Leachability and distribution of zinc applied to an acid soil as controlled‐release zinc chelates

Abstract

Fertilizers that contain zinc (Zn)‐EDTA and Zn‐lignosulfonate (Zn‐LS), which can also be coated with rosin, were placed at the top of columns of an acid Calcic Palexeralf soil which were periodically irrigated. The liberated Zn remained mostly on the top of the column when the source of Zn was Zn‐LS but Zn migrated through the column when Zn‐EDTA was applied. The use of a coating on the Zn‐EDTA fertilizer diminished the loss of Zn by leaching from 52% to 20% at the end of the experiment at the highest coating percentage (36%). The distribution of the Zn in the soils was studied by fractionation and showed that added Zn remained in the soils in more favorable forms for uptake by plants in comparison with the control soil. The labile fraction (F1) and especially that organically complexed increased, and the percentage corresponding to the residual fraction that was 89% in the native soil diminished in all cases being in the most favorable case by 25%. Correlations between the extracted fractions (r=0.57–0.99, P<0.01%) showed that, in general, a dynamic equilibrium existed between them. The DTPA‐extractable Zn also correlated positively with the most labile Zn fractions, although the significance level depended on the depth.     

Prediction of residual effects of zinc sulfate on growth and zinc uptake of corn plants using three zinc soil tests

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.     

Comparison of four extractants and chemical fractions for assessing available zinc and copper in soils of India

Abstract

Relative suitability of different extraction procedures for estimating available zinc (Zn) and copper (Cu) in soils was assessed using DTPA, 0.1 N HCl, ammonium acetate+EDTA, and double acid (HCl+ H₂SO₄) as extractants and rice as a test crop in Neubauer experiment. The relationships between Zn concentration and uptake of Zn by rice plants and Zn extracted by the different methods showed that DTPA‐TEA, pH 7.3, could very suitably be used to assess Zn availability in soils. However, 0.1 N HCl was better for assessing the Cu availability in soils to the rice plants. Water‐soluble and exchangeable fractions of Zn and Cu had significant positive correlations with Zn and Cu concentrations, respectively obtained by all the four extractants tested. The results also showed that DTPA and ammonium acetate+EDTA extracted organically bound Zn, whereas DTPA, 0.1 N HCl and ammonium acetate+EDTA extracted organically bound Cu. Water‐soluble, exchangeable and organic matter bound fractions exhibited significant relationships with Zn and Cu concentrations, their uptake and rice dry matter yield.     

Navy bean responses to zinc fertilizers

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.     

Influence of soil pH and application of zinc on the yield and uptake of selected nutrient elements by rice

Abstract

Rice grown on a recently water‐leveled Crowley silt loam that contained less than 1.8 μg g^‐1 of 0.1 N HCl‐extractable Zn with pH levels ranging from 6.8 to 7.7, responded to Zn application. Each kg ha of applied Zn as Zn chelate, 14.2 % Zn, resulted in increases of +673, +477, and +2026 kg rice ha^‐1 at pH 6.8, 7.3, and 7.7, respectively. There was a critically low concentration of Zn in rice plants at the midtillering, first joint, and panicle differentiation stages of plant development when no Zn was applied. A yield response to applied Zn was obtained when the concentration of Zn in rice tissue was less than 15 μg g^‐1.

Application of Zn resulted in a significant increase in the uptake of N by rice plants at each of the three stages of plant development. Application of Zn also resulted in relatively large and significant increases in the uptake of Zn from the soil irrespective of soil pH. The uptake of Zn by rice plants at each of the growth stages showed a two‐ to three‐fold increase following Zn application when soil pH was 6.8 and 7.3. Also, the uptake of Zn by rice plants following Zn application showed a four‐fold increase at midtillering, a five‐fold increase at first joint, and a six‐fold increase at panicle differentiation, respectively, when soil pH was 7.7.     

Phosphorus and zinc fertilization effects on dry matter yield and phosphorus and zinc uptake by Crambe

Crambe (Crambe abyssinica Hochist.) is an oilseed crop high in euricic acid with industrial applications in production of nylon, plasticizers, and lubricants. Little information is available on crambe response to phosphorus (P) and zinc (Zn) fertilization. This glasshouse study was conducted to evaluate the response of crambe to four rates of P and five rates of Zn fertilizer application to a soil with 10 mg/kg NaHCO₃‐extractable P and 0.6 mg/kg DTPA‐extractable Zn. Phosphorus fertilizer, but not Zn fertilizer, increased the dry matter yield of plant tops. Phosphorus response was consistent in both 35‐ and 62‐day‐old plants. Zinc response was most consistent in 35 day‐old plants. Significant interactions were observed between P and Zn for dry matter weight, P:Zn ratio, and Zn uptake at 35 days. No significant interactions were observed at 62 days. Analysis of the data showed a negative correlation coefficient between P or Zn treatment and tissue concentration or uptake for the opposite element.     

Evaluation of efficient soil test methods for Zn and their critical vales in salt‐affects soils for rice

Abstract

Soil pot culture experiment was conducted on 22 soils of Balewal‐Phaguwala‐Narike (BPN) and 24 soils of Isri‐Langrian‐Narike (ILN) associations using rice (PR 106) as test crop at 0 and 7.5 ppm Zn levels. Chelating extractants 0.005M DTPA, 0.01M EDTA‐(NH₄)₂CO₃ and 0.05M EDTA, extracted more soil Zn than double‐acid and were significantly correlated with each other as well as with soil pH and clay in BPN and only with clay in ILN soil association. Soil CaCO₃ governed the double‐acid extractable Zn in these soils. Dry matter yield and Zn uptake by rice significantly increased with 7.5 ppm Zn application. The response was higher in ILN than BPN soil association, The DTPA method gave the highest correlation with Bray's yield and Zn uptake (r =0.72 and 0.55) followed by 0.05M EDTA (r ‐ 0.75 and 0.61) or EDTA‐(NH₄)₂CO₃ (r =0.70 and 0.61). The predictability of rice yield improved from 18–27 to 27–35, 32–43, 34–44 and 51–55 percent as a result of stepwise inclusion of pH, CaCO₃, organic carbon (OC) and clay respectively in the regression equation alongwith Zn extracted by chelating agents.

The critical levels of DTPA, EDTA‐(NH₄)₂CO₃ and EDTA extractable Zn significantly differed in the two associations and were 0.69, 0.82 and 1.24 ppm in BPN and O.BC, 1.09 and 1.42 ppm in ILN soil association. Soil properties further affected the critical levels. This for DTPA available Zn was 0.80 and 1.03 ppm in soil containing less and greater than 2% CaCO₃, 1.03 and 0.80 ppm in soils containing less and greater than 0.25% OC. These values for EDTA‐(NH₄)₂CO₃ available Zn were 1.09 and 0.91 ppm Zn in soils containing less and greater than 15% clay suggesting that critical levels of Zn for each category of soil properties should be considered while making recommendations of Zn fertilization of crops.,     

Effects of zinc fertilizer amendments on yield and grain zinc concentration under controlled environment conditions

The application of zinc (Zn) fertilizer to lentil is an agronomic strategy that has the potential to improve yield and enhance grain Zn concentration. A pot study was conducted to determine if Zn fertilizer applied to three popular Saskatchewan lentil cultivars could increase yield and concentration of Zn in the grain. The effects of soil and foliar applied Zn forms, including ZnSO₄, Zn chelated with EDTA, Zn lignosulphonate, and a control were evaluated. Forms of Zn were not found to significantly increase yield (P = 0.828) or grain Zn concentration (P = 0.708) in any of the lentil cultivars tested. Fertilization with soil applied ZnSO₄ resulted in significantly (P < 0.0001) higher amounts of residual available Zn in the soil relative to other Zn treatments. Soil fertilized with ZnSO₄ had 1.13 mg kg^?1 diethylenetriaminepentaacetic acid (DTPA)-extractable Zn compared to 0.84 mg Zn kg^?1 and 0.77 mg Zn kg^?1 in the soil and foliar applied chelated Zn, respectively.     

Prediction of available heavy metals by six chemical extractants in a sewage sludge‐amended soil

Abstract

In a field experiment conducted during three years in a sandy‐loam, calcareous soil, one aerobically digested sewage sludge (ASL) and another anaerobically digested sewage sludge (ANSL) were applied at rates of 400, 800, and 1,200 kg N/ha/year, and compared with mineral nitrogen fertilizer at rates of 0, 200, 400, and 600 kg N/ha/year in a cropping sequence of potato‐corn, potato‐lettuce, and potato, the first, second, and third year, respectively. Results showed that the highest values of soil extractable metals were obtained with aqua regia, whereas the lowest levels with DTPA. All metal (Zn, Cu, Cd, Ni, Pb, and Cr) gave significant correlations between metal extracted with the different extractants and metal loading applied with the sludges. The metal extractable ion increased over the control for Zn, Cu, Cd, Ni, Pb, and Cr extracted with DTPA, EDTA (pH 8.6) and 0.1 N HC1, for Zn, Cd, Ni, Pb, and Cr extracted with EDTA (pH 4.65) and AB‐DTPA, and for Zn, Cd, Ni, and Cr extracted with aqua regia. The level of metal‐DTPA extractable resulted highly correlated with that obtained by the other methods, except the Ni‐aqua regia extractable. The soil extractable elements which showed significant correlations with metals in plant were: Zn, Cu, Cd, and Ni in potato leaves, Cd, Ni, and Pb in corn grain, and Zn and Cd for lettuce wrapper leaves. In general, all the chelate based extractants (DTPA, EDTA pH 4.6, EDTA pH 8.6, AB‐DTPA) were equally useful as indicator of plant available metals in the soil amended with sludge.     

Relative toxicity of cadmium,lead, and zinc on barley

Abstract

The relative toxicity of cadmium (Cd), lead (Pb), and zinc (Zn) on the growth performance of barley (Hordeum vulgare L.) was measured. Lead and Zn resulted in an increase in dry matter production at the lower additions. All the Cd and the higher Pb and Zn additions resulted in significant decreases in growth over the controls, the roots showing a greater decrease in dry matter accumulation than did shoots. Roots accumulated higher amounts of Cd, Pb, and Zn in direct proportion to that soil‐applied. A significant inverse relationship between relative yield and tissue element concentration was observed. Toxicity occurred in the following order: Cd > Pb > Zn. Threshold concentration, critical tissue concentrations, and loading rates to produce a 10% yield reduction were also calculated. Our study indicates the possibility of estimating barley yield based on plant tissue Cd, Pb, and Zn concentrations.     

Effects of zinc complexes on the distribution of zinc in calcareous soil and zinc uptake by maize

The movement and availability of Zn from six organic Zn sources in a Typic Xerorthent (calcareous) soil were compared by incubation, column assay, and in a greenhouse study with maize (Zea mays L.). Zinc soil behavior was studied by sequential, diethylenetriaminepentaacetate, and Mehlich-3 extractions. In the incubation experiment, the differences in Zn concentration observed in the water soluble plus exchangeable fraction strongly correlated with Zn uptake by plants in the greenhouse experiment. Zinc applied to the surface of soil columns scarcely moved into deeper layers except for Zn-ethylenediaminetetraacetate (EDTA) that showed the greatest distribution of labile Zn throughout the soil and the highest proportion of leaching of the applied Zn. In the upper part of the column, changes in the chemical forms of all treatments occurred and an increase in organically complexed and amorphous Fe oxide-bound fractions was detected. However, the water soluble plus exchangeable fraction was not detected. The same results were obtained at the end of the greenhouse experiment. Significant increases were found in plant dry matter yield and Zn concentration as compared with the control treatment without Zn addition. Increasing Zn rate in the soil increased dry matter yield in all cases but Zn concentration in the plant increased only with Zn-EDTA and Zn-ethylenediaminedi-o-hydroxyphenyl-acetate (EDDHA) fertilizers. Higher Zn concentration in plants (50.9 mg kg(-)(1)) occurred when 20 mg Zn kg(-)(1) was added to the soil as Zn-EDTA. The relative effectiveness of the different Zn carriers in increasing Zn uptake was in the order: Zn-EDTA > Zn-EDDHA > Zn-heptagluconate >/= Zn-phenolate approximately Zn-polyflavonoid approximately Zn-lignosulfonate.     

Tillage,lime, and poultry litter effects on plant concentrations of zinc,manganese, and copper

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.     

Effects of zinc fungicides and different zinc fertilizer application methods on soluble and total zinc in potato plant shoots

Abstract

The experiment was carried out to evaluate the effects of fungicides [with or without zinc (Zn)] and different Zn fertilizer application methods (no fertilizer; soil application; shoot application; soil plus shoot application) on the soluble and total Zn in the dry matter of potato shoots. Zinc fertilizer was applied to the shoots at 20 and 45 days after plant emergence (DAE), immediately before plant sampling. At 25 DAE, Zn fungicide increased soluble and total Zn in the fourth leaf. The same occurred, at 45 DAE, with the Zn fertilizer applied to the shoots. It were not observed significant increases on both soluble and total Zn contents in the fourth leaf of plants that received soil Zn fertilization. Even in the leaves with 262 mg Zn kg^‐1, there was no phytotoxicity symptoms. The total Zn concentration at 20 DAE was the best index correlated to potato tuber yield reaching 50.9 mg Zn kg^‐1 in the fourth leaf of plants at the highest marketable tuber yield treatment. Plant nutrient element contents [phosphorus (P), calcium (Ca), magnesium (Mg), copper (Cu), iron (Fe), and manganese (Mn)] were not affected by the treatments.     

Soil test for available zinc in acid soils of Venezuela

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.     

Estimation of critical limit for zinc in rice soils

Abstract

Twenty surface soil samples were collected from Nainital Tarai (foothills of Himalya) where “Khaira”; disease (Zn deficiency of rice) is prevalent. Rice (Oryza sativa L. variety IR‐8) was grown in pots for 8 weeks after transplanting. Experiments were conducted to determine the suitability of five soil Zn extractants: dilute acid (HCl + H₂SO₄) mixture; DTPA‐(NH₄) ₂CO₃, pH 7.3; dithizone; NH₄OAc, pH 4.6; and 2N MgCl₂ to predict Zn deficiency. Critical values for soil available Zn were established for rice by the old and new Cate and Nelson procedures¹.

Zinc extracted from the soils with dithizone; NH₄OAc, pH 4.6; 0.2N MgCl₂. and DTPA‐(NH₄) ₂CO₃ pH 7.3 was significantly correlated with the uptake of Zn by the rice plants. The correlation between Zn extracted with the dilute acid (HCl + H₂SO₄) mixture and plant Zn was not statistically significant. The ex‐tractants which extracted greater quantities of Zn gave higher critical values and vice versa. It is concluded that all extracting solutions except the dilute acid (HCl + H₂SO₄) mixture were found to he suitable for predicting available Zn in rice soils of Tarai.     

The zinc status of some Nova Scotia soils and crops

Abstract

Ranges for total, 0.1N HCl and EDTA‐(NH₄)₂CO₃ extractable Zn in 69 samples of surface soil (0–15 cm), representing nine soil series, were 14–108, 0.9–10.5 and 0.5–8.0 ppm respectively. Total Zn in barley (Hordeum vulgare), carrot (Daucus carata sativa), corn (Zea mays L), grape (Vitis spp.), onion (Allium cepa), pea (Pisum sativum, strawberry (Fragaria spp.), and wheat (Triticum spp.) leaves and in barley and wheat grain ranged from 13.5 to 80.6 ppm.

The results suggest that, with the possible exception of corn leaf samples from one location, Zn levels in plant tissue were adequate. However, the results also indicate that liming strongly acid sandy soils reduces Zn availability and may induce a deficiency in Zn sensitive crops.     

Assessment of zinc availability to rice in mollisols of North India

Abstract

The objectives of this study were to (1) characterize zinc (Zn) fractions and their relation to Zn extracted with mixed‐bed ion exchange resin capsules and (2) assess the relationships between the latter and Zn uptake by rice in 12 Mollisols from North India. The Resin Adsorption Quantity (RAQ) of Zn was measured after 1 and 14 days of anaerobic incubation. Six organic and inorganic Zn fractions were determined on anaerobic soil. Zinc uptake by rice was studied in a greenhouse experiment. Soil Zn fractions under reduced conditions followed the order residual Zn (80%)>carbonates and amorphous oxides bound Zn (12%)>weakly organically bound Zn (3%)>crystalline oxides bound Zn (2%)>strongly organically bound Zn (2%)>water soluble + exchangeable Zn (1%). RAQ‐Zn was best correlated with Zn bound to carbonates and amorphous oxides. Due to negative interactions between bicarbonate and Zn uptake, correlations between relative dry matter yield or total Zn uptake and the different Zn fractions, DTPA‐Zn measured on dry soil, or RAQ Zn were not significant. Adjusting soil test values according to soil pH improved the prediction of relative dry matter yield, but further studies are required to determine whether the resin capsule can be used as a soil test for Zn in calcareous soils.     

Comparison of soil zinc extractants for detection of applied zinc and prediction of leaf zinc concentration

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.     

Comparison of Multi-element to Single‐Element Extractants for Macro‐ and Micronutrients in Acid Soils from Spain

Abstract

Different chemical reagents are used to assess plant‐available nutrients from soils with similar properties. The use of different extractants is a serious limitation when comparing results between different soil‐testing laboratories, often leading to large differences in fertilizer recommendations for similar crops.

In this study, 80 samples from acid soils from Galicia (Spain) were used to compare several soil nutrient extractants. Traditional and tested extractants for acid soil such as Bray 2 and ammonium acetate were used to evaluate multielement extractants such as ethylenediaminetetraacetic acid–ammonium acetate (EDTA‐aa), ammonium bicarbonate–diethylenetriaminepentaacetic acid (AB‐DTPA), and Mehlich 3.

Linear regression analyses were performed to relate the amount of each nutrient obtained by traditional soil extractants to the amount obtained by multielement extractants. Strong correlation was found between extractable Bray 2 P and Mehlich 3 P (r²=0.97, slope=0.87, and intercept=?0.48). The slope of the regression line between EDTA‐aa‐extractable calcium (Ca) and that from ammonium acetate (Aa) approached 1∶1 (r²=0.86). Similar results were obtained for magnesium (Mg) (r²=0.99). Soil zinc (Zn) concentrations extracted by Mehlich 3 and EDTA‐aa were similar; slope of the regression line was 0.95 (r²=0.88). With regard to copper (Cu), Mehlich 3 extracted approximately 20% more Cu than EDTA‐aa.

The results showed that Mehlich 3 and EDTA‐aa are suitable for assessment of plant available phosphorus (P), potassium (K), Ca, Mg, Cu, Zn, and iron (Fe) in acid soils.     

Changes in cadmium and zinc phytoavailability in agricultural soil after amendment with papermill sludge and biosolids

Abstract

The co‐disposal of papermill sludge with biosolids is seen as an alternative soil amendment to papermill sludge and inorganic fertilizer. The objectives of this study were to assess the suitability of co‐disposal of papermill sludge and biosolids by measuring changes in the soil physicochemical properties and the phytoavailability of cadmium (Cd) and zinc (Zn). Biosolids were applied with papermill sludge as an alternative source of N to inorganic fertilizers at rates calculated on the basis of C:N ratios of the amendments and common papermill sludge disposal practices. Perennial ryegrass (Lolium perenne L.) was grown on amended soils for 6 months under glasshouse conditions. The papermill sludge amendment alone increased soil pH and the rate of carbon degradation compared to the control (no amendment) and biosolid co‐disposal amendment. There was no difference in dry matter yield per pot of ryegrass between the treatments. Cadmium concentrations in plant tissue increased through the trial with the application of biosolids and papermill sludge. These findings were correlated well with the sorption properties of the soils for Cd as derived from isotherms. However, Zn uptake was unaffected by the application of the papermill sludge and biosolids.