Zinc and copper mobility in experimentally disturbed oxisol and ultisol soil columns.
In recent years, sewage sludge has been applied regularly on soils to improve their conditions for plant growth. Recycling of sewage sludge in soils can be beneficial from the aspect of essential plant nutrients and organic matter supplement to soil and plant system. Application of sludge could be one of the most useful and environmental approaches to solve the problems of waste disposal. However, the use of this product can result in several risks due to high content of heavy metals in such sludge. Heavy metals transferred from sewage sludge to soil and subsequently to plants and groundwater become potential environmental and health risk . Distribution (downward movement) of heavy metals in soil is an important issue which should be studied in order to identify the ability of the heavy metals to move through subsoil and eventually lost in groundwater. The important factors controlling their mobility are pH, organic and inorganic ligands .
According to Fadiran et al. , sewage sludge contained high concentration of zinc and Cu in the mobile fraction could possibly be due to the low pH of the sludge. The presence of heavy metals in sewage sludge in high concentrations can be a threat to the soil and water environment. The study of the mobility of heavy metals helps informed the decision makers on the application of sewage sludge for agricultural purposes.
Leaching is defined as the loss of elements with percolating water. Since heavy metals are among the elements that are washed away into the underground water; the leaching of metals is serious in the soils of the humid region and less significant in the soils of arid area. Leaching of heavy metals from polluted sites is an important pathway for them to be dispersed to the wider environment . Therefore, a study of the mobility of heavy metals such as Zn and Cu in soils treated with sewage sludge seems to be necessary and a justified practice. The main purpose of the present study was to investigate the influence of sewage sludge on the leaching characteristics of Zn and Cu.
MATERIALS AND METHODS
Two soil types, Oxisol (Munchong Series) and Ultisol (Bungor Series) were used in this study. Soil samples were taken from the topsoil (0-20 cm depth) from two sampling sites located in Peninsular Malaysia. The sewage sludge used was obtained from a national sewerage company Indah Water Konsortium (IWK) Sewage Treatment Plant at Bandar Tun Razak, Kuala Lumpur, Malaysia. The sludge and soil samples were air-dried, passed through 2 mm mesh sieve and prepared for their physico-chemical analyses.
Column Leaching Experiments:
A leaching experiment was conducted using 30 cm PVC plastic columns in order to study leaching and vertical mobility of Zn and Cu.
Packing the columns:
Before packing the columns, the soils were air-dried at room temperature and then thoroughly homogenized; one kilogram was used for each column. All homogenous soils were incubated in 18 PVC columns: (2 types of soils "Oxisol and Ultisol") x (3 treatments as T1, T2 and T3) x (3 replicates).The columns were covered at the bottom by a permeable inert tissue to prevent soil losses, after which the soil columns were incubated at room temperature for 6 months and were irrigated weekly with deionized water to make a total of 2500 mm. The leachates were collected by a PET container. The weekly addition of water was controlled to make sure that waterlogging condition was avoided.
The treatments were:
T1. Untreated soils (control);
T2. Soils treated with 10% sewage sludge without planting. This treatment was to evaluate the potential leachability of Zn and Cu as a result of the sewage sludge application, and;
3. Soils treated with 10% sewage sludge and cultivated with Hibiscus cannabinus.
The plants were allowed to grow for 6 months in a glasshouse to assess the mobility of Zn and Cu after cultivation. The experiment was laid out using CRD design, with three replications.
The leaching process occurred in PCV columns that were filled with soil to a height of 25 cm. The soil columns were washed with 2500 mm of distilled water, which was divided into four equal doses. This amount of water was equivalent to the annual rainfall in Peninsular Malaysia. The leachates were collected and analyzed. The leachates prior to metals concentration analysis were stored at 4[degrees]C, additionally and pH was measured immediately after collecting the leachates.
When the leaching process was over and done with, the soil columns were divided into five equal segments and allowed to dry at the ambient temperature. Then, soil samples were collected for Zn and Cu analysis in order to assess their distribution inthe soil columns.
Leachates were analyzed for pH, Zn and Cu and anions (S[O.sub.4], P[O.sub.4], Cl and N[O.sub.3]) contents. The pH in the leachate was determined by a pH meter. Zinc and copper was determined using ICP-OES (Perkin-Elmer, Optima 3000). Anions (S[O.sub.4], P[O.sub.4], Cl and N[O.sub.3]) were determined using Ion Chromatograph Model Metrohm 882 Compact IC Plus 1.
Texture was determined by the pipette method of Kettler et al. . The pH was determined by a pH meter (soil: water ratio at 1:2.5) . Cation exchange capacity was determined according to the method of Ariyakanon and Winaipanich . Total carbon and total nitrogen were analyzed using LECO CNS analyzer  and available P was extracted by Bray and Kurts  method and the P was measured by an auto analyzer (Lachat Quick Chem FIA+USA). Total Zn and Cu were extracted by aqua-regia method which was made using HCl and HN[O.sub.3] solution (3:1) . The metals were determined using inductively coupled plasma--optical emission spectrometry (ICP-OES) (Optima 8300, PerkinElmer, USA).
Data collected from this study were analyzed by analysis of variances and Tukey for mean comparison using SAS version 9.4 (SAS Institute, Inc., Cary, N.C., USA).
Principal Component Analysis (PCA):
A principal component analysis (PCA) was used to group the most prominent anion with Zn and Cu in soil column leaches. The PCA was carried out using Statgraphics plus 5.1.
General Characteristic of Soil and Sewage Sludge:
The physico-chemical properties of the soils and sewage sludge are summarized in Table 1. The soils were naturally acidic with sandy clay loam texture. The Ultisol recorded slightly lower pH (4.77) than that of the Oxisol (5.36); cation exchange capacity (CEC) of the two soils was low which was consistent with that reported by Shamshuddin and Fauziah . On the other hand, the pH of the sewage sludge was high with a value of 6.04. Total nitrogen (TN) in the sludge was 2.90 % which was in line with that of Rosenani et al. . The concentration of Zn and Cu was within the range of heavy metal in the sewage sludge reported by Alloway , where Zn concentration (82-5894 mg [kg.sup.-1]) was greater than that of Cu (13-3580 mg [kg.sup.-1]).
It seemed that the properties of the soils were affected by sewage sludge treatment, whereby the mean of soil pH increased in the soils treated with sewage sludge (T2).A noticeable change in soil pH clearly indicated a radical modification in the soil properties. Moreover, there were positive correlations between CEC, available P, TC, TN and the rate of sewage sludge application, where the highest value was found in the soil treated with 10% sewage sludge. The results showed that the sewage sludge could be an important source of Zn and Cu in soils for crop production shown by their high concentrations in the Oxisol and Ultisol treated with 10% sewage sludge. However, it is of interest to indicate that the lowest concentration of Zn and Cu was in the treatment having plant (T3) due to their uptake by it.
Sewage sludge modified soil porosity, where in the Oxisol, its value was increased from 57.00 % in T1 to 60.00% in T2. For the Ultisol, it was from 55.00% in T1 to 58.00% in T2. However, the cultivated Oxisol and Ultisol (T3) showed the highest value of 67.00 and 65.00 %, respectively due to the effects of roots of the plants on soil structures.
Changes in the leachates pH are shown in Table 2. The results showed a significant difference (p[less than or equal to]0.05) among the treatments in terms of leachates pH. The highest of leachates pH was in the order of leachates from soils treated with 10% sewage sludge without planting (T2)>leachates from soils treated with 10% sewage sludge with plants (T3)>leachates from untreated soils (control-T1).
Soil pH tended to decrease with time due the outflow of ions from the soil column which led to the increase of acidity in the leachate. In leachates from Oxisol, there was a clear decrease of pH from 5.40 to 4.40 in T1, from 5.87 to 5.15 in T2 and from 4.70 to 4.44 in T3. Lower pH was observed in the leachates from Ultisol, where decrease of pH from 4.70 to 4.01 in T1, from 5.36 to 4.23 in T2 and from 4.24 to 3.95 in T3 was observed. Lowest pH was found in leachates collected at the fourth month. There were differences in pH values between leachates from Oxisol and Ultisol, where the pH of leachates from Oxisol was higher compared to that from the Ultisol in all treatments.
Zinc and copper in leachate:
The quantity of Zn and Cu eluted from soil columns is reported in Figure 1 and 2. The results of the leaching experiment are presented as breakthrough curves. The highest concentration of Zn and Cu in the leachate was found in the soil amended with sewage sludge (T2) only rather than those from other treatments (T1 and T3).The order of leachability was Zn > Cu in all treatments. The leaching patterns of Zn were approximately 0.02-24.9 mg[L.sup.-1], while the concentrations of Cu in the majority of leachate were consistently very low (0-4 mg[L.sup.-1]). It is of interest to indicate that the concentrations of the leached Zn ions through the soil columns packed with the Ultisol (24.90 mg[L.sup.-1]) were higher than the corresponding ones that occurred through the soil columns packed with the Oxisol (22.85 mg[L.sup.-1]).
The peak concentration of Zn and Cu occurred at the 4th leachate period for all treatments. Thereafter, the concentrations of the metals declined rapidly. Besides, Cu was not readily leached from the soil columns due to its high affinity for OM, and it tended to accumulate in the soils .
The results showed that Ultisol was more capable of leaching Zn and Cu than Oxisol. This means that concentrations of the studied metal ions were affected by soil type. The comparison between the metal content of the eluates from treated and untreated soils revealed a significant increase in Zn, but not in Cu, in the fourth eluate. This is probably due to a high enough Zn ion concentration in the treated soils to cause an appreciable increase in the leachate, while the Cu ion concentration was not sufficient for this increase to take place.
Generally, it is obvious that the washable Zn and Cu ions tended to decrease with progressing time of leaching. The leaching process did not affect the trend of the Cu elution curves, probably because soils organic matter are strong absorbers of Cu. Copper ion disappeared and it was not detectable in elution from T3. This may be because the excess amount of Zn and Cu could be removed from the soils and up taken by H. cannabinus.
[FIGURE 1 OMITTED]
[FIGURE 2 OMITTED]
Cumulative Zn and Cu concentrations in the leachate:
The cumulative Zn and Cu concentrations in the leachates are shown in Figure 3. The finding revealed that water was able to mobilize Zn and Cu from the soil columns by aqueous complex reactions. There were differences among the cumulative Zn and Cu concentrations in the leachates under different treatments. The lowest cumulative Zn and Cu concentrations was for T3, while the highest cumulative Zn and Cu concentrations was for T2. This means that soil cultivation leads to a reduction in the concentrations of Zn and Cu in soils treated with sewage sludge. These micronutrients are required for the healthy growth of the plants growing in them.
Normally, Cu is not readily leached from columns due to its high affinity for organic matter and it tends to accumulate in surface soils (van Schaik et al., 2010). In this study, the maximum concentration of Cu in the leachates from Oxisol (11.67 mg[L.sup.-1]) was higher than that of the Ultisol (8.69 mg[L.sup.-1]). However, the opposite was true for the Zn concentration where the maximum concentration of Zn in the leachates from Ultisol was 82.35 mg[L.sup.-1], while that of the Oxisol was 62.91 mg[L.sup.-1].
[FIGURE 3 OMITTED]
Relation between leachability of Zn, Cu and leachate pH:
Significant correlations were clearly appeared according to Pearson correlation between pH and the two studied metals (Zn and Cu) concentrations in leachates (Table 3). In all treatments, highly significant correlations were appeared at four months between the studied heavy metals and pH especially in leachates of uncultivated amended soils (T2), where the highest correlation values r = 0.80 and 0.82 for Zn and Cu respectively. Zinc and copper concentrations in the leachates were strongly related to the pH decrease, these results were in agreements with Csavina et al.  who found higher heavy metals solubility as pH values decreased.
In addition, the results indicated that no correlations were observed among Zn, Cu and pH at the first leachate (1th month).Moreover, it is worth to note that Cu concentrations were not detectable in a cultivated soils amended with sewage sludge (T3), where no valuable relation could be concluded. In addition, weak correlations were observed during 6th month in leachates of uncultivated amended Oxisol leachates (T2) with r = 0.45 and 0.48 respectively for Zn and Cu. A similar value was shown with leachates of untreated Ultisol (T1) during the 5th month with r = 0.45 for Zn. In addition, no correlations were observed during the 3th and 6th months in leachates of cultivated Ultisol (T3) with r = 0.27 and 0.48, respectively for Zn.
The results of the current study clearly indicated the role of pH on leachability of Zn and Cu from Oxisol and Ultisol (Figure 4 and 5).The pH has a great impact solubility and mobile of Zn and Cu where. The solubility of heavy metals is an important property that controls the move and leaching from soil columns.
[FIGURE 4 OMITTED]
[FIGURE 5 OMITTED]
Anion content in the leachates:
Figure 6 and 7 show the variation in Cl, S[O.sub.4], N[O.sub.3], and P[O.sub.4] concentrations in the leachates from Oxisol and Ultisol. The level of anions present in the leachates was dependent principally on the treatments. Leachates from the untreated Oxisol and Ultisol (T1) were found to have lower concentrations of all the anions compared to those of the treated soils (T2). In case of leachates of untreated Oxisol and Ultisol, the concentrations of P[O.sub.4] and S[O.sub.4] were high compared to N[O.sub.3] and Cl. While In case of leachates of soils treated with sewage sludge, the concentrations of N[O.sub.3] and Cl were high compared toP[O.sub.4] and S[O.sub.4].
However, in this investigation, leachates from the treated Oxisol and Ultisol (T2) were found to have considerably high concentrations of all the anions, like chlorides, nitrates, sulphate and phosphate. However, the concentration of Cl, S[O.sub.4], N[O.sub.3], and P[O.sub.4] were low in the leachates of the treated Oxisol and Ultisol planted with plants.
The increase in N[O.sub.3]and Cl in leachates of treated soils could be ascribed to the anion content of the sewage sludge. The present of high concentration of N[O.sub.3] and P[O.sub.4] in leachates of soils treated with sewage sludge may possibly indicator to domestic pollution 
[FIGURE 6 OMITTED]
[FIGURE 7 OMITTED]
Principal Component Analysis:
Leachate components are related to each other according to principle component analysis (PCA).The PCA method was applied to obtain the degree of association among Zn, Cu, N[O.sub.3], S[O.sub.4], Cl and P[O.sub.4] of soil columns leachate. The results of the principal component analysis are given in Figure 8.
For the untreated Oxisol and Ultisol, the first factor (Zn) was responsible for 49.70 % of the total variance in the leachates of untreated Oxisol and it was responsible for 45.92% of the total variance in the leachates of untreated Ultisol. The second factor (Cu) explained 27.43 % and 18.82% of total variance of leachates of untreated Oxisol and Ultisol, respectively. Zn and Cu were positively connected with the amounts of leached Cl and S[O.sub.4], while they were not connected with the amounts of N[O.sub.3] and P[O.sub.4] leached.
In the case of the soils treated with 10% sewage sludge, there were differences among the components of the leachates of treated Oxisol and Ultisol. For the treated Oxisol, the first factor (Zn) explained 44.11% of the total variance, while the second factor (Cu) explained 22.20% of the total variance. In the case of the treated Ultisol, the first factor (Zn) explained 32.11% of the total variance and the second factor (Cu) explained 30.59% of the total variance. Zinc was positively connected with the amounts of leached N[O.sub.3] and S[O.sub.4].
For the cultivated soils, the main factor (Zn) explained 36.60% of the total variance in cultivated Oxisol, while it was responsible for 34.45 % of the total variance in the cultivated Ultisol. Zinc was positively connected with amounts of leached S[O.sub.4] in both soils.
[FIGURE 8 OMITTED]
Zinc and copper distribution due to leaching process:
At the end of the leaching process, it was found that zinc in the soil had lower concentration compared to that of Cu (Figure 9 and 10). This phenomenon was very conspicuous especially in the first layer (0-5 cm) in both soils. As expected, Cu had little mobility throughout the columns. Mostly, Cu remained at the bottom layers (15-20 cm) and (20-25 cm). It is important to note that the movement of Zn and Cu through the Oxisol and Ultisol was influenced by the types of the treatment. Higher concentrations of the metals were in T2 compared to the others, especially T3. These results could be due to their uptake by the tested plants. In general, the upper layer of the soil columns had lower Zn and Cu content than the second layer, which in turn lower than those below it. This means that Zn and Cu moved down to the lower of the soil columns during the leaching process.
In the Oxisol columns, the highest concentration of Zn (15.16 mg [kg.sup.-1]) was observed in the fourth layer (15-20 cm) of T2, while the highest concentration of Cu (17.90 mg [kg.sup.-1]) was observed in the fifth layer (20-25 cm) of T2. These phenomena were repeated for the experiment on Ultisol. For this soil, the highest concentration of Zn was 14.36 mg [kg.sup.-1], while that of Cu 16.96 mg [kg.sup.-1].
The results clearly demonstrated that sewage sludge addition played a role in the downward movement and leaching behavior of Cu in two treated soils. This is consistent with the study of Fadiran et al.  who stated that the unavailable Cu for leaching was due to the fact that Cu is bound to organic matter in sewage sludge. It is pertinent to note that the downward movement and leaching behavior of Zn is more than that of Cu which could be due to the higher solubility rate of Zn in comparison to that of Cu.
[FIGURE 9 OMITTED]
[FIGURE 10 OMITTED]
Leachate as a source of Zn and Cu:
The characteristics of soils varied among all treatments. A marked increase in Zn and Cu concentration has been recorded in the Oxisol and Ultisol amended with sewage sludge and these metals can be leached down the soil profile during rainy season. However, the leachability of Zn and Cu was very different in the sense that Zn was more mobile compared to that of Cu (Figures 1 and 2). Copper is generally less mobile in soils since they are strongly bound to the colloid surface and with organic matter in sewage sludge , which explained why its concentration in the leachates was low. However, previous studies have shown that dissolved organic matter may play a significant role in governing the mobility of Cu by forming insoluble or soluble complexes. It was reported that the low molecular weight of organic acids influencing the mobilization of heavy metals like Cu For example, fulvic acid enhanced the adsorption of Cu on hematite below pH 6 , which explained why Cu concentration in the leachates of planted soils was very low.
The highest concentration of Zn and Cu was found for the soils treated with 10% sewage sludge (T2), which means that sewage sludge application must have enhanced the level of Zn and Cu in the Oxisol and Ultisol. The increase was greater in Ultisol than that of the Oxisol, probably related to the difference in the pH of the treated soils.
The leaching of Zn and Cu and hence the risk of pollution of the ground water depends on the properties of metals and soils themselves. It is believed that leaching of heavy metals from soils have the ability to accumulate metals in the surrounding area . However, the concentration of Zn and Cu ions in soils after leaching event differs according to the type of treatment. Data from this study showed the following order: soils treated with sewage sludge (T2) > without sewage sludge (control: T1) > soil treated with sewage sludge and cultivated (T3).
Leachability of Zn and Cu as a function of pH:
This study showed that the pH of the leachates was influenced by soil type. As shown in Table 3, there were significant correlations between Zn and Cu concentration in leachate pH. The changes of pH were related to the ion exchange in the soil column between protons in soil particles and other cations, whereby below pH5 Zn and Cu were moderately mobile in the soil, and this mobility increased with decreasing pH .
The leaching trend for the two studied metals indicates the dependence of the release and leachability of Zn and Cu on pH changes. In this study, it is clear that the process of the leaching of Zn and Cu have been influenced by decreasing of pH values (Figure 4 and 5). The pH had significant effect on the concentrations of Zn and Cu in leachates, whereby the highest concentrations were found at lowest pH values. However, these high concentrations of Zn and Cu were decreased markedly when pH leachates beginning gradually increased. Which mean that the pH is the most important factor that controls the concentration of Zn and Cu in the leachates .
Downward Movements and Distribution of zinc and copper in soil columns:
Many factors such as pH and organic matter can affect the movement or alter the accumulation of Zn and Cu in soils. The distribution of zinc and copper in the various depths of soil columns are shown in (Figures 9 and 10). The findings indicate that most of the Zn and Cu retained by the lowest layers. In both soils, zinc had lower concentration compared to that of copper specifically in the first layers (0-5 cm). Copper shows relatively little variation in total content across soil columns due to little mobility in tested soils. Hence, it was observed that Cu had the highest concentration at most soil depth intervals while Zn was the least at most depth intervals. The high organic matter status of the sewage sludge might have favored metal-organic matter complexation that could reduce Cu mobility in soils treated sewage sludge. The changes in polarity of dissolved organic matter may inhibit the movement of heavy metals in soil system .
It is believed that water is able to increase Zn and Cu mobilization in soil columns. The downward movements of these heavy metals could result in a substantial redistribution into such soils with the risk of groundwater pollution. Earlier studies demonstrated that the H+ in the water moves and displaces the cations from their binding sites and enhance the concentrations of these cations in the soil-water system .
Knowledge of leaching processes that govern the mobility of heavy metals such as Zn and Cu in the soils is necessary for the protection of the environment especially in tropical regions.
Based on the findings, the addition of sewage sludge to Oxisol and Ultisol columns yielded noticeable concentrations of Zn and Cu in their leachates. The order of leachability was Zn > Cu in all treatments. It worth to mention that the concentrations of these metal varied according to the treatments following the order: soils treated with 10% sewage sludge without planting (T2)> untreated soils (control: T1) > soils treated with 10% sewage sludge and planted (T3). Moreover, the leachate derived from soils treated with 10% sewage sludge demonstrates exceedingly high values for almost all anions, including N[O.sub.3], P[O.sub.4], Cl and S[O.sub.4].Leachates from the planted soil contained lower Zn and Cu concentrations due to their uptake by the plants. The pH was a variable that influenced Zn and Cu leachability and movement. It can concluded the downward movement and leaching behavior of Zn is more than that of Cu e due to the higher solubility rate of Zn in comparison to that of Cu that may pose potential environmental risks in long-term.
We wish to acknowledge Universiti Putra Malaysia for financial and technical supports.
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(1) Aishah Ramadan Mohamed, (1) Shamshuddin Jusop, (1) Fauziah Che Ishak, (2) Arifin Abdu
(1) Department of Land Management, Faculty of Agriculture, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia.
(2) Department of Forest Management, Faculty of Forestry, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia.
Received 12 April 2016; Accepted 10 May 2016
Address For Correspondence:
Shamshuddin Jusop, Department of Land Management, Faculty of Agriculture, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia;
Table 1: Physico-chemical properties of the soils and sewage sludge Properties Unit Oxisol T1 T2 T3 pH 5.36 5.84 5.30 CEC ([cmol.sub.c] 8.00 9.39 8.34 [kg.sup.-1]) Av. P (mg [kg 10.70 24.00 18.21 .sup.-1]) Total Zn (mg [kg 38.30 58.45 13.89 .sup.-1]) Total Cu (mg [kg 35.50 48.10 6.33 .sup.-1]) TC (%) 1.75 2.53 2.23 TN (%) 0.13 0.31 0.12 Porosity (%) 57.00 60.00 67.00 Sand (%) 66.48 Clay (%) 28.01 Silt (%) 5.44 Texture Sandy clay loam Properties Ultisol Sewage Sludge T1 T2 T3 pH 4.77 5.37 4.85 6.04 CEC 10.33 11.22 9.72 26.28 Av. P 15.50 26.80 19.18 55.00 Total Zn 38.43 58.70 27.87 454.95 Total Cu 37.90 49.70 9.95 86.7 TC 2.01 5.23 4.30 34.36 TN 0.13 0.68 0.37 2.90 Porosity 55.00 58.00 65.00 -- Sand 62.69 -- Clay 28.37 -- Silt 8.89 -- Texture Sandy clay loam -- TN = total nitrogen, TC = total carbon, Av. P= Available P Table 2: Changes in leachate pH with time Soil Treatment Months 1 2 T1 5.40 [+ or -] 0.10a 5.30 [+ or -] 0.10b Oxisol T2 5.87 [+ or -] 0.10a 5.37 [+ or -] 0.10b T3 4.70 [+ or -] 0.10a 4.60 [+ or -] 0.09b T1 4.70 [+ or -] 0.10a 4.33 [+ or -] 0.11b Ultisol T2 5.36 [+ or -] 0.01a 5.11 [+ or -] 0.11b T3 4.24 [+ or -] 0.01a 4.17 [+ or -] 0.10b Soil Treatment Months 3 4 T1 4.60 [+ or -] 0.10c 4.40 [+ or -] 0.09d Oxisol T2 5.33 [+ or -] 0.10c 5.15 [+ or -] 0.09d T3 4.51 [+ or -] 0.10c 4.44 [+ or -] 0.08d T1 4.14 [+ or -] 0.01c 4.01 [+ or -] 0.01e Ultisol T2 4.64 [+ or -] 0.01c 4.23 [+ or -] 0.01e T3 4.15 [+ or -] 0.01c 3.95 [+ or -] 0.01e Soil Treatment Months 5 6 T1 4.70 [+ or -] 0.09c 5.20 [+ or -] 0.10b Oxisol T2 5.25 [+ or -] 0.11c 5.29 [+ or -] 0.10b T3 4.46 [+ or -] 0.08c 4.50 [+ or -] 0.10b T1 4.12 [+ or -] 0.01d 4.24 [+ or -] 0.02c Ultisol T2 4.33 [+ or -] 0.01d 4.45 [+ or -] 0.01c T3 4.12 [+ or -] 0.01d 4.20 [+ or -] 0.01c Mean [+ or -] standard deviation of monthly average monitoring data Means for same row and with the same letter are not significantly different at p[less than or equal to]0.05 (Tukey test) Table 3: Pearson correlation coefficient (r) between Zn and Cu in the leachate and pH (N=108) Soil Treatment Element Months 1 2 3 T1 Zn 0.48 0.65 * 0.57 * Cu 0.45 0.70 * 0.75 * Oxisol T2 Zn 0.27 0.67 * 0.67 * Cu 0.48 0. 64 * 0.23 T3 Zn 0.23 0.66 * 0.66 * Cu -- -- -- T1 Zn 0.27 0.57 * 0.73 * Cu 0.44 0.75 * 0.62 * Ultisol T2 Zn 0.13 0.67 * 0.45 Cu 0.20 0.76 * 0.57 * T3 Zn 0.49 0.62 * 0.27 Cu -- -- -- Soil Treatment Element Months 4 5 6 T1 Zn 0.73 * 0.57 * 0.57 * Cu 0.67 * 0.67 * 0.75 * Oxisol T2 Zn 0.80 * 0.73 * 0.45 Cu 0.82 * 0.48 0.48 T3 Zn 0.57 * 0.73 * 0.57 * Cu -- -- -- T1 Zn 0.54 * 0.45 0.57 * Cu 0.66 * 0.57 * 0.66 * Ultisol T2 Zn 0.62 * 0.67 * 0.48 Cu 0.79 * 0.77 * 0.23 T3 Zn 0.81 * 0.66 * 0.48 Cu -- -- -- * Significant at p<0.05;--No valuable relation
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|Author:||Mohamed, Aishah Ramadan; Jusop, Shamshuddin; Ishak, Fauziah Che; Abdu, Arifin|
|Publication:||American-Eurasian Journal of Sustainable Agriculture|
|Date:||Jun 1, 2016|
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