EVALUATING THE AGRONOMIC EFFECTIVENESS OF HUMAN FAECAL
COMPOST ON MAIZE YIELDS, ITS INFLUENCE ON SOIL CHEMICAL
PROPERTIES AND SOIL FAUNA ABUNDANCE
NYAKEOGA KWAMBOKA VIOLET
(A57/81591/2012)
Thesis submitted in partial fulfillment of the requirements for the award of Master
of Science Degree in Sustainable Soil Resource Management
FACULTY OF AGRICULTURE
UNIVERSITY OF NAIROBI
2015
i
DECLARATION
I hereby declare that this is my original work and has not been submitted for the award of
a degree in any other university.
Signature……………………………… Date………………………
Nyakeoga K. Violet
(Candidate)
Supervisors
Signature………………………… Date……………………………..
Prof. Nancy K. Karanja.
(University of Nairobi)
Signature……………………… Date……………………………..
Dr. Fredrick O. Ayuke
(University of Nairobi)
ii
DEDICATION
I dedicated this work to my daughter, Bravian.
iii
ACKNOWLEDGEMENT
I am indeed grateful to the Almighty God for the gift of life and strength to successfully
complete this work. I am greatly indebted to my supervisors, Professor Nancy Karanja,
Dr. Fredrick Ayuke, and Solomon Kamau for guiding me in research. To Camilla, for
finding it necessary to fund my study, to Jack, for ensuring that the Peepoo bags were
delivered to Kabete as soon as we needed them, and therefore making it possible for the
study to go on. To Dr. Annika Nordin for the financial support provided and being my
mentor. I also acknowledge my fellow students, seeing and chatting with them helped me
move on, ‗at least am not alone‘ I thought. To all who in one way or another contributed
to the study, much appreciation, your efforts did not go to waste.
Finally yet importantly, am grateful to my family, my parents Mr. and Mrs. Kennedy
Nyakeoga, who made an important decision to take me to school, my husband Geoffrey
for his love and support and my daughter Bravian, you are the reason I had to work
harder!
iv
TABLE OF CONTENTS
DECLARATION .............................................................................................................................. i
DEDICATION ................................................................................................................................. ii
ACKNOWLEDGEMENT .............................................................................................................. iii
LIST OF TABLES ......................................................................................................................... vii
LIST OF ABBREVIATIONS ....................................................................................................... viii
ABSTRACT .................................................................................................................................... ix
CHAPTER ONE .............................................................................................................................. 1
1. INTRODUCTION ................................................................................................................... 1
1.1. Background information .................................................................................................. 1
1.2. Problem statement and Justification ................................................................................ 4
1.3. Objectives ........................................................................................................................ 7
1.3.1. Overall objective ...................................................................................................... 7
1.3.2. Specific objectives ................................................................................................... 7
1.4. Hypotheses ....................................................................................................................... 7
CHAPTER TWO ............................................................................................................................. 8
LITERATURE REVIEW ................................................................................................................ 8
2.1. Soil fertility management for sustainable agriculture ...................................................... 8
2.2. Organic soil amendments as nutrient sources ................................................................ 10
2.1. Use of human excreta ..................................................................................................... 12
2.2. Nutrient release from organic matter ............................................................................. 16
2.3. Influence of organic inputs on soil macrofauna ............................................................. 17
Influence of organic fertilizers on nematodes ............................................................................ 19
CHAPTER THREE ....................................................................................................................... 20
MATERIALS AND METHODS ................................................................................................... 20
3.1. Study Site Description ................................................................................................... 20
3.2. Baseline soil analysis ..................................................................................................... 20
3.2.1. Soil sampling ......................................................................................................... 20
v
3.2.2. Procedures for Chemical Analysis ......................................................................... 21
3.5. Experimental design and treatments .............................................................................. 26
3.6. Land preparation, planting, weeding and harvesting ..................................................... 27
3.7. Soil macrofauna sampling .......................................................................................... 28
3.7.1. Assessment of soil nematodes ................................................................................ 29
3.8. Chemical characterization of soils after treatment ......................................................... 30
3.9. Plant sampling ................................................................................................................ 30
3.10. Statistical analysis and data management .................................................................. 31
CHAPTER FOUR .......................................................................................................................... 32
RESULTS ...................................................................................................................................... 32
4.1. Soil chemical properties from the study area ................................................................. 32
4.2. Chemical characteristics of manures and composts ....................................................... 33
4.3. Effect of compost and manure application on soil chemical properties ........................ 35
4.3.1. Effects of amendments on Nitrogen ....................................................................... 35
4.3.2. Organic carbon ....................................................................................................... 36
4.3.3. Phosphorus ............................................................................................................. 37
4.3.4. Exchangeable bases (Ca, Mg, and K) .................................................................... 37
4.3.5. Soil pH ................................................................................................................... 38
4.4. Agronomic effectiveness of manures and composts on growth of maize at the field
Station, Kabete ........................................................................................................................... 41
4.5. Grain yield and stover weight ........................................................................................ 42
4.6. Effects of manures and composts on fauna in soils of Kabete field station ................... 43
4.6.2. Effects of organic amendments on soil nematodes .................................................... 47
CHAPTER FIVE ........................................................................................................................... 49
5. DISCUSSION ........................................................................................................................ 49
5.3. Agronomic effectiveness of organic manures on performance of maize ....................... 52
5.4. Influence of manures and composts on soil macrofauna ............................................... 53
5.5. Effect of organic amendments on soil nematodes.......................................................... 54
vi
CHAPTER SIX .............................................................................................................................. 56
6. CONCLUSION AND RECOMMENDATIONS ................................................................... 56
REFERENCES .............................................................................................................................. 57
vii
LIST OF TABLES
Table 1: Chemical characteristics of soil from Kabete field Station ................................ 32
Table 2: Chemical characteristics of composts and manures used in the study ............... 34
Table 3a:Chemical properties of soils treated with manures and composts(season 1) ..... 39
Table 3b:Chemical properties of soils treated with manures and composts(season 2) ..... 40
Table 4: Maize dry biomass yield from Kabete field trials at 3, 6 and 9 weeks after
planting (mean of two seasons)......................................................................................... 41
Table 5: Maize stover and grain yield in response to manures and composts (mean of 2
seasons) ............................................................................................................................. 43
Table 6: Soil macrofauna abundance across the different treatments............................... 45
Table 7: Nematode numbers/200 cm
3
of soil treated with manure and composts ........... 48
viii
LIST OF ABBREVIATIONS
RPM
Revolutions per minute
NPK
Nitrogen, Phosphorus, and Potassium
FAOSTAT
Food and Agriculture Organization Statistics Division
SSA
Sub Saharan Africa
NGOs
Non-Governmental Organizations
FYM
GENSTAT
Farm Yard Manure
General Statistical Package
ISFM
Integrated Soil Fertility Management
UN Habitat
United Nations Human Settlements Programme
SOM
Soil Organic Matter
TDS
Total Dry Solids
TSBF
Tropical Soil Biology and Fertility Institute
Ppm
Parts Per Million
DAP
AAS
Diammonium Phosphate
Atomic Absorption Spectrophotometer
ix
ABSTRACT
Low soil fertility status has been stated as the main cause of poor crop yields in many
sub-Saharan countries. This challenge can be addressed by using cheap and readily
available options. One such option is human excreta. Human excreta contain millions of
tons of nutrients. It is estimated that in a year, humans excrete an equivalent of 20 -30%
of global annual fertilizer industry production. Unfortunately, most of the nutrients end
up in water bodies through wastewater and surface runoff. A study was conducted at
Kabete, Nairobi Kenya to evaluate the response of crops to application of human faecal
compost, herein after referred to as peepoo compost, as well as its influence on soil
fertility and soil fauna diversity and abundance. The treatments included two composts;
Peepoo compost (from human fecal matter) and commercial compost (vermitech
compost), two manures; cow manure, poultry manure, inorganic fertilizer (DAP), and no-
input control. Peepoo compost was prepared using human excreta collected in peepoo
bags from Kibera. The treatments were in 5 m by 4 m plots replicated three times in a
randomized complete block design. Organic amendments were applied at the rate of 5 t
ha
-1
, while fertilizer at the recommended rate of 26 kg P ha
-1
at planting and 60 kg N ha
-
1
for topdressing. Maize (Zea mays) was used as test crop. The soil samples were
analyzed for chemical and biological parameters. Soil macrofauna were collected using
soil monoliths, while nematodes were sampled using steel core ring samplers and
extracted using the centrifuge technique. The crop yield, soil chemical and soil fauna data
x
obtained was then subjected to statistical analysis using Genstat statistical software, 14
th
edition.
Amending soil with peepoo and vermitech compost, poultry and cow manure, had
significant effect on soil chemical properties (P=0.005). There was an increase in soil
total N across all treatments with Peepoo compost recording the highest increase of 19 %
compared to the control. Plots treated with vermitech compost and cow manure recorded
16 % and 6 % increases in N, respectively while poultry manure and inorganic fertilizer
recorded the lowest values for total N. The highest organic carbon values were recovered
from plots amended with Peepoo and vermitech compost and cow manure (25.8, 25.1,
and 25.1 g kg
-1
respectively. Peepoo compost treated plots recorded the highest P value of
24.45 mg kg
-1
, followed by poultry manure treated plots (14.50 mg kg
-1
), cow manure
(12.20 mgkg
-1
) and vermitech compost (14.32 mgkg
-1
). Earthworms were significantly
higher in plots that were treated with composts and manures. Peepoo compost recorded
53 individuals m
-2
while vermitech compost, poultry, and cow manure amended plots had
earthworm densities of 49, 42, and 38 individuals m
-2
respectively. The control and
fertilizer recorded 32 individuals m
-2
and 27 individuals m
-2
. Application of organic
amendments also increased free-living nematodes coupled by a decline in plant parasitic
nematodes.
Maize grain yield was also significantly different (p<0.001) across the treatments. Plots
treated with Peepoo compost recorded the highest grain yield of 8.8 t ha
-1
, followed by
Vermitech compost 7.1 t ha
-1
, poultry manure (6.4 t ha
-1
), cow manure (5.5 t ha
-1
) and
xi
inorganic fertilizer(4.9 t ha
-1
). Control plots recorded the lowest grain yield of 2.2 t ha
-
1
.These results show that Peepoo compost made from sanitized human excreta is a good
fertilizer that can be used to substitute and/or supplement commercial fertilizers, a
starting point towards improving soil and crop productivity in Kenya.
1
CHAPTER ONE
1. INTRODUCTION
1.1. Background information
Declining crop yields and productivity in African countries, is largely a result of low soil
fertility due to nutrient mining by crops coupled with sub-optimal fertilizer use (Fosuet
al., 2007). This is aggravated by the high population leading to small land holdings that
are less than one hectare (Gikonyo and Smithson 2004), resulting in continuous farming
and nutrient mining. (Lekasi et al., 2001; Braun et al., 1997). Continuous farming on
poor soils without replenishing the nutrients that are lost through crop harvest causes low
agricultural productivity due to declined soil fertility (Twomlow and Bruneau, 2000;
Bationo et al., 2012). Studies particularly with crops such as maize, rice and grain
legumes have shown that use of fertilizer is essential to enhance productivity in sub-
Sahara Africa (SSA) (Sanchez et al. 1997). Fertilizers widely regarded as an essential
input in crop production. However, studies have shown that fertilizer application cannot
be relied on alone to address the challenge of low soil fertility in SSA (Jenssen 1993).
They are frequently unavailable and unaffordable to most smallholder farmers (Bationo
et al., 2012). Africa‘s average annual fertilizer use is only at 20 kg ha
-1
compared to the
global average of 96 kg ha
-1
(Heisey and Mwangi 1996; Camara and Heinemann 2006).
For instance, in central highlands of Kenya, farmers who use inorganic nitrogen
fertilizers, apply at rates between 15-25 kg N ha
-1
, which is below the recommended 40
kg N ha
-1
(Kimani et al, 2004
2
In an effort to produce enough food that will meet the rising demand, more chemical
fertilizers continue to be applied to the soil. Continuous monocropping without
application of organic inputs such as poultry manure, farmyard manure, and composts
results in mining of plant macro and micronutrients and depletion of soil organic matter.
Use of composts, animal manures, and human waste may be a significant step in soil
fertility improvement under intensive farming as it restores some of the exhausted
nutrients from the soil. Organic sources supply nutrients through mineralization and in
the process improve physicochemical and biological properties of the soil. In addition,
these organic fertilizers release nutrients gradually in synchrony with crop demand
(Bationo et al., 2012). Organic fertilizers also play a very important role in enhancing
productivity of many tropical farming systems through decomposition and subsequent
release of nutrients to the soil (Cheryl et al., 2001). The major challenge associated with
the use of organic materials is that they occur in insufficient amounts (Otinga et al.,
2013) and use of human faecal waste which is a continually produced resource could
bridge the gap. Its use is jeopardized by the negative image coupled by concerns on its
effects on the environment and health risks.
Studies on use of human feacal matter as a fertilizer have been reported. Guzha et al.
(2005) reported an improvement of soil qualities and increased maize yields as a result of
application of human faeces and urine combined than only fertilizing with urine. Kutu et
al. (2010) observed increase in spinach yields only when faeces were applied in
combination with urine. Other studies have shown that human excreta is rich in major
3
macronutrients (N, P, and K) as well as micronutrients (Schouw et al., 2002). One person
produces approximately 5.7 kg of nitrogen, 0.6 kg of phosphorus and 1.2 kg of potassium
per year (Wolgast, 1993).
Negative attitudes as well as concerns about environmental and health hazards have
greatly hindered the use of human faecal matter as a valuable source of nutrients for
crops. To improve this situation, attempts have been made to find novel ways of treating
and enhancing the quality of human excreta to make it safe for use as a fertilizer. Such
approaches include urine separation from excreta, composting alone or mixed with other
organics (Malkki 1999) and sanitization of human waste using ammonia-based method
(Nordin 2010).During composting, the high temperatures accumulated kill pathogens
present thus sanitizing the material. Human excreta used in this study was sanitized using
the ammonia technology. Inactivation of pathogens was achieved using urea (6g per
peepoo bag) which is broken down by enzymes which are naturally occurring in feaces to
form ammonia and carbonates. Ammonia inactivates the pathogens (bacteria, virus and
parasites) within two to four weeks. As urea is broken down, the pH value of the material
increases and the hygienisation process begins. Increase in pH is very important in
determining the availability of ammonia that inactivates the pathogens.
Co (NH
2
)
2
+ 3H
2
O
urease
2NH
4
+
+ OH
-
+ HCO.................................Equation 1
4
Another major obstacle in the reuse of human waste is social acceptance. Education,
sensitization, and addressing concerns of target consumers are important ways to
successfully build acceptance of human waste reuse (Murray 2011).
1.2. Problem statement and Justification
Declining soil fertility poses a major challenge to increased food production by small-
scale farmers in sub-Saharan Africa (Sanchez et al., 1997; Sanginga and Woomer 2009).
Other constraints such as low nutrient holding capacities, high acidity, low organic
matter, poor soil structure, and low water-holding capacity also play a role in reducing
productivity of the soils (Mafongoya et al., 2007). Effective soil fertility management
remains a big challenge in Africa despite the major efforts from research centers, NGOs,
Governments and farmers and their organizations (Onduru et al., 2007). Though use of
commercial fertilizers offer a possible option of reversing the trend, their high cost poses
a major challenge to small-scale farmers in this region. Identifying alternative means of
addressing this challenge is very important (Bationo et al., 2004; FAOSTAT, 2004;
Kimani et al., 2007). The alternative identified should be efficient, effective, affordable,
and accessible to resource poor farmers (Bationo et al., 2007). Human waste is one such
alternative whose value is highly underestimated in many tropical developing countries
thus stagnating its use as a source of nutrients for plant growth.
According to the Kenya National Census (2009), Kenya‘s population has grown from
10.9 Million in 1969 to 38.6 Million in 2009. More than 34% (13 million) of Kenya‘s
5
total population lives in urban areas (UN-Habitat, 2009). Managing human waste in
urban areas that are densely populated and with limited infrastructure is posing a big
challenge especially in the urban informal settlements. Mineral fertilizers and organic
materials such as manure and crop residues have been used to a large extent to enhance
soil fertility status and thus improve crop yields (Bationo et al., 2007, Okalebo et al.,
2004). The ever-increasing costs, scarcity, and competition for alternative uses of these
materials necessitate the search for local, readily available, and cheap nutrients sources
(Bationo, 2012; Okalebo et al., 2006).One such alternative is human waste that is
produced daily in any given society and can be recycled thus harvesting the nutrients
therein. Human waste has been reported to be rich in major macronutrients (N, P, and K)
as well as micronutrients (Schouw et al., 2002).
A study by Rockström et al. (2005) showed that annual excreta production in sub-
Saharan Africa is so high that it corresponds to more than 100% of the local application
of mineral fertilizers. If this is applied to the soil, then agricultural production can be
enhanced at a low cost. Countries such as China have been able to maintain their soil
fertility status, regardless of the high population through reuse of human waste (Bracken
et al., 2007). Recycling excreta into soils may help to reduce overreliance on chemical
fertilizers besides protecting water bodies against contamination by human waste
(Nordin, 2010). Use of human waste in agriculture may not only provide a simple
solution to sanitation problems but will also enhance soil fertility (Nordin 2010). If
human wastes, animal manure, and crop residues are recycled, then the fertility of arable
6
land can be maintained, because the recycled products contain the same amounts of plant
nutrients as were taken up by the crops and animals (Jonsson et al., 2004). The annual per
capita waste is about 520 kg, which contain approximately 5.7 kg of nitrogen, 0.6 kg of
phosphorus and 1.2 kg of potassium per year (Wolgast, 1993) and some micronutrients in
a form useful to plants. If the nutrients in the faeces of one person were used for grain
cultivation, it would support one person grain requirement of 250 kg per year (Wolgast
1993). However, the risks associated with its handling, such as disease transmission, as
well as cultural barriers limit exploitation of the resource. Nutrients removed by crops
have to be replaced in order to maintain high agricultural yields over the years.
Otherwise, the result is an annual net loss of nutrients from the soil. Therefore, it is
important that nutrients from human excreta be recycled, to close the nutrient loops of
society (Nordin 2010).
Recycling of organic waste returns nutrients back to the soil, rather than burying them in
the subsoil where they may be leached to groundwater therefore contaminating the
aquifers (Kuo et al., 2004). The offensive odour from some fresh organic wastes also
makes it unpleasant for people handling the wastes. Stabilization of organic wastes prior
to land application is highly desirable to eliminate odor and vector attraction and to make
nutrients in the wastes, particularly N, readily available for plant use. Stabilization of
organic wastes is possible through composting, which is a microbiologically mediated
process (Kuo et al., 2004).
7
1.3. Objectives
1.3.1. Overall objective
Production of high quality compost from human excreta for use by smallholder
farmers in Kenya
1.3.2. Specific objectives
1. Determine effects of human faecal compost on soil chemical properties.
2. Evaluate agronomic effectiveness of compost from human faecal matter on maize
yield.
3. Evaluate influence of human faecal compost on abundance and diversity of soil
fauna.
1.4. Hypotheses
1. Human faecal compost will significantly improve soil nutrient status and maize
yields.
2. Soil fauna diversity will increase in response to application of human faecal
compost.
8
CHAPTER TWO
LITERATURE REVIEW
2.1. Soil fertility management for sustainable agriculture
Soil fertility depletion is ―the fundamental biophysical root-cause of declining per capita
food production in Africa‖ according to Sanchez et al. (1996). Kenya is among those
countries that lose large amounts of nutrients annually on average 42 kg N, 3 kg P and 29
kg K ha
-1
per year through erosion, volatilization, and leaching (Smaling, 1993). Poor
management of available resources has damaged the environment due to further land
degradation. In developed countries, for example, over-application of inorganic and
organic fertilizer has led to environmental contamination of water supplies and soils
(Conway and Pretty 1991; Bump and Baanante, 1996). On the contrary, in developing
countries, harsh climatic conditions, population pressure, land constraints such as small
land holding sizes, and abandonment of the traditional soil management practices have
often reduced soil fertility (Stoorvogel and Smaling 1990; Bump and Baanante 1996).
Soil fertility decline processes include nutrient depletion, and nutrient mining (removal of
nutrients without inputs), acidification (decline in soil pH), loss of soil organic matter
(SOM), and increase in toxic elements such as aluminum (Hartemink, 2006).
Despite the fact that Sub-Saharan Africa is clearly identified as a future hotspot for food
insecurity due to the low agricultural yields, countries in these region can increase their
food production both at national and household level by adopting` integrated soil fertility
management (ISFM) (Bationo and Waswa, 2011). Use of inorganic fertilizer has been
9
responsible largely, for sustained increases in per capita food production in Asia, Latin
America as well as for commercial farmers in southern Africa (Sanchez et al., 1997).
They are also considered to be the most efficient way to reverse soil nutrient depletion
(Bationo et al., 2007). However, other studies have shown that continuous use of
inorganic fertilizers causes soil deterioration with regards to its chemical, physical, and
biological properties and health (Mahajan et al., 2008). The adverse negative impacts of
inorganic fertilizers together with their ever increasing prices have necessitated the use of
organic fertilizers as a source of nutrients (Bationo et al., 2012, Satyanarayana et al.,
2002). Organic materials such as FYM have traditionally been used by farmers to
enhance soil fertility (Satyanarayana et al., 2002).
Integrated soil fertility management entails the use of mineral fertilizers, organic inputs,
and improved germplasms combined with the knowledge on how to adapt these practices
to local conditions, which aim at optimizing efficient agronomic use of the applied
nutrients and thereby improving crop productivity. Alternative uses of crop residues and
other organic materials from the field for use as animal fodder, firewood, or as
construction material is one major factor that limits their use in soil fertility management
and soil conservation (Kirchhorf and Odunze 2003). Use of human waste to substitute
other organic materials such as cow manure, poultry manure and crop residues, will
ensure a sustainable supply of organic manure for use in ISFM. The concept of ISFM
focuses on how to manage these scarce nutrient resources efficiently (Bationo et al.,
2012, Bationo et al., 2011). The overall strategy for increasing crop yields and sustaining
10
them at a high level must include an integrated approach to the management of soil
nutrients, along with other complementary measures, which recognizes soil as the
storehouse of essential plant nutrients and that the way in which nutrients are managed
will have a major impact on crop production, soil fertility, and agricultural sustainability.
2.2. Organic soil amendments as nutrient sources
The use and management of organic inputs for supply of crop nutrient and soil
improvement has been in existence for a long time just like arable agriculture itself
(Cheryl et al., 2001). In addition to supplying nutrients, organic inputs have other
benefits. These benefits include: replenishing soil organic matter, increasing the crop
response to mineral fertilizer, improving the soil‘s moisture storage capacity, regulating
soil chemical and physical properties that affect nutrient storage and availability as well
as root growth, supplying essential elements not contained in mineral fertilizers,
improving the availability of phosphorus for plant uptake, and ameliorating problems
such as soil acidity (Bationo et al., 2012).
Organic inputs used in soil fertility management consist of livestock manures, crop
residues, household organic refuse, composted plant materials, and other plant biomass
harvested from within or outside the farm for purposes of improving soil productivity
(Kihanda et al., 2004). Organic inputs derived from plant remains provide most of the
essential nutrient elements, but usually in insufficient quantities. Because of their
richness in carbon, organic resources provide an energy source for soil microorganisms.
11
The microorganisms drive the various soil biological processes and therefore affect
nutrient transformation in the soil. As these organic materials undergo the process of
decomposition in soil, they contribute to the formation of soil organic matter (SOM)
(Bationo et al., 2012). During decomposition, the organic materials interact with soil
minerals forming complex substances that influence nutrient availability; for example
binding toxic chemical elements such as aluminum or releasing phosphorus bound to soil
mineral surfaces (Bationo et al., 2012). Nutrients from organic resources are slowly
released compared with mineral fertilizers. This enhances continuous supply of nutrients
throughout the growing season. The slow release further reduces nutrient losses, for
instance through leaching (Bationo et al., 2012).Under undisturbed natural vegetation
such as permanent forests or grasslands, the nutrients are recycled within a closed loop
since little or no residues are taken out of the system. However, in arable system, the rate
of SOM formation is usually low and the nutrient release cannot match crop nutrient
demand. Organic inputs applied to the soil control the rate, pattern, and extent of growth
and activity of soil organisms and provide the source of carbon, energy and nutrients for
the synthesis of soil organic matter (Kimani et al., 2004). The practice of applying
organic material to soil can increase the humus content of soils by 15-50%, depending on
soil type, in addition to increasing soil aggregate stability and root permeability (Kimani
et al., 2004). However, these organic materials occur in insufficient amounts and have
other competitive alternative uses such as construction, source of fuel and animal feed.
12
This constraints their use and human excreta therefore becomes important due to its
availability and quantities produced.
2.1. Use of human excreta
Human excreta contain elements that can be used as fertilizer for growing crops
(Heinonen-Tanski and Wijk-Sijbesma, 2005). Since matter can neither be created nor
destroyed, consumed plant nutrients such as nitrogen, phosphorus, potassium, and
micronutrients leave the human body in form of excreta, with only a small proportion
stored in cells or excreted via respiration or sweat (Jönsson et al., 2004). If human and
animal excreta were to be treated or composted and used as a fertilizer, it would be
possible to increase crop yields in a cost-effective way as well as protect water bodies
from contamination (Winker et al., 2009). Use of human excreta as fertilizer has been in
practice since time immemorial ((Muskolus, 2008) in European cities, towns and rural
areas. In China, Vietnam and Japan, human excreta are used frequently as ‗night soils‘
generally, without any known problems for agricultural productivity. With continued use
of human excreta, China has been able to maintain their soil fertility status despite the
high population. However, poor handling is often associated with health problems such as
high prevalence of enteric pathogens in the population, noted in China by Xu et al.
(1995) and increased intensity hookworm infection in Vietnamese women (Humphries et
al., 1997).
13
Human excreta have been reported to have excellent plant nutritional value in terms of
providing nitrogen (N), phosphorus (P) and potassium (K) (Kirchmann and Pettersson,
1995; Mnkeni and Austin, 2008; Kutu et al., 2011). Besides supplying macro- and
micronutrients, human faeces contain organic matter, which is important in increasing the
water-holding and ion-buffering capacity of the soil, serves as food for the
microorganisms and improves the soil structure (Jönsson et al., 2004). Reports indicate
that one person produces 4193 g faeces day
-1
(total dry solids) and 0.61.2 L urine day
-1
(Schouw et al., 2002). Human waste contains as much as 6070% of nutrients from
agricultural fields which are waste (Kirchman and Petterson,1995). Human waste, both
urine and faeces, have a great potential for improving fertility status of impoverished
soils. Urine is reported to have a high content of readily available N, P, and K and its
fertilizing effect is similar to that of nitrogen-rich chemical fertilizers. On the other hand,
faeces have high contents of phosphorus and potassium in organic form. However,
nitrogen is only slowly released since it is organically bound in undigested food remains
(Kirchman and Petterson, 1995). Reuse of human excreta will reduce the pollution effects
that result from unsafe excreta disposal and excess use of chemical fertilizers and protect
surface and groundwater. Effective reuse of human excreta would also reduce the
waterborne enteric microbiological diseases, as there would be less contaminated
wastewater (Heinonen-Tanski and Wijk-Sijbesma, 2005).
Human excreta are by products of human metabolism and are products formed every day
in every human society (Heinonen-Tanski and Wijk-Sijbesma, 2005; Jönsson et al., 2004