of soil and plant Zn for green gram (Phaseolus aureus Roxb.). The order of extractability by the different extractants was 6N HCl>0.1N HCl>EDTA (NH₄)₂CO₃<EDTA NH₄OAc DTPA+CaCl₂>1M MgCl₂. Critical levels of 0.48 ppm DTPA × CaCl₂ extractable Zn, 0.80 ppm EDTA NH₄OAc extractable Zn, 0.70 ppm EDTA (NH₄)₂CO₃ extractable Zn, and 2.2 ppm 0.1N HCl extractable Zn were estimated for the soils tested. The critical Zn concentration in 6 weeks old plants was found to be 19 ppm. The 0.1N HCl method gave the best correlation (r=0.588^**) between extractable Zn and Bray's per cent yield, while with DTPA+CaCl₂, it was slightly low (r=0.542^**). The DTPA + CaCl₂ method gave significant (r=0.73^**) correlation with plant Zn concentration. The 0.1N HCl gave the higher correlation with Zn uptake (r=0.661^**) than DTPA (r=0.634^**) 6N HCl and 1M MgCl₂ method gave nonsignificant positive relationship with Bray's per cent yield. For noncalcareous soils apart from the common use of DTPA+CaCl₂, 0.1N HCl can also be used for predicting soil available Zn. The use of 0.1N HCl would be much cheaper than DTPA and other extractants used in the study.     

Soil flushing of a sandy loam contaminated with Pb(II), PbS4 (s), PbCO3 (3), or Pb‐Naphthalene: Column results

Column‐scale oil flushing of a sandy loam contaminated with either Pb(II) (500 mg/kg Pb), PbSO₄ (10,000 mg/kg Pb), PbCO₃ (10,000 mg/kg Pb), or Pb‐naphthalene (400 mg/kg Pb, 333 mg/kg naphthalene) was investigated. HCl (0.1 N), EDTA (0.01 M), and CaCl₂ (1.0 M) were selected as the soil‐flushing solutions based on soil‐washing experiments. For the Pb‐only tests, Pb removal efficiencies were 85, 100, and 78% for HCl, EDTA, and CaCl₂, respectively. For PbSO₄ (s), Pb removal efficiencies were 32, 100, and 96% for HCl, EDTA, and CaCl₂, respectively, and for PbCO₃ were 97, 100, and 14% for HCl, EDTA, and CaCl₂, respectively. Larger amounts of flushing solutions were required for the remediation of PbSO₄‐and PbCO₃‐contaminated soils compared with the Pb‐only tests, most likely because of slower dissolution kinetics and the neutralization of HCl by CO₃ ^‐2 For Pb‐naphthalene, Pb removal efficiencies were 78 and 72% for HCl and EDTA, respectively, which compared well with soil‐washing results but were less than those observed in Pb‐only column studies.     

Simultaneous extraction of soil phytoavailable cadmium,copper, and lead by chelating resin membrane

Cadmium, copper, and lead were extracted from suspensions of contaminated soils using metal chelating exchange resin membranes. Nine soils with widely varying properties and Cd, Cu and Pb levels were tested. Soil suspensions made up with 4 g in 40 mL deionized water were equilibrated with 5 cm² Ca-saturated Chelex exchange resin membrane which was retained inside a polypropylene bag and shaken at 150 rpm for 24 hrs. Resin membrane extractable Cd, Cu and Pb of the soils were correlated with Cd, Cu, and Pb uptake by young wheat seedlings grown in these soils and compared with soil Cd, Cu, and Pb extracted by 0.1 M HCl, 0.01 M CaCl₂, and 0.005 M Diethylenetriamine pentaacetic acid (DTPA). The amounts of Cd, Cu and Pb extracted by the Ca-saturated Chelex membrane from all tested soils correlated well with those absorbed by young wheat seedlings. The Ca-saturated Chelex membrane extractable Cd, Cu and Pb of the soil had the strongest correlation with plant uptake Cd, Cu and Pb among the extraction methods we tested. It was demonstrated that the Ca-saturated Chelex membrane extraction is an appropriate method in simultaneously estimating Cd, Cu and Pb phytoavailability of soil and is applicable to a wide range of soils.     

Soil isotopically exchangeable zinc: A comparison between E and L values

The objectives of the present paper were: (i) to determine isotopically exchangeable zinc using two isotopic exchange methods (E and L values) in a series of polluted and non-polluted Swiss agricultural soils, and (ii) to evaluate the ability of chemical extraction methods to estimate plant-available soil Zn using isotopic techniques. The surface horizon (0–20 cm) of seven polluted and non-polluted soils representing a wide range in physico-chemical properties and Zn contents were sampled. An isotopic exchange kinetics (IEK) approach was used to assess, in a batch experiment, the isotopically exchangeable Zn content (E value). In order to determine the L values, a pot experiment was carried out with Lolium multiflorum (cv. Axis) in a growth chamber using a ⁶⁵Zn-isotope dilution technique. Total Zn uptake and the isotopic composition (⁶⁵Zn/^stableZn) were determined in Lolium multiflorum for five successive cuts. The amounts of zinc extracted by different chemicals were compared with L values and regression parameters were estimated. The isotopic composition in soil extracted by DTPA and EDTAAc at the end of the pot experiment was also determined. Results showed that the equation describing the increase of isotopically exchangeable Zn with time could be extrapolated to three months for polluted and non-polluted neutral and acidic soils, and that the results were not different from the amount of isotopically exchangeable Zn experimentally determined with Lolium multiflorum (L value). In alkaline soils however, results suggest that either ⁶⁵Zn sorption occurred in the batch experiment or that the concentration of Zn in the soil solution had been overestimated, leading to an overestimation of the E value compared to the L values. Furthermore, the specific activities measured in DTPA and EDTA extractions at the end of the pot experiment were significantly different compared to the specific activity of the plant, showing that both these chelating agents extract neither all the available soil Zn nor only the available soil Zn for plants. Abbreviations: C _Zn– concentration of Zn in a soil water extract (mg Zn L^?1); C _Zn?Plant– concentration of Zn in plant shoots (mg Zn kg^?1 DM); DTPA – diethylene triamine pentaacetic acid; E _1\min– amount of Zn isotopically exchangeable within one min (mg Zn kg^?1 soil); E _(t)\exp– amount of Zn isotopically exchangeable after t min derived from experimental results (mg Zn kg^?1 soil); E _(t)pred– amount of Zn isotopically exchangeable after t min predicted using kinetic parameters derived from a 100 min long isotope exchange kinetic experiment together with C _Zn, and Zn_HNO3 (mg Zn kg^?1 soil); EDTA – ethylene diamine tetraacetic acid; IC_P– isotopic composition of Zn in plant shoots; IC_DTPA– isotopic composition of Zn in the soil DTPA extract; IC_EDTA– isotopic composition of Zn in the soil EDTA extract; IC_SE– isotopic composition of Zn in the soil extracts; IEK – isotope exchange kinetics; L value – amount of plant available Zn (mg Zn kg^?1 soil); Lolium multiflorum; TEA – Triethanolamine; Zn_DTPA– Zn extractable by 0.005 M DTPA + 0.01 M CaCl2 + 0.1 M TEA; Zn_EDTA?NH4Ac– Zn extractable by 0.5 M NH₄Ac, 0.02 M EDTA; Zn_{EDTA?Ca(NO3)2}– Zn extractable by 0.005 M EDTA, 0.01 M Ca(NO₃)₂; Zn_KCl– Zn extractable by 1 M KCl; Zn_CaCl2– Zn extractable by 0.01 M CaCl₂; Zn_NaNO3– Zn extractable by 0.1 M NaNO₃; Zn_HNO3– Zn extractable by 2 M HNO₃.     

The in vitro Germination of Pollen of Setaria sphacelata

The effects of various substances upon germination and tube growth of pollen of Setaria sphacelata were investigated in hanging-drop culture. Both sucrose (0.6–0.7 M) and boron (1–5 ppm, as borate) are essential for germination. Comparable results were obtained with boric acid, sodium tetraborate and tri-n-butyl borate as boron sources, but sodium tetraphenylboron was inhibitory. Good germination and growth were obtained with raffinose and cellobiose, alone or in combination with sucrose (total 0.5 M); 0.25 M rhamnose, lactose and glycerol were without effect, and xylose, galactose and glucose were slightly inhibitory in the presence of 0.25 M sucrose; 0.25 M arabinose, fructose, mannose, sorbose, maltose, mannitol and sorbitol completely inhibited germination, even in the presence of 0.25 M sucrose. IAA and GA (0.01–10 ppm) could not replace or supplement the effects of borate on germination and growth, indicating the pollen to be self-sufficient in this respect. Riboflavin (0.1–10 ppm) and calcium pantothenate (1–100 ppm) stimulated germination and growth, whereas 0.01–10 ppm of thiamine, pyridoxine, nicotinic acid and ascorbic acid were generally without effect. Although copper sulphate, manganese sulphate, zinc sulphate and ammonium molybdate could not replace boric acid, 1.0 ppm of copper, manganese and zinc stimulated germination and growth in the presence of boron. In no instance were tubes found comparable in length to those required for fertilisation in vivo. It was concluded that the pollen probably requires a complex mixture of substances, including sucrose and borate, before this can be achieved in vitro.     

The critical level of copper in sierozem soils of haryana as evaluated with different extractants

Summary The relative efficiency of seven extractants for estimating available Cu in sierozem soils of Haryana was studied. Bulk samples of 15 soils ranging in neutral normal amm. acetate extractable Cu from 0.12 to 0.20 ppm were subjected to screen-house study. The quantities of Cu extracted with neutral normal amm. acetate, Morgan’s reagent (pH 4.8)N ammonium acetate (pH 4.8), 0.1N HCl, 0.02M EDTA, critrate-EDTA and DTPA from soils were examined for their correlation with responses of maize in terms of Bray’s percentage yield and percentage Cu uptake. The highest coefficient of correlation was obtained between Cu extractable with neutral 1N NH₄OAc and Bray’s per cent yield and per cent Cu uptake. All other methods showed lower values of correlation. The critical level of available Cu estimated with use of neutral normal NH₄OAc was 0.16 ppm. Below this value, responses to applied Cu can be expected.     

A suitable extractant for assessing plant-available copper in different soils (peaty,red and alluvial)

Summary Relative efficiency of five chemical extractants for the extraction of available Cu in four different soils and its uptake by rice seedlings was studied in a pot culture experiment. The Cu extracted by 0.1N HCl showed significant relationship with plant uptake whereas the values for other extractants except 0.05M EDTA did not approach the level of significance. Among the soil properties studied, pH and CaCO₃ correlated negatively and organic matter and CEC positively with Cu uptake by rice plants.     

Effects of soil acidification on the chemical extractability of Fe,Mn, Zn and Cu and the growth and micronutrient uptake of highbush blueberry plants

Summary The effects of soil acidification and micronutrient addition on levels of extractable Fe, Mn, Zn and Cu in a soil, and on the growth and micronutrient uptake of young highbush blueberry plants (Vaccinium corymbosum L. cv. Blueray) was investigated in a greenhouse study.Levels of 0.05M CaCl₂-extractable Fe, Mn, Zn and Cu increased as the pH was lowered from 7.0 to 3.8. However, the solubility (CaCl₂-extractability) of Fe and Cu was considerably less pH-dependent than that of Mn and Zn. With the exception of HCl-and DTPA-extractable Mn, micronutrients extractable with 0.1M HCl, 0.005M DTPA and 0.04M EDTA were unaffected or raised only slightly as the pH was lowered from 6.0 to 3.8. Quantities of Mn and Zn extractable with CaCl₂ were similar in magnitude to those extractable with HCl, DTPA and EDTA whilst, in contrast, the latter reagents extracted considerably more Cu and Fe than did CaCl₂. A fractionation of soil Zn and Cu revealed that soil acidification resulted in an increase in the CaCl₂- and pyrophosphate-extractable fractions and a smaller decrease in the oxalate-extractable fraction.Plant dry matter production increased consistently when the soil pH was lowered from 7.0 to 4.6 but there was a slight decline in dry matter as the pH was lowered to 3.8. Micronutrient additions had no influence on plant biomass although plant uptake was increased. As the pH was lowered, concentrations of plant Fe first decreased and then increased whilst those of Mn, and to a lesser extent Zn and Cu, increased markedly.     

Effects of natural and artificially induced reduction on soil solution phosphorus in rice soils

The effect of natural and artificial reduction on P extractability from soils used for rice production and the relation of these values to response to fertilizer P were investigated. Soil solution P increased from a mean of 3.8 mg P·kg^?1 soil for naturally oxidized slurries of 28 soils to 19.8mg P·kg^?1 when the soils were naturally reduced. The mean values were further increased to 40.8 and 45.3 mg·kg^?1 when the soils were reduced with 0.1M Na₂S₂O₄ and 0.2M Na₂S₂O₄, respectively. These P-values compare with 18.2 mg kg^?1 when the dry soils were extracted with Bray No. 1 extractant. When the yields of rice were correlated with solution and extracted P, the R²'s for the quadratic relationships were 0.40^**, 0.31^*, 0.34^**, 0.30^*, and 0.55^** for the naturally oxidized, the naturally reduced, 0.1M Na₂S₂O₄, 0.2M Na₂S₂O₄ and Bray No. 1, respectively. The Cate-Nelson calculation confirmed the superiority of the weak acid Bray extractant and the critical value of 8.6 mg P·kg^?1 soil needed for satisfactory yields of rice. There was little response of rice to added fertilizer P on soils with solution P-values greater than 0.09 mg P·l^?1 in oxygenated soil slurries. Some soils with solution P of this order and high amounts of Bray No. 1 extractable P still gave modest responses to fertilizer P. Although natural or chemically induced reduction increased soil solution P, it did not improve prediction of yield response of rice to added fertilizer P.     

Effects of liming on the extractability of Fe,Mn, Zn and Cu from a peat medium and the growth and micronutrient uptake of highbush blueberry plants

Summary Levels of extractable micronutrients in a peat and the growth and nutrient uptake of young highbush blueberry plants (Vaccinium corymbosum L cv. Blueray) were studied in a greenhouse experiment in response to liming and two rates of addition of Fe, Mn, Zn and Cu.Levels of extractable micronutrients showed different trends with liming depending upon the extractant used and the element being considered. Levels of 0.05M CaCl₂-extractable Fe, Mn and Zn decreased as the pH was raised whilst those of Cu first decreased and then increased again. There was a general decline in 0.1M HCl-extractable Fe, Mn and Cu with increasing pH but levels of Zn were not greatly affected. Levels of 0.005M DTPA extractable Fe, Mn Zn and Cu generally declined but those extractable with 0.04M EDTA were either unaffected or increased as the pH was raised. Levels of CaCl₂-extractable Mn and Zn were the same order of magnitude as those extractable with HCl, DTPA and EDTA. In contrast, the latter reagents extracted considerably more Fe and Cu than did CaCl₂.Dry matter yields of plants were increased as the pH was raised from 3.9 to 4.3 but then decreased markedly as the pH was raised further to 6.7. With increasing pH, concentrations of plant Fe generally increased those of Mn were decreased and those of Zn and Cu were not greatly affected except for a marked decline in plant Cu at pH 6.7.     

Influence of FeEDDHA and soil temperature on the growth of two soybean varieties

Bulk samples of 30 surface soils characterized in the National Cooperative Soil Survey of Louisiana were collected at the original sites and planted with sorghum-sudangrass in the greenhouse. The native K was exhausted by a total of four croppings. The available soil K was extracted with 1N NH₄OAc 7.0 and 0.1N HCl while the difficultly available-K was extracted by 0.3N NaTPB (sodium tetraphenylboron). In addition, the mica content was estimated by differential dissolution. All soils except Dundee produced the greatest dry matter yield in the first crop with steadily decreasing production in the succeeding crops. The same pattern was shown in the K uptake. It appears that the first crop removed a large portion of the exchangeable K. There was a high degree of relationship between plant uptake of K and exchangeable K in the soils (r²=0.89^**). Uptake by the subsequent crops was generally controlled by the K in the micaceous minerals (r²=0.89^**). Since there was a high coefficient of determination between mica-K and difficulty available-K (r²=0.91^**) one also finds that uptake of K by crops 2, 3 and 4 was also well correlated to difficultly available K (R²=0.94^**). The uptake of K that was not originally in the exchangeable form was also highly related to difficultly available-K (R²=0.51^**). Contribution from the Department of Agronomy, Louisiana Agricultural Experiment Station, Louisiana State University Agricultural Center, Baton Rouge. Part of the M.S. theses of the senior authors. Former Graduate Students and Prof. of Agronomy, respectively.     

Zinc influences nodulation,disease severity,leaf drop and herbage yield of alfalfa cultivars

Zinc deficiency is an important limiting factor in sustainable crop production and is a factor often overlooked in determining the benefits and overall success of alfalfa pastures in rotations. A field experiment was conducted to investigate the effects of zinc and alfalfa cultivars on nodulation, herbage yield, leaf drop and disease severity (Phytophthora root rot disease and common leaf spot disease) in alfalfa (Medicago sativa L.). Ten cultivars of alfalfa (Hunter River, Hunterfield, Sceptre Aurora, Genesis, Aquarius, Venus (Y8622), PL69, P5929 and PL34HQ) were tested at two levels of zinc (+Zn: 4 kg ha^–1, -Zn: no zinc added) on a Zn-deficient soil (DTPA zinc of top 0–15 cm soil was 0.4 mg kg^–1 soil, while 15–30 cm subsoil Zn was 0.1 mg kg^–1 soil) under field conditions. Zinc application significantly increased number and dry weight of nodules, herbage yield and leaf to stem ratio of alfalfa plants. There was a significant reduction in leaf drop, and occurrence of Phytophthora root rot (caused by fungus Phytophthora megasperma f. sp. medicaginis) and common leaf spot (caused by fungus Pseudopeziza medicaginis) diseases with Zn application. Alfalfa cultivars had a differential response to low Zn. Hunter River and Hunterfield were the most affected by omitting zinc application, while Sceptre, PL34HQ and Aquarius were comparatively less affected. The present study suggest that Zn nutrition effects nodulation, leaf drop, disease occurrence and production potential of alfalfa. The alfalfa cultivars have differential ability to low Zn supply. Growing of Zn-efficient cultivars and adequate Zn nutrition may also improve the N₂-fixation by alfalfa on low-Zn soils.     

Heavy metal composition of polysomal fractions following cadmium challenge

Endogeneous levels of zinc and copper were found to be 1.2±0.1×10⁻² and 0.3±0.1×10⁻² μg/A260 unit, respectively, in polysomal fractions from control animals; cadmium, however, was undetectable. In experimental animals (injected with cadmium) zinc, copper, and cadmium were found in polysomal fractions isolated by two different methods. One hour after a cadmium injection there was a rise in both the zinc and copper content of the polysomal fractions, which then declined steadily to below control levels by 16 h. Neither zinc nor cadmium were dialyzable from these fractions by a TRIS buffer; however, addition of 0.01M EDTA to the buffer resulted in removal of 75% of the zinc and all of the detectable cadmium. The addition of cadmium (CdCl₂) to control supernatants (adjusted to the cadmium concentration present in supernatants 6 h after in vivo exposure) resulted in metal binding to polysomal fractions in levels comparable to those observed after in vivo exposures to the metal. When cadmium was added in the form of cadmium thionein, a smaller fraction of the metal was isolated with the polysomal fraction. Cadmium bound to polysomal fractions in vivo (24 h after exposure) was sensitive to release by protease digestion, but insensitive to release by ribonuclease digestion.     

Evaluation of the electro-ultrafiltration technique (EUF) as a measure of the K supplying power of Quebec soils

The electro-ultrafiltration (EUF) method has been used to evaluate the short-term and long-term supplying power of soils for many essential plant nutrients. The objective of this study was to compare the capacity of EUF with other extraction techniques to predict the plant availability of soil K and K fertilizer responsiveness by 10 cuts of alfalfa (Medicago sativa L.) growing over a 366-day period. Increasingly higher average concentrations of soil K were extracted by EUF at 50 V and 20°C (29 mg kg^-1), EUF at 200 V and 20°C (48 mg kg^-1), 0.002 M SrCl₂ (55 mg kg^-1), EUF at 200 V and 80°C (85 mg kg^-1), 0.1 M HCl (105 mg kg^-1), Mehlich 3 (119 mg kg^-1), 1 M NH₄OAc (120 mg kg^-1) and boiling 1 M HNO₃ (601 mg kg^-1). The large content of vermiculitic minerals in the silt and clay fractions is responsible for EUF desorbing more K in 55 minutes than NH₄OAc in 29 out of 30 soils. The total amount of K desorbed by EUF at 80°C was as effective as Mehlich 3-extractable K in predicting K uptake for the first three cuts and was best among the extracting procedures after boiling 1 M HNO₃ in predicting the long-term K supply, the uptake of K from non-exchangeable sources and the relative yield of alfalfa over 10 cuts. The desorption of soil K with EUF provides a better evaluation of the K-supplying power of Quebec soils than the extractants currently used, especially on a long-term basis.Contribution no. 396.     

Accumulation of heavy metals in the metal-tolerant fern,Athyrium yokoscense,growing on various environments

The accumulation of copper, zinc and cadmium inA. yokoscense collected from Ashio (copper-contaminated area), Bandai (zinc- and cadmium-contaminated area) and Tama (non-contaminated area), has been investigated. Copper and zinc were accumulated most highly in the root, whilst cadmium was accumulated more in the leaf. The root ofA. yokoscense growing in areas contaminated with metals contained maximum amounts of Cu (5, 989 mg. kg⁻¹ dry weight) and Zn (6,384 mg.kg⁻¹ dry weight), while in the leaf from the Bandai area 164.8 mg Cd.kg⁻¹ dry weight was accumulated. These amounts are far greater than those found inA yokoscense growing on the non-metalliferous habitat (Tama). Twenty five times more zinc and three times more cadmium were found in the dead leaf than in the living leaf. InA. yokoscense growing on soils containing more than 1,000 mg Cu or Zn.kg⁻¹ dry weight, the uptake of copper by the root increased considerably with increasing copper content in the soils, while the uptake of zinc increased only slightly compared with the increase of zinc in the soils.     

Evaluation of suitable extractant for available lead in soils

Summary Four extractants were used to extract Soil-Pb from alluvial soils and the amounts of Pb extracted was correlated with Pb concentration in wheat crop. Of all the reagents, the Grigg's reagent was found to extract maximum amount of Pb from soils and the N NH₄OAc the least. A highly significant correlation (r=0.295) was observed between Grigg's reagent extractable Pb and Pb concentration in wheat plants followed by ammonium acetate (r=0.238). While 0.02M EDTA did not show any significant correlation, a negative significant correlation was observed with 0.1N HCl. re]19750512     

Influence of Soil Organic Matter on Copper Extraction from Contaminated Soil

Column experiments of copper extraction from four contaminated soils characterized by a content of Soil Organic Matter (SOM) ranging from 1% to 25% are presented and discussed. The extraction was performed by flushing the soil with an aqueous solution of a sodium salt of ethylene diamminotetraacetic acid (EDTA). Preliminary tests were performed on a soil containing 25% of organic matter, to investigate the influence of pH, concentration and volumes of EDTA on its chelant action and on the dissolution of SOM. Having selected the optimal conditions for the extraction process, a further series of tests was conducted on the four soils to evaluate the influence of organic content on copper extraction yields. EDTA solutions at 0.01 M, 0.05 M, 0.1 and 0.2 M were injected at 0.33 ml/s; copper and organic matter extraction yield were determined. At a pH of 5, 15 pore volume (PV) of a solution containing 0.05M EDTA, extracted about 99% of copper contained by the soil with the higher organic matter content. Under the same conditions, and for soil with > 6% SOM, extraction yields over 80% were achieved, while at lower organic content, copper extraction was dramatically reduced. This was attributed to the formation of highly stable copper-humate complexes and to their increasingly dissolution that occurred in the soils with higher organic matter level.

Experimental tests performed at different contamination levels (1200 mg/kg, 2400 mg/kg) showed that EDTA extraction effectiveness also depended upon initial soil Cu concentration.     

Genotypic variation in zinc efficiency and resistance to crown rot disease (Fusarium graminearum Schw. Group 1) in wheat

A crown rot disease in wheat caused by the fungusFusarium graminearum Schw. Group 1 is a widespread problem in chronically Zn-deficient Australian soils. A link between crown rot and Zn deficiency was established by Sparrow and Graham (1988). This paper reports a test of a further hypothesis, that wheat genotypes more efficient at extracting zinc from low-zinc soils are more resistant to infection by this pathogen. Three wheat cultivars (Excalibur, Songlen and Durati) of differential Zn efficiency were tested at three zinc levels (0.05, 0.5 and 2.0 mg Zn kg⁻¹ of soil) and three levels ofF. graminearum S. Group 1 inoculum (0.1 g and 0.3 g kg⁻¹ live chaff-inoculum and control having 0.1 g kg⁻¹ dead chaff inoculum). Six weeks after sowing dry matter production of shoots and roots was decreased byFusarium inoculation at 0.05 mg and 0.5 mg kg⁻¹ applied Zn.Fusarium inoculum at 0.1 g was as effective as 0.3 g kg⁻¹ for infection and decreasing dry matter. The infection at the basal part of culm decreased significantly by increasing the rate of Zn application. Excalibur, a Zn-efficient cultivar (tolerant to Zn deficiency) produced significantly more shoot and root dry matter, and showed less disease infection compared with Zn-inefficient cultivars (Durati and Songlen) at low (0.05 mg Zn kg⁻¹ soil) and medium (0.5 mg Zn kg⁻¹ soil) Zn fertilization rates. Higher rate of Zn fertilization (2.0 mg Zn kg⁻¹ soil) reduced the disease level in Durati to the level of Excalibur but the disease level of Songlen was still high, indicating its high Zn requirement and or sensitivity to crown rot. The data on Zn uptake show that Excalibur, being Zn-efficient, was able to scavenge enough Zn from Zn-deficient soil, we suggest that besides sustaining growth Excalibur was able to build and maintain resistance to the pathogen; inefficient cultivars needed extra Zn fertilization to achieve performance comparable to that of Excalibur. The present study indicates that growing Zn-efficient cultivars of wheat along with judicious use of Zn fertilizer in Zn-deficient areas where crown rot is a problem may sustain wheat production by reducing the severity of the disease as well as by increasing the plant vigour through improved Zn nutrition. ei]Section editor: R Rodriques-Kalana     

Toxicity of common biocides used in aquaculture to embryos and larvae of Brachymystax tsinlingensis Li

Brachymystax tsinlingensis Li is a threatened fish species endemic to China. With the problems of environmental factors and seeding breeding diseases, it is important to further improve the efficiency of seeding breeding and the basis of resource protection. This study investigated the acute toxicity of copper, zinc and methylene blue (MB) on hatching, survival, morphology, heart rate (HR) and stress behaviour of B. tsinlingensis. Eggs (diameter: 3.86 ± 0.07 mm, weight: 0.032 ± 0.004 g) of B. tsinlingensis were selected randomly from artificial propagation and developed from eye-pigmentation-stage embryos to yolk-sac stage larvae (length: 12.40 ± 0.02 mm, weight: 0.03 ± 0.001 g) and exposed to different concentrations of Cu, Zn and MB for 144 h in a series of semi-static toxicity tests. The acute toxicity tests indicated that the 96-h median lethal concentration (LC₅₀) values of the embryos and larvae were 1.71 and 0.22 mg l⁻¹ for copper and 2.57 and 2.72 mg l⁻¹ for zinc, respectively, whereas the MB LC₅₀ after 144-h exposure for embryos and larvae were 67.88 and 17.81 mg l⁻¹, respectively. The safe concentrations of copper, zinc and MB were 0.17, 0.77 and 6.79 mg l⁻¹ for embryos and 0.03, 0.03 and 1.78 mg l⁻¹ for larvae, respectively. Copper, zinc and MB treatments with concentrations greater than 1.60, 2.00 and 60.00 mg l⁻¹, respectively, led to a significantly low hatching rate and significantly high embryo mortality (P < 0.05), and copper and MB treatments with concentrations greater than 0.2 and 20 mg l⁻¹ led to significantly high larvae mortality (P < 0.05). Exposure to copper, zinc and MB resulted in developmental defects, including spinal curvature, tail deformity, vascular system anomalies and discolouration. Moreover, copper exposure significantly reduced the HR of larvae (P < 0.05). The embryos exhibited an obvious change in behaviour, converting from the normal behaviour of emerging from the membrane head first to emerging tail first, with probabilities of 34.82%, 14.81% and 49.07% under copper, zinc and MB treatments, respectively. The results demonstrated that the sensitivity of yolk-sac larvae to copper and MB was significantly higher than that of embryos (P < 0.05) and that B. tsinlingensis embryos or larvae might be more resistant to copper, zinc and MB than other members of the Salmonidae family, which benefits their resource protection and restoration.     

The influence of some soil and plant factors on the concentration of copper in perennial ryegrass

Summary The absorption and transport of Cu were studied in perennial ryegrass grwon on 21 soils under controlled environment conditions. Neither the concentration, nor the total amount, of Cu in the shoots was related to available Cu in the soils as assessed by extraction with 0.05M EDTA, 0.005M DTPA, or 1.95 per cent HNO₃. The concentration in the roots and, more especially, absorption per unit weight of root (i.e. μg Cu g dry wt⁻¹) were, however, highly correlated with available soil Cu. This suggests that, unless the extent of exploitation of the soil by roots is taken into account, measurements of available Cu will not be effective in predicting uptake by plants. On average, 63 per cent of the Cu absorbed by the roots was retained in the roots, and variation in the proportion retained was related to the transport of nitrogen from roots to shoots. On some soils the concentrations of N and Cu in the shoots were significantly correlated, and variation in N concentration accounted for a considerable proportion of the variance in the Cu concentration at later harvests. The relative importance of the measured soil (pH, organic matter) and plant (dry weight, N content) factors changed markedly over 6 successive harvests.