Relationships between soil properties and feeding activity of soil fauna in acid forest soils

We investigated the relationships between soil chemical properties, humus form, and feeding activity in eight forest sites in Northrhine‐Westphalia, Germany. The study sites varied in forest type (oak, oak‐hornbeam, spruce, and pine). Three study sites were located under the same climatic conditions, and five study sites were distributed all over Northrhine‐Westphalia. We determined humus form, soil chemical properties, and feeding activity in three replication plots per site. We used the bait‐lamina test to determine feeding activity of soil fauna. Independent of forest type, all study sites were very acid with pH(CaCl₂) values in the Ah horizon between 2.8 and 4.0. The three study sites located under the same climatic conditions showed very homogenous soil chemical properties (pH in Ah: 2.9–3.0), whereas the five other sites varied significantly due to their soil chemical parameters (pH in Ah: 2.8–4.0). All single sites presented feeding activities with a very low spatial heterogeneity. Forest types and climatic conditions were not related to activity of soil fauna. Feeding activity and thickness of the O layer were strongly negatively correlated, whereas the activity was strongly positively correlated to soil pH in the five study sites with a wide range of soil chemical parameters. The three extremely acid forest sites presented significant differences in feeding activities that were not related to soil chemical properties.     

Effect of crop residue biochar on soil acidity amelioration in strongly acidic tea garden soils

Strongly acidic soil (e.g. pH < 5.0) is detrimental to tea productivity and quality. Wheat, rice and peanut biochar produced at low temperature (max 300 °C) and differing in alkalinity content were incorporated into Xuan‐cheng (Ultisol; initial pH_{soil/water = 1/2.5} 4.12) and Ying‐tan soil (Ultisol; initial pH _{soil/water = 1/2.5} 4.75) at 10 and 20 g/kg (w/w) to quantify their liming effect and evaluate their effectiveness for acidity amelioration of tea garden soils. After a 65‐day incubation at 25 °C, biochar application significantly (P < 0.05) increased soil pH and exchangeable cations and reduced Al saturation of both tea soils. Association of H⁺ ions with biochar and decarboxylation processes was likely to be the main factor neutralizing soil acidity. Further, biochar application reduced acidity production from the N cycle. Significant (P < 0.05) increases in exchangeable cations and reductions in exchangeable acidity and Al saturation were observed as the rate of biochar increased, but there were no further effects on soil pH. The lack of change in soil pH at the higher biochar rate may be due to the displacement of exchangeable acidity and the high buffering capacity of biochar, thereby retarding a further liming effect. Hence, a significant linear correlation between reduced exchangeable acidity and alkalinity balance was found in biochar‐amended soils (P < 0.05). Low‐temperature biochar of crop residues is suggested as a potential amendment to ameliorate acidic tea garden soils.     

土壤调理剂和生草互作对果园酸化土壤化学性质及产量的影响

土壤调理剂和生草技术是改善果园土壤质量、提高苹果产量和品质的有效措施.通过大田试验,设置不同类型的土壤调理剂和生草的裂区试验,主区为土壤调理剂处理:不施土壤调理剂(CK)、生石灰(QL)、化学土壤调理剂(KB)、腐植酸类土壤调理剂(SC)和生物有机肥(BOM),副区为清耕(CT)和生草(GR)处理,共设10个处理,研究...     

Boron adsorption characteristics of some acidic alluvial soils in relation to soil properties

Abstract

We investigated boron (B) adsorption characteristics for 16 acid alluvial soils as a function of equilibrium B concentration (0–80 μg/mL) and the effect of soil properties on such adsorption. The adsorption data for the soils could be described by Freundlich, Temkin, and BET isotherm equations over the entire concentration ranges studied, and by Langmuir and Eadie‐Hofstee equations only over a limited range. In general, the B adsorption capacity and the energy of retention of the soils calculated from different equations are low, the average Langmuir adsorption maxima and bonding energy constant being 21.47 μg/g and 0.113 mL/μg, respectively, making B susceptible to leaching losses. Simple and multiple regression analysis show that the adsorption capacities are significantly influenced by organic carbon (C), cation exchange capacity (CEC), and different forms of aluminium (Al) content in soils. The energy related constants are also influenced by the forms of Al in soils. Existence of significant correlations between constants obtained from different equations confirmed the adsorption characteristics of the soils.     

Spatial distribution of soil physical properties of alluvial soils: a geostatistical approach

Knowledge of spatial variation of soil is important in site-specific farming and environmental modeling. Soil particles size and water distribution are most important soil physical properties that governing nearly all of the other attributes of soils. The objectives of this study were to determine the degree of spatial variability of sand, silt and clay contents, and water content at field capacity (FC), permanent wilting point (PWP), and available water content (AWC) of alluvial floodplain soils. Data were analyzed both statistically and geostatistically to describe the spatial distribution of soil physical properties. Soil physical properties showed large variability with greatest variation was observed in sand content (68%). Exponential and spherical models were fit well for the soil physical properties. The nugget/sill ratio indicates except clay all other soil physical properties were moderate spatially dependent (37–70%). Cross-validation of the kriged map shows that prediction of the soil physical properties using semivariogram parameters is better than assuming mean of observed value for any unsampled location. The spatial distribution of water retention properties closely followed the distribution pattern of sand and clay contents. These maps will help to planner to develop the variable rate of irrigation (VRI) for the study area.     

Tillage and N application effects on crop yield,N uptake and soil properties in a corn-based rotation

The objective of this study was to determine the influence of tillage methods (conventional tillage (CT) and minimum tillage (MT)) and N rates (0, 50, 150, 250 kg N ha^?1) on crop yield, N uptake and soil organic carbon (SOC), bulk density (BD), total N (TN), electrical conductivity (EC), pH and soil nutrient contents on a clay-loam near Hashtgerd, Iran. A successive corn-based rotation (2012–2014) was conducted as a split-plot in a randomized complete block design in which tillage methods were considered as main plots, and N rates as subplots. Tillage had no significant effect on corn 2012 and canola 2012–2013 grain yields. CT and MT systems showed different critical N rates to reach their maximum grain yield in corn (2013) and wheat (2013–2014). MT system required more N application to reach its maximum grain yield. Tillage × N rate effect on none of the soil properties was significant. Tillage had no significant (P ≤ 0.05) effect on soil pH, BD, TN and SOC. However, soil EC of 0–5 cm depth in MT system was higher than CT system by 64%. MT system under higher N application could increase corn grain yield, but on the other hand probably adversely changes soil chemical properties.     

Copper and zinc uptake by celery plants grown on acidic soil amended with biosolids

For trace elements, such as copper (Cu) and zinc (Zn), the bioavailability of these elements, Cu and Zn, in biosolids is important because both are essential elements and both are potential contaminants when biosolids are land applied. A greenhouse study was conducted in factorial experiment based on a completely randomized design (CRD) with four replications on a soil treated with four rates of Cu (0, 50, 100, and 150 mg/kg) and four rates of Zn (0, 150, 300, and 450 mg/kg) on celery plants to investigate the distribution and mobility of these elements as well as growth and antioxidant changes of celery. The results of antioxidant changes were inconclusive due to irregular changes with Zn and Cu applications. However, generally the results show that Cu did not affect superoxide dismutase (SOD) or peroxidase (POD) activities in most of the treatments. On the other hand, Zn stimulated SOD and POD activities in most of the treatments. The photosynthesis rate decreased with the applications of Cu and Zn at the rates above 100 and 300 mg/kg and increased in low Cu concentration (50 mg/kg) compared to S (soil without biosolid).     

Yield and uptake of fertilizer nitrogen by direct-drilled winter barley growing on a chalk soil

Abstract. This paper reports the growth and yield of grain and the utilization of fertilizer nitrogen applied on either one or two occasions in spring to a crop of winter barley established by direct drilling on a chalk soil in southern England. Nitrogen, as ammonium nitrate, was applied at rates of 0 to 140 kg N ha⁻¹ in a range of proportions on two occasions (March and April 1981); nitrogen-15 was used to facilitate study of the nitrogen utilization by the crop.
When sampled before the second top-dressing in April, the greatest number of tillers were found on plants treated with 70 and 100 kg N ha⁻¹ in March. The total above ground dry matter production at harvest was greatest when the split nitrogen dressing totalled more than 100 kg N ha⁻¹, although the apparent efficiency of nitrogen usage (kg DM per kg N applied) was greatest when 60 kg N ha⁻¹ was divided equally between the two application dates. Grain yield was heaviest (6.471 ha⁻¹) at the largest rate of nitrogen applied (140 kg N ha⁻¹); the lightest yield from the nitrogen treated crops was recorded from 100 kg N ha⁻¹ applied as a single dressing in April that stimulated shoot production and decreased individual grain weight. The recovery in grain and straw of labelled fertilizer nitrogen applied only in March averaged 42.2% and was 49.8% when the nitrogen was applied only in April. The recovery of nitrogen applied in both March and April at the total rate of 100 kg N ha⁻¹ but split 30/70 or 70/30 was 44.5% and 42.5% respectively. Non-fertilizer sources of nitrogen contributed 60.7–71.7% of the total nitrogen uptake by the crop at harvest.     

不同土壤的还原状况对铁镉形态转化和水稻吸收的影响

采用土壤-蛭石联合培养,以填充蛭石的网袋模拟根际,置于红壤、水稻土、盐土中后淹水栽培水稻13 d.试验结果表明,水稻栽培期问,红壤、水稻土、盐土pH变化范围分别为6.05 ～6.78、6.47 ～7.33、6.42 ～7.44;有机质处理下,除红壤根际pH明显升高外,其余土壤根际和非根际pH均有所下降.各土壤对照根际Eh保持在233 ～ 385 mV;有机质处理使根际Eh下降,同时也导致除盐土外的非根际Eh上升.土壤还原溶解Fe与蛭石吸附Fe的90％以上均米自铁锰氧化物结合态铁(Oxide-Fe)组分,与溶液Eh、pe+ pH均有显著相关性,表明两表面同为Fe的氧化还原反应,但方向相反.水稻根表Fe膜的形成与根际氧化还原状况有关,在对照根际(高Eh)环境下,根表Fe含量随pH升高而降低,在有机质处理根际(低Eh)环境下则随pH升高而升高;在红壤中,根表Fe膜阻碍Fe的吸收,在水稻土和盐土中,根表Fe膜促进Fe吸收.根表Cd含量与根内Cd、地上部Cd有显著正相关;在红壤中,根表Fe膜阻碍了水稻Cd的吸附和吸收;水稻土和盐土中,根表Fe膜促进了水稻Cd的吸附和吸收.     

Yield and N uptake as affected by soil tillage and catch crop

Two field trials with spring barley (Hordeum vulgare L.) were conducted at two locations in Denmark in order to evaluate the effects of tillage and growth of a catch crop on yield parameters under temperate coastal climate conditions. Ploughing in autumn or spring in combination with perennial ryegrass (Lolium perenne L.) as a catch crop was evaluated on a coarse sand (Orthic Haplohumod) from 1987 to 1992 at three rates of N fertiliser application (60, 90 and 120 kg N ha⁻¹ year⁻¹). Rotovating and direct drilling were also included as additional tillage practices. The experiment was conducted on a 19-year-old field trial with continuous production of spring barley. Ploughing in autumn or spring in combination with stubble cultivation and a catch crop, in addition to minimum tillage, was evaluated in a newly established field trial on a sandy loam (Typic Agrudalf) from 1988 to 1992. Yield parameters and N concentrations in grain and straw were determined. On the coarse sand, N uptake in the grain in ploughed plots without a catch crop was significantly greater when spring ploughed as opposed to autumn ploughed, but grain and straw yields did not differ significantly. Grain yield, straw yield and total N uptake did not differ significantly between direct drilled and autumn ploughed plots, but the trend was for grain yield to be lower with direct drilling. After 19 years of catch crop use, yield parameters in ploughed plots were greater than in plots without catch crops. This was most pronounced in the autumn ploughed plots. Rotovating the catch crop in the spring decreased grain yield compared with underploughing the catch crop in autumn or spring. No significant interactions were found between tillage and N rates. On the sandy loam, grain as well as straw yield and total N uptake were not significantly affected by catch crop or time of ploughing. Grain yield was significantly lower with reduced tillage (stubble cultivation in autumn) than in all other treatments.     

Relationships between soil pH and microbial properties in a UK arable soil

Effects of changing pH along a natural continuous gradient of a UK silty-loam soil were investigated. The site was a 200 m soil transect of the Hoosfield acid strip (Rothamsted Research, UK) which has grown continuous barley for more than 100 years. This experiment provides a remarkably uniform soil pH gradient, ranging from about pH 8.3 to 3.7. Soil total and organic C and the ratio: (soil organic C)/(soil total N) decreased due to decreasing plant C inputs as the soil pH declined. As expected, the CaCO₃ concentration was greatest at very high pH values (pH > 7.5). In contrast, extractable Al concentrations increased linearly (R² = 0.94, p < 0.001) from below about pH 5.4, while extractable Mn concentrations were largest at pH 4.4 and decreased at lower pHs. Biomass C and biomass ninhydrin-N were greatest above pH 7. There were statistically significant relationships between soil pH and biomass C (R² = 0.80, p < 0.001), biomass ninhydrin-N (R² = 0.90, p < 0.001), organic C (R² = 0.83, p < 0.001) and total N (R² = 0.83, p < 0.001), confirming the importance of soil organic matter and pH in stimulating microbial biomass growth. Soil CO₂ evolution increased as pH increased (R² = 0.97, p < 0.001). In contrast, the respiratory quotient (qCO₂) had the greatest values at either end of the pH range. This is almost certainly a response to stress caused by the low p. At the highest pH, both abiotic (from CaCO₃) and biotic Co₂ will be involved so the effects of high pH on biomass activity are confounded. Microbial biomass and microbial activity tended to stabilise at pH values between about 5 and 7 because the differences in organic C, total N and Al concentrations within this pH range were small. This work has established clear relationships between microbial biomass and microbial activity over an extremely wide soil pH range and within a single soil type. In contrast, most other studies have used soils of both different pH and soil type to make similar comparisons. In the latter case, the effects of soil pH on microbial properties are confounded with effects of different soil types, vegetation cover and local climatic conditions.     

Zinc adsorption characteristics of selected calcareous soils of Iran and their relationship with soil properties

Abstract

The apparent recovery of applied zinc (Zn) by plants is very low in calcareous soils of Iran because most of it is retained by the soil solids. Subsamples of 24 surface soil (clay 130–530 g kg^‐1; pH 7.7–8.4; electrical conductivity 0.63–3.10 dS m^‐1; organic matter 6.0–22.0 g kg^‐1; cation exchange capacity 8–20 cmol kg^‐1; calcium carbonate (CaCO₃) equivalent 180–460 g kg^‐1) representing 13 soil series in three taxonomic orders were equilibrated with zinc sulphate (ZnSO₄) solutions and the amount of Zn disappeared from solution after a 24‐h shaking period was taken as that adsorbed (retained) by the soil solids. The adsorption data were fitted to Freundlich (X=AC^B) and Langmuir [X=(K‐bC)/(1+K#lbC)] adsorption isotherms. Backward stepwiseprocedure was used to obtain regression equations with isotherms coefficients as dependent and soil properties as independent variables. Freundlich A and Langmuir K were found to be highly significantly related to pH and clay and increasing as these soil properties increased. But Langmuir b was related only to clay and Freundlich B showed no significant relationship with any of the properties studied. The distribution coefficient (also called maximum buffering capacity), calculated as the product of Langmuir K and b, was also found to be highly significantly related to pH and clay. It is concluded that pH and clay content of calcareous soils are the most influential soil properties in retention of Zn.     

Micronutrients distribution in salt-affected soils of the Punjab in relation to soil properties

Salt-affected soils in arid and semi-arid tracts of the Indian Punjab are prone to deficiency of micronutrients. Nine profiles from alluvial terraces, sand dunes and palaeochannels in the southwestern Punjab were investigated for total and diethylenetriamine-penta-acetic acid (DTPA) extractable Zn, Cu, Mn and Fe. Soil physiography exerted significant influence on the spatial distribution of micronutrients. Total contents varied from 20–78 for Zn, 8–32 for Cu, and 88–466 mg kg^?1 for Mn and 0.82–2.53% for Fe. DTPA-extractable contents varied from 0.10–0.98 for Zn, 0.14–1.02 for Cu, 0.54–13.02 for Fe and 0.82–9.4 mg kg^?1 for Mn. Total contents were higher in fine-textured soil than in coarse-textured soils. Concentration of micronutrients in the surface layer was low and there occurred more accumulation in the Cambic horizon. Organic carbon, pH, clay, silt and calcium carbonate exerted strong influence on the distribution of micronutrients. DTPA extractable Zn, Cu, Mn and Fe increased with increasing organic carbon but decreased with increase in pH and calcium carbonate content. Total micronutrient contents increased with increase in clay, silt and calcium carbonate contents and decreased with increase in sand content.     

The effects of applied crop residues on losses of Fe, Mn, Cu and Zn in run-off from a soil prone to crusting

Tillage practices may reduce the organic matter content in near-surface soil horizons causing crust formation. Surface conditions may cause an increase in surface run-off, thus enhancing contaminant transfer of heavy metals or an acceleration in nutrient loss. This study examines the effect of applying crop residues to the surface of tilled soils on heavy metal losses by run-off. Losses in iron (Fe), manganese (Mn), zinc (Zn) and copper (Cu) were analysed. Run-off and sediment yield were measured on 1 m² plots using a rainfall simulator with a constant 65 mm/h intensity. Four successive rainfall applications were performed, the first three at 25 mm each and the last at 65 mm. Added corn straw varied between 0 and 4 t/ha in the five studied treatments. After 140 mm cumulative rainfall, total heavy metal losses were as follows: Fe from 137 to 950 mg/L, Mn from 2.3 to 12.83 mg/L, Cu from 0.09 to 0.72 mg/L and Zn from 0.31 to 2.46 mg/L. Dissolved fractions were as follows: Fe from 0.014 to 0.229 mg/L, Mn from 0.034 to 1.45 mg/L, Cu from 0.002 to 0.013 mg/L and Zn from 0.02 to 0.12 mg/L. Total concentrations of the studied elements decreased exponentially due to the effect of corn straw on soil loss. However, dissolved contents of Fe and Cu scarcely varied. Significant positive linear correlations were observed between total heavy metal content and soil and sediment loss by run-off. It is concluded that the addition of straw to a soil of low fertility prevents heavy metal loss.     

Effectiveness of crop straws,and swine manure in ameliorating acidic red soils: a laboratory study

Purpose

Crop straws and animal manure have the potential to ameliorate acidic soils, but their effectiveness and the mechanisms involved are not fully understood. The aim of this study was to evaluate the effectiveness of two crop (maize and soybean) straws, swine manure, and their application rates on acidity changes in acidic red soils (Ferralic Cambisol) differing in initial pH.

Materials and methods

Two red soils were collected after 21 years of the (1) no fertilization history (CK soil, pH 5.46) and (2) receiving annual chemical nitrogen (N) fertilization (N soil, pH 4.18). The soils were incubated for 105 days at 25 °C after amending the crop straws or manure at 0, 5, 10, 20, and 40 g kg^?1 (w/w), and examined for changes in pH, exchangeable acidity, N mineralization, and speciation in 2 M KCl extract as ammonium (NH₄⁺) and nitrate plus nitrite (NO₃^??+?NO₂^?).

Results and discussion

All three organic materials significantly decreased soil acidity (dominated by aluminum) as the application rate increased. Soybean straw was as effective (sometimes more effective) as swine manure in raising pH in both soils. Soybean straw and swine manure both significantly reduced exchangeable acidity at amendment rate as low as 10 g kg^?1 in the highly acidic N soil, but swine manure was more effective in reducing the total acidity especially exchangeable aluminum (e.g., in the N soil from initial 5.79 to 0.50 cmol₍₊₎ kg^?1 compared to 2.82 and 4.19 cmol₍₊₎ kg^?1 by soybean straw and maize straw, respectively). Maize straw was less effective than soybean straw in affecting soil pH and the acidity. The exchangeable aluminum decreased at a rate of 4.48 cmol₍₊₎ kg^?1 per pH unit increase for both straws compared to 6.25 cmol₍₊₎ kg^?1 per pH unit from the manure. The NO₃^??+?NO₂^? concentration in soil increased significantly for swine manure amendment, but decreased markedly for straw treatments. The high C/N ratio in the straws led to N immobilization and pH increase.

Conclusions

While swine manure continues to be effective for ameliorating soil acidity, crop straw amendment has also shown a good potential to ameliorate the acidity of the red soil. Thus, after harvest, straws should preferably not be removed from the field, but mixed with the soil to decelerate acidification. The long-term effect of straw return on soil acidity management warrants further determination under field conditions.

     

Comparison of DTPA and resin extractable soil Zn to plant Zn uptake

Abstract

Extraction of soil zinc with routine chemical extractants does not always reflect differences in Zn availability as detected by plant uptake. This study was undertaken to explore and compare the use of an ion exchange resin and diethylenetriaminepentaacetic acid (DTPA) for extracting soil Zn as related to plant Zn uptake. Beans were grown in 1989 following differential cropping with corn and beans or fallow in 1988 on a Portneuf silt loam near Kimberly, Idaho. Two Zn fertilizer treatments were imposed across previous cropping treatments. A batch method for determining resin extractable soil Zn was established.

Both plant Zn concentration and Zn uptake by beans in 1989 were significantly higher in Zn fertilized than unfertilized treatments regardless of previous crop; and higher in plots previously cropped with corn than beans or fallow, regardless of Zn treatment. DTPA and resin extractable soil Zn were significantly higher in Zn fertilized plots compared to unfertilized plots but did not differ between previous cropping treatments. Resin and DTPA extractable soil Zn concentrations were positively correlated. Resin extracted soil Zn correlated better with plant Zn concentration and Zn uptake throughout the growing season than DTPA extracted soil Zn, particularly in plots that had been fallowed or previously cropped with corn. Resin may be extracting labile soil Zn not extracted with DTPA and, therefore, be better simulating plant uptake. Both extraction methods correlated better with Zn uptake when evaluated within cropping treatments, emphasizing the need to consider previous crop when calibrating soil tests.     

Interactions between crop residues application and mycorrhizal developments and some soil-root interface properties and mineral acquisition by plants in an acidic soil

The addition of plant residues and the appropriate management of arbuscular mycorrhizal (AM) symbioses have been tested in an acidic soil, an Andisol from Southern Chile, to ascertain whether these agro-technologies help plants to withstand potential mineral deficiency and the toxicities inherent to the low pH conditions. Firstly, the effects of legume (lupine) and non-legume (wheat) crop residues on some key root-soil interface activities (including AM development), on mineral acquisition by the plants, and on the yield of wheat growing in the test Andisol were investigated in a pot experiment under greenhouse conditions. Both lupine and wheat residues were added at a rate equivalent to 300 g m^-2 to the natural soil. These organic amendments increased soil pH (wheat more than lupine), P availability and AM development (lupine more than wheat), plant performance and mineral acquisition (wheat more than lupine). Because of an increase in mycorrhizal activity, which appeared to be involved in the effect of the added crop (particularly lupine) residues, the role of the AM symbiosis was further investigated in a tailored inoculation assay, using a selected AM fungus (Glomus etunicatum), in interaction with lupine and wheat residues. A significant effect of AM inoculation on the reduction of Zn and Cu, and Mn and Al acquisition was demonstrated, which could be of interest in acid soils with regard to potential toxicity problems.     

Effectiveness of different soil amendments to reduce the Pb and Zn extractability and plant uptake in soils contaminated by anticorrosion paints beneath pylons

Red lead (Pb₃O₄)‐ and ZnO‐containing anticorrosion paints in the past have been extensively applied to high‐voltage steel pylons which has led to heavy metal (HM) soil contaminations in their vicinity. Since pylons are commonly found on agricultural land, there is a potential risk of HM plant uptake. This is promoted by the fact that in contrast to the moderate total Pb contents (several 100 mg kg^–1) in three nutrient‐poor and acidic pylon soils the Pb amounts extractable with NH₄NO₃ were extremely high, reaching almost 20% of total Pb. A 18‐week field pot trial (three harvests in a six‐week interval) using Lolium multiflorum was conducted to study the HM plant uptake and the efficiency of the four soil additives, lime (LI), Novaphos (NP), water‐treatment sludge (WS), and ilmenite residue (IR) in reducing the plant uptake and NH₄NO₃‐extractability of Pb and Zn in the soils. Lead concentrations in L. multiflorum shoots grown in the untreated soils reached maximum values of 128 mg (kg dry weight)^–1. Novaphos was most efficient in decreasing shoot Pb (–90%) followed by LI (–78%) and WS (–73%). For Zn, too, LI (–82%), NP, and WS (both –66%) substantially reduced plant uptake. Ilmenite residue was generally only poorly efficient. The dry‐matter yield in the NP, LI, and WS treatments was significantly increased. While the relationship between Pb‐NH₄NO₃ and Pb‐plant was high when considering the three harvests separately (R > 0.93) a poor relationship (R = 0.63) exists over all harvests together. This was attributed to different transpiration rates affecting the HM flux into the plants, since the temperature regime changed greatly during the cultivation period. For Zn, no such close relationship between the NH₄NO₃‐extractable soil fraction and shoot Zn was found, most likely due to antagonistic effects from Mg which greatly varied in the three soils.