Waste material in agriculture may be defined as the undesirable products from biological, organic or industrial sources. These wastes have been known to be of immense importance as potential raw material in soil conservation and management for sustainable agriculture. Soil organic waste is composed mainly of carbon, nitrogen, oxygen, hydrogen, sulphur and phosphorus, but the most studies focus on carbon and nitrogen.

            According to Williams (1988); municipal waste is valuable in conditioning the soil, thereby enhancing crop performance. Municipal waste forms which increases soil water holding capacity, also helps to protect crop from drought and prevent the leaching of nutrients.
            Municipal waste is measured by their ability to supply essential plant nutrients and improve soil physical properties (Wheel et al. 1988). The agronomic potentials of municipal waste could also be assessed through the physical observation of crop response and performance on soil due to the amended material (Parret et al. 1989).
            Many agriculturists in times past have studied what effect municipal waste (solid waste) amended soil would have on the soil’s eminent chemical properties. The cultivated plants take up these material, metals and elements either as mobile ions present in the soil solution through the roots or through foliar adsorption (Khaleel  et al. 1988). This uptake of the metal/element by plants results in the bioaccumulation of these elements in the plant.

2.2       What is Municipal waste (Solid Waste)
            Municipal waste is the term used to describe non-liquid waste materials arising from domestic, trade, commercial, agricultural, industrial activities and from public service (Aibor and Olurunad, 2006). The United State Environmental Protection Agency (USEPA) defined municipal waste as any useless, unwanted or discarded materials with insufficient liquid content to free flowing. According to the federal environmental protection agency now the Federal Ministry of Environment (1995), defines municipal waste are useless, unwanted or discarded materials that arise from man’s activities within the environment and cannot be discarded through a sewer pipe. The non-free flowing or sticky nature of municipal waste gives rise to the accumulation of it on some habitable parts of the earth surface. History has it that the manipulation of the environment that produced waste may have begun with the domestication of fire (Encyclopedia Britannica, 1996).
            The amount of waste produced by human activities is increasing in most parts of the world, accompanied by the problems of disposal which in turn affects the final disposal point which is the soil (Microsoft Encarta 2010). The volume and types of municipal waste as a result of continuous economic growth, urbanization and industrialization, is experiencing a rapid increase all over the country. It is estimated that in 2006 the total amount of solid waste generated globally reached 202 billion tones, representing 7% annual increase since 2003. It is further estimated that between 2008 and 2011 the global generation of municipal waste will rise by 37.3%, equivalent to roughly 8% increase per year (Global Waste Management Market Report, 2008). According to Salmon Chuck (2009), it is estimated that an average Nigerian generates about 0.49kg of solid waste per day with households and commercial centers contributing almost 90% of the total urban waste burden.
            Until recently, Nigerians had not been concerned with the amount of waste they generate. Their concern had not gone beyond physical removal of waste from the streets. It has been common practice to dispose off refuse by the expedite method. Such methods might be by open dumping or the use of an open dump site, directly on the soil. But with an increasing population and rapid urbanization, municipal waste is pilling up faster than finding the appropriate place to put them (Sada and Odemerho, 1989).
            A study in Nigeria showed that municipal wastes are produced in the urban areas to a mean rate of 0.43kg per individual a day (Sridhar et al. 1985). This is evident as it is not uncommon going through the length and breath of the country without locating heaps of refuse littering the entire landscape. This is a result of improper disposal and waste management plans.
            The wastes of the early people were mostly food stuffs and other less harmful substances that broke down easily by natural decay processes. Pre-historic populations were also much smaller and were spread over layer areas and as a result people were less concentrated in one place and caused fewer problems (Sridhar et al.1984). Furthermore, most of the decayed wastes (Food stuff etc) became compost, which then helps in making the soil more fertile. In Nigeria, just like in the rest of the world rapid urbanization and population growth have brought about a proportional increase in the amount of waste that is generated. The inability to manage these wastes effectively in most developing and some developed countries becomes an issue of great concern. Apart from the destruction of the   aesthetics landscape by municipal waste dumped indiscriminately, some of the municipal solid wastes contain both organic and inorganic toxic pollutants such as heavy metal which threaten the productivity and stability of soil and also human health and the entire ecosystem (Sridhar et al. 1985).
            Composition of municipal wastes provides a description of the constituents of the waste and it differs widely from place to place. The most striking difference is the inorganic content which is much higher in low income areas than the high income areas. This reflects the difference in consumption pattern, cultural and educational differences. In higher income areas, disposable materials and packaged food are used at higher quantities. This results to the soil having a higher calorific value, lower specific density and lower moisture content.
            Municipal waste management according to Ibrahim (2002) is the scientific way or established procedure and sanctioned legislation for the collection, transportation and disposal of waste products which is economically feasible and environmentally viable.
            The biggest challenge with municipal waste management in most Nigerian cities is not only the volume of the wastes, but also the composition of the wastes. All categories of wastes including toxic or non toxic, biodegradable or non-biodegradable, recyclable or non-recyclable are dumped together making the management very difficult. The reason(s) for this perturbing occurrence in developing countries may not be far fetched, it could be as a result of lack of awareness, and poverty, population growth, and high urbanization rate combined with the lack of government policies on waste management and separation.
            In places where there are government policies, the agencies saddled with the mandate to enforce the policies are either funded by the government or are not monitored for efficiency (Mato, 1999).

2.3 Characteristics of municipal waste
            Municipal wastes have very unique properties. They are known to mineralize and release available plant nutrient as a result of microbial attack. It is also used particularly on soils that are infertile (Kurl et. al, 1997). On the other hand, marginal, erodible, sloppy and generally less productive soil would benefit from the exposure to municipal waste material, especially waste material having a high degree of microbial stability (parent et. al, 1999). Such material could release plant available nutrient at a very high rate. Materials like undecomposed animal manure, green manures and activated sewage sludge are subjected to rapid microbial decomposition, and material such as municipal sewage sludge could be more resistant to microbial attack and release their nutrients at a relative slower rate.
            Municipal waste impaired a beneficial and long term residual improvement on soil physical properties because of its high level of municipal waste instability. Otori and Santana 1996 and Schleich 1986 noted that municipal sewage sludge material improves the productivity of the soil more than inorganic fertilizers owing to its slow release of nutrients. Most municipal sewage sludge and residue are low in their content of macro and micro-nutrients compared with the chemical fertilizer (Parr and Flornick, 1989).

2.4 Effect of municipal solid waste on soil properties
            According to Yondowei et al; (1986), the term refuse dump means those materials that the primary generators or producers abandon within the urban areas and which require decomposition upon abandonment.
            Refuse are those materials, which degenerates to organic material after which it has undergone decay and mix with the soil, it replenishes one or more of the nutrients which plants needs to grow property. Although plants will grow to some extent in almost all sandy soil, refuse matter content is necessary to produce healthy plants in quantity.
            Refuse dumps are manufactured from the abandoned waste materials such as phosphate, potassium, potash gas and petroleum phosphate. They are usually produced as solids in powder or granules and as liquid. Plant cannot absorb nutrients that are free element, for this reason refuse constitutes nutrient elements in order to be available to the plant. The grade of such refuse is defined by its content of primary nutrients, although other nutrients may be present in varying quantities (Ezedinma, 1997). Refuse contains major elements in required quantity as the crop plant may need for its growth. Nitrogen is obtained from the air and makes it into refuse form by being combined with hydrogen from natural gas or petroleum distillate. Phosphorus is applied to soil as ammonium phosphate or Super Di-Phosphate. The basic materials for its manufacture are phosphate rock treated with sulphuric acid. There are however, different types of refuse on the bases of nutrients they supply. When a refuse is decayed and supply only a few nutrient to the soil it should be seen as an incomplete refuse nutrient element.
            Refuse has much effect in crop yield. The rate of its application required will vary with the type of the crop, the stage of growth, and the soil fertility. Mbagwu (1989) stated that most crop grown in Nigeria
, and the soil structure, particularly in the savannah area and as soil which shave been exhausted by extensive cropping, responds well to refuse dump soil sites, this response is because of the high nitrogen to moderate potassium content, where as more positive results have been obtained from soil in the refuse dump sites areas. Refuse dump matter content maintains correct soil consistency, controls the soil acid content necessary to provide and maintain soil that will produce high crop yield.
            Matt (1970) reported that soil that is low in organic matter content level could not be expected to sustain it’s imposed family system, but with the application of refuse on the soil will increase the soil micro-organism, with the needed organic matter contained in the non-refuse dump soil.
Epstein et al. (1976) reported that refuse enhances the physical, biological and chemical properties of the soil. Hall (1983) added that refuse matter diminishes the hazards of erosion and land slide by returning completely the crop nutrients that help in soil particles aggregation. Also refuse releases deposits of nutrients which increases soil aggregation, structural stability, water holding capacity, infiltration rate and reduces the power of erosive agent.
            Allison (1973) noted that the decrease in the refuse use on soil results to degradation of soil structure, low infiltration rate, poor aeration, water logging of soil, low cation exchange capacity and acceleration of runoff and erosion, which leads to the loss of natures resource base.
            Wahab (1980) disclosed that refuse that was not controlled will lead to an increase of soil pH. Hence refuse improves soil nutrition status and aids in crop productivity and yield. Since refuse usually contain the entire major plant nutrient in the right proportions, while the physical properties of the soil such as depth, texture and structure contributes to its productivity, the use of refuse for cropping or agricultural activities is profitable, Conazi (1986).
            Refuse soil and non-refuse soil structure are different as a result of the nutrient content value of each. Alexander (1977) revealed that refuse site has more organic matter which was induced by the presence of refuse matter. A variety of products are formed from the original refuse. As the organic material undergoes further decomposition, they are converted to brown and black organic complex which is generally known as humus. Conclusively for effective long term sustainability, the question of how fertile is soil, is crucial, for their ability to supply essential plant nutrients, improve soil physical properties, increase crop yield, and maintain durable soil productively. A research on this, laid on the agronomic potential of refuse matter and the decomposition of the original material on the soil properties can not be over emphasized.
            Refuse site is a land disposal area at which solid wastes are disposed of in a manner that does not protect the enviroment. Refuse site is susceptible to open burning, and is exposed to elements, diseases, vectors and scavengers. These planned heaps of uncovered waste, often burned and surrounded by a pool of stagnated polluted water, rat, flies and domestic animal roaming freely and families of scavengers picking through the waste is not only an eyesore but a great environmental hazard (Christian Zurbrugg, 1999).
            Scavenging is disruptive to good dump site operation. It presents safety hazards to both scavengers themselves and dump site employees. It reduces productivity by delaying waste compaction and removal. In addition the fire set on the waste to facilitate scavenging is a great environmental hazard (Defteris, 1998).
The agronomic value of municipals waste is measured by their ability to supply the plant essential nutrients, and improve soil physical properties, (Khaled et. al, 1981). On marginal soil, it improves the structure and water retention capacity which may be all that is needed to ensure a better soil enviroment for root development and nutrient uptake. Soil with good structure improves physical properties which is secondary to enhance the fertility status associated with waste application.
The agronomic benefit of municipal waste could also be assessed through the physical observation of crop response and performance due to the amendment (Parr et. al, 1986). Crop yield response to addition of municipal waste material are highly variable and is dependent upon soil type, the crop, climatic condition, management systems and types of municipal waste material used. Therefore productivity is a determining factor in discovering if a particular waste material is suitable as a soil amendment relative to another waste material (Parr et. al, 1986). The poor physical condition of the tropical soil could be attributed to cultivators, erosion and intensive weathering.
Mbagwu (1992) reported that the major physical constraint to high level of crop production oN degraded soil was high bulk density resulting from confined cultivation. Highly weathered alfisol, exisols and utisols have inherent low waste retention capacity due to low content of colloidal materials, and the resulting consequence of this is reduced porosity. Infiltration rate and saturated hydraulic conductivity and low available water capacity.
Soil erosion is also a factor responsible for the rapid degradation and breakdown of good structure exhibited in tropical forest soil as manifested in low bulk density and high infiltration rate and hydraulic conductivity. Generally, some of these physical properties includes; water holding capacity, water retention bulk density, particle size density, micro and macro porosity, saturated hydraulic conductivity, water infiltration, total and available water capacity, aggregate stability, plastic limit, soil structure and electrical conductivity.
Some chemical qualities of the soil are discussed below:
Cation Exchange capacity (CEC)/Effective cation Exchange capacity (ECEC)
Cation exchange capacity is defined as the total sum of exchangeable cations that can be absorbed by 1g of the soil. It is measured in miliequivalent. It is the capacity of the soil colloids to absorb nutrients. Using ammonium acetate (NH2OAC) method (Jackson 1958). The cation exchange capacity of soil varies with;
1.         The kind of clay
2.         The percent of clay and
3.         The percent of organic matter
            It should be pointed out that the cation exchange capacity (CEC) in most soils increases with pH value, only the so-called permanent charges of clay and a small portion of the charges or organic colloids held ions that can be replaced by cation exchange.
            As the pH is raised, the hydrogen held by the remainder of the organic and inorganic colloids becomes ionized and is replaceable. Also this absorbed aluminum hydroxyl ions are removed forming AI(OH)3 thereby releasing additional exchange sites on the mineral `colloids. The net result is an increase in the cation exchange capacity. In most cases the cation exchange capacity is determined at a pH of 7.0 or above. These means that it includes most of those charges depended of pH as well as the more or less permanent ones. The cation exchange capacity as mentioned above is expressed in terms of equivalents, or more specifically as milliequivalents per 100 grams.
            The effective cation Exchange capacity (ECEC) is used for soils which are not base saturated, that is pH less than 7. The effective cation exchange capacity gives rise to the cation exchange capacity of the soil near its neutral pH. Methods such as NH4 acetate or barium chloride extractions determine the ECEC of the soil particularly those dominated by variable charged clay. The effective cation exchange capacity (ECEC) is calculated by summing the exchangeable acidity. Aluminum saturation is the percentage of ECEC occupied by the exchangeable aluminum and is written as ECEC =meq/1000g=exchangeable k+ exchangeable Ca + exchangeable acidity.
While aluminum saturation = Exchangeable A13   x    100
                                                                    ECEC                       1
            Two groups of absorbed cations tend to have opposing effects on soil acidity and alkalinity. Hydrogen and aluminum tend to dominate acid soils, both contributing to the concentration of H+ ions in the soil solution. Absorbed hydrogen contributes directly to the H+ ion concentration in the soil solution.
            A13+ ions do so indirectly through hydrolysis. Most of the other cations called exchangeable bases change the soil towards alkalinity. The proportion of the cation exchange capacity occupied by these bases is called the percentage base saturation. Colloid complexes in arid-region soils are practically saturated with base. As the base saturation is reduced, due to the loss in drainage of lime and other metallic constitutes, the pH also is lowered to a definite proportion. This is in line with the common knowledge that leaching tends ordinarily to increase the acidity of humid-region soils (Bates et, al.). This is calculated as:

Base saturation         =          Total Exchangeable bases   x  100
                                                Cation exchange capacity         1
            Percentage base saturation =          Meg exchange bases
                                    (PBS)                                                  X100
pH   (Power of Hydrogen)
            The ph value of a solution is the logarithm to base 10 of the reciprocal of the +I ion concentration it may be state conveniently as follows;
pH       =          log10     1     This can be determined by electric method
            The concentration of the H ion (and consequently the pH) is related mathematically to the concentration of the OH ion: this determines the percentage of H+ in the soil. If there is preponderance of H+ in the soil the soil will be acidic and alkaline. And if the proportion of H+ and OH is equal the soil is neutral. This pH determines the acidity or alkalinity of soil.
Mineral content
            This is the amount of mineral nutrient that is contained in the soil. The percentage mineral composition of plants varies considerably according to soil, climate and crop variety. The essential elements other than the CHO are generally regarded as the mineral nutrients. The mineral elements are all obtained from the soil.
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