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1.
Abstract

Many soil extractants have been developed for determination of zinc (Zn) availability to plants. The optimum soil Zn extractant should be useful not only for prediction of plant Zn concentration but also for detection of applied Zn levels. The objectives of this study were: i) to compare soil Zn extradants for detecting applied Zn and for predicting peanut leaf Zn over a range of soil pH levels, and ii) to correlate other soil‐extractable Zn levels with Mehlich‐1. Soil and peanut leaf samples were taken from a field study testing pH levels as the main plots and Zn application rates in the sub‐plots. Extractable Zn was determined on soil samples using Mehlich‐1, Mehlich‐3, DTPA, MgNO3, and many dilute salt extradants of varied strength and pH. Correlation of extractable soil Zn to cumulative applied Zn levels revealed Mehlich‐1, Mehlich‐3, DTPA, and AlCl3 extradants to be among the best indicators of applied Zn. Leaf Zn concentration was best correlated with soil Zn extracted by dilute salts, such as KCl, CaCl2, NH4Cl, CaSO4, and MgCl2. Including soil pH as an independent variable in the regression to predict leaf Zn considerably improved R‐square values. The DTPA‐extractable soil Zn levels were very well correlated with Mehlich‐1‐extractable Zn. Mehlich‐3 extracted about 20% more soil Zn than Mehlich‐1, but Mehlich‐3 soil Zn was not as well correlated to Mehlich‐1 soil Zn as DTPA soil Zn. Lower pH solutions extracted more of the applied Zn, but more neutral solutions extracted Zn amounts which were better correlated with Zn uptake. On the other hand, Mehlich‐1, which had a lower pH, had better correlations with both applied Zn and leaf Zn than did Mehlich‐3. Shortening the DTPA extraction time to 30 minutes resulted in better correlations than the standard two hour extraction time. Chloride (Cl) was the best anion tested in relation to soil applied Zn recovery in combination with potassium (K), calcium (Ca), and aluminum (Al), and Cl optimized leaf Zn correlations for ammonium (NH4), K, Ca, and magnesium (Mg). The larger the valence of the cation, the better the correlation with applied Zn and the poorer the correlation with leaf Zn.  相似文献   

2.
Abstract

Zinc toxicity of peanuts (Arachis hypogaea L.), resulting from excessive amounts of Zn applied to previous crops, has been observed for many years in a limited number of peanut fields in Georgia. A tentative critical value of 12 mg/kg of Mehlich No.1 extractable soil Zn has been reported, but soil pH should be considered in establishing a more precise critical value since availability of soil Zn is affected greatly by soil acidity. A 3‐year study was conducted on a Tifton loamy sand (thermic, Plinthic Paleudults) to evaluate the relationship between soil pH and soil Zn on concentration of Zn in peanut leaves. Factorial treatments were 0, residual, medium, and high rates of Zn and soil pH levels near 5.5, 5.9, 6.2, and 6.8. Pod yields were not affected by treatments and Zn toxicity was not observed. Leaf Zn was affected more by soil pH than by soil Zn, but correlation coefficients were highest where both soil pH and soil Zn were included in the determination. A regression equation, based on soil pH and soil Zn, showed that an increase in soil Zn from 1.0 to 10.0 mg/kg increased leaf Zn 202 mg/kg at soil pH 4.6 and only 9 mg/kg at pH 6.6. Data from growers’ fields, in which samples were collected from eight healthy and toxic areas, indicated that a leaf Ca:Zn ratio of 50 or less was required for Zn toxicity of peanuts rather than high concentrations of leaf Zn per se.  相似文献   

3.
Minimum tillage cropping systems and the use of animal manures on cropland are becoming more prevalent. An experiment was initiated to determine the effects of tillage and lime/gypsum variables on uptake of zinc (Zn), manganese (Mn), and copper (Cu) by corn (Zea mays L.) and to show correlations between plant uptake of these metals and soil pH and Mehlich 1‐extractable soil metals where poultry litter was used as a nitrogen (N) source. Surface soil samples were taken in the spring and fall for two years from a long‐term tillage experiment that had been in place for nine years. There were two tillage treatments [conventional (CT) and no‐tillage (NT)] and six lime/gypsum treatments (control, 8,960 kg gypsum ha‐1 every fourth year, 4,480 kg lime ha‐1 every fourth year, and three treatments of 8,960 kg lime ha‐1 in a four‐year period divided by application times into 1, 2, and 4 treatments). Poultry litter was applied each year of the two‐year experiment at a rate of 8.96 Mg ha‐1 on a dry weight basis. Soil samples were analyzed for pH and Mehlich 1‐extractable Zn, Mn, and Cu, and plant tissue (small plant, ear leaf, stalk, and grain) was analyzed for Zn, Mn, and Cu concentrations. Lime treatments resulted in lower Zn in the small plant and ear leaf for CT, but not for NT. Plant Mn was decreased by lime and gypsum rates for small plant, ear leaf, stalk and grain for both years for CT and NT. Correlations for plant Zn versus soil pH were generally non‐significant, except for one year for ear leaf Zn (R=‐0.413**). Correlations for soil pH and plant tissue Cu were all nonsignificant. Correlations for plant Mn and soil pH were strong with R values over 0.80. Plant Mn response to treatments was found at a pH range of 4.2 to 5.8 for ear leaf and pH 5.2 to 6.2 for stalks. Plant Mn and Zn versus Mehlich 1‐extractable soil Mn and Zn, respectively, were negative. This response was possibly due to oxidation‐reduction and non‐incorporation of the lime for Mn and non‐incorporation of the lime for Zn. Also, the poultry litter was high in Zn (447 mg kg‐1), which could have masked pH effects. It was concluded that soil sampling for plant micronutrients for NT, especially where a waste material high in micronutrients is applied, can give erratic and even erroneous results. However, lime and tillage treatments had a predictable effect on micronutrient uptake as related to soil pH.  相似文献   

4.
Abstract

The objective of this research was to mesasure the effect of intercropping corn (Zea mays L.) with velvet bean (Mucuna pruriens) oil corn yields, soil fertility, and weed control in northern Belize. Two soils were used which are widespread in the area. These soils are high in clay (simectitc) and are well supplied with bases. One soil, the Louisville, has a black surface horizon overlying light gray to white calcareous weathered coral. The other soil was Xaibe which consists of a reddish‐brown clay over hard limestone “cap rock”; at 30–40 cm. Both soils had a relatively high organic carbon (C) and total nitrogen (N) content. We classified the Louisville as Calciustert and the Xaibe as a Ustropept. The treatments used (carried out annually in 1990, 1991, and 1992) were residue burn (B), bum plus fertilizer (BF), a velvet bean intercrop (G), and a velvet bean intercrop plus fertilizer (GF). Velvet bean intercropping did not have a positive effect on corn yields on these soils. For adequate yields to be maintained, it appears that fertilization with N, phosphorus (P), potassium (K) and certain micronutrients are required. We did obtain some indication that velvet bean intercropping will reduce weed population, including a serious infestation of cogongrass (Jmperata cylindrica). Velvet bean did not maintain the soil N content Corn yields decreased on the Louisville soil at San Victor from a range of 2,804 kg/ha to 3,181 kg/ha in 1990 to 1,783 kg/ha to 2,065 kg/ha in 1992. There were no significant treatment effects in any year. With the Xaibe soil, no yields were obtained in 1990 because of weed competition. In 1991, yields ranged from 555 kg/ha to 1,146 kg/ha (no significant treatment effects). In 1992, the fertilized plots, BF and GF, had corn yields of 1,391 kg/ha and 1,592 kg/ha, respectively. The unfertilized plots, B and G, had corn yields of 751 kg/ha and 699 kg/ha, respectively. We did obtain sufficient information valuable for persons making fertilizer recommendations on similar types of soil. The Mehlich 3 and the ammonium bicarbonate‐DTPA extractant (the latter extractant similar to that used in Belize) did not give good correlations between P and K leaf levels and corn yields. Where soil test P and K were often adequate, corn ear leaf levels were deficient (and presumably yields were reduced because of this metabolic deficiency). We concluded from both soil tests and leaf analyses that the micronutrients copper (Cu), manganese (Mn), and molybdenum (Mo) are seldom, if ever, limiting plant growth and grain yield, although there appears to be seasonal differences. With both soils, soil tests were not good indicators of zinc (Zn) concentrations in the leaf. In 1992, soil tests indicated adequacy of this element, although leaf Zn was deficient in all plots on the Louisville soil in 1990, most plots in 1992, and several plots on the Xaibe soil in both years.  相似文献   

5.
Abstract

The variability in corn yield responses to applications of Zn fertilizer appears to be associated with several complex soil and climatic factors that affect the availability of endogenous soil Zn to the crop under specific conditions. Among the soil chemical properties that influence availability of endogenous Zn are soil pH, organic matter content, and extractable P. Over a period of several years, soil and plant analysis data were collected from 54 field experiments, field trials, and diagnostic visits to producer's fields. These data were subjected to multiple regression analysis, resulting in an equation: Znleaf = 37.14 + 1.513 Znst ‐4.04 pHst ‐ 1.791 ln(Pst/100) where Znst, pHst, and Pst were 0.1N HC1 extractable soil Zn (kg/ha), 1:1 soil‐water pH, and Bray's 1 extractable soil P (kg/ha), respectively. These factors accounted for 67% of variation in leaf Zn, which was a large portion of the variability in Znleaf considering that climatic conditions, management levels, and varietal differences were uncontrolled in most instances. Using the previously published critical level in the leaf opposite and below the ear as 17 μg Zn/g, these data can be used to set required soil test levels of Zn at different levels of extractable P and soil pH. Inadequate levels of extractable Zn would range from 2.5 (at pH 6.0, P = 70 kg/ha) to, 9.5 kg/ha (at pH 7.5, P = 420 kg/ha).  相似文献   

6.
Abstract

A field experiment was conducted to determine whether Zn applied for pathogen control could accumulate to a level which would be toxic to snapbeans, cucumbers, or corn. Zinc sulfate (ZnSO4) was applied at rates varying from 0 to 363 kg Zn/ha on a Flainfield loamy sand to approximate 3, 9, 27 and 81 years of fungicidal treatment.

Even at the high rate of Zn, yields of snapbeans, cucumbers, or corn generally were not reduced. As rates of applied Zn increased, there was a corresponding increase in the level of Zn in the leaf tissue of all crops grown. At the high Zn rate, snapbean and cucumber leaf tissue accumulated over 350 ppm Zn. Available soil Zn was extracted with 0.1N HCl, EDTA, or DTPA. Highly significant correlations were observed between the Zn removed by each extractant and plant tissue Zn, thus, indicating that the various extractants were equally effective in predicting Zn uptake.

Very little downward movement of Zn was observed. Two and one‐half years after application, the Zn had leached to a depth of only 30 cm in the soil profile at the higher Zn rates.

These data indicate that application of Zn‐containing fungicides and bactericides should not cause a Zn toxicity problem on the Plainfield sand in the foreseeable future.  相似文献   

7.
Abstract

All mineral phosphates in soil dissolve more completely when HCl is mixed with H2SO4 than with the HCl alone. It was hypothesized that a new extracting solution of H2SO4 alone with the same ionic strength or the same acidity as the Mehlich P1 extractant would extract similar amounts of soil phosphorus (P) as the Mehlich P1 soil test. Thirty six acid soils from Alabama, Georgia, North Carolina, South Carolina, and Colorado were used in this study. These acid soils reflect wide ranges in parent materials, texture, pH, organic matter, and available soil P. They were analyzed for available soil P with the Mehlich P1 soil test and with the two H2SO4 methods: Method A has an extracting solution of same ionic strength (0.0875M) as the Mehlich P1 extractant, and Method B was an extracting solution of the same acidity (0.0375M) as the Mehlich P1 extractant. Correlations between the results of Mehlich P1 with Method A and Method B were 0.994 and 0.997, respectively. The measured test precision was <3.5% for all three methods. The new H2SO4 methods are simple and faster to conduct under routine operations than the original Mehlich P1 extractant, and because of the high correlations, the H2SO4 methods should predict crop response to P as well as the original Mehlich P1 extractant for acid soils.  相似文献   

8.
Abstract

Leaf N and soil nitrate and ammonium levels were monitored in 1986 and 1987 following N fertilization of 8–9 year old highbush blueberries. Urea was applied at 76 kg N/ha in a single application at bud break or in two applications (split) at bud break and petal fall. Controlled release fertilizers (CRF), of two different residual effects (Osmocote 3 mo., Osmocote 8 mo.) were applied at 38 kg N/ha or 76 kg N/ha at bud break. Compared to controls, N applications increased soil ammonium and nitrate levels early in the season and leaf N levels throughout the season. Urea provided a greater increase in leaf N and soil ammonium levels than CRF. Split urea applications increase leaf levels slightly over single urea treatments. Fertilizers increased soil ammonium and nitrate levels below the root zone, indicating that some leaching losses occurred.  相似文献   

9.
Abstract

A significant portion of chemical zinc (Zn) fertilizers applied to calcareous soils is not absorbed by the first crop and may, therefore, affect the growth and chemical composition of the subsequent crops. This is called the residual effect of Zn. Soil tests may be used to predict such effects. The present experiment was conducted to study the residual effects of zinc sulfate (ZnSO4) on the second crop of corn (Zea mays L.) grown on selected highly calcareous soils of Iran and to compare the suitability of three soil tests for prediction of the effects. Twenty highly calcareous soils of southern Iran (16–58% calcium carbonate equivalent; pH 7.9–8.5), previously treated with three levels of Zn (0, 10, and 20 mg Zn/kg as ZnSO4) and under one crop of corn, was used in greenhouse to grow a second crop of corn without additional Zn fertilizer but with uniform application of nitrogen (N), phosphorus (P), and iron (Fe). Soils were sampled before the second crop and extracted with three Zn extradants, DTPA, EDTA‐(NH4)2CO3, and EDTA. Dry weight of plant tops and Zn concentration and uptake after eight weeks under the greenhouse conditions were used as the plant responses to residual Zn. Statistical analyses including F‐test and multiple regression equations showed that the overall effect of previously‐applied Zn on dry matter was nonsignificant, but Zn concentration and uptake were significantly increased. The three soil tests predicted the Zn concentration and uptake equally well. Moreover, DTPA and EDTA soil tests could predict the dry matter of plants at the highest level of previuosly‐applied Zn (20 mg Zn/kg), especially when selected chemical properties of soil, namely, calcium carbonate equivalent or organic matter content, were considered in the regression equations.  相似文献   

10.
Abstract

Zinc (Zn) deficiencies have been identified in Venezuela with increasing frequency in recent years. However, there are no established critical values for available Zn in the acid soils of this country. Greenhouse studies were initiated to evaluate five extractants, DTPA, DTPA‐HCl, Na‐EDTA, 0.1N hydrochloric acid (HCl), and Mehlich 1 to predict Zn availability in 14 acid soils with corn as the test crop. Significant and positive correlations were found between Zn extracted among the five extractants. Zinc extracted was not related with soil pH and organic matter content, but with the cation exchange capacity and clay content. The Na‐EDTA extractant was found to be the most suitable as an indicator of Zn‐deficient acid soils, the critical Zn value being 2.4 mg#lbkg‐1.  相似文献   

11.
Abstract

The relative effectiveness of Mehlich I (.025N H2SO4 + .05N HCl) and Mehlich III (0.2N CH3COOH + 0.25N NH4NO3 +.015N NH4F + .013N HNO3 + .001M EDTA) extractants as predictors of Mn, Cu and Zn uptake was assessed in a greenhouse experiment with four Delaware soils. The soils were adjusted to eight pH levels by addition of Ca(OH)2 or elemental S, and received comparable amounts of Mn, Cu and Zn as either (1) MnSO4 + CuSO4 + ZnSO4 or (2) Poultry Manure. Mehlich 1 and III extractable Mn and Zn, but not Cu, were well correlated in most instances. Excellent correlations were obtained between Mn uptake and Mehlich I and Mehlich III extractable Mn, for all soils and sources. In general, however, neither Zn nor Cu was found to correlate well with plant uptake. Based on this study, conversion to Mehlich III, as a routine soil test extractant for micronutrients, would not result in a significant improvement over the currently used Mehlich I extractant.  相似文献   

12.

To study the availability of sludge-borne Zn, Cu, Cd, Ni and Pb over time, a field study was conducted. Anaerobically digested sewage sludge (dried on sandbeds) from Huntsville and Chicago were applied to a Decatur silty clay loam soil (clayey, kaolinitic, thermic, Rhodic Paleudult), pH 6.2, for 5 consecutive yr. The sludges were applied at rates of 0, 20 (annual application for 5 yr) and 100 mt ha?1 (single application). Corn (Zea mays L.) and sudangrass (Sorghum sudanenses) were grown on the sludge-treated plots as test crops in 1987. Plant tissue samples were collected at different growth stages. Soil samples collected from the sludge-treated plots were extracted for Zn, Cu, Cd, Ni and Pb by 0.1 M HCI, DTPA, Mehlich 1 and Mehlich 3 extractants. Statistically, Mehlich 1, Mehlich 3, DTPA and 0.1M HCI extractants all gave highly significant correlations with the plant accumulation of Zn, Cu, Ni and Cd, with DTPA giving the highest at any growth stage for both corn and sudangrass, but they gave poor correlations for Pb. Zinc removed by four extractants was more highly correlated with Zn accumulation by corn (r=0.72** to 0.93** p=0.01) and sudangrass (r=0.50** to 0.96**, p=0.01) than other metals. Based on higher significant linear correlation coefficients (r), DTPA would be the extractant of choice for both crops; however the advantage to using the Mehlich 3 extractant is that, with a shorter shaking time of 5 min (compared to 2 hr for DTPA), it may be better suited for routine analysis of large numbers of soil samples.

  相似文献   

13.
Abstract

Information on the redistribution of applied micronutrients into different fractions as a result of lime application is important to predict plant accumulation of nutrients and to select appropriate chemical extraction procedures for evaluation of micronutrient availability. The present work was carried out to study the influence of liming on the availability and redistribution of zinc (Zn) and copper (Cu) among soil fractions. Additionally, the effect of liming was evaluated on the recovery of these micronutrients by different chemical extractants (Mehlich‐1, Mehlich‐3, and diethylenetriaminepentaacetate (DTPA), which were correlated with Zn and Cu concentrations in corn (Zea mays L.) plants and soil fractions (exchangeable, organic matter, amorphous iron oxides, and crystalline iron oxides). The results showed that Zn added to soil samples that did not receive lime was retained mainly in the exchangeable and organic matter fractions. The liming resulted in distribution of Zn into iron oxides and as a result decreased the plant accumulation of Zn. Mehlich‐3 was the most efficient extractant to predict the plant accumulation of Zn in the acid soils, whereas DTPA was the most efficient in the limed soils. The oxide crystalline fraction was the major fraction responsible for retaining Cu in the soils. However, Cu added to soil was distributed mainly into organic matter. Mehlich‐3 was the most suitable extractant for predicting the bioavailability of Cu in limed or unlimed soils.  相似文献   

14.
Abstract

Canola plants (Brassica napus cv. Eureka) were grown in soil culture with seven levels of zinc (Zn) supply (0, 67, 133, 200, 267, 533, and 1,067 μg Zn/kg soil) for 39 days. Critical Zn concentrations in young leaf blades and petioles were established for the diagnosis of Zn deficiency in canola plants during vegetative growth by assessing the relationship between the Zn concentration in the leaves and shoot dry matter on 22 and 39 days after sowing (DAS). Zinc concentrations in leaf blades and petioles increased with increasing Zn supply, but Zn concentrations were always 50% higher in the youngest open leaf (YOL) than in the youngest mature leaf (YML). The relationship between shoot dry matter and Zn concentrations in leaf petioles exhibited Piper‐Steenbjerg curvature, indicating their unsuitability for Zn‐deficiency diagnosis either alone or by inclusion with leaf blades. By contrast, inclusion of leaf mid‐ribs with leaf blades did not alter the relationship between shoot dry matter and Zn concentrations, nor the critical Zn concentration. Critical Zn concentrations in the YOL, YOL+1, and YOL+2 blade on 39 DAS, corresponding with the stem elongation stage, were 15–17, 9–10, and 7–8 mg Zn/kg dry matter, respectvely. In comparison, the critical Zn concentration in the YOL+2 leaf blades with mid‐ribs was 7–8 mg Zn/kg dry matter. In conclusion, during the vegetative stage up to stem elongation, YOL+2 leaf blades which are also the YML are recommended for the diagnosis of Zn deficiency in canola plants with the critical Zn concentration being 7–8 mg Zn/kg dry matter.  相似文献   

15.
Abstract

Experiments were conducted to study the effects of various Zn carriers and rates on the growth and Zn uptake of Sanilac navy beans. Plants were grown under greenhouse and growth chamber conditions for 2, 4, 6 or 8 weeks on a Wisner silty clay loam soil low in available Zn. Plant growth responded to the various Zn fertilizers except at 4 weeks where no response was obtained. Only ZnZnEDTA and ZnNa2EDTA increased growth at 2, 6 and 8 weeks while ZnSO4, ZnHEIDA, ZnNTA and Zn(NO3)2 did not give consistent responses at all of these periods. The Zn carriers did not influence uptake until 6 weeks after planting.

Zinc rates began to influence plant growth at about the bloom stage, 6 weeks after planting with 2.0 kg/ha Zn as ZnNa2EDTA and 3.3, 6.6 and 13.2 kg/ha Zn as ZnSO4 giving higher responses than 0.7 or 1.3 kg/ha Zn as ZnNa2EDTA. The most consistent increase in Zn uptake at 2, 6 and 8 weeks was obtained with 6.6 and 13.2 kg/ha Zn applied as ZnSO4. No differences in uptake were obtained at 4 weeks between all the rates of Zn that were used. The data herein indicate that the stage of growth at which plant response to Zn fertilizers is evaluated may be very critical.  相似文献   

16.
不同水分状况下施锌对玉米生长和锌吸收的影响   总被引：3，自引：3，他引：3  
选择潮土(砂壤)和土(粘壤)两种质地不同的土壤,进行盆栽试验,研究不同土壤水分条件下施锌对玉米生长和锌吸收的影响。结果表明,施锌显著增加了玉米植株根、茎、叶以及整株干物质重;缺锌条件下玉米植株根冠比、根叶比和根茎比趋向增大。施锌显著提高了玉米植株各器官中锌的浓度和吸收量,并明显促进锌向地上部运移。干旱胁迫抑制了玉米植株生长,根冠比、根茎比、根叶比增大;随着土壤水分供应增加,植株生长加快,各器官生物量以茎和叶增加大于根。水分胁迫下,在潮土上玉米叶片中锌浓度上升;在土上叶片中锌浓度下降。但增施锌后,根和茎锌浓度增加幅度较大,叶片增加幅度较小;施锌和水分胁迫对根和茎锌浓度的交互作用极显著。水分胁迫下,玉米植株对锌的吸收总量减少。水分胁迫和锌肥施用对玉米叶片、茎锌吸收量的交互作用十分显著,但对根锌吸收量的交互影响不显著。  相似文献   

17.
Abstract

Predictive soil tests were used to detect possible need for Cu, Zn, and Mn fertilizers for the optimum production of watermelons (Citrullus lanatus (Thumb.) Masf.) in north and central Florida. Predictive Mehlich‐I soil testing indicated a possible response to additions of Mn and Cu but not to additions of Zn at three locations: Gainesville, Dunnellon, and Live Oak. Results showed no total marketable yield response to selected Cu, Zn, and Mn treatments at any of the three sites. Yields for the Gainesville, Dunnellon, and Live Oak sites were 41.5, 29.0, and 38.0 Mg/ha, respectively, well above the state average watermelon yield of 19.0 Mg/ha. Tissue analyses at the Gainesville and Live Oak sites showed Cu, Zn, and Mn levels within or above suggested sufficiency ranges. This study indicates that current University of Florida interpretations for the Mehlich‐I extractant can identify sites with adequate extractable Cu, Zn, and Mn levels, thus avoiding unnecessary fertilization. At no time were University of Florida Cu, Zn, or Mn interpretations and recommendations found to be limiting for watermelon production.  相似文献   

18.
The purpose of the present study was to compare the ability of three micronutrient soil-test extractants [diethylenetriaminepentaacetic acid (DTPA), Mehlich 3, and Soltanpour and Schwab] to determine plant-available concentrations of manganese (Mn), iron (Fe), and zinc (Zn) in three soils (from parent material Marl, Gneiss schist, and Peridotite) from central Macedonia, northern Greece. In black plastic bags containing 3 kg of air-dried soil, self-rooted olive plants (cv. Chondrolia Chalkidikis) were grown for about 5 months and irrigated with distilled water during the experimental period. At the end of the experimental period, the three extractants were evaluated, based on correlation analysis among leaf micronutrient concentrations, total plant micronutrient content of olive plants, and soil micronutrient concentrations determined by each extractant. The largest extractable concentrations of Mn, Fe, and Zn were determined by Mehlich 3, compared to the other two soil-test extractants. However, for the correlation analysis, the greatest correlation coefficient between leaf Mn (and total plant Mn content) and soil extractable Mn was achieved when DTPA was used (varying from 0.76 to 0.88, depending on soil type). Therefore, it is concluded that DTPA was a better extractant to determine plant-available Mn than the other extractants for the three soils studied. For correlations between leaf Fe and Zn concentrations and also for total plant Fe and Zn content, and soil extractable concentrations, the type of extractant and soil type play a very important role in determining the best correlation. This means that in each soil type the greatest correlation was achieved with the use of other extractant. For example, for Fe in the Marl and Peridotite soils the best correlation was found for Mehlich 3, whereas in the Gneiss schist the best correlation was achieved for DTPA (R = 0.72–0.94). For Zn, in the Gneiss schist soil the best extractant in determining plant available concentration was Soltanpour and Schwab (R = 0.49–0.60), whereas in the other two soil types DTPA was found to be the most reliable extractant (R = 0.51–0.78). Therefore, soil type should be carefully and thoroughly studied by the researchers in similar future experiments.  相似文献   

19.
Abstract

Forages in the Northeast generally do not contain enough Zn to meet the National Research Council (NRC) recommended allowance for dairy cattle (40 mg/kg Zn). A study was undertaken to determine if foliar or soil application of Zn could increase Zn levels in alfalfa herbage to the NRC recommended allowance.

Alfalfa was treated with Zn by foliar applications of 0.34 and 0.68 kg/ha and soil application of 4.07 kg/ha. An untreated check was also included in the study. Average herbage Zn levels were 33.1 and 50.1 mg/kg for the low and high foliar applications, respectively. These levels were significantly higher than that of the check, 18.9 kg/ha. Average herbage Zn levels for the soil applied Zn treatment was 23.4 mg/kg. This level was also significantly higher than that of the check.

Although foliar Zn application significantly raised herbage Zn levels above those of the check, the results were erratic. The 40 mg/kg level was reached only one‐third of the time with the 0.34 kg/ha foliar application and two‐thirds of the time with the 0.68 kg/ha foliar application. Due to lower yields in comparison with cut 1, foliar application was more effective in raising herbage Zn levels in cuts 2 and 3. Foliar application of Zn does not appear to be a reliable means of insuring adequate herbage Zn levels for dairy cattle.  相似文献   

20.
Abstract

Six noncrisphead lettuce cultivars (Lactuca sativa L.) were grown in pots, using soil from field plots that had been amended annually with 90 MT/ha of an industrial sludge as part of a continuous study initiated in 1981. Two greenhouse experiments (each replicated 6 times) were completed—one in the spring and one in the fall. Variables included 6 cultivars, 2 soil pH levels and 2 soil Zn levels. All variables appeared to influence Cd accumulation in the leaf tissue. Uptake of Cd and Zn increased with decreasing soil pH for all cultivars. ‘Grand Rapids’ accumulated the least leaf Cd and ‘Summer Bibb’ the most. A positive correlation between leaf Zn and leaf Cd was observed, but the correlation between soil Zn and leaf Cd was variable.  相似文献   

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