INTRODUCTION
Application of organic wastes as a source of organic matter is a common
practice to improve soil properties (Baran, 2001). Land disposal of organic waste
materials may directly or indirectly alter the trace element status of the soil by
affecting elements solubility or dissociation kinetics (Del et al., 1993). Distribution
of trace element between soil and solution is the key to evaluated the
environmental impact of the metals. Despite the complexity of possible reaction,
several important soil factors controlling the distribution of heavy metals between
soil and solution have been identified (Sposito, 1989 and Temminghoff et al.,
1998).
The effect of soil pH on soil solution concentrations and extractability of
metals have been studied. He and Singh (1993) found that peat addition
increased DTPA-extractable Cd in soil due to decrease in soil pH caused by peat
application. Arnesen and Singh (1999) found that the lowing of pH in peatamended
soil decreased the sorption of Cd, Cu, Zn and Ni in the soil. Organic
matter makes strong complexes with heavy metals (Krogstad, 1983). The
amount of organic matter in soils affects the binding of heavy metals in soil and
speciation in soil solution (Lo et al., 1992). High organic matter content or
addition of organic matter increases the extractability of Zn (Arnesen and Singh,
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1999). Amendment with organic matter and the resulting degradation may
change the soil pH and thereby indirectly affect the bio-availability of metals.
Many authors have found that all types of organic material increased the
extractability of Zn in soil (Arnesen and Singh 1999). Also, Hossien, (2008)
stated that the pH of treated soils with lemon waste was decreasesd slightly with
increasing with the amount of lemon waste and time of sampling. Moreover,
Gigliotti et al. (1996) observed significant increase with Cu, Zn, Pb and Cr
concentrations in clay-loam calcareous soil amended with urban waste compost.
Furthermore, Romero et al. (2005) found that the mount of soluble and AB-DTBA
extractable Pb and Zn the mine tailing were increased by application of the olivemill
solid waste and to a lesser degree, by the compost from the olive waste.
Addionally, Hamidpour et al. (2012) in 3-years field study, conducted to assess
effects of composted municipal waste on some properties, distribution of Zn, Cu
in a calcareous soil and uptake of these metals by wheat, showed that
application of composted municipal waste decreased the soil pH and a significant
increaseed the concentrations of Zn and Cu with increasing number and rate of
compost application. Also, Bloomfileld and Pruden (1975) stated that the
availability of Cu, Zn, Mn, Fe and P in soils increased with increasing the applied
amount of lemon waste and time of incubation.
The objective of this study was, therefore, to evaluate the effect of three
organic materials (compost, olive waste and lemon waste) on the availability of
(Fe, Mn, Cu and Zn) as a function of pH in calcareous soil.
MATERIALS AND METHODS
The Used Soil and Organic Wastes: Soil was collected from surface horizon (0-
30 cm) from Matruh city at north western coast of Egypt. The soil was air-dried,
ground and passed through a 2-mm sieve.
The tested organic materials were combost , olive waste and lemon waste
which were ground and passed through 6.35 mm sieve. The main properties of
the soil and the organic materials were determined according to the methods
outlined by page et al. (1982). Some physical and chemical properties and the
amounts of heavy metal of the sample and organic materials are given in Tables
(1 and 2).
Incubation trial: The rates of organic material added the soil were 0, 0.5, 1.0,
1.5 and 2 % of the air-dried soil on dry weight basis. The soils were homogenized
with the dry organic materials and filled in plastic pots (4 cm deep and 10 cm
diameter). Each pot consisted of 100 g soil with the various rate of organic
materials. During the incubation periods (4, 8, 12 and 16 weeks) and the ambient
temperature was 23 to 30 C° at the summer, the distilled water was added to
each pot to keep the moisture content close to the filed capacity. Each treatment
was repeated three times and the experimental layout was split plot design. Soil
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samples were taken on the 4th (1st time), 8th (2nd time) 12th (3rd time) and 16th (4th
time) weeks after incubation and analyzed for pH and DTPA extractable Fe, Mn,
Cu and Zn. (Lindsay and Novvell, 1978).
Sample analysis: Soil pH and electrical conductivity (EC) was measured in 1:2,
soil: water ratio according to Jackson (1973). Organic matter content in soil was
determined by the method of Walkley and Black (Jakson, 1973). Particle size
distribution was determined according the method outlined in Black (1965).
Available Fe, Mn, Cu and Zn in soils were extracted with a DTPA method (0.005
M DTPA + 0.005M CaCl2+ 0.1M TEA, pH 7.3), according to Lindsay and Novvell,
(1978). The organic materials were tested by digestion in H2SO4 and H2O2
(Lowther, 1980) for total heavy metals determination. The concentration of Fe,
Mn, Cu and Zn were measured by atomic absorption spectrophotometer (AAS).
The obtained data were statistically analyzed according to the technique of
analysis of variance (ANOVA) and the least significant difference (L.S.D) was
used to test the difference between the treatment means, as described by
Gomez and Gomez (1984).
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Table (1): some physical and chemical properties of the used soil
soil properties means
Particle size distribution (%)
Clay 25
Sand 42
Silt 33
Textural class Loam
EC (dS/m) 1:2 0.29
pH 1:2 8.13
O.M (%) 1.30
CaCO3(%) 25.4
Water Soluble anions (mg/kg)
HCO3
- 5.600
Cl- 2.800
SO4
= 0.029
Water Soluble cations (mg/kg)
Na+ 14.0
K+ 9.33
Ca+2 9.40
Mg+2 5.40
Available micronutrients (mg/kg)
Fe 0.202
Cu 0.145
Zn 0.746
Mn 1.335
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Table (2): Some chemical properties of the used organic materials
Chemical organic materials
property Olive waste compost Lemon waste
pH (1:2) 5.6 7.02 3.26
EC(dS/m), 1:2 7.3 7.10 7.20
O C (%) 40.7 17.4 86.0
Total N (%) 5.16 5.32 6.68
Total P (%) 0.042 0.013 0.044
Soluble cations (mg/kg)
K+ 38.7 23.5 40.7
Na+ 22.5 27.5 15.0
Ca+2 24. 0 16. 0 14.0
Mg+2 7.80 4.0 2.30
Soluble anions (mg/kg)
SO4
= 40.5 49.11 51.25
Cl- 20. 0 22. 0 21. 0
Available micronutrients (mg/kg)
Fe 0.427 2.634 1.923
Zn 2.500 3.146 1.079
Cu 0.006 0.226 0.437
Mn 0.180 3.284 0.600
RESULTS AND DISCUSSION
Soil pH: Table (3) showed a significant effect of organic material type at each
time of sampling, on the soil pH except at the second time of sampling.
Table (4) indicated a significant effect by decrease as results of present of
organic material, whether with respect to the type or the rate and their interaction,
except at the second time of sampling on soil pH. The decreases in pH were
noted with increasing time of sampling. The fourth time of sampling was
significant lower soil pH.
Table (4) showed also significant effects of the different organic materials
on soil pH all incubation periods, except at the second time of sampling for pH.
The lowest value of pH (averaged 7.32) was recorded at the fourth time of
sampling with olive waste. Soil pH has decreased slightly due to the acidity
indicated by the disposal of raw olive waste. It can be concluded, therefore, that
due to the carbonate content of the soil, the surface application of olive waste
does not markedly affect soil pH (Mechri et al., 2007).
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Regarding to the effect of organic material rate on soil pH, the data
presented in (Table 4) indicated that the rate of organic material has significant
effect on pH at each time of sampling, except at that of the second time.
Decreasing pH values with increasing rate of organic material were observed at
each time of sampling and with increasing time of incubation. These results are
agree with those obtained by Hossien (2008), Claudia et al. (2012) and
Kavvadias et al. (2012).
The interaction effect of organic waste types and rate of application the
results showed significant decreased of soil pH, except at the second time of
sampling (Table 3). The highest value of soil pH was observed at the first time of
sampling without organic material (8.05). On the other hand, the lowest values of
pH were found at the fourth time of sampling using 2% olive waste (pH=7.01).
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Table (3): soil pH as affected by type and rate of organic
materials and incubation periods
Organic material Time of Soil Sampling
Type Rate, % 1st time 2nd time 3rd time 4th time
Olive Waste
0.0 8.05 8.00 7.80 7.79
0.5 8.00 7.94 7.65 7.40
1.0 7.94 7.91 7.60 7.26
1.5 7.89 7.80 7.52 7.16
2.0 7.80 7.76 7.04 7.01
Compost
0.0 8.05 7.80 7.80 7.79
0.5 8.00 7.98 7.71 7.50
1.0 7.96 7.90 7.60 7.31
1.5 7.92 7.80 7.55 7.12
2.0 7.90 7.78 7.25 7.09
Lemon Waste
0.0 8.05 8.00 7.80 7.79
0.5 7.96 7.90 7.63 7.54
1.0 7.87 7.80 7.56 7.25
1.5 7.73 7.69 7.40 7.12
2.0 7.70 7.50 7.15 7.07
Statistical significance (LSD 0.05)
O.M type (M) 1.65E-07 N 9.53E-08 0.032
Rate of O.M (R) 2.13E-07 N 1.23E-07 0.042
M x R 0.412 N 2.38E-08 8.348E-3
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Available Trace Elements in soil:
Table (5) showed that the organic material types, rates of application and
their interactions significantly influenced the amounts of available Fe, Cu, Zn and
Mn in soil at all time of samplings, except those of available Cu at the fourth time
of sampling and available Zn at the first and third time of sampling. Also, the
means of available Fe, Cu, Zn and Mn (Table 6) showed that the compost gave
the highest values of available Fe, Mn and Zn at the fourth time of sampling
(5.41, 22.04 and 5.02 mg/kg soil, respectively). However, the olive waste gave
the highest value of available Cu (5.11 mg/kg soil) at the fourth time of sampling
and the lemon waste gave the lowest value of available Zn at the first time of
sampling (1.80 mg/kg soil). It is also leas that, the olive waste gave the lowest
value of available Fe and Mn at the first time of sampling (0.67 and 16.32 mg/kg
soil, respectively), while the compost gave the lowest value of available Cu at the
first time of sampling (1.30 mg/kg soil).
Generally, the amounts of available Fe, Cu, Mn and Zn were increased with
increasing organic material application rates and increasing time of sampling
(Table 5). The highest values of available Fe (6.16 mg/kg soil), Zn (6.21 mg/kg
soil), Mn (23.87 mg/kg soil) and Cu (6.71 mg/kg soil) were recorded for 2%
organic materials rate at the fourth time of sampling. The increases of available
micronutrients could be explained by the production of CO2 and forming H2CO3
during organic material decomposing. Nader et al. (2008) reported that the
Table (4): Mean values of soil pH at each time of sampling
as affected by the type and rate of organic materials
Treatments
Time of Sampling
1st time 2nd time 3rd time 4th time
Organic material type
Olive Waste 7.80 7.76 7.04 7.01
Compost 7.90 7.78 7.25 7.09
Lemon Waste 7.70 7.50 7.15 7.07
LSD 0.05 1.65E-07 N 9.53E-08 0.03
Rate of organic material, %
0.0 8.05 7.93 7.89 7.79
0.5 7.99 7.94 7.66 7.48
1.0 7.92 7.87 7.59 7.27
1.5 7.85 7.76 7.49 7.13
2.0 7.80 7.68 7.15 7.06
LSD 0.05 2.13E-07 N 1.23E-07 0.04
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solubility increased of micronutrients in the soil may be due to lowering pH and
air water balance. The compost applied causes high amount of O.M, and its
oxidation and degradation would increase the micronutrients availability in soil
(Gallardo-lara and Nogales, 1987). Increasing concentrations of Zn and Fe after
organic waste application were also reported by Ageel and Hamed (2007).
According to Piotrowska et al. (2006), the increase of extractable Fe can be
attributed to the fact that this metal catalyze the oxidative transformation of
phenols present in soil.
The interaction between organic waste type and rates of application had
significant effect on the amounts of available Fe, Cu, Zn and Mn at all time of
sampling, except available Cu at fourth time of sampling and Zn at first and third
sampling, (Table 5). The highest values of available Fe, Zn and Mn were
obtained at the fourth time of sampling with 2 % compost (7.10, 7.44 and 24.88
mg/kg soil, respectively). On the other hand, the highest value of available Cu
was obtained at the fourth time of sampling with 2% olive waste (7.45 mg/kg
soil). However, the lowest values of available Fe, Cu, Zn and Mn were obtained
at the first time of sampling without organic materials.
Table (7) showed regression equations for the relation between the
available Fe (Y1), Cu (Y2), Zn (Y3) and Mn (Y4) and the organic material rate (X).
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Table (5): The amounts of available Fe, Cu, Zn and Mn in the soil (mg/kg) at each time of sampling as affected
by type and rate of material application
Organic
material
Fe Cu Zn Mn
Time of Sampling Time of Sampling Time of Sampling Time of Sampling
Type Rate, %
1st
time
2nd
time
3rd
time
4th
time
1st
time
2nd
time
3rd
time
4th
time
1st
time
2nd
time
3rd
time
4th
time
1st
time
2nd
time
3rd
time
4th
time
Olive Waste
0.0 0.31 0.34 0.34 0.34 0.73 1.30 1.30 1.30 1.41 1.47 1.47 1.47 15.22 15.53 15.53 15.53
0.5 0.39 0.75 0.8 4.49 1.02 1.89 3.49 4.48 1.64 1.96 2.64 2.95 15.6 15.88 15.96 18.74
1.0 0.44 1.05 1.43 5.9 1.36 2.57 5.14 5.41 2.33 2.55 2.87 3.02 15.9 16.52 18.00 18.79
1.5 0.65 1.61 2.19 6.19 1.37 2.59 5.78 6.91 2.74 2.86 3.29 3.84 16.84 17.98 19.80 20.33
2.0 1.54 3.11 3.22 6.48 2.03 3.9 7.01 7.45 2.96 3.56 3.73 4.19 18.09 21.00 21.12 22.48
Compost
0.0 0.31 0.34 0.34 0.34 0.73 1.30 1.30 1.30 1.41 1.47 1.47 1.47 15.22 15.53 15.53 15.53
0.5 0.56 0.61 0.96 6.32 0.96 1.76 2.27 3.11 1.86 1.87 2.19 4.76 15.93 16.67 17.98 22.88
1.0 0.77 0.86 1.14 6.45 1.09 2.03 3.21 3.75 2.10 2.49 3.00 5.03 16.21 18.00 19.80 22.90
1.5 1.15 1.54 2.21 6.83 1.46 2.76 3.5 5.33 2.53 3.2 3.8 6.38 18.14 21.24 19.93 24.00
2.0 1.28 1.74 3.39 7.1 1.61 3.07 5.25 6.23 3.72 4.08 5.43 7.44 20.38 23.8 23.96 24.88
Lemon Waste
0.0 0.31 0.34 0.34 0.34 0.73 1.30 1.30 1.30 1.41 1.47 1.47 1.47 15.22 15.53 15.53 15.53
0.5 0.41 0.65 0.85 3.22 1.46 2.76 3.32 4.12 1.34 1.68 3.08 3.14 15.86 15.89 16.92 18.2
1.0 0.83 0.73 1.22 4.01 1.75 3.35 3.86 4.74 1.81 2.08 3.35 3.64 16.13 17.22 18.61 20.00
1.5 1.16 1.42 1.28 4.18 2.02 3.89 3.91 5.77 2.05 2.54 3.73 6.75 16.9 19.06 20.91 24.00
2.0 1.35 1.52 2.18 4.90 2.17 4.19 4.52 6.45 2.4 2.86 4.81 7.01 17.74 20 49 24.25
STATISICAL SIGNIFICAN LSD, 0.05
O.M type (M) 0.005 0.0046 0.0019 0.0062 0.0033 0.002 0.037 N N 3.37E-08 N 4.77E-08 0.137 0.126 1.155 0.031
Rate of O.M (R) 0.006 0.0036 0.0025 0.0079 0.0043 0.003 0.047 N N 4.35E-08 N 6.15E-08 0.176 0.162 1.492 0.04
M x R 1.181 8.93E-04 1.52E-04 1.54E-03 8.38E-04 4.82E-04 9.15E-03 N N 8.40E-09 N 1.19E-08 7.69E-03 0.288 0.031 0.01
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Table (6): Means of Fe, Zn, Mn and Cu (mg/kg) at each time of sampling as affected by the type and rate of
organic materials
Treatments
Fe (mg/kg) Cu (mg/kg) Mn (mg/kg) Zn (mg/kg)
Time of Sampling Time of Sampling Time of Sampling Time of Sampling
1st
time
2nd
time
3rd
time
4th
time
1st
time
2nd
time
3rd
time
4th
time
1st
time
2nd
time
3rd
time
4th
time
1st
time
2nd
time
3rd
time
4th
time
Organic material type
Olive Waste 0.67 1.37 1.59 4.68 1.30 2.45 4.54 5.11 16.32 17.38 18.08 19.17 2.22 2.48 2.8 3.09
Compost 0.81 1.02 1.61 5.41 1.17 2.18 3.11 3.94 17.18 19.05 19.44 22.04 2.32 2.62 3.18 5.02
Lemon Waste 0.81 0.93 1.17 3.33 1.63 3.1 3.38 4.48 16.37 17.54 24.19 20.4 1.8 2.12 3.29 4.4
LSD 0.05 0.005 0.005 0.0019 0.006 0.003 0.002 0.035 N N 3.37E-08 N 4.77E-08 0.137 0.126 1.155 0.031
Rate of organic material, %
0.0 0.32 0.34 0.34 0.34 0.73 1.30 1.30 1.30 15.21 15.53 15.53 15.53 1.41 1.46 1.47 1.47
0.5 0.45 0.67 0.87 4.68 1.15 2.14 3.03 3.90 15.8 16.15 16.95 19.94 1.61 1.84 2.64 3.62
1.0 0.68 0.88 1.26 5.45 1.4 2.65 4.07 4.63 16.08 17.25 18.8 20.56 2.08 2.37 3.07 3.9
1.5 0.99 1.52 1.89 5.73 1.62 3.08 1.40 6.00 17.29 19.43 20.23 22.78 2.44 2.87 3.61 5.66
2.0 1.39 2.12 2.93 6.16 1.94 3.72 5.95 6.71. 18.74 21.6 31.36 23.87 3.03 3.5 4.66 6.21
LSD 0.05 0.006 0.004 0.0025 0.008 0.004 0.003 0.047 N N 4.35E-08 N 6.15E-08 0.176 0.162 1.492 0.04
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A specific relationship was found between Fe, Cu, Zn or Mn and organic material
rate for the three materials at the first or fourth time of sampling. The comparison
of the slopes of Fe, Cu, Zn and Mn regression equations gives a quantitative
expression of the efficiency of organic waste rates for each organic material type.
The comparison of slopes at the first time of sampling and at the fourth time of
sampling with olive waste for Fe showed that, the efficiency of organic material
rates was 513.97 %, while for Zn, the efficiency was 150.71 %. On the other
hand, with olive waste for Cu, the efficiency of organic material rates were 499.32
%, but for Mn, the efficiency of organic material rates was 221.92%.
The comparison of slopes at the first time of sampling and at the fourth time
of sampling with compost for Fe showed that, the efficiency of organic material
rates were 554.55 %, while for Zn, the efficiency of organic material rates were
362.07 %. On the other hand, the efficiency of organic waste rates was 534.51 %
for Cu, but the efficiency of organic material rates was 158.18 % for Mn. The
comparison of the slopes at the first time of sampling and at the fourth time of
sampling with lemon waste for Fe; the efficiency of organic material rate was
356.18 %, while for Zn, the efficiency was 546.1 %. On the other hand for Cu, the
efficiency of organic material rate was 347.38 %, but the efficiency of organic
material rate was 53.28 % for Mn.
Conclusion:
The application of compost increased the amounts of DTPA- extractable Fe,
Mn and Zn with different degrees. The concentrations of micro elements in the
present study were higher after 16 weeks of incubation than in the first period of
incubation, probably due to degradation of the organic materials and release of
metals, which were complexes with organic matter at the beginning of incubation.
Organic matter content and the pH value of the soil are relatively easy to change
due the application of the organic waste materials. Therefore, the effect of
organic matter and pH on the extractability of micro elements deserves special
attention.
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Table (7): The liner regression between the available Fe, Zn, Mn and Cu and organic material rates after 4 and 16
weeks of incubation
Time of Organic Regression Equation
Sampling material Fe Cu Zn Mn
After4
weeks
olive waste Y1=0.122+0.544 X R2=0.852 Y2=0.712+0.590 X R2=0.960 Y3=1.364+0.84 X R2=0.984 Y4=14.934+1.396 X R2=0.958
compost Y1=0.308+0.506 X R2=0.992 Y2=0.718+0.452 X R2=0.989 Y3=1.418+0.754 X R2=0.996 Y4=14.670+2.506 X R2=0.947
lemon waste Y1=0.246+0.566 X R2=0.986 Y2=0.938+0.688 X R2=0.955 Y3=1.264+0.538 X R2=0.959 Y4=15.154+1.216 X R2=0.987
After16
weeks
olive waste Y1=1.884+2.796 X R2=0.869 Y2=2.164+2.946 X R2=0.950 Y3=1.828+1.266 X R2=0.952 Y4=16.076+3.098 X R2=0.962
compost Y1=2.602+2.806 X R2=0.778 Y2=1.528+2.416 X R2=0.991 Y3=2.268+2.73 X R2=0.955 Y4=18.074+3.964 X R2=0.840
lemon waste Y1=1.314+2.016 X R2=0.898 Y2=2.860+2.390 X R2=0.950. Y3=1.464+2.938 X R2=0.967 Y4=15.748+0.648 X R2=0.978
Y1=Fe Y2=Cu Y3=Zn Y4=Mn X == Rate of O.M
