PHYSICAL AND CHEMICAL PROPERTIES OF SOIL IN EKOLI EDDA | AFIKPO SOUTH LGA OF EBONYI STATE



CHAPTER ONE
1.0                                                 INTRODUCTION
            Soil which has over the years been a basic resources for agricultural production and the most important possession and asset of farmers, is made up of different features and characteristics that make it unique, (Brady and Wiels, 1999). Under natural condition, the level or rate at which soil build up is anchored on the differences that exist between the additions and losses of organic matters, physical, chemical properties and other variables that form soil.

            These additions could be from animal and plant decay while losses are enhanced or caused by immobilization and to a certain degree burning sometime lead to leaching causing soil loss beyond the root zone. The soil organic matter is also a characteristics constituent of the soil ecosystem and it controls the soil physical, biological and chemical properties (Olayinka 1990).
            Fire is the most fundamental and effective cultural and land treatment tool in the hands of humans (Goldammer and Grulzen 1993). Earliest evidence of the use of fire dates back to 1.5million year’s age, when natural fire regimes were successfully altered by humans (Brain and Sillen 1988). Large areas of forest formation have been shaped and maintain by anthropocentric fires, and in most regions of the earth, human caused fires are more important that natural fires. (Goldammer and Grutzen, 1993). Burning destroys the litter layer and so diminishes the amount of organic matter returned to the soil. The organisms that inhabit the surface soil and litter layer are also eliminated. For future decomposition to take place, energy has to be invested first in rebuilding the microbial community before plant nutrients can be released. Fallow lands and bush are burned before cultivation; this provides a rapid supply of phosphorous to stimulate seed germination. However, the associated loss of nutrients, organic matter and soil biological activities has served long-term consequences. Bush burning is a typical type of cultivation practiced in Ali-Ogo Ekoli in Ebonyi state South East Nigeria, the system involves essentially cutting and burning of the vegetations before cultivation. 
            Burning of vegetation in these area has a catastrophic effect, affects the ecosystem and physiochemical characteristics and properties of the soil. Much attention has not been paid to the effect of bush burning on physical and chemical properties of the soil. The effects of the heating processes caused by severe bush fire on soil are a result of burning severity, which is determined by the peak temperatures and duration of fire (Certini, 2005). Low to medium fire severity resulted in darkening of the topsoil while high severity fire (>600oc) cause pronounced reddening of the topsoil, accompanied by an increase in both munsell value and chroma (Ulery and Graham, 1993 ; Ketterings and Bigham, 2000).
      With a review of bush burning on soil properties, Certini (2005) concluded that low to moderate severity fires result in a renovation of the dominate vegetation by the elimination of undesired species and transient increase in pH and available nutrients in the soil, while severe burning generally lead to a great significant loss of organic matter, deterioration of both structure and porosity, leaching and erosion, among other drawbacks. Burning influences soil temperature, which in turn affects soil physio-chemical processes such as seed germination, root growth, plant development and bio-microbial activity (Potter et al, 1987). Based on the concentration, the main objectives of the research work is to determine changes in physio-chemical properties of Ali-ogo soil under the influence of bush fire.

1.1       SPECIFIC OBJECTIVE
The specific objectives are to determine
i.          Changes in physical properties of the soil
ii.         Changes in the chemical properties of the soil
iii.       Effect of bush burning on heavy metal accumulation in soil 

CHAPTER THREE
3.0                                         MATERIALS AND METHOD
STUDY AREA
            The research was conducted at Ali-ogo Ekoli Edda under the management of Ekoli in Afikpo south Local Government area of Ebonyi State Abakaliki South East Nigeria. Ebonyi State lies within latitude 6o, 45N and longitude 8o, 65E in the derived savannah zone of the southern Agro-ecological zone Nigeria. The area that was used lies in the humid tropics with high rainfall and high temperature, the mean annual rainfall of this zone for 2009 and 2010 based year was 1466. 32mm obtained from 87 rain days with a fairly defined peak rain period of six months from April to September.
            The maximum and minimum temperature is 32.180c and 17,40c respectively while the relative humidity ranges from 50-87% and mean of 68.42%. The soil belongs to the order spodic horizon and association derived from humid climate. The soil textural class is sand loam.

SOIL SAMPLING
            Within each location, a soil sample was collected from the soil depth 0 – 30cm and bulked (composite soil sample). The bulked soil sample was mixed up thoroughly and three (3) representative samples that have been collected were labeled in a sample bag. Each sample becomes a replicate. These soil samples was used to determine the soil chemical properties after these set of samples, another soil sample was collected with soil auger attached with core sampler at the depth of 0 – 30cm respectively, and was used to determine the physical properties and heavy metals accumulation in the soil.

LABORATORY METHODS
The physical parameters to be analyzed are:
The bulk density was determined using the core method and constant heat methods using Blake and Hartage method (1986).
Total porosity was determined using the method described by Obi (2000).
Soil Moisture content was determined using the gravimetric method by the formula
Weight of wet soil – weight of oven dried soil x 100 divided by weight of wet soil.
Soil hydraulic conductivity was determined using method by Klute, 1986.
Infiltration rate was determined by the method as described by Landon, 1991.
Soil temperature was determined using soil thermometer
Soil texture was determined using the hydrometer method described by Bouycous (1962), Day (1965).

SOIL CHEMICAL PROPERTIES
Organic carbon was determined using the walkey- black method (Nelson and Sommers 1982).
Organic matter content was obtained by multiplying the percentage organic carbon by a factor of 1.724.
Exchangeable cation Ca, k, Mg, and Na was extruded with ammonium acetate and their amount in filtrated determined by Perkins Elmer atomic absorption spectrophotometer (A .A. S)
Exchangeable acidity determination was done by titration methods (Tel and Rao, 1982).
Nitrogen was determined using macro-Kjehdal method (Bremmer and Mulvacy 1982).
Available phosphorus was determined using Bray 2 method by Bray and Kurtz (1998).
Total acidity and exchangeable bases was determined according to procedures by Tel and Hargarty (1984)
Soil pH was determined using glass electrode pH meter in water (Mclean 1982).
   HEAVY METAL DETERMINATION
The heavy metals were determined using the Atomic Adsorption spectrophotometer machine (AAS) the following were the heavy metals that were analyzed Zn, Bo, Fe, and Mo.

3.1       DATA ANALYSIS
Data collected was analyzed using coefficient of variation Steal and Tone (1980). And the soil property was rated using Landon, 1984 and Melson, 1990.

CHAPTER FOUR
4.0                                      RESULT AND DISCUSSION
4.1       THE EFFECT OF BUSH BURNING ON CHEMICAL PROPERTIES OF SOIL
pH
The pH of the experimental site revealed that the burnt area was statistically different from the unburnt area when compared with each other. The pH of the unburnt and burnt area was 5.97 and 6.15 respectively. The result shows that the burnt area was 5units more acidic than the unburnt area. This is because during the combustion process, several previously bound nutrients are released in their elemental or radical form. These processes is described by the National Wildlife Coordinating Group (2001), certain cations, are stable at typical combustion temperature and remain onsite after burning in form of ash. If in the ash form are subsequently leached into the soil where they exchange with H+ ions, the resulting increase in H+ ions in solution increases the pH of the burnt area and ash deposited after burning is composed mostly of salts, these salts can effectively increase soil pH by capturing the salt cations as they leach through the soil profile. The result shows moderately to slightly acidic in the unburnt are and burnt area (Ulery et al., 1993)

TOTAL NITROGEN
The result of the effect of bush burning on total N of the soil shows no statistical significance difference in the unburnt and burnt area. The result was 0.12 and 0.09% respectively. There was 3% slight increase in total nitrogen of the unburnt area. This is as a result that all of the nitrogen in soils is contained in and is an essential part of the organic matter or humus and also the nitrogen in soil results from biological fixation and from accumulation of plant residue over a long period of time. The level of nitrogen recorded low to medium in the unburnt and burnt area. The decrease of nitrogen in burnt area is as a result of heating which causes decrement and because some are lost through volatilization (Fisher and Binkly, 2000).

CALCIUM 
The calcium of the experimental site revealed that there was statistical difference in calcium level of the unburnt and burnt area when compared together. The result was 2.88 and 1.86Cmol/100g respectively. This shows that there was an increase in calcium of the unburnt area than that of the burnt area. This is because calcium is present in adequate amounts in most soils; calcium is a component of several primary and secondary minerals in the soil. It increases in unburnt area because calcium is not considered a leach able nutrient; however it will move deeper into the soil. Because of this, and the fact that many soils are derived from limestone bedrock, many soils have higher level of Ca (Goh et al., 1996). The decrease in calcium level of the burnt area may be caused by environmental factors and it could be removed in particulate form by convention in smoke columns or by surface wind transport during and after burning (Goh and Phillips, 1991). The calcium in the soil recorded medium to high (Landon, 1991).

AVAILABLE PHOSPHORUS
The effect of bush burning on available phosphorus recorded 43.29 and 8.04Cmol/100g for the unburnt and burnt area. This shows that there was statistical difference of phosphorus in both areas. The increase of phosphorus in unburnt area may be as a result of phosphate precipitation and dissolution. Phosphate precipitation is a process in which phosphorus react with another substance to form a solid mineral and dissolution of phosphate mineral occurs when the mineral dissolves and releases phosphorus, the reaction of phosphate with another  substances to form a solid mineral aids the increase of phosphorus in the unburnt area and also the increase implies that there was no disturbance in the compartment of available phosphorus in the unburnt  while there is a decrease of phosphorus in the burnt area due to fire severity which induced losses of available phosphorus through volatilization. This is in line with the findings of Cade-Manun et al (2000). The result recorded marginal to rich classes of phosphorus in critical level for available phosphorus (Serrasolsas and Khanna, 1995).

MAGNESIUM
The magnesium of the experimental site revealed that there was statistical difference when the unburnt and burnt area was compared together. The level of magnesium in the unburnt and burnt area was 0.69 and 0.47mg/l respectively. The unburnt area is 22% high than that of the burnt area. This may be because magnesium is held on the surface of clay and organic matter particles and the soil pH of the unburnt area is not as high as that of the burnt area (George et al., 1994). The magnesium level recorded low according to its rating and availability (Simard et al., 2001).


POTASSIUM
The result of the effect of burning on potassium content of the soil showed that there was difference when the unburnt and burnt area was compared with one another. The level of potassium in the unburnt and burnt area of Ali-ogo Ekoli soil was 0.26 and 0.36Cmol/100g soil. There was 10% more in potassium level of the burnt area and this may be as a result of environmental factors like wind and rainfall which played a major role in the concentration of potassium after burning in the burnt area (Ulery et al., 1993). Generally, the level of potassium is recorded medium classes of potassium availability in the soil (Wild, 1987).

SODIUM
The sodium of the research site showed that there was no statistical significant from the unburnt and burnt area when compared together. The sodium of the unburnt and burnt area was 0.15 and 0.10Cmol/100g soil respectively. The slight reduction in sodium of the burnt area may be as a result of leaching since sodium is weakly held by the soil colloid (Simard et al., 2001). The level of sodium in the soil recorded low according to its classification which is deficient in the unburnt and burnt soils (Kotisch et al., 1987).

EXCHANGEABLE CATION
The result of the effect of bush burning on exchangeable cation of the soil showed that there was statistical difference when the two areas were compared together. The result of both the unburnt and burnt area was 14.00 and 17.00mg/100g soil. There was high differential value increase of exchangeable cation in the burnt area which was in accordance with the findings of Parkinson, 1998. The increase may be as a result of ash deposit in the burnt area that makes the soil acidic. This recorded high exchangeable cation value according to the ranking (Kattering et al., 2000).

EFFECTIVE CATION EXCHANGE CAPACITY
The effect of bush burning on effective cation exchange capacity revealed the following result 3.49 and 3.88mg/100g in unburnt and burnt area respectively. From the result, there was 39% increase of effective cation exchange capacity in the burnt area. The reason of this increase may be as a result of ash deposit on the burnt area and ash deposited contains Fe³+, Mg²+ which provide exchange site for ion interactions to take place. Soils with large amount of cation exchange capacity are chemically stable (Parkinson, 1998). The effective cation exchange capacity recorded medium according to its classification (Oswald et al. 1999; Badia and Matni, 2003).

EXCHANGEABLE SODIUM PERCENTAGE
The effect of burning on exchangeable sodium of the soil showed that there was significant difference when the unburnt and burnt area was compared together. The result of the unburnt and burnt area was 2.86 and 3.23% respectively. There was 37% more exchangeable sodium in the burnt area and this increase may be as a result of ash deposit that leads to cation concentration in the burnt area. Kattering et al., (2000), Parkinson, (1998).

EXCHANGEABLE ACIDITY
The exchangeable acidity of the experimental site showed that there was no statistical significant from the unburnt and burnt area. The value recorded was 0.47 and 0.47Cmol/100g respectively. The unburnt and burnt area recorded low values in its classification according to Landon 1991. (Badia  et al.,  2003).
BASE SATURATION
The result of the effect of bush burning on percentage base saturation of the soil showed that there was statistical difference when the unburnt was compared with the burnt area of Ali-ogo Ekoli. The percentage base saturation in the unburnt and burnt area was 80.44 and 87.72% respectively. There was about 728% more base saturation in the burnt area. This may be as a result of the proportion of the cation exchange site in the burnt area that are occupied by the various cations (H, Ca, Mg, k).The surfaces of soil mineral and organic matter have negative charged cations. Cations with one positive charge (H, K, Na) will occupy one negatively charged site and cations with two positive charges (Ca, Mg) occupied two sites on the burnt area according to the findings of Serrasolsas and Khanna (1995).

ORGANIC CARBON
Organic carbon is the amount of carbon bound in and organic compound. The effect of burning on unburnt and burnt area of Ali-ogo Ekoli showed that there was significant difference in both the unburnt and burnt area. The result of th4e unburnt and burnt area was 12.29 and 6.29% when compared with one another. There was difference of about 600% more of organic carbon in the unburnt area than that of the burnt area. The reason of high level of organic carbon in the unburnt area may be as a result of leave fall, plant and animal decay and excess litter layer on the soil surface of the unburnt area which are not disturbed nor altered (Fortner et al., 2007). The organic carbon content of the unburnt and burnt area recorded medium to high in the rating of organic carbon content. Also, the decrease in organic carbon of the burnt area may be as a result of denaturation of organic carbon present in the soil as supported by the findings of Guinto et al., 1999 who found that fire induced a reduction in organic carbon ratio of soil.

TABLE 1:  EFFECT OF BUSH BURNING ON SOIL CHEMICAL PROPERTIES 

pH
H2O
EC
(mg/100g)
ESP
(%)
OC
(%)
Total N
(%)
Avail P
(Cmol/100g)
Ca
(Cmol/100g)
Mg
(Mg/L)
K
(Cmol/100g)
Na
(Cmol/100g)

EA
(Cmol/100g)

Bs
(%)
ECEC
(Mg/100g)
Unburnt Area (A)
5.97a
14.00a
2.86a
12.29a
0.12a
43.29a
2.88a
0.69a
0.26a
0.15a
0.47a
80.44a
3.49a
Burnt Area (B)
6.15b
17.00b
3.23b
6.29b
0.09a
8.04b
1.86b
0.47b
0.36b
0.10a
0.47a
87.72b
3.88b
F-LSD P = 0.05
0.01
0.05
0.12
2.4
NS
6.42
0.12
0.01
0.03
NS
NS
2.14
0.01

 
Figures with the same super sample are not statistically significant.

4.2       THE EFFECT OF BUSH BURNING ON SOIL SELECTED PHYSICAL PROPERTIES       
BULK DENSITY
The effect of burning showed statistical difference in the unburnt and burnt area of Ali-ogo Ekoli. The result recorded 1.53 and 1.69cm‾³ in unburnt and burnt area respectively. This result shows that there was 16% increase in bulk density in the burnt area; the reason may be due to high clay, silt and sand content in the burnt area (Webster and Wilson, 1980). The bulk density of the unburnt and burnt area recorded low bulk density according to the rating of Landon, 1991. The slight increase of bulk density of the burnt area may also be because of collapse of aggregates and clogging of voids by the ash (Certini, 2005).

TOTAL POROSITY
Total porosity does not provide any direct information about the size of the individual pores, or their functions. It is an expression of the total volume of a soil that may act as a store for air and water. The result of the effect of bush burning on total porosity of the unburnt and burnt area was 40.37 and 36.23%. The reason for decrease in total porosity of burnt area may be as a result of destruction of soil structure by fire which also affects pore size distribution in the surface horizons of the burnt soil (DeBano et al., 1998). According to Landon 1991, the two values of unburnt and burnt area are of very high classes in the classification rating.

HYDRAULIC CONDUCTIVITY
The effect of burning on hydraulic conductivity of soil showed statistical difference in the unburnt and burnt area when compared together. The result recorded 30.21 and 31.42Cmhr­‑¹ respectively. This shows that there was 121% more of hydraulic conductivity of the burnt area, this result may be because the size, shape, and continuity of the pore spaces, structure and the soil texture of the burnt area was altered and tempered with by fire (Thomas et al., 1996). According to soil permeability classification, the result recorded very rapid hydraulic conductivity according to the classification (Landon, 1991).

MOISTURE CONTENT
The result of the unburnt and burnt area of Ali-ogo Ekoli recorded 12.0 and 16.0% when compared with one another. There was more moisture content in the burnt area. The reason may be due to burning of the organic matter, plant residues that cover the soil surface that may have seal the soil surface and crusting has been burnt off thereby making the soil to be moisture absorber (Roth, 1985). The moisture content of the unburnt and burnt area recorded high according to the rating. (Landon, 1991)

SAND, SILT AND CLAY
The percentage sand fraction for the unburnt and burnt area was 56.4 and 62.4% respectively. There was an increase in sand fraction of the burnt area due to high temperature that may lead to breakdown of soil particles causing the soil to be coarse. Ulery et al.,(1993). The fraction of silt and percentage clay fraction has the following results 32.10 and 20.91% for silt fraction of the unburnt and burnt area and 11.5% and 16.7% for clay fraction of the unburnt and burnt area respectively. There was decrease in silt fraction of the burnt area which was as a result of high temperature fusing the silt fractions hence its reduction. Kattering et al.(2000). The increase in percentage clay of the burnt area shows that the fire severity was high enough to lead to fusion of clay fraction of the soil. (Imeson et al., 1992; Kattering et al., 2000).
The above results showed that the resultant effect of fire on soil texture could be due to the irregular pattern of fire severities which leads to different types of textural classes. The textural class of the unburnt and burnt area is sandy clay loam according to the textural classification (Imeson et al., 1992; Martin and Moody, 2001). Soil coarsening at some parts of the burnt area occurred which was in accordance with the findings of Mermut et al, (1997) who reported that selective removal of fine fractions could be caused by environmental action of rain through erosion. Also, exposure of the soils to high temperature results in the fusion of clay and silt fraction into sand- size particles (Kattering et al., 2000).   

TABLE 2: EFFECT OF BUSH BURNING ON SOILS SELECTED PHYSICAL PROPERTIES


TP
(%)
BD
(Cm3)
HC
(C mhr-1)
MC
(%)
SAND
(%)
CLAY
(%)
SILT
(%)
TEXTURAL CLASS
Unburnt Area (A)
40.37
1.53
30.21
12.0
56.4
11.5
32.1
SANDY CLAY
Burnt Area(B)
36.23
1.60
31.42
16.0
62.4
16.7
20.91
CLAY LOAM
F-LSD P=0.05
0.41
0.01
0.51
0.28
21.0
21.0
18.1


4.3       THE EFFECT OF BUSH BURNING ON SOIL SELECTED HEAVY METALS
ZINC
The result of the effect of bush burning on zinc content of soil showed that there was statistical difference when the unburnt and burnt area was compared with one another. The zinc level in the unburnt and burnt area of Ali- ogo soil was 0.26 and 0.58Cmol/100g respectively. There was 32% more zinc in the burnt area than the unburnt area. The reason for higher level of zinc in the burnt area may be as a result of breaking down of soil solid particles by fire which help to release the zinc content of the soil because most zinc stays bound to the solid particles (Swif et al., 1993).
Generally, the level of zinc in the burnt and unburnt areas recorded low to medium classes of zinc sufficiency. This means that response of zinc application will be high in both unburnt and burnt areas (White, 1987).

BORON
The boron content of the experimental site revealed that there was statistical difference in the comparison of the unburnt and burnt areas. Boron level in Ali- ogo Ekoli unburnt and burnt areas was 34.50 and 28.9Cmol/100g soil respectively. There was an increase in Boron level in the unburnt area and decrease of boron level in the burnt area. The reason of accumulation of boron in the unburnt area may be because boron is present and accumulates in organic matter and is freely available to plants in all except alkaline soils (Reid and Parkinson, 1981). Also, the level of boron in burnt area decreased as a result of fire severity and volatilization and ash deposition on the burnt soil will make the soil to be alkaline. The boron content of the unburnt and burnt area recorded low to medium classes of boron sufficiency in the soil (Ulery, 1993).

IRON
The effect of burning on iron shows that there was difference in iron level of the unburnt and burnt areas. The two areas recorded 105.8 and 191.4Cmol/100g respectively. This showed that there was 450% more iron in unburnt area, the reason of higher iron content of the unburnt area may be as a result of iron been immobile and its stickiness to soil solid particles (Webster et al., 1980). The level of iron in unburnt and burnt area recorded medium classes of iron sufficiency and reduction in iron content of the burnt area may be due to long duration of fire that leads to high temperature of the burnt area (Kattering et al., 2000).

MOLYBDENUM
The effect of bush burning on molybdenum shows the following results 56.90 and 35.90Cmol/100g in unburnt and burnt area respectively. This result showed that there was 2100% molybdenum in the unburnt area. This high level of molybdenum in the unburnt area may be due to the fact that molybdenum does not occur naturally as a free metal in soil, but rather in various oxidation states in minerals (Reiss et al., 2000). The level of molybdenum in unburnt and burnt area recorded high classes of molybdenum excessively and a decrease of molybdenum in burnt area is as a result of fire severity and high temperature of the burnt soil (Kattering et al, 200S0; Ulery, 1993).

TABLE 3: EFFECT OF BUSH BURNING ON SOIL SELECTED
HEAVY METALS

Zn
(Cmol/100g)
Bo
(Cmol/100g)
Fe
(Cmol/100g)
Mo
(Cmol/100g)
Unburnt Area (A)
0.26
34.50
105.9
56.90
Burn Area (B)
0.58
28.90
101.4
35.90
F-LSD P=0.05
0.02
1.21
1.2
10.1

CHAPTER FIVE

5.0       SUMMARY, CONCLUSION AND RECOMMENDATION
5.1       SUMMARY
 The properties of soils at Ali-ogo Ekoli in Ebonyi state south – east Nigeria have undergone changes due to annual cycles of bush burning. Results from this research work suggested that soil properties vary in their response to burning in the unburnt and burnt area. This work tested three things first, the effect of fire on soil chemical properties showed that pH was favoured by fire in the burnt area but at unburnt area, it was not favoured. Percentage base saturation, exchangeable cation, cation exchange capacity, potassium and magnesium were favoured by burning in the burnt area; total nitrogen, sodium and exchangeable acidity are not statistically significant in the unburnt and burnt area. The effect of bush burning on soil selected heavy metals showed that zinc was favoured by fire, Boron, Iron, and Molybdenum were not favoured by bush burning.
5.2       CONCLUSION
From the results of my study, the following conclusion could be drawn. Firstly, that burning can significantly alter the chemical properties like pH, exchangeable cation, exchangeable sodium percentage, potassium, exchangeable cation exchange capacity and percentage base saturation. However, it also alter the physical properties of the burnt area like bulk density, hydraulic conductivity and moisture content but only the sand and clay of the burnt area was increased due to burning while there reduction in silt of the burnt area.

5.3       RECOMMENDATION

The use of fire as a management tool in forest agriculture in Ali-ogo Ekoli in Ebonyi state south – east Nigeria is likely to continue since it is cheap to implement and reduce their cost of labour. However, there should be sensitization on the effect of bush burning on forest soil and environment if not adequately controlled.

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