In order to study the effect of Tehran municipal solid wastes compost on manganese accumulation in soil and to determine its concentration in any readily available plant forms (exchangeable and carbonates-bonded), Mn-oxides bonded fraction, organic matter bonded fraction, and residual fraction in a calcareous soil, a factorial experiment based on completely randomized block design (RCBD) was conducted in research field of Shahed university at different levels of municipal solid wastes compost (0, 15, 30, and 60 ton/ha) as first factor and application times (one- or two-year compost application) as second factor in three replications. Results showed that, by increasing compost level, total Mn concentration, DTPA-extractable concentration, and amounts existing in all five fractions were increased, so lowest and highest amounts of Mn were observed in control and 60 ton/ha compost application. Based on results from Mn fractionation using Tessier consecutive extraction method, Mn fractions in all samples were in the following order: residual > Fe-Mn oxides > carbonates-bonded > organic matter-bonded ≫ exchangeable fractions in which residual fraction (RE) at first and second year was dominant rather than other fractions by 34.28–43.04 and 34.28–49.48 percent, respectively. Mn concentration in Fe-Mn oxides-bonded fraction at both years was considerable. Mn amounts in Fe-Mn oxides- bonded, application times were decreased.
The importance of microelements for plants has already been well documented in the literature. Manganese is an essential micronutrient for all organisms, playing an important role in tissue and bone formation, in reproductive functions, and in carbohydrate and lipid metabolisms and is an important cofactor in numerous enzymes [
Physiochemical forms of nutrients among soil components determine nutrients mobility and transferring and consequently their availability. By considering the different forms of heavy metals in soil and their changes, we could become aware of nutrients status and eventually we can plan for decrease of their absorption by plant and consequently preventing their contaminant effects by reducing transfer of these nutrients to food chain and water resources [
In order to determine plant’s available form of nutrients, different extractors were used. It should be noted that initial purpose of each chemical extraction method is to evaluate the available amount of a nutrient for plants [
Nadaska et al. [
The aim of the present research was to determine the fractionation of manganese in the soil in the conditions of two-year application of Tehran municipal solid waste compost in a calcareous soil. Our study can contribute to better understanding of the multidirectional transformation of those elements and to an evaluation of the amount of bioavailable forms.
In order to evaluate the different levels of Tehran municipal solid waste compost on manganese (Mn) concentration and distribution in different soil fractions, an experiment was conducted in research station of agriculture faculty of Shahed University (35°34′N latitude and 51°34′E longitude). With regard to slow releasing of metals from municipal solid waste (MSW) compost, in addition to different compost application levels, compost application times are tested. Therefore, experiment was conducted as split plot (compost amounts in main plots and application times in secondary plots) in three replications on 2011-2012 and 2012-2013 cropping years. But considering homogenous conditions in experimental blocks and nonsignificant errors in main plots, traits were analyzed as factorial based on completely randomized block design (RCBD). Experimental factors including four levels of MSW application (0, 15, 30, and 60 ton/ha) were considered as first factor and compost application times (annual and biannual application) as second factor. So, main plot characterized in first year and different treatment levels were added to plots on April 2012. On April 2012, plots were divided into two parts and in one part compost was added to soil in equal amount of previous year.
After few months and reaching balance in soil, 24 soil samples were collected from surface soil of plots and after air-drying and sieving from 2 mm sieve, some of soil physical and chemical properties were determined, including saturation percent, saturated extract preparing, EC and pH [
Results from determination of soil physical and chemical properties before applying treatments are presented in Table
Results of soil physical and chemical properties.
Texture | O.C (%) | EC (dS/m) | pH | CCE (%) | CEC (cmol/kg) | Fe (mg/kg) | Mn (mg/kg) | ||
---|---|---|---|---|---|---|---|---|---|
Total | Available | Total | Available | ||||||
Loam | 1.17 | 10 | 8.28 | 11.5 | 12.13 | 25712.5 | 2.78 | 1247.92 | 11.89 |
Table
Analysis of variance and mean square values of total manganese, DTPA, and various components of municipal solid waste compost in two years.
Sources of variation | Degree of freedom | Mn | ||||||
---|---|---|---|---|---|---|---|---|
EX | CA | FM | OM | RE | DTPA | Total | ||
Repeat | 2 | 0.0047 | 23.752 | 20.839 | 0.063 | 715.367 | 1.845 | 158.327 |
MSW | 3 | 6.224 | 5114.509 | 1239.928 | 7.563 | 83627.076 | 18.613 | 34566.166 |
Application time | 1 | 0.484 | 338.701 | 606.417 | 12.499 | 54102.51 | 37.697 | 4686.376 |
Time × MSW | 3 | 0.077 | 144.723 | 85.137 | 1.769 | 6955.364 | 4.308 | 1130.339 |
Error | 14 | 0.00465 | 41.417 | 17.148 | 0.065 | 360.789 | 1.609 | 38.9 |
Coefficient of variation | 1.575 | 2.805 | 1.105 | 4.258 | 8.757 | 8.77 | 0.47 |
Table
Mean comparison of total and DTPA-extractable concentrations and existing amounts in 5 different soil fractions for Mn, respectively, at different levels of MSW.
MSW | Mn | ||||||
---|---|---|---|---|---|---|---|
T ha | EX | CA | FM | OM | RE | DTPA | Total |
(mg kg | |||||||
Control | 3.156 | 192.64 | 356.347 | 4.466 | 290.42 | 11.889 | 1247.917 |
15 | 3.871 | 220.827 | 372.06 | 5.945 | 388.83 | 14.802 | 1288.458 |
30 | 4.825 | 246.453 | 378.833 | 6.493 | 431.04 | 15.269 | 1324.375 |
60 | 5.461 | 258.413 | 390.8 | 7.088 | 574.71 | 15.847 | 1425.272 |
Similar letters in each column show nonsignificant difference at 5% probability level according to Duncan’s multiple range test.
Formation of stable metal complexes could decrease solubility of metal ions in soils [
Table
Mean comparison of total and DTPA-extractable concentrations and existing amounts in 5 different soil fractions for Mn, respectively, at application times.
Application times | Mn | ||||||
---|---|---|---|---|---|---|---|
T ha | EX | CA | FM | OM | RE | DTPA | Total |
(mg kg | |||||||
One time | 4.186 | 233.34 | 369.483 | 5.276 | 373.77 | 13.198 | 1307.532 |
2 times | 4.47 | 225.827 | 379.537 | 6.72 | 468.73 | 15.705 | 1335.479 |
Similar letters in each column show nonsignificant difference at 5% probability level according to Duncan’s multiple range test.
In the present study, consecutive extraction method, as described by Tessier et al. [
Table RE > FM > CA ≫ OM > EX
Residual fraction (RE) in first and second year was dominant rather than other fractions in 34.28–43.04 and 34.28–49.48 percent, respectively.
Fe and Mn oxides fraction (FM) at both years was considerable, so after one year compost application changed from 42.07 percent in control treatment to 33.46 percent in 60 ton/ha compost. These amounts for second year of compost application reached 29.98 percent in 60 ton/ha treatment. As realized, Mn amounts in reductive fraction, after increasing compost levels and compost application times, were decreased. Exchangeable fraction’s (EX) proportion at first year for control, 15, 30, and 60 ton/ha was 0.37, 0.38, 0.45, and 0.46 percent of total extracted fractions and for second year in all treatments was very low because of higher increase in proportion of other fractions.
Proportion of carbonates-bonded fraction (CA) was considerable for Mn. Its proportion from total Mn for compost treatments by 0, 15, 30, and 60 ton/ha at first year were 22.74, 24.53, 24.99, and 22.47 percent and at second year were 22.74, 20.21, 21.40, and 19.52 percent. Mn proportion organic matter bonded fraction (OM) at one-year application was 0.49 to 0.55 and at two-year compost application was 0.52 to 0.69 percent.
Ghaffari Nejad and Karimian [
Results from interactions of different levels of municipal solid wastes compost and application times on Mn concentration at different fractions are shown in Figure
Effect of interactions between compost application levels and compost application times over two consecutive years on various components of manganese concentration in soil. Letters a–g indicate significant difference between means according to Duncan multiple range test at 5% probability level.
Mn concentration in exchangeable phase (instable position) increased from 3.156 mg/kg soil at control treatment to 5.563 mg/kg in two-year application of 60 ton/ha compost. Oxidation and reduction of soil Mn could occur simultaneously (but independently) at close positions [
Higher amounts of Mn in other soil fractions (stable positions) are related to residual fraction and the lowest amount is related to organic matter-bonded fraction. Mn existed in reductive, oxidative, and residual fractions significantly increased by increasing compost application at one-year as well as increasing application times from one-year to two-year. Mn content increasing could be due to the effect of time on conversion of soil Mn to more stable form. Also, results showed that almost in all studied samples, carbonate-bonded fraction after residual and Fe and Mn oxides has the highest Mn amounts. Mn amount in this fraction after addition of compost levels, separately in each year, significantly increased (
Organic matter-bonded fraction was followed by residual, Fe-, and Mn-oxides and carbonates-bonded fractions. Changes of this fraction are in the range between 4.46 mg/kg in control and 7.74 mg/kg in two-year 60 ton/ha compost application which is lower than carbonate-bonded, Fe and Mn oxides, and residual fractions but higher than that for exchangeable fraction. Mn in the form of organic matter bonded form increased by addition of compost from 0 to 15, 30, and 60 ton/ha at first and second years by 4.7, 23.76, 44.17, and 61.65, 67.26, and 73.54 percent (Figure
Fractionation of manganese after one-year (a) and two-year (b) application of municipal solid waste compost.
Results from correlation between soil physical and chemical properties and total and available forms as well as exchangeable, carbonates-bonded, Fe-Mn oxides-bonded, organic matter bonded, and residual fractions of Mn are shown in Table
Correlation coefficient between soil physical and chemical properties and total and available forms of Mn.
Mn Forms | EC | pH | OC | CCE | CEC |
---|---|---|---|---|---|
ds m | — | % | cmol | ||
EX | 0.98 | −0.88 | 0.93 | −0.36 | 0.98 |
CA | 0.90 | −0.83 | 0.78 | −0.50 | 0.86 |
FM | 0.91 | −0.89 | 0.95 | −0.40 | 0.93 |
OM | 0.81 | −0.84 | 0.92 | −0.33 | 0.82 |
RE | 0.89 | −0.83 | 0.94 | −0.39 | 0.90 |
DTPA | 0.91 | −0.99 | 0.93 | −0.60 | 0.88 |
| |||||
Total | 0.94 | −0.80 | 0.94 | −0.38 | 0.95 |
Ghaffari Nejad and Karimian [
Results showed that, by increasing compost level, total concentration of Mn and DTPA-extractable concentrations in all fractions increased, so that lowest and highest amounts of Mn were observed in control and 60 ton/ha compost application.
Mn fractionation showed that the highest amount was associated with residual fraction and the lowest amount was for organic matter bonded fraction. Mn existed in Fe-Mn oxides and organic matter-bonded and residual fractions increased by increasing compost application amount at first-year and two-year compost application further increased Mn content in all fractions. This represents the effect of time on conversion of more amounts of soil Mn to more stable forms. Also, results showed that, almost in all studied samples, carbonates-bonded fraction after residual and Fe-Mn oxides fraction had the highest Mn amounts. Exchangeable fraction (EX) contribution at first year for 0, 15, 30, and 60 ton compost/ha was 0.37, 0.38, 0.45, and 0.46 percent from the sum of all extracted fractions and in second year very low amounts were obtained, but exchangeable Mn amount after addition of compost and increase in application time to two years significantly increased.
The authors declare that they have no competing interests.
The authors gratefully acknowledge the support of Iran National Science Foundation (INSF) for conducting the present study.