The gray soil colours and CaCO3 concretions characteristic of

The pot experiment will be carried
in a screen house at Sokoine University of Agriculture, where TMV1 maize
variety and TXD 306 rice variety will be sown in 5 kg potted soils, replicated
three times. Nitrogen fortified urban bio-waste and mineral fertilizers will be
used. The amount of Nitrogen fortified urban bio-waste to be applied will depend
on the result of characterization of the material. The experiment will be
carried out using the complete randomized design (CRD). Four seeds will be sown
per pot, and then thinned to two plants per pot, 12 days after sowing (DAS).
The pots will be regularly watered when necessary to raise the soil moisture to
about field capacity. Data on growth parameters of the two crops as described
under field experiment will be recorded.

6.3
Pot experiment

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Nitrogen fortified biowaste
materials will be acquired from Guavay Company Limited in Dar Es Salaam and
characterized at SUA Soil Laboratory to determine the levels of agricultural
important nutrients.

6.2
Acquisition of NFUB and characterization

The study will be carried out at Dakawa
Irrigation Scheme in Mvomero District, Morogoro. The soil of the area is very
deep (> 150 cm), moderately well drained, with gray to very dark gray soil
colours and CaCO3 concretions characteristic of calcic horizon in
subsoil. Soil texture is sandy clay loam throughout the pedon. pH are medium
(5.5 – 7.0) to very high (7.0 – 8.5) respectively for topsoil and subsoil. OC
and N levels are very low; CEC and exchangeable bases are low to medium. Bulk
densities are high (1.8 gcm-3) to very high (>1.9 gcm-3)
for topsoil and subsoil, respectively. Subsurface (95 – 100 cm) and
intermediate (45 – 50 cm) horizons retain more water than the surface (0 – 5
cm) soil, corresponding with increasing clay content with depth.

6.1
Study area

6.0
MATERIALS AND METHODS

 

The
use of compost can affect soil microbial diversity, as reported by Zaccardelli et
al., (2013a) who showed a clear positive effect on the number of
spore-forming bacteria, with an increase directly correlated with the dose of
compost. Also in stressed soil, with high saline content, the use of compost
can determine an improvement of biological fertility (Lakhdar et al.,
2009). Ouni et al., (2013) investigated the effects of composts,
produced by MSW and palm wastes, at several doses (0, 50, 100, and 150 t ha-1)
on saline soil. They observed an increase of soil organic matter and
consequently an improving of microbial biomass and several enzyme activities
but the results were different in presence of the highest dose of compost (150
t ha-1), where a reduction of some activities was registered. This
behaviour could be likely attributed to the potential toxic effect of the trace
elements present in this particular compost (Garcia-Gil et al., 2000;
Crecchio et al., 2004); Lakhdar et al., (2011) tested the use of
compost from MSW and sewage sludge to enhance the fertility of degraded soils
in the Mediterranean region. A clay loamy soil was amended with 0, 40, and 80 t
ha-1 of MSW compost or sewage sludge. A significant increase of all
the measured activities (arylsulphatase, dehydrogenase, phosphomonoesterase and
b-glucosidase) after 70 days at either 40 t ha-1 or 80 t ha-1
(ranged between 16%-160% and 10%-81%, respectively) was registered.

In
a study conducted for three years, in intensive farm under greenhouse
conditions, Morra et al., (2010) used different doses of compost (15,
30, 45 t ha?1) and compost (at dose of 15 t ha?1)
combined with mineral N fertilizer to investigate the effects of exogenous
organic matter on soil enzymatic activities. They found that soil respiration,
fluorescein diacetate hydrolases and phosphomonoesterase activities increased
after compost application. The magnitude of the activity increased with compost
rate and with cumulative compost amendment. In general, the broad-scale soil
biological properties, such as soil respiration, fluorescein diacetate
hydrolases and phosphomonoesterase activities were positively affected by
compost supply, demonstrating shifts in microbial performances related to C, N
and phosphorus cycles in soil (Iovieno et al., 2009). Scotti et al.,
(2015) proposed compost application to soils under intensive farming systems
combined with woody scraps to achieve significant changes in biological
parameters. The authors found a rapid and intense boost of enzymatic activities
(dehydrogenase, phosphomonoesterase and b-glucosidase) after organic amendments,
especially after the second yearly amendment, demonstrating that repeated use
of organic amendments should be planned to trigger microbial activity and
functionality and improve consequently soil biological fertility.

Organic
amendments, once added to the soil, favour the growth and diversity of
microbial communities, highlighting a strong correlation between soil
biological fertility and soil organic C content (Chakraborty et al.,
2011).

5.3 Effect
of bio-waste on soil biological properties

Numerous
researches have been addressed on soil nutrient supply after the application of
organic amendments. As a consequence of the application of organic amendments,
which increase organic C stock, soil cation exchange capacity (CEC)
increases. High values of CEC allow retaining essential nutrient cations making
them available for crop productions (Bulluck Iii et al., 2002). In
addition, also anions as phosphorus showed an increased solubility subsequently
to organic material application (Zaccardelli et al., 2013b; Scotti et
al., 2015).

Although
compost application could promote nitrification process, if compared with
mineral fertilization it reduces N leaching, decreasing the possibility of
nitrate groundwater contamination (Shiralipour et al., 1992; Montemurro et
al., 2007).

The
addition of chemical fertilizers generally leads to a rapid mineral N release,
while organic amendments induce a slow mineral N release, but extended over
time (Claassen and Carey, 2006). Weber et al., (2007) reported that the
slow mineralization of N in soils under compost amendment improves not only the
soil fertility, but also the conditions of organic matter mineralization. In
fact, they found an increase of humic acid/fulvic acid ratio in compost amended
soil which might be partly due to the original composition of humic substances
in the compost, where humic acids always predominate over fulvic acids.

Intensive
agriculture, without organic amendments for the restoration of soil organic C
stock, negatively affects soil chemical properties producing a reduction in
soil C content, that, in turn, produces deleterious effects on soil microbial
biomass, soil enzymatic activities, functional and species diversity, besides a
drastic increase in soil salinity (Bonanomi et al., 2011a). A large body
of empirical studies carried out in different agricultural systems demonstrated
that the application of organic amendments in the form of compost is an
effective tool to recover soil organic C stock (Hargreaves et al., 2008;
Zhang et al., 2015). C/N ratio is considered an important parameter to
predict organic C mineralization rate and dynamical patterns of the nutrient
release (Parton et al., 2007; Berg and McClaugherty, 2008). Organic C or
N can limit microbial growth when C/N ratio is above the threshold value of
~25-30. Therefore, a crucial step for a sustainable management of soil quality
is to identify organic amendments with specific biochemical quality that
effectively balance the trade-off between organic C stock recovery and nutrient
mineralization. Generally, when organic C enters the soil, the amount retained
depends not only on its biochemical quality but also on its interactions with
soil mineral components i.e. sand, silt, and clay fractions as well as
carbonate and organic C content (Piccolo, 1996; Clough and Skjemstad, 2000). As
suggested by Bonanomi et al., (2014b), in soils with characteristics far
from C saturation, such as low organic C content and high clay fraction,
exogenous organic matter is more easily absorbed and less exposed to microbial
attack. On the other hand, in different conditions closer to C saturation, such
as a sandy soil with high C content, mineral particles are less able to
interact with organic compounds thus leaving more available compounds to
microbial degradation.

5.2 Effect
of bio-waste on soil chemical properties

As
widely reported in literature, the use of organic amendments increases soil
organic matter (Thangarajan et al., 2013; Khaliq and Abbasi, 2015), and
as consequence soil aggregate stability, water holding capacity and soil
porosity (Celik et al., 2004; Leroy et al., 2008), thus improving
soil quality. Sometimes, organic amendments can affect indirectly soil physical
properties. Lucas et al., (2014) demonstrated that organic amendments
containing high amount of bioavailable C derived from cellulose, can
promote fungal proliferation and improve soil structure through stabilization
of soil aggregates, suggesting a use of organic amendments to manipulate soil
microbial community structure and to promote aggregation in soils. 

5.1 Effect
of bio-waste on soil physical properties

5.0  LITERATURE REVIEW

 

(iii)                   
 To assess the field response of rice and maize
crops under application of optimum amount of nitrogen fortified urban
bio-waste.

(ii)  To establish the optimum amount of the nitrogen
fortified urban bio-waste required for potential yield of rice and maize crops
through pot experiment.

(i)    To characterize nitrogen fortified bio-wastes as
organic fertilizer.

4.3.2      
Specific
objectives

 

To assess the effectiveness of the nitrogen
fortified urban bio-waste application for small scale rice and maize crop
production.

4.3.1
General objective

4.3.0      
Objectives

However,
some literatures articulate that such material have low nutritional value due
to their poor nutrient releasing capacity (Båth & Rämert, 2000; Sikora
& Enkiri, 2001; Nevens & Reheul, 2003), consequently necessitates the application
of large quantity in order to attain a significant yield change (Svensson et al., 2004). Contrastingly, high rates
of compost application may increase N loss potential by leaching (Mamo et al., 1999). This alerts the need for
looking at improved bio-wastes which would adequately release nutrients while
sustaining the soil quality. Therefore this study aims at filling this gap by
evaluating the nitrogen fortified urban bio-wastes as organic fertilizer for
small scale maize and rice production which has not yet paid much research
attention.

A
number of empirical studies have acknowledged bio-wastes as the most important
source of organic carbon in soils (Tandon, 1992; Stone and Elioff, 1998;
Gilbert, 2015) and that can reduce soil degradation (Dulac, 2001). Additionally,
multiple benefits derive from the use of compost as fertilizer, for example an
increase in organic C content and microbial activity (Scotti et al.,
2015), a greater concentration of plant nutrients like N, P K and Mg, and a
root reinforcement (Donn et al., 2014). Also, the improving of soil
porosity with a consequent increase of water available for plants (Scotti et
al., 2013),

Soil
strategy pays a growing attention to the role of organic matter in soils in
order to ensure soil fertility, biodiversity and to prevent desertification
(ECCP, 2001). In increasingly intense agricultural practices, soils are
progressively vulnerable, especially in the tropics where rapid carbon turnover
(3–5 times faster than in temperate regions) and extraction, decreasing
nutrient retention and water storage capacity, and decreasing erosion
resistance are highlighting the need of carbon and plant nutrient replenishment
(Smith et al., 2015). This can be
achieved by recycling organic waste into agriculture (Smith et al., 2015).

4.2
Problem statement and justification

 

On the other side of coin, bio-wastes
have been generation increasing on a worldwide scale, mainly driven by growing
global population, urbanization and economic growth, coupled with changing
production and consumption behavior (Karak et
al., 2012). Ensuring adequate management of these wastes is acknowledged as
one of the main challenges of the twenty-first century and considered a
fundamental element for sustainable development (Scheinberg et al., 2010; Wilson 2015).
Consequently, mismanagement of these wastes poses a considerable threat to
public health via attraction of insects, rodents and other disease vectors,
contamination of surface and groundwater supplies (Reddy and Nandini 2011).
Moreover, uncontrolled disposal of the wastes is likely to pose environmental
problem through emission of methane, a major greenhouse gas (Bogner et al., 2008). Opportunities for
improvement remain particularly pronounced in urban low- and middle-income
settings, where solid waste management is characterized by low waste collection
coverage, lack of treatment and inadequate disposal. Many appropriate solutions
are hindered given the fast and unregulated growth of settlements in
topographically often challenging areas, lack of financial resources,
ineffective organizational structures, lack of viable business models, low
political priority setting by governments and minimal enforcement of policy and
legislation (Marshall and Farahbakhsh 2013; Zurbrügg 2013). Adverse effects on
human health, the environment, social and economic development are the consequence
(Guerrero et al. 2013). Therefore, advancing on bio-waste management is an
ideal entry point for overall municipal solid waste management improvements
(Srivastava et al. 2014; Wilson 2015). Besides reducing public health threats
(Ahmad et al. 2007) and environmental burden (Friedrich and Trois 2011),
returning resource value of waste into the economy reflects the paradigm shift
towards a circular economy focused on ‘closing loops’ through recovery, while
at the same time considering new business opportunities and economic growth
(Ghisellini et al. 2016; Witjes and Lozano 2016). Bio-waste treatment in a
circular economy addresses resource scarcity, for instance the depleting
nutrients stocks such as phosphorus (Zabaleta and Rodic 2015). It can also act
as driving force for overall waste management when, for instance, the economic
value of biowaste-derived-products incentivizes waste collection or the new
revenue opportunities enhance financial sustainability of the system (Lohri et
al. 2014).

Soil
is a dynamic natural system that lies at the interface between earth, air,
water, and life, providing critical ecosystem service for the sustenance of
humanity (Needelman, 2013). Preservation of soil quality is among the great
challenges and opportunities we have to face in the 21st century.
Soil quality is usually defined as the capacity of soil to interact with the
ecosystem in order to maintain the biological productivity, the quality of
other environmental compartments, thus promoting the health of plants and
animals, including humans (Doran and Parkin, 1994). Soil quality may quickly
deteriorate because of intensive management, stabilize with time under proper
management, and improve in the long time by supplying of organic matter.
Decline in soil organic matter under intensive farming systems is a major cause
of soil fertility loss. Organic matter plays a critical role in soil ecosystem
because it provides substrates for decomposing microbes (that in turn supply mineral
nutrients to plants), improves soil structure and water holding capacity
(Abiven et al., 2009), increases natural suppressiveness against
soil-borne pathogens (Bonanomi et al., 2010), and reduces heavy metal
toxicity (Park et al., 2011). In this context, a recovery of depleted
soil organic matter and its maintenance to an adequate level is a critical
task. It has been shown that application of organic amendments such as compost
is a reliable and effective tool to ameliorate soil structure and both chemical
(Scotti et al., 2013) and biological fertility of soils (Ros et al.,
2003), as well as to suppress soil-borne pathogens (Zaccardelli et al.,
2013a).

4.1 Introduction

INTRODUCTION,
JUSTIFICATION AND OBJECTIVES