ABSTRACT
Cassava processing produce large amount
of waste (cassava peel as the major by-product) and is generally
considered to contribute significantly to environmental pollution. In
spite of all the important agricultural and nutritional roles played by
cassava, its food value and waste (cassava peels) is greatly compromised
by the presence of endogenous cyanogenic glycosides; linamarin and
lautrstralin which under several prevailing tropical condition is
readily hydrolysed to liberate hydrogen cyanide,transferred into a
solution and subsequently deteriorate the ground water and crop quality.
Hence the need to investigate the effect of cassava peels compost on
the macronutrient (nitrogen, phosphorus and potassium) content of
agricultural soils on which they are dumped using composting.
After digestion of the soil samples
(compost soil and control soil) the concentration of hydrogen cyanide
was deduce using titrimetric method, the pH was obtained using pH meter
and the macronutrient content (potassium, nitrogen and phosphorus) was
obtain using the atomic absorption spectrophotometer, UV
spectrophotometer and vanadomolybdo phosphoric method. The analysis
result shows that the amendment (cassava peel) used for composting
slightly increase the cyanide concentration, potassium content and
drastically reduce the major macronutrient(nitrogen and phosphorus) and
the pH of the soil thereby making the soil strongly acidic and unhealthy
for plant growth. It was observed from the result that the cyanide
concentration in the compost soil increase as the rate of decomposition
of the cassava peel present in the compost increases. The result
obtained; for phosphorus and cyanide a zero order reaction and the rate
constant was observe to be 0.012and 0.467 using the method of
determination of order and rate constant stated in the literature.
CHAPTER ONE
INTRODUCTION
1.1 Background of Study
Cassava (Manihot esculenta crantz)
is one of the most important food crops in Africa. It is the third most
important food in the tropics after rice and maize. It derives its
importance from the fact that its starchy, tuberous roots are a valuable
source of cheap calories, especially in developing countries where
calories deficiency and malnutrition are widespread (Yeoh et al., 1998);
Cassava contains the potentially toxic compounds like the cyanogenic
(hydrogen cyanide which is released from damage tissues in any part of
plant) glycosides, primarily as linamarin which liberate hydrogen
cyanide (HCN) upon hydrolysis and lotaustralin in small quantity.
Consumption of cassava and its product is thought to cause cyanide
poisoning with symptoms of vomiting, nausea, dizziness, stomach pains,
weakness, headaches, diarrhea and occasionally death (Akintonwa and
Tunwasha,1994). Cassava processing generates solid and liquid residues
that are hazardous in the environment including cassava peels, waste
water, cassava leaves etc. Cassava peels which are regarded in many
areas in Nigeria as waste are biodegradable waste that is rich in crude
protein (5.29%) and fat (1.18%). Most often cassava peels are commonly
found in farm locations and processing sites as heaps that are generally
perceived as hazard to the environment. These materials, however, could
be utilized more effectively and substainably through recycling.
Cassava peels like many organic waste material are potential source of
organic nutrient to plant . Management of cassava peels include direct
incorporation into the soil, feeding them to livestock, burning or
processing them into a more stable organic fertilizer called compost
(Hoitink,2007). The abundance, as well as low cost of cassava peels in
Oleh community has necessitated a research on its effect on agricultural
soil on which they are dumped to act as compost. Composting cassava
peels eliminate the problem of waste disposal and increase the manurial
value of the materials. With the advent of biotechnology approaches,
there are opportunities for economic utilization of agro industrial
residues such as cassava peels waste (Omisore et al., 2009).
With the advancement of industrial age
resulting to take-over of farmlands, there is need to increase and
maximize the nutritive life of the available farmland, this can be
achievable by humidification of soil instead of adding chemical
fertility. In order to convert the increased problem of waste disposal,
compositing agricultural-waste to enrich the soil fertility becomes very
important. Organic matter are excellent source of plant available
nutrient and their addition to the soil could maintain high microbial
population activities and as such it is often preferred as alternative
to commercial mineral fertilizers. Composting is the decomposition of
organic matter such as fruit and vegetables scraps, grass, leaves etc,
composting begins the process of breaking down organic material into
what will eventually become humus in the soil. Agricultural wastes are
essentially of plant origin and therefore contain the entire nutrients
essential for plant growth. Plant and animal waste are freely available
to be composted to supply nutritious organic matter needed by
agricultural soil. Generally, organic fertilizers contain relatively low
concentration of the actual plant nutrients, and are not immediately
available for plant utilization. Hence, the fortification of organic
wastes and their composts as a source of organic nutrients are
imperative for sustainable agriculture. According to Neemat and Khaled
(2012), traditional composting has been recognised as a low cost and
environmentally sound process for treatment of organic wastes (Hoitink
and Kuter 1986). Furthermore, the rapid decomposition and raised
temperature during composting produced a relatively homogeneous,
odor-free, pathogen-free and easy to handle product. Bevacqua and
Mellano (1993) reported that the compost treated soils had lower pH and
increased levels of organic matter, primary nutrients, and soluble
salts.
Primary macronutrients needed by plants
are nitrogen, phosphorus and potassium. These nutrients are taken up in
large quantities by plants. The primary macronutrients are the most
common nutrient deficiencies due to the highest demands by plants.
Nearly all soils lack sufficient available nitrogen for ideal plant
growth (Cogger, 2005).
1.2 Problem Statement
Cassava processing produces large
amount of waste (cassava peel is the major by-product) and is generally
considered to contribute significantly to environmental pollution (FAO
2001). A cassava starch production unit processing 100 tons of tubers
per day has an output of 45 tons of fresh by-product, which may cause
environmental problems when left in the surrounding of processing plants
or carelessly disposed (Aro et al., 2010). In Nigeria (Oleh community
as a case study) cassava wastes (peels) are usually left to rot away in
open (agricultural soil) thereby altering the presence of heavy metal
present in the agricultural soil, the pH of the soil and the content of
macronutrient available for plant growth or burnt to create space for
accumulation of yet more waste heaps thereby resulting in health hazard.
The heaps emit carbon dioxide and produce a strong offensive smell (Aro
et al., 2010) when burnt.
The main toxic principle which occurs
in varying amount in all parts of the cassava plants is a chemical
compound called linamerin. It often co- exists with its methyl homologue
called methyl- linamarin or lotaustralin. Linamarin is a cyanogenic
glycoside which is converted to toxic hydrocyanic acid or prussic acid
when it comes into contact with linamarase, an enzyme that is released
when the cells of cassava roots are ruptured (Philbrick et al., 1997).
However, ingested linamarin can liberate cyanide in the gut during
digestion therefore consumption of raw cassava root result in cyanide
poisoning with symptoms of vomiting, nausea dizziness, stomach pains,
headache and death. Cassava peels which contains large amount of
cyanogenicglucosides and pomace (large amounts of biodegradable organic
matter) may cause surface water pollution especially if they are stored
under heavy rain or simply disposed of in water surface ( Pandey et al.,
2000).
1.3 Aim and Objectives of Study
The aim of this study is to analyse the
effect of organic wastes (cassava peels) compost generated in Oleh
community on the macronutrient (nitrogen, phosphorus and potassium)
content and the pH of agricultural soil; experimental and kinetic study.
To achieve this aim, the following objectives are considered:
i. Prepare compost using cassava peels from Oleh community;
ii. Analyse the macronutrient content of the compost and the control agricultural soil;
iii. Test the pH of the compost and the control soil;
iv. Analyses the amount of cyanide present in the compost soil and control soil.
v. To determine the kinetics of the macronutrient
1.4 Scope of Study
The scope of the study is to investigate
the effect of cassava peels compost on the macro nutrient content and
pH of agricultural soil.
1.5 Relevance of Study
Cassava as an important root crop in
Africa, widely grown throughout the tropical Africa contain cyanide,
generally the cyanide content is substantially higher in the cassava
peels. Cyanide is both widely available and easily accessible throughout
the world. The compound is not frequently encountered, as it is a
potential terrorist agent used as poison and contaminant in the past.
Cassava peels may have the ability to cause some certain change in the
soil like altering the pH of the soil, improve or reduce the
macronutrient content of the soil, alter theheavy metals contents of
soil and pollute the water body when dumped on a water surface hence the
need to assess the effect of cassava peels compost on the macronutrient
content of agricultural soil in Oleh community.