Soil science
zahra movahedirad; Mohsen Hamidpour
Abstract
Introduction
Recently, layered double hydroxides (LDH) have attracted considerable attention. LDHs have found applications in numerous cases particularly slow-release fertilizers for essential nutrients for plants. Several studies have reported the release of nitrate and phosphorus from LDHs. The metal ...
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Introduction
Recently, layered double hydroxides (LDH) have attracted considerable attention. LDHs have found applications in numerous cases particularly slow-release fertilizers for essential nutrients for plants. Several studies have reported the release of nitrate and phosphorus from LDHs. The metal hydroxide layer can structurally incorporate micronutrients such as Zn, Cu, and Mn. According to recent research, LDHs have a suitable potential for releasing micronutrients. No information regarding ratios M2+/M3+ in LDHs and the influence of malic acid on the release of Zn, Mn, and Mg from LDHs is available. This study aimed to investigate the effects of malic acid and the ratio of divalent cation (M2+) to trivalent cation (M3+) on the kinetics release of Zn, Mn and Mg from Mg-Zn-Mn-Al-LDH intercalated with nitrate.
Materials and Methods
All chemicals used in this study including malic acid (C4H6O5), KCl, Zn (NO3)2.6H2O, Mn(NO3)2.4H2O Mg(NO3)2.6H2O and Al(NO3).9H2O were of analytical grades, purchased from Chem-Lab or Merck Chemical Corporations. The solutions were made with the decarbonated ultrapure water (electrical resistivity = 18 MΩcm). The LDHs were synthesized by co-precipitation method at constant pH = 9.2-9.6. Two types of LDHs were synthesized with varying the M+2(Zn+Mn+Mg)/M+3(Al) 3:1 and 4:1 in the precursor solution while being stirred vigorously in a nitrogen atmosphere. The pH was kept at 9.2-9.6 by adding volumes of 3 M NaOH. The crystals of LDH were ripened in the mixture for 2 h and after that, the precipitates were centrifuged at 3000 rpm for 20 min and washed several times with distilled water and placed in an oven at 70 °C for 8 hours to dry. The chemical composition of the synthesized LDHs was determined by furnace atomic absorption spectrophotometry (SavantAA, GBC) after acid digestion. The physical, chemical, and morphological characteristics of the LDHs were determined using X-ray diffraction analysis (Panalytical x Pert ProX-ray diffractometer), Fe-SEM (Sigma VP), FT-IR (Nicolet iS10 spectrometer), and BET (BELSORP Mini II) techniques.
A batch study was done to determine the effect of different ratios of M2+/M3+ in LDHs and the effect of malic acid on release of Zn, Mn, and Mg from LDH (3:1) and LDH (4:1). Briefly, 0.01 g of synthesized LDH were put in a centrifuge tube mixed with 10 ml background electrolyte (KCl 0.01 M) and 1.25 mM malic acid in initial pH=6-7 and constant temperature (25±0.5 °C). Blank samples (without ligand) were also considered. Suspensions were shaken at periods ranging from 5 to 720 min agitation (180 rpm). Then, the supernatant solution was separated using a centrifuge at a speed of 4000 rpm for 20 minutes. Zn, Mn, and Mg concentrations in supernatant solutions were determined by graphite furnace atomic absorption spectrophotometry. The effect of pH in the range of 5 to 10 on the release of Zn, Mn, and Mg from LDH was also studied. Two equations (pseudo-second-order and Elovich) were used to fit the kinetics data.
Results and Discussion
. The results showed that the calculated molar ratio of divalent cation to trivalent cation is similar to their molar ratio in the solution prepared for the synthesis of LDH samples. The X-ray diffraction patterns of LDH (3:1) and LDH (4:1) samples show the existence of strong and sharp peaks for 003 and 006 plates. Accordingly, the reflections of the 003 and 006 plates reveal the layered structure of the synthesized LDH materials. Two bands of FT-IR spectrums around 3480 and 1620 cm-1 for all synthesized LDH materials designate stretching vibrations of the O-H group of hydroxide layers and the interlayer water molecules. The sharp characteristic band around 1382 cm−1 in LDH (3:1) and band around 1354 cm-1 in LDH (4:1) is attributed to the antisymmetric stretching mode of nitrate anion in LDH. The specific surface area of LDH (3:1) and LDH (4:1) were 5.50 m2g-1 and 16.54 m2g-1 respectively. The average pore diameters in LDH (3:1) and LDH (4:1) were 1.92 nm and 2.55 nm, respectively.
Time-dependent cumulative release of Zn, Mn, and Mg from LDH (3:1) and LDH (4:1) in the presence and absence of malic acid was investigated. Time-dependent Zn, Mn, and Mg release from LDH (3:1) and LDH (4:1) was accelerated in the presence of malic acid. The Zn, Mn, and Mg release from the LDHs was likely to be separated into two stages. In the initial stage from 0 to 60 min, the release rate of Zn, Mn, and Mg was rapid, then either remained constant or slightly enhanced during 60–720 min. In this research, among the non-linear models used to determine the release kinetics of Zn, Mn, and Mg, the result with the highest R2 values was chosen. The R2 values were 0.91–0.99, 0.93–0.99, 0.93–0.99, 0.89-0.99, and 0.55–0.86 for pseudo-first-order, pseudo-second-order, Elovich, power function, and parabolic diffusion, respectively. So, pseudo-second-order and Elovich models were used to analyze kinetic data. The amounts of release of Zn, Mn and Mg were higher from LDH (4:1) than from LDH (3:1) because of greater specific surface area, volume, and pore diameter in LDH (4:1). On the other hand, the presence of divalent cations in this structure has increased its instability. A comparison of metal release versus time profiles exhibited that dissolution was greatly dependent on the pH.
Conclusions
The results of this research showed that the release of Zn, Mn, and Mg from LDHs was dependent on time, ligand, solution pH, and the type of LDH. Based on the results of fitting the kinetics models to the experimental data, the release rate of Zn, Mn, and Mg from LDH (4:1) was higher than LDH (3:1). In both types of LDH, the presence of malic acid led to an increase in the rate and amount of release of Zn, Mn, and Mg compared to the absence of malic acid. Although the results of this research showed that it is possible to influence the amount and rate of release of Zn and Mn by synthesizing these compounds in different ratios of divalent to trivalent cations, to confirm the efficiency of LDH as a slow-release fertilizer in calcareous soils, greenhouse studies are needed.
Soil science
Kh. Salarinik; M. Nael; M. Sayyari; S.S. Moosavi
Abstract
IntroductionApplication of agricultural waste composts, in addition to improving soil fertility, has positive effects on the quality of agricultural products and the environment by reducing the use of chemical fertilizers and recycling agricultural waste. Spinach (Spinacea oleracea L.) is a suitable ...
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IntroductionApplication of agricultural waste composts, in addition to improving soil fertility, has positive effects on the quality of agricultural products and the environment by reducing the use of chemical fertilizers and recycling agricultural waste. Spinach (Spinacea oleracea L.) is a suitable plant for studying the effects of composts and chemical fertilizers due to some physiological characteristics such as high antioxidant activity and oxalic acid, significant amount of mineral compounds and vitamin C, and nitrate accumulation. Despite relatively extensive studies on the effect of different composts on plants, no study has been conducted so far to investigate the effect of grape pomace (GP) composts on plants in Iran. Therefore, the objectives of the present study were: 1- to investigate the effect of different GP composts on yield, nutrient elements, and some physiological parameters of spinach in comparison with two levels of urea fertilization in a pot experiment in two consecutive growing seasons, and 2- to investigate the relationship between nutrient elements and physiological indicators of spinach based on principal component analysis. Materials and MethodsTo investigate the effects of GP composts on yield, nutrient elements, and physiological parameters of spinach (Persius hybrid), an outdoor pot experiment was conducted in a randomized complete block design with eight compost treatments, two levels of urea fertilizer (46%), and a control treatment (C0) in three replications and two consecutive growing seasons (spring and fall). Compost treatments included: High grape pomace (HG) (60-63%) with chickpea straw and alfalfa (HG-Ch-A), high GP with chickpea straw and sugar beet pulp (HG-Ch-B), high GP with alfalfa and sugar beet pulp (HG-A-B), high GP combined with chickpea straw, alfalfa, and sugar beet pulp (HG-All); four other compost treatments included low level of grape pomace (LG) (37-42%) combined with other residues/wastes similar to the first four treatments (LG-Ch-A, LG-Ch-B, LG-A-B, and LG-All). Urea fertilizer treatments included: 150 kg per hectare (C150) (two-stage top dressing) and 500 kg per hectare (C500) (three-stage top dressing). Prior to planting, the composts were separately mixed into the soil (sandy loam) at a rate of 2% by weight(. The first crop was grown for 50 days in May 2018 and the second crop was grown for 45 days in September 2018. In both seasons, plant samples were taken in the early morning at the end of the growing season to determine the fresh and oven-dried weight of shoot and root samples, leaf area, nutrient elements, and some physiological indicators. Some of the shoot samples were wrapped in aluminum foil and stored in a freezer (-20 °C) to determine the amount of chlorophyll (type a, type b, and total), carotenoids, total phenol, vitamin C, and antioxidant activity. Oxalic acid, zinc, iron, copper, sodium, potassium, phosphorus, calcium, magnesium, and nitrate were determined in oven-dried samples. One-way ANOVA was applied separately to spring and fall data, and mean comparisons were made using Duncan's test at the 0.05% level. Principal component analysis was used to determine the relationships between nutrient elements and physiological indicators of spinach. Results and DiscussionThe LG-Ch-A and C500 treatments (in spring cultivation), and the LG-A-B, LG-All, and HG-All treatments (in fall cultivation) had the highest leaf number, leaf area, and yield and were significantly difference from the C0 treatment. The high yield in C500, LG-Ch-A, LG-All, and HG-All treatments was associated with nitrate accumulation in spinach. In both cultivations, there was a significant positive correlation between the amount of P, K, Mg and Zn in spinach and the amount of these elements in the corresponding composts. A synergistic relationship was also observed between P and Mg; P and Zn; and Mg and Zn in spinach. On the other hand, an antagonistic relationship was observed between Ca and Mg in spinach because a high concentration of calcium inhibits magnesium uptake by reducing cell permeability. In both seasons, the chemical fertilizer treatments showed the highest amount of chlorophyll and carotenoids because these compounds increase with increasing nitrogen availability. On the contrary, the amount of antioxidant activity was significantly higher in compost treatments than in chemical treatments. In the spring cultivation, the highest and lowest amount of oxalic acid and oxalic acid/Ca ratio were observed in the LG-Ch-B and HG-All treatments, respectively. Interactions between nutrients and physiological indicators were observed. The uptake of all micronutrients, P, and Mg (in both cultivations) and K (in the fall cultivation) was inhibited by high Ca concentration. With the decrease of micronutrients uptake, an increase in nitrate accumulation may occur because micronutrients are present in the structure of nitrate reducing enzymes. The interdependence between Mg and oxalic acid/Ca (in spring), K and oxalic acid (in fall), and Na and oxalic acid/Ca (in fall) may be related to the role of oxalates in the uptake of mineral ions by plants, since oxalates are usually combined with Na, Mg, Ca, and K in the form of soluble and insoluble salts. ConclusionThe use of urea chemical fertilizer (at two levels) and agricultural waste composts had different effects on the physiological indicators, growth and nutrients in spinach. Spinach grown in soils treated with composts rich in P, K, Mg, and Zn had higher nutritional value. The grouping of treatments by principal component analysis showed that chemical and control treatments were clearly separated from compost treatments with high amount of chlorophyll, carotenoid, nitrate, K, and Zn and low amount of oxalic acid, oxalic acid/Ca ratio, antioxidant activity, phenol, and Na. In general, the use of C500, LG-Ch-A, LG-All and HG-All treatments is not recommended due to nitrate accumulation in spinach.
Soil science
M. Amarloo; M. Heshmati Rafsanjani; M. Hamidpour
Abstract
IntroductionApplication of natural organic matter derived components, i.e. humic acid, as fertilizer is a suitable way to improve soil fertility and increase yield and quality of agricultural products. Many researchers reported positive effects of humic acid on water holding capacity, soil aeration, ...
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IntroductionApplication of natural organic matter derived components, i.e. humic acid, as fertilizer is a suitable way to improve soil fertility and increase yield and quality of agricultural products. Many researchers reported positive effects of humic acid on water holding capacity, soil aeration, root formation and development, microorganism activities, and availability of mineral nutrients in soil. Antagonistic interaction between soil phosphorus and some micronutrients, especially in calcareous soils, can cause micronutrients deficiency in plants. With regard to positive effects of organic compounds on bioavailability of mineral nutrients, it seems that humic acid can positively affect the phosphorus interaction with micronutrients. Therefore, investigation of the effects of humic acid incorporated into irrigation water, phosphate and iron fertilizers application, on nutrients concentration in plants and their interactions is considerable.Materials and MethodsThis study was carried out to investigate the effects of application of humic acid in irrigation water, and phosphate and iron fertilizers in soil, on corn growth and concentration of P, Fe, Mn, Zn, and Cu in corn tissues. To this aim, a factorial experiment was conducted based on completely randomized design, with three replications in greenhouse. The factors included humic acid in 0, 70, and 140 mg kg-1 levels, (7 times as fertigation during growth season; total use equal to 0, 490, and 980 mg kg-1 of soil, respectively), phosphorus (P, as monocalcium phosphate monohydrate) in 0 and 50 mg kg-1 levels, and Fe (as ferrous sulfate heptahydrate) in 0, 10, and 20 mg kg-1 levels. P and Fe treatments were mixed with 4 kg of air-dried soil (<2 mm in diameter) and filled to the pots. Six seeds of maize (Zea maye L. cv. Single cross 704) were seeded per pot, and three seedlings were finally kept and grown for two months. After harvest, fresh and dried weight of shoots were measured. The roots were accurately extracted from the soil, washed, dried at 65◦C, and weighed. Sample digestion and measuring concentration of P, Fe, Mn, Zn, and Cu were done according to conventional methods (P by a UV-Visible Spectrophotometer and metal elements by the GBS Savant Atomic Absorption Spectrometer). Statistical analyses were done by the IBM SPSS Statistics version 26 software.Results and DiscussionAccording to this study results, the main effect of humic acid, on P concentration and dry matter of shoots and roots, was statistically significant. In presence of P (2nd P level), 490 and 980 mg kg-1 humic acid levels significantly increased the mean of dry matter compared to blank while humic acid had no significant effect on means of shoots and roots dry matter in 1st level of P (no P application). Increasing humic acid level from 490 to 980 mg kg-1, significantly decreased mean of shoots dry matter. The interaction effect between humic acid and the other two factors exhibited statistical significance concerning root dry matter. The treatment combination of 50 mg kg-1 of P, 490 mg kg-1 of humic acid, and 20 mg kg-1 of Fe yielded the highest mean root dry matter, which was 97% greater than that of the control. The 2nd level of P significantly increased the means of shoots P concentration in all levels of humic acid and Fe factors, compared to those of the 1st P factor level. There was no significant difference between means of shoots P concentration in different levels of humic acid and Fe factors, at the 1st level of P factor, separately. On the other hand, at the 2nd level of P factor, significant differences were observed between the means of P concentration for both other factors (significant interaction between P and humic acid, and between P and Fe Factors). Applying humic acid could significantly increase the means of shoots P concentration at the 2nd level of P factor, but there was no significant difference between those of 490 and 980 mg kg-1 levels. About the effect of Fe factor on shoots P concentration, only 10 mg kg-1 level of Fe significantly increased it. The main effect of the P and humic acid factors and interaction of the P and Fe factor on roots P concentration, were statistically significant. Roots P concentration increased significantly by 490 and 980 mg kg-1 humic acid levels. A significant increase of roots P concentration was observed in the 1st P factor level and 10 mg kg-1 level of Fe compared to the blank, and in 50 mg kg-1 level of P, Fe factor had no significant effect on it. The results showed that humic acid could not improve P uptake by corn from the soil with low available phosphorus (Olsen extractable P lower than 4 mg kg-1). The humic acid factor had no significant effect on Fe concentration of corn shoots, but its main effect and its triple interaction, with two other factors, on Fe concentration of the roots were statistically significant. There was no significant difference between the means of roots Fe concentration at the 1st level of P factor (9 treatments, various levels of humic acid and Fe factors). The highest mean of root's Fe concentration was found in treatment of the highest level of each factor, significantly more than those of the most of other treatments. About the Mn concentration in corn tissues, the Mn concentration in shoots was significantly increased by P fertilizer application, and Mn concentration in roots was significantly affected and increased by 490 and 980 mg kg-1 humic acid levels. The means of Mn concentration of roots in 490 and 980 mg kg-1 humic acid were not significantly different. The Zn concentration of corn shoots was significantly affected by interaction of the P and humic acid factors as the highest mean of it was in 0 mg kg-1 of P and 980 mg kg-1 humic acid levels, and there was no significant difference between those of other levels. The Zn concentration of corn roots was significantly increased by P applying and affected by the interaction of humic acid and Fe factors. When humic acid was at zero concentration level, Fe application of 20 mg kg-1 significantly decreased the Zn concentration of corn shoots while with humic acid application (490 and 980 mg kg-1) no significant difference was observed between the means. This result showed that humic acid can decrease the antagonistic effects of Fe and Zn in soil. The Cu concentration in shoots was significantly affected by the P and Fe factors. Usage of P fertilizer significantly increased the Cu concentration of corn shoots; on the contrary, the 2nd and 3rd levels of Fe factor (Fe applications) significantly decreased Cu concentration in shoots of corn. Moreover, using humic acid could significantly increase Cu concentration of corn roots without any significant interaction with the other two factors.ConclusionThe findings suggest that in soils with very low available P, humic acid alone does not enhance the growth and dry matter yield of corn. However, the efficiency of phosphate fertilizer can be enhanced by applying humic acid fertilizer through irrigation water. Additionally, humic acid has been observed to mitigate antagonistic effects between P and certain micronutrients, as well as reduce antagonistic interactions among metal micronutrients. For the positive effect of humc acid on growth and adequate chemical composition of corn, concentration of 490 mg kg-1 humic acid is recommended.
Soil science
Tahmeineh Gheitasi Ranjbar; M. Nael
Abstract
IntroductionConventional cropping systems, dependent on heavy application of chemical fertilizers, are not ecologically and environmentally sustainable; they are a threat for soil and water quality and, in consequence, for plant and human health. Nitrogen fertilizers are heavily applied in conventional ...
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IntroductionConventional cropping systems, dependent on heavy application of chemical fertilizers, are not ecologically and environmentally sustainable; they are a threat for soil and water quality and, in consequence, for plant and human health. Nitrogen fertilizers are heavily applied in conventional leaf vegetable production systems to obtain maximum growth and yield. However, the excess nitrogen tends to accumulate in leaf vegetables in the form of nitrate, which pose serious human health hazards. Therefore, to supply nitrogen from non-chemical sources, such as organic amendments, is a sustainable practice for production of leaf vegetables. Spent mushroom substrate (SMS), which is the remaining material after the harvest of mushroom, is produced in large quantities (5 kg SMS for 1 kg of mushroom) and is enriched with organic carbon, N, P, K, and micronutrients. Therefore its reuse as a soil amendment not only provides essential elements for plants but also improves soil quality. Similarly, incorporation of green manures, especially legume green manures, into cropping systems is a sustainable practice for soil fertility and soil quality management. In this study, we aimed to investigate the short-term effects of two soil organic amendments (spent mushroom substrate and alfalfa residues) and their combination, in comparison to inorganic N fertilizer (urea), on soil fertility, and selected essential nutrients, and nitrate accumulation in a leaf vegetable, test plant (spinach). Materials and MethodA one-season pot experiment was led in a randomized complete block design with three replications in experimental greenhouse of Bu-Ali Sina University. Treatments were comprised of two levels of spent mushroom substrate (SMS-1: 2% SMS, and SMS-2: 5% SMS), two levels of alfalfa green manure (AGM-1: 1% AGM, and AGM-2: 3% AGM); two levels of the mixture of SMS and AGM (SMS+AGM-1: 1% SMS plus 0.5% AGM; and SMS+AGM-2: 2.5% SMS plus 1.5% AGM); two levels of urea fertilizer (U-1; 120 kg/ha, and U-2: 360 kg/ ha); and control. Selected properties of the initial soil and both organic amendments were determined. Spinach (Spinacea oleracea L.) was seeded as leaf vegetable, test plant in early autumn 2017. After ten weeks, spinach were harvested and the aboveground and root dry weights were determined. Moreover, the content of NO3-, P, Fe, Cu, Zn, and Mn in edible parts were measured. Soil samples were analyzed for EC, pH, total organic carbon, available P and K, and alkaline phosphatase activity.Results and DiscussionAll soil quality indicators were significantly affected by the treatments. TOC was significantly increased in all of the organic treatments compared to the chemical and control treatments. The maximum increase in TOC was observed in SMS-2, SMS+AGM-2, and AGM-2 treatments, compared to the control (134, 130 and 107%, respectively). A decreasing trend in TOC was detected in the high level of urea treatment (U-2) compared to the control which can be explained by the faster decomposition of soil organic matter in the presence of higher inorganic N inputs. Both organic amendments (in both levels) and the higher level of urea (U-2) decreased soil pH compared to the control. The initial low pH of SMS (5.6) and AGM (6.2), in the first case, and oxidation of urea to nitrate, in the latter, may justify this observation. In contrast, soil EC increased under the both organic amendments relative to the control and U-1 treatments. Moreover, the adverse effect of SMS on soil salinity was greater than AGM due to the initial differences in their corresponding source materials (5.8 vs. 3.0 ds/m). Available K was significantly increased in the second level of all organic treatments compared to the chemical and control treatments. As for available P, all organic treatments, except AGM-1, led to the significantly higher P than the chemical and control treatments. It is reported that organic materials compete with mineral particles for P adsorption and increase its availability. Moreover, all organic treatments, except SMS-1, significantly increased phosphatase activity compared to the chemical and control treatments. This could contribute to the mineralization of organic materials and increase available P. Spinach yield was affected by the experimental treatments. The highest increase in shoot dry weight occurred in SMS+AGM-2 and AGM-2 treatments by 235 and 230%, respectively, compared to the control. Moreover, the second level of all organic treatments as well as the first level of SMS plus AGM treatment significantly increased yield compared to the chemical treatments. Spinach P content was significantly higher in all organic treatments, except SMS-1 and AGM-1, compared to the chemical and control treatments. Organic amendments, by decreasing the surface adsorption of P and increasing soil microbial biomass, promote the availability of P for plants. Spinach nitrate content ranged from 265 (in control) to 7807 mg/kg (in U-2). According to the critical limit of nitrate in spinach (4000 mg/kg) presented by European Union, only U-2 treatment led to over-accumulation of NO3-. The two levels of AGM treatments and SMS+AGM-2 resulted in the comparable amounts of nitrate as the recommended amount of urea (U-1). A narrow variation in spinach Cu content (from 6.1 in SMS+AGM-2 to 9.8 mg/kg in AGM-2), all within the standard range reported for plants (5-20 mg/kg), was observed among the treatments. Spinach Fe content was increased under all organic treatments relative to the control, although some disparities were not significant. The lowest Fe was detected in U-2. It is reported that excessive N may diminish root growth and, in turn, reduce nutrient uptake. Spinach Zn content varied from 44.8 (in control) to 71.5 mg/kg (in SMS-2), which was close to the higher limit of standard range (20-50 mg/kg) reported for vegetables, but lower than toxic concentration range (200-400 mg/kg). Spinach Mn content varied from 17.4 (in control) to 32.1 mg/kg (in SMS-2), which was close to the lower limit of the standard range (40-400 mg/kg) reported for plants.ConclusionThe most appropriate treatments in view of improving yield and soil quality (i.e., optimum TOC, P, and K; and lower EC) as well as tolerable nitrate accumulation were SMA+AGM-1 and SMS-1 in decreasing order. These treatments are preferred over the chemical treatments (U-1 and U-2).
A. Abtahi; M. Hoodaji; M. Afyuni
Abstract
The objectives of this research were to study the effect of three kinds of biosolids applications such as urban compost, sewage sludge, cow manure and chemical fertilizers (sulphates of Zn, Fe) concentration on soil and corn plant. Two calcareous soils having different textures (sandy loam and clay loam) ...
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The objectives of this research were to study the effect of three kinds of biosolids applications such as urban compost, sewage sludge, cow manure and chemical fertilizers (sulphates of Zn, Fe) concentration on soil and corn plant. Two calcareous soils having different textures (sandy loam and clay loam) were used in order to study the uptake of the above zinc and iron by corn. This study was carried out in pots in a greenhouse using a factorial experiment design which was block completely randomized and each treatment was replicated three times. The levels of biosolids used were 0, 25, 50 Mg ha-1 and chemical fertilizers applied were as (Zn and Fe) sulphates. Seventy five days after corn seeds were sown; young plants at 4 to 5 leaf stage were harvested and made ready for chemical analyses. Results of the soil analysis showed that in sewage sludge treatment (50 Mg ha-1) the CEC, and the DTPA extractable (Zn and Fe) increased significantly compared to control and other treatments in soils. Cow manure treatment (50 Mg ha-1) had a significant effect on OM, and EC. Result of the plant analysis showed that in the sewage sludge treatment the concentration of Zn in the roots, and the concentrations of Zn, Fe in the shoots increased significantly. In general, corn yields increased significantly in the sewage sludge treatment compared to the other treatments in clay loam soils. Generally, the results of this study showed that biosolid application including sewage sludge increased concentration of micronutrients (Zn and Fe) in soil and corn plant.
