Biochar reduced soil extractable Cd but increased its accumulation in rice (Oryza sativa L.) cultivated on contaminated soils

Purpose

This study focused on the effects and mechanisms of biochar amendment to Cd-contaminated soil on the uptake and translocation of Cd by rice under flooding conditions.

Materials and methods

Pot and batch experiments were conducted using Cd-contaminated soil collected from a field near an ore mining area and a cultivar of Oryza sativa ssp. indica. Biochar derived from rice straw under anaerobic conditions at 500 °C for 2 h was mixed with the soil at the rate of 0, 2.5, and 5%.

Results and discussion

The application of 5% biochar reduced CaCl₂-extractable soil Cd by 34% but increased Cd concentration in brown rice by 451%. Biochar amendment decreased water-soluble Fe²⁺ in soils and formation of Fe plaques on roots and weakened the Fe²⁺-Cd²⁺ competition at adsorption sites on the root surface. Biochar increased water-soluble Cd in the soil and consequently Cd uptake by rice roots by releasing water-soluble Cl^?. Biochar application also reduced the proportion of cell wall-bound Cd in the root, which caused easier Cd translocation from the cortex to the stele in the root and up to the shoot.

Conclusions

Rice straw biochar (with high concentration of water-soluble Cl^?) reduced CaCl₂-extractable soil Cd but increased Cd concentration in rice under flooding condition.

     

Root-associated bacteria containing 1-aminocyclopropane-1-carboxylate deaminase improve growth and nutrient uptake by pea genotypes cultivated in cadmium supplemented soil

The effect of inoculation with Pseudomonas brassicacearum Am3, Pseudomonas marginalis Dp1 and Rhodococcus sp. Fp2 containing 1-aminocyclopropane-1-carboxylate deaminase (ACCD) on growth and uptake of N, P, K, Ca, S, Fe and Cd in shoots of pea (Pisum sativum) genotypes VIR188, VIR1658, VIR3429 and VIR4488 was studied in pot experiment with non-polluted and Cd-supplemented (10 mg Cd kg⁻¹) sod-podzolic soil. The growth-promoting effect of bacteria depended on plant genotype and bacterial strain. Only Rhodococcus sp. Fp2 had no ACCD activity in vitro in the presence of Cd and did not stimulate pea growth in Cd-supplemented soil. Inoculation with bacteria counteracted the Cd-induced inhibition of nutrient uptake by plants probably through stimulation of root growth and enhancement of nutrient uptake processes. Nutritional effects of the bacteria were specific with respect to the nutrient.     

Some interactions of cadmium with other elements in plants

Abstract

Cadmium in solution culture at 10^‐4 M decreased Mn concentrations in bush beans (Phaseolus vulgaris L. C.V. Improved Tendergreen) at both low and high concentrations of Mn (noncompetitive inhibition). When Mn was decreased, the concentrations of Fe and several other ions were simultaneously increased, particularly in leaves and roots. Toxicity due to the 10^‐6 M Cd and the 10^‐4 M Mn was additive in the experiment. When barley (Hordeum vulgare L. Atlas57)was grown in amended soil, 15μg Fe as DTPA (diethylene triamine pentaacetic acid) per g soil resulted in increased uptake of Cd and in somewhat greater yield depression for soil pH of 3.9, 6. 0, and 7.6. Acidification of soil without DTPA also increased Cd uptake to high levels with associated yield decrease. The Cd decreased the uptake of Mn and Cu most when CaCO₃ had also been added to the soil. When salts were added to soil with Cd before bush beans were grown, KCl (200 μg K/g soil), and equivalent KH₂PO₄ increased Cd concentrations of leaves while CaSO₄ and KCl did so for roots. In bush beans with different levels of Cd and Zn, there were no yield interactions, but some interactions of Cd on Zn concentrations in leaves, stems, and roots at the high Zn level.     

Amelioration of Cadmium Contaminated Soils Using Cation Exchangers

ABSTRACT

The contamination of soil and water with cadmium (Cd) is an environmental issue worldwide. Using lettuce (Lactuca sativa cv. ‘Cos’) in a glasshouse-based growth trial, two cation exchange materials [a zeolite and a kaolin amorphous derivate (KAD)] were examined for their ability to remove Cd from the soil solution and hence decrease the uptake of Cd by plants. Zeolite (applied at a rate of 2.5 t ha^{? 1}) was ineffective at reducing Cd uptake and accumulation in lettuce. When applied at a rate of 2.5 t ha^{? 1}, the KAD significantly reduced Cd uptake in all soils examined (ranging from a 26 to 64% reduction). Thus, KAD is considered to be potentially beneficial for the growth of plants in Cd-contaminated soils, although care must be taken to ensure that growth is not limited by deficiencies of the other nutrients for which KAD has a high affinity.     

Chelating resin membrane method for estimation of soil cadmium phytoavailability

Abstract

A metal chelating exchange resin membrane was used to extract soil cadmium (Cd) and to evaluate the plant uptake of Cd from soils. Eight soils with widely varying properties and Cd levels were tested. Soil suspensions (4 g in 40 mL deionized water) were equilibrated with 5 cm² Ca‐Chelex membrane which was retained inside a polypropylene bag and shaken at 150 rpm for 24 hrs. Resin membrane extractable Cd of the soils were correlated with Cd uptake by young wheat seedlings grown in these soils and compared with soil Cd extracted by several commonly used chemical extractants. The amounts of Cd extracted by the Ca‐Chelex membrane from all tested soils were correlated with those absorbed by young wheat seedlings or those extracted by the tested chemical extractants. The Ca‐Chelex membrane extractable Cd of the soil, however, had the strongest correlation with plant uptake Cd. It was demonstrated that the Ca‐Chelex membrane extraction is an appropriate method in estimating Cd phytoavailability of soil and is applicable to a wide range of soils.     

Underlying dynamics and effects of humic acid on selenium and cadmium uptake in rice seedlings

Purpose

Natural organic acids, such as humic acid (HA), play crucial roles in biogeochemistry of anions and cations in soil due to their numerous functional groups on their surfaces. Selenium (Se) and cadmium (Cd) could bind strongly to HA; nevertheless, it is still unclear as to the effects of HA on Se and Cd uptake in rice which will be focused on in this paper.

Materials and methods

Pot experiments were carried out at Huazhong Agricultural University, Wuhan City, Hubei Province, China. Agricultural soils were treated with different concentrations of HA (0, 4, and 8 g kg^?1 soil) and Se (Se^IV or Se^VI) (0 and 2 mg kg^?1 soil) as well as with base fertilizer 3 days prior to planting. For Cd treatment, experimental soils were treated with Cd (0 and 2 mg kg^?1 soil) 1 month before sowing. For element determination, root (after DCB extraction) and shoot samples were digested with a mixed solution of HNO₃-HClO₄, and the Se and Cd in digest solution were measured by HG-AFS and ICP-MS, respectively. Fe, Se, and Cd in iron plaque were extracted by DCB extraction and measured by AAS, HG-AFS, and ICP-MS, respectively.

Results and discussion

HA reduced Se (or Cd)-induced growth stimulation and Se and Cd uptake in rice seedlings, whereas iron plaque formation varied little with different treatments. HA inhibited Se^IV (or Se^VI) uptake in rice seedlings by reducing Se translocations from soil to iron plaque (or by increasing Se adsorption capacity of iron plaque and decreasing Se transport from iron plaque to root). HA reduced Cd uptake in rice seedlings by reducing Cd transport from soil to iron plaque and from iron plaque to root. Compared with single addition of Se^IV or Se^VI or HA, adding HA combined with Se^IV or Se^VI could further reduce Cd uptake in rice seedlings, whereas Se contents of aerial tissues did not change obviously.

Conclusions

HA inhibited the accumulation of Se (Se^IV or Se^VI) and Cd in rice seedlings; nevertheless, the mechanism was different. Compared with adding Se (or HA) alone, application of Se mixed with HA might be a more effective way to produce Se-enriched and Cd-deficient crop in Cd-contaminated soil.

     

Assessing the immobilization efficiency of organic and inorganic amendments for cadmium phytoavailability to wheat

Purpose

Rapid industrialization in China accelerated environmental pollution by xenophores and trace metals particularly cadmium. Numerous studies have been conducted to address soil contamination using organic and inorganic amendments under pot or incubation conditions, but few were performed under field conditions, particularly in the wheat-growing areas. This study aims to investigate the effectiveness of pre-applied soil amendments for Cd immobilization, changes in soil pH, and metal uptake by wheat.

Materials and methods

In this study, 12 treatments, i.e., control (CK), lime, DaSan Yuan (DASY), DiKang No. 1 (DEK1), biochar, Fe-biochar, Yirang, CaMgP, and green stabilizing agents (GSA-1, GSA-2, GSA-3, and GSA-4), were evaluated for Cd immobilization in incubation and field experiments. Changes in soil pH and available metal content with amendments were monitored from 30 to 150 days of incubation. Single extraction method and DTPA-extractable and sequential extraction procedures were employed to assess the variations in available Cd contents of field soil. The impact of soil amendments on Cd uptake and bioaccumulation in food part of wheat was measured at harvesting stage in a contaminated site.

Results and discussion

Lime treatment increased soil pH by 32% and reduced available Cd to 0.213 mg kg^?1, as compared to CK (control) in the incubation experiment (0.343 mg kg^?1). Effects of the amendments on wheat growth, soil pH, and Cd phytoavailability were reported. Wheat biomass was highest in treatment GSA-2 (13,880 kg ha^?1) and GAS-4 resulted in an increase in grain yield (5350 kg ha^?1). Soil pH of the treated field at harvesting stage increased up to 6.50, 6.50, and 6.47 by application of GSA-4, GSA-2, and lime, respectively. Cadmium contents in wheat grain were declined significantly in the treatments of GSA-2, GSA-4, and lime.

Conclusions

Results of this study revealed a significant decrease in available Cd concentration with the application of amendments. Composite amendments were more effective in terms of metal uptake and bioaccumulation in wheat. In addition, our results indicate the effectiveness of composite amendments in stabilizing Cd in contaminated soil.

     

Fractionation of soil cadmium from some new zealand soils

Abstract

The concentrations and forms of soil cadmium (Cd) in 12 different New Zealand topsoils were investigated using a sequential fractionation procedure. Total soil Cd concentrations were low and ranged between 0.03 μg g^‐1 to 1.34 μg g^‐1 and were highly correlated with total soil phosphorus (r²=0.85, P<0.01). Results indicated that there was a wide range in the concentrations of Cd associated with individual soil fractions and large variations between soils. On average for all soils, the smallest proportion of Cd was in exchangeable forms, i.e., 3%, with 12% in the crystalline oxide fraction, 13% in the amorphous oxide fraction and the greatest proportion of Cd associated with the organic 34% and residual 38% fractions. There was evidence to show that a soil extractant which is commonly used to predict plant uptake of Cd from soils, i.e., 0.04 M ethylene diamine terra acetic acid (EDTA), extracts Cd from both exchangeable and organic forms of soil Cd.     

Response of leguminosae to cadmium exposure

Bush bean and pea plants grown in a sandy substrate and treated daily with nutrient solutions containing either 50 and 125 pM cadmium (Cd), added as cadmium nitrate [Cd(NO₃)2], were analyzed for dry matter production, total Cd content, and extractable Cd. Cadmium depressed dry matter production of both plant species. Bush bean plants accumulated larger amounts of Cd in tissues and displayed lower Cd tolerance than pea plants. The high accumulation of Cd in roots of bush bean does not seem to prevent Cd translocation. Pea plants show a higher exclusion capacity at the root level, suggesting that membrane selectivity rather than apoplastic compartmentation may act as a defence mechanism against Cd toxicity. Gel‐permeation chromatography and voltammetric analyses showed that part of water‐soluble Cd extracted from tissues of pea and bush bean was as free metal ion (Cd²⁺). In addition, Cd into the nutrient solution induced progressively the synthesis of water‐soluble proteins at low molecular weigth in tissues of both plant specie. In root extracts of pea and bush bean, Cd was also associated with “like‐protein”; fraction with apparent molecular weight >30 KDa.     

Effect of Cattle Slurry on the Growth of Spinach Plants in Cd-contaminated Soil

ABSTRACT

In this work the effect of the addition of different amounts of cattle slurry (CS) to a Cd contaminated soil, was studied regarding its effect in spinach plants. Two levels of Cd contamination (2 and 10 mg/kg) and three levels of CS addition were evaluated (2.5, 5 and 10 g CS/100 g soil). Spinach was shown to be a tolerant species, able to accumulate relatively high amounts of Cd (up to 367.7 mg/kg in the leaves), exceeding the limits established by European regulations for leaf vegetables. The addition of 2.5 and 5 g CS/100 g to soil containing 2 mg/kg Cd did not reduce the uptake of this metal but allowed the plants to grow as much as the control. The addition of 10 g CS/100 g lead to a reduced Cd uptake but also to a lower plant growth compared to the lower CS levels. The combined effects of Cd and CS changed element content in the plant, but without causing severe toxicity or deficiency effects.     

Effect of water treatment sludge on growth and elemental composition of tomato (Lycopersicon esculentum) shoots

Abstract

The impact of a water treatment sludge on the fertility of a silt loam soil was assessed by monitoring the yield and elemental composition of tomato (Lycopersicon esculentum) shoots in a greenhouse study. Application of sludge at rates from 2–10% (air dry weight basis) raised the soil pH from 5.3 to 8.0 which enhanced plant growth. A substantial reduction in metal (Cd, Zn, Cu, Ni) uptake was observed with sludge amendments, even at the highest rates. The alkaline nature of this sludge (pH=9.3, calcium carbonate equivalence=53%) suggests its potential use as a liming material for agricultural soils. Overly alkaline conditions should be avoided however, as high application rates combined with ammonia fertilization had an antagonistic effect on plant growth, possibly from P deficiency induced by struvite (MgNH₄PO₄) formation.     

The significant contribution of mycorrhizal fungi and earthworms to maize protection and phytoremediation in Cd-polluted soils

Mycorrhizal fungi and earthworms can individually or interactively influence plant growth and heavy metal uptake. The influence of earthworms and arbuscular mycorrhizal (AM) fungi either alone or in combination on maize (Zea mays L.) growth and cadmium (Cd) uptake was investigated in a calcareous soil artificially spiked with Cd. Soils were contaminated with Cd (10 and 20 mg Cd kg⁻¹), inoculated or un-inoculated with the epigeic earthworm Lumbricus rubellus and two AM fungal species (Rhizophagus irregularis and Funneliformis mosseae) for two months of growth under greenhouse conditions. Generally, earthworms alone increased both shoot P uptake and biomass but decreased shoot Cd concentration and root Cd uptake. AM fungi individually often increased total maize P uptake, declined shoot Cd concentration, and consequently produced higher total biomass. However, R. irregularis enhanced shoot Cd uptake at low Cd level and root Cd uptake at high Cd level. In plants inoculated with F. mosseae species, earthworms increased shoot biomass and Cd uptake, decreased root biomass and Cd uptake at all Cd levels, and increased shoot Cd concentration at low Cd level. In plants colonized by R. irregularis species, however, earthworm addition decreased maize biomass only at high Cd level and root Cd concentration and total maize Cd uptake at both Cd levels. Earthworm activity decreased Cd transfer from the soil to maize roots at low Cd level, but this was counterbalanced in the presence of F. mosseae. Mycorrhizal symbiosis significantly reduced the transfer of Cd from roots to shoots, independence of earthworm effect. Overall, it is concluded that L. rubellus and AM fungi, in particular F. mosseae isolate, improved maize tolerance to Cd toxicity both individually and interactively by increasing plant growth and P nutrition, and restricting Cd transfer to the aboveground biomass. Consequently, the single and interactive effects of the two soil organisms might potentially be important not only in protecting maize plants against Cd toxicity, but also in Cd phytostabilization in soils polluted by this highly toxic metal.     

Determination of mobile heavy metal fraction in soil: Results of a pot experiment with sewage sludge

Abstract

The development of a method using a chelating resin to assess heavy metal mobility in soil and the first results obtained from a pot experiment with sewage sludge additions were studied. The resin was Chelex 100 with the calcium (Ca)‐form of the resin proving to be best suited for the extraction. The efficiency of recovery of the heavy metals from an aqueous solution ranged from 81.2% for cadmium (Cd) to 102% for copper (Cu) within 24 hours. For heavy metal extractions from a soil sample, a 96 hour extraction period was found to be optimum. The extracted heavy metal portion was comparable with the results obtained with an ammonium acetate (NH₄AOc) extraction. Total heavy metal contents in the substrate of the pot experiment did not show a significant influence due to the sewage sludge treatments, although considerable amounts of heavy metals were added by the sewage sludge. This effect can be both due to the incomplete recovery of heavy metals by an aqua regia extraction and leaching losses of these elements from the pots. Rape (Raphanus sativus L.) plants did not have any heavy metal contents which might indicate a high availability in soil, with the Cd and Cr contents in the rape biomass being partly lower in the sewage sludge‐treated pots than in the control plants; however, zinc (Zn) uptake slightly increased with increasing sewage sludge treatments. The Chelex 100 extraction procedure was correlated with Cd plant uptake, while the NH₄AOc extraction procedure was better related to the Zn uptake by rape plants.     

Iron oxide as an iron source in potting‐soil mixtures

Abstract

A commercial product of Fe oxide‐metallic Fe at rates of 2 and 10 pounds per cubic yard (1.2 and 6 kg per cubic meter) in soil‐sawdust and soil‐bark mixtures was useful when Fe‐inefficient plants were grown in containers. A high Zn level in the Ys₁/Ys₁ Fe inefficient corn inbred (Zea mays L.) was associated with low Fe status. High Fe levels seemed to suppress Cd uptake.     

Effect of soil treatment with cereal straw and method of crop establishment on field pea (Pisum sativum L.) N2 fixation

The effects of soil incorporation with cereal straw (nil, 2.5, 5 and 10 t straw ha^?1) and direct drilling on the proportion and amount of pea N derived from biological N fixation were investigated in three field experiments. Fixed N was determined by¹⁵N dilution using barley as a reference plant. The three sites were on acidic, red clay-loams in the cropping zone of southeastern Australia. Seasonal plant available soil N, as determined by the N accumulated in barley, was 31, 56 and 158 kg N ha^?1, for the three sites. Incorporated straw reduced soil nitrate at sowing by 10–50 kg N ha^?1 (0–30 cm), and 5 or 10 t straw ha^?1 reduced barley uptake of N by 10–38 kg N ha^?1. However, reducing plant available soil N was generally ineffective for increasing the N fixed by pea. Fixed N increased only at the site with the least plant-available N, and only one-third of the increase could be attributed to lower soil N uptake by pea. There was no evidence that direct drilling pea increased fixed N by decreasing crop uptake of soil N. It is proposed that a lower requirement for soil N by pea as compared to barley, and availability of mineral N beneath the soil layer treated with straw, minimise the effectiveness of straw incorporation for increasing the N fixed by pea.     

Effects of water and organic manure coupling on the immobilization of cadmium by sepiolite

Purpose

Natural sepiolite (SP) has proven effective on the in-situ immobilization remediation of Cd-contaminated soils. But the practical remediation effect may largely influenced by water management and the application of organic manure. The effects of chicken manure (CM) on SP-amended soils were investigated under normal and saturated water conditions using a pot experiment with Brassica campestris L.

Materials and methods

Cd-contaminated paddy soils were amended with CM, SP, and CM?+?SP with no amendment as control. The amount of sepiolite was 0.5% (w/w, the same below) either in SP or CM?+?SP amended soils, while the amount of CM was 0.5, 1.0, and 2.0% in CM and CM?+?SP-amended soils. The plant metal contents, fresh weight, and soluble sugar content of plant edible parts were measured on harvest. Soil Cd was extracted by diethylenetriaminepentaacetic acid (DTPA) and HCl to estimate the mobility of heavy metal. Soil pH and dissolved organic matter (DOM) of rhizosphere soil were determined. The electronegative charges of soils were also measured using the zeta potential.

Results and discussion

The application of CM and increasing soil moisture on SP-amended soil increased plant growth to a greater extent than the application of SP alone. The application of CM along with the increase of soil moisture decreased Cd uptake and translocation in plants grown on SP-amended soil compared to the application of SP alone. Cd content of edible plant parts reached a minimum of 0.24 mg kg^?1 with the application of 2.0% CM on SP-amended soils under water-saturated conditions, which was approximately 50% lower than the Cd concentration found when applying SP alone.

Conclusions

The results of this study suggest that the application of sepiolite on Cd contaminated soil can effectively reduce Cd uptake by B. campestris L., and the addition of CM combined with effective water management also appears to further reduce Cd absorption and accumulation.

     

Effects of arbuscular mycorrhizal inoculation on cadmium accumulation by different tobacco (Nicotiana tabacum L.) types

The effect of arbuscular mycorrhiza (AM) on cadmium (Cd) uptake by tobacco (Nicotiana tabacum L.) was studied in a pot experiment. Three commercial varieties, Basma BEK, K326 and TN90, representing three distinct tobacco types, were each grown in a different soil with nutritional conditions matching as closely as possible their requirements for field production. Cd concentrations in these soils were within the background range. Each variety was either non-mycorrhizal or inoculated with one of five AM fungal isolates. Cd concentration in leaves was decreased by inoculation with selected isolates in the K326 and TN90 variety grown in acidic soils. In contrast, it was increased by inoculation with most isolates in the Basma BEK variety grown in a basic soil with low Cd availability. Besides, plants of all three varieties had significantly higher leaf concentrations of phosphorus and nitrogen in some inoculated treatments. The percentage of root colonisation was mostly low in the inoculated treatments. In the Basma BEK and TN90 variety, the tested AM fungal isolates differed in their ability to colonise roots, but no correlation was found between the root colonisation of an isolate and its effects on the Cd concentrations in tobacco leaves. One isolate influenced most pronouncedly Cd concentrations and improved mineral nutrition in all the three combinations of variety and soil despite its low colonisation levels. AM symbiosis probably affected Cd uptake of tobacco by indirect mechanisms such as stimulation of root growth or mycorrhizal plant mediated changes in chemical or biological soil properties.     

Cadmium Uptake and Distribution by Different Maize Genotypes in Maturing Stage

Abstract

A pot experiment was conducted to investigate the effects of different cadmium (Cd) concentrations of phaeozem on growth and uptake of Cd and mineral nutrient copper (Cu) and zinc (Zn) by three maize genotypes in the mature stage. The results showed that the dry‐matter accumulation of shoots was inhibited by added Cd for Jidan209 and Jitian6, but this did not influence Chunyou30. The root biomasses decreased significantly for Jitian6 and stimulated Jidan209 and Chunyou30. Yields of three genotypes of maize were decreased by increasing soil Cd concentrations. Among them, Chunyou30 had a high tolerance and Jitian6 was most sensitive to Cd. The accumulation order of Cd in different parts of plants was root > leaf > stem > grain. The percentage of absorbed Cd by roots was 70–85% of total absorbed amount. Cadmium uptake by maize in the mature stage had a significant genetic variation: Jitian6 > Jidan209 > Chunyou30 for root, stem and leaf, and Jidan209 > Jitian6 > Chunyou30 for grain, respectively. Increase of soil Cd had no significant effect on Zn concentration of leaves, but there was a significant genetic variation: Chunyou30 > Jidan209 > Jitian6 (P=0.023). Cu concentration of leaves was increased significantly with increase of soil Cd (P<0.01), but no genetic variation was observed.     

Comparative Effect of Two Different Types of Phosphate on Cadmium Uptake by Radish (Raphanus sativa L.) Grown in Arable Soil Affected by Mine Activity

To evaluate the effect of type of phosphate (P) material on reducing soil cadmium (Cd) extractability and radish Cd uptake in the field, two different P materials, fused superphosphate (FSP) and dipotassium phosphate (K₂HPO₄), were applied at rates of 0, 33.5, 100.5, and 167.5 kg P ha^?1 before seeding radish (Raphanus sativa L.) in a Cd-contaminated soil. Plant-available Cd concentration in soil and total Cd uptake by radish increased with increasing FSP application but decreased with K₂HPO₄. The significant decrease in soil pH and negative charge of soil by FSP application led to an increase in bioavailable Cd fraction in soil and in Cd uptake by radish. However, K₂HPO₄ increased soil pH and negative charge of soil and decreased bioavailable Cd fractions. Soil pH and negative charge of soil played an important role in controlling Cd uptake by radish in soil to which phosphate was applied.     

Effects of nitrogen-containing fertilizers on solubility and plant uptake of cadmium

In a pot experiment, three N-fertilizers, differing in NO^? ₃ and NH⁺ ₄; content, were compared in terms of their effects on the extractability of soil Cd in 1M ammonium acetate at pH 7 and on the uptake of native and added Cd by winter rape (Brassica napus L. var. oleifera Metzger). In another similar experiment the Cd-availability in soils receiving NPK-fertilizer applied in a concentrated, granulated form was compared to that in soils receiving a uniform application of dissolved NPK-fertilizer. Both loamy sand and clay soils were used. With the N-fertilizers levels of extractable soil Cd and plant Cd-contents were lowest in the nitrate of lime treatment, highest in the ammonium sulphate treatment and intermediate in the nitro-chalk treatment. The addition of 1 mg kg^?1 DW Cd to the soil increased Cd-levels but did not change the response pattern. There was a strong association between the effects of the various fertilizers on Cd availability and their effects on soil pH: the stronger the acidifying effect the higher the Cd availability. When applied at a low dose, granular NPK was more effective than dissolved NPK at enhancing plant uptake of Cd from both soils, but this was not the case when applied at a higher dose to the sand. The two forms of NPK differed little in their effect on extractable soil Cd. Plant uptake of Cd was greater from soils receiving granular NPK with a high Cd-content than from those receiving granular NPK low in Cd. In both experiments extractable Cd was taken up to a greater extent from the sand than from the clay. An increase in fertilizer dose generally resulted in an increase in levels of soil-Cd and in Cd concentrations in the plants.