1 INTRODUCTION
Land is an essential factor in agricultural
productivity. Population increase, industrialisation,
and urbanisation in the quest to development have
drastically reduced the available arable land, and this will continue as
population and industrial activities increase, and urbanisation
expands on a daily basis. As the population is
increasing, so is the demand for agricultural products especially food, which
no one can do without (Ikuli, 2017). The drastically
reducing available arable land will also affect agricultural productivity.
Available land per capita (land per person) in Nigeria in the 1960s (1963 –
1969) ranged from 0.513 – 0.633 hectares (5130m2 – 6330m2),
but now as at 2013, the available arable land was 0.197 hectares (1970m2)
and 2015 0.188 hectares (1880m2) per person (FAO, 2017). Today farmers still practice shifting
cultivation, to maintain the soil health for better productivity. With the
continual reduction of available arable land, as a result of population
increase and development, there is the tendency that a time will come, when
there will be no more land for the farmers to shift to after cultivation on a
particular land, which means they will continue to plant whatever they want on
that same piece of land, whenever they want to plant, which will have negative
effect on the health of the soil, and in turn reduce productivity as a result
of loss of vigor.
The continuous use of
inorganic nutrients sources; like inorganic fertilizers and other synthetic
products also damage the soil life. This is because, most of these inorganic
substances that are not utilised by the plants when
applied, are leached into the soil, thereby increasing the level of
contaminants and pollutants in the soil.
To prevent or control
such unforeseen circumstances, there is the need to employ strategies that will
mitigate the drivers of the soil health, which are the microbes. Activities of
microbes in the soil increase the level of organic matter in the soil. Increase
in soil organic matter (SOM) in the soil in turn; improve the health of the
soil. In every 1% increase in the soil organic matter, a 1,000-pound weight of
Nitrogen (N) is produced, a 100-pound weight of potassium, phosphate, and
sulfur each are produced (www.bontera.com; www.motherearth.com). The activities
of microbes balance and improve the soil structure and texture (Havlin et al.,
2006; Ikuli and Ogidi,
2017). Their activities help in increasing phosphorus mobility. Their
activities reduce bulk density of the soil and improve the bufa
capacity of the soil, due to the complication of organic matters. Increasing
SOM reduces both chemical fertilizer runoff and nutrients leaching.
Microbe-rich soil attracts organisms, help restore and maintain the natural
balance of soil: Arthropods, Nematodes, Earthworms, Fungi, Bacteria and
Protozoa (Havlin et
al., 2006; Grotz, 2014).
Microbial soil
enhancers are natural sources of humic acid, fulvic acid, amino acid, minerals, vitamins, proteins and
carbon for plants (Grotz, 2014). According to Havlin et al.
(2006), they reported that Andersons Production Ltd said that Biological
Farmers of Australia (BFA) recommended that all fertilizer inputs (solid or
liquid) should be combined with a carbon source. This creates a stable
carbon-nutrient bond. As a result, the nutrients will be less prone to
leaching, volatilisation, becoming insoluble and
causing damage to the soil life. Natural soil enhancers increase crop
productivity, strengthen root growth and promote nutrients absorption. It
increases the natural immunity of the crop, water holding capacity of the soil,
and provide a conducive environment for soil microbial
activities.
In order to
acknowledge and make judicious use of the important roles microbes play in soil
improvement for better productivity, sustainable maintenance of the soil health
and control to an extent, the possible effect of limited land for agricultural
cultivation, it is therefore necessary to examine the effect of microbial soil
enhancers on cassava production in this region. This is because cassava is a
major crop grown in this region.
The objective of this
study is to provide alternative sources of nutrients that will maintain soil
health and enhance productivity.
2 MATERIALS AND METHOD
The research was conducted in the Faculty of
Agriculture Teaching and Research Farm, Abuja campus, University of Port
Harcourt, Port Harcourt. Latitude 4º 54¹ 34¹¹ N, Long.
6º 55¹ 24¹¹ E. With a temperature range from 23ºC to
35ºC and a total rainfall range of 2000 – 3000mm per annum from May 2017 to May
2018.
2.1 Land Preparation and Plot Layout
A total land area of 477m2 was
cleared, ploughed and was partitioned into 24 plots. Each plot’s size was 5m
x2m, with eight treatments and three replicates. The distance in-between
treatments and replicates were 1.5m apart. Treatments were arranged in a
randomized complete block design.
2.2 Planting Material and Planting
Cassava (Manihot esculenta C.) stem cuttings; TME 419 and
TMS3168/UMUCASS/36 (YELLOW ROOT) were obtained from University of Port Harcourt
Faculty of Agriculture Teaching and Research farm, Choba
Port Harcourt, Rivers State, Nigeria.
2.3 Treatment Material
A microbial soil enhancer "Bontera", a liquid concentrate was obtained from Organico, A division of Amka
Products in South Africa.
2.4 Planting
Cuttings of cassava stems were planted 1m
apart giving a plant population of 25 plants per plot (10,000 plants/ha).
2.5 Treatments
Only water was required (control).
To the second treatment only Bontera was added (1L/ha at planting, foliar application 4
weeks after planting- every 4 weeks until maturity).
One hundred (100%)
percent fertilizer (farmer standard) + 1 L Bontera/ha
at planting, foliar application 4 weeks after planting- every 4 weeks until
maturity.
Only 100% fertilizer was applied.
Seventy-five (75%) percent
fertilizer + 1 L Bontera/ha at planting, foliar
application 4 weeks after planting- every 4 weeks until maturity.
Seventy-five (75%) fertilizer only
Fifty (50%) percent fertilizer + 1 L Bontera/ha at planting, foliar application 4 weeks after
planting- every 4 weeks until maturity
Fifty (50%) percent
fertilizer only.
2.6 Treatment Dilution and Application
Soil Application- 2.5ml of Bontera was added to a liter of water and applied to each
plot designated for microbial soil enhancer treatments at planting.
Foliar Application – 2ml of Bontera per liter of water was sprayed onto the leaves and
crop.
2.7 Fertilizer Application
NKP 15:15:15 fertilizer was applied at the
designated rates on the eighth week after planting. 20g/plant was applied to
100% fertilizer rate, 15g/plant was applied to 75% fertilizer rate and
10g/plant to 50% rate of fertilizer application.
3 DATA COLLECTION
3.1 Soil Sample
Before commencement of the study, soil
samples were randomly collected from the experimental site. The collection
depth was 0-15cm and 15-30cm. Some of the soils were instantly taken to the
laboratory for microbial flora/fauna analysis.
Some soil samples were viewed under OLYMPUS
electronics microscope, and micro fauna were identified and counted. Menica (2005) method was adopted for microbial flora
identification and count. While some were air-dried, crushed and sieved to pass
through 2mm sieve and used to conduct a complete physical and chemical soil
analysis adopting Olsen et al, 1954; Mehlich, 1984; Stewart, et
al, 1974 methods and Atomic Absorption Spectrophotometer (AAS). After
harvest, soil samples were also collected from each treatment in all replicates
for microbial soil flora/fauna and complete physical and chemical soil
analysis.
4 GROWTH ANALYSIS/ MEASUREMENT
The plant height, leaf area, growth rate,
plant canopy, canopy volume, and leaf area index of the plants were measured.
The measurement started four weeks after planting. The measurement was taken in
four weeks interval. Measurements were made on ten (10) plants and the averages
taken from each unit.
5 HARVESTING/YIELD
At maturity, harvest was done manually. After
harvesting, the fresh weight of each was taken immediately using a manual weighing
balance. The length, circumference, and number of roots from 10 stands from
each treatment were also taken.
6 STATISTICAL ANALYSIS: SAS Soft
word was used for the statistical analysis.
7 RESULT
7.1 Microbial Flora/Fauna
For the soil health to be optimal, the
population of the different general or class of microbes must be balanced. To
obtain a balanced statue, nutrients and environmental conditions must be
conducive. A balanced statue is when the microorganisms are in a well-rationed
population of bacteria, fungi, protozoa, nematode and earthworm
(www.motherearth.com). The microbial
flora and fauna of the soil before planting and treatment were 80.64% bacteria,
19.05 fungi, 0.16% protozoa, and 0.15% nematode. After the treatment, it
revealed that in control; 86.21% and 79.30% of bacteria constituted the
microorganism population in plots that TME419 and TMS1368/UMUCASS/36 popularly
known as YELLOW ROOT were planted respectively. For the plot that TME419 was
planted, 2.59% fungi, 8.62% protozoa and 2.59% of nematode made up the
microorganism population. While for YELLOW ROOT, 15.42% fungi, 0.88% protozoa,
and 4.41% nematode made up the microbial population. For the soil treated with
microbial soil enhancer only, the plot which TME419 was planted constituted of
91.46% bacteria, 3.66% fungi, 1.22% protozoa, and 3.66% nematode, while the plot
planted with YELLOW ROOT constituted 92.86% bacteria, 3.57% fungi, 2.14%
protozoa, and 1.43% nematode. For the soil treated with microbial soil enhancer
and 100% NPK fertilizer, 74.77% bacteria, 18.69% fungi, 1.87% protozoa, and
4.67% nematode constituted the soil microbial flora and fauna that TME 419 was
planted. While 93.02% bacteria, 3.10%
fungi, 2.33% protozoa, and 1.55% nematode made up the microbial population in
the plot that YELLOW ROOT was planted. In the soil that only 100% fertilizer
was applied; and in the plot where TME 419 was planted, 98.04% bacteria, 0.33%
fungi, 0.65% protozoa, and 0.98% nematodes made up the soil microbial
population. While the plot where YELLOW ROOT was planted constituted of 46.48%
bacteria, 43.48% fungi, 6.21% protozoa, and 3.73% nematodes. For the soil
treated with microbial soil enhancer and 75% fertilizer, 40% bacteria, 56%
fungi, 2.40% protozoa, and 1.60% nematodes constituted the microbial flora and
fauna population. While 90.09% bacteria, 0.45% fungi, 6.76% protozoa, and 2.76%
nematodes made up the population of the microbial community in the plot that
YELLOW ROOT was planted. In the soil where only 75% fertilizer was used for
treatment, and for the plot with TME419, 77.52% bacteria, 11.63% fungi, 7.75%
protozoa and 3.10% nematode made up the microbial population while for the plot
that YELLOW ROOT was planted, 87.91% bacteria, 5.49% fungi, 3.30% protozoa and
3.30% nematodes constituted the microbial community. For the soil treated with
microbial soil enhancer and 50% fertilizer, 95% bacteria, 1.59% fungi, 1.59%
protozoa and 1.59% nematodes made up the microbial flora/fauna population in
the plot where TME419 was planted and 83.33% bacteria, 11.91% fungi, 2.38%
protozoa, and 2.38% nematodes made up the soil microbial population in the plot
YELLOW ROOT was planted. For the soil treated where only 50% fertilizer, 60%
bacteria, 35% fungi, 3%protozoa, and 2% nematodes summed up the microbial
community in the plot that TME419 was planted. While 84.75% bacteria, 3.39%
fungi, 6.78% protozoa, and 5.08% nematodes constituted the microbial
flora/fauna population where YELLOW ROOT was planted as presented in table 1
and 2.
8 DISCUSSION
From the results shown in table 3, the pH of
all the treatments is in the range that all nutrients will be accessible by
plant easily. The result simply indicates that the activities of the microbes,
generated in the soil, resulting from the application of the microbial soil
enhancer, which is a prebiotic, improved the availability of these nutrients.
It clearly showed that the number of nutrients removed was highest in the
control where neither fertilizer nor microbial soil enhancer was applied,
especially, Nitrogen (N), phosphorus (P) and potassium (K) that are needed in
large quantity in a crop like cassava in this study. It was also observed that
the treatment with both microbial soil enhancer and inorganic fertilizer (NPK),
at 50% (10g/plant) rate had the highest yield (52.92 ton/ha), the highest
organic matter, and increase in other nutrients especially, P, Fe, and Zn that are
essential for plant growth, development, and productivity. This indicates that
with microbial soil enhancer and 50% fertilizer, both the plants and
microorganisms were favored. The nutrients available were sufficient for both groups,
and facilitated immobilisation; which is the
conversion of nutrients from inorganic (soluble) form to organic form, making
it not readily available to plants and microorganisms, to control excesses and mineralisation; which is the conversion of nutrients from
not readily available state, to readily available state through microbial
activities, in the forms plants take them up. The result also revealed that
among the cultivars used, Yellow Root (TMS 3168/UMUCASS/36) was more favored
and does better than TME 419 in most of the treatments. The prebiotic applied,
facilitated the multiplication of microbes which in turn increased the nutrient
status of the soil, through immobilisation and mineralisation. The humic and fulvic substances, in this microbial soil enhancer,
facilitated the increase of many essential nutrients and organic matter.
However, there was no significant difference at 0.5 level of probability, in
the nutrients and organic matter levels, irrespective of increase and decrease
among all the treatments.
8.1 Microbes and Soil Improvement
These microorganisms, bind soil particles
together through their secretion activities. These activities improve the soil structure, increases soil water infiltration and also
improve the water holding capacity of the soil (Ingham, 2009; Hoorman, 2016). They decompose organic remains through
enzymes released into the soil. The microbial waste that protozoa and nematodes
excrete is ammonia (NH+4), which is one of the forms through which plants
take up nitrogen. Nitrite bacteria (Nitrosomonas
spp.) convert the ammonia into nitrites (NO-2) and Nitrate bacteria
(Nitrobacter spp.) convert nitrites to nitrate (NO-3).
According to Lowenfels and Lewis (2006), aerobacteria
of the different genus; Aerobacter and actinomycetes bacteria of the genus Streptomyces, give a
soil a good earthy smell. Aerobic bacteria use oxygen to decompose most carbon
compounds. Azobacter, Azospirillum,
and Clostridium do not need a host plant to fix nitrogen into the soil (Hoorman et al, 2011).
They live freely in the soil. The soil structure is also improved by the
polysaccharides or glycoproteins produced by bacteria, which coats the surface
of the soil particles by cementing sand, silt, and clay into a stable structure
(Hoorman, 2016). Bacteria in the genera, like
Bacillus, Sporosarcina, Spoloactobacilus,
Desulfotomaculum, and Clostridium produce urease
enzyme and is used for bio mediation and soil rehabilitation techniques (Kucharski et al,
2006). Penicillium possesses an important property,
which is its ability to act in as low as 3-4ºC where root development and
phosphorus availability are usually limited. Rhizobacteria
are good plant growth promoters. They colonize the plant roots and stimulate
growth. Bacillus spp. Are good in solubilizing
phosphorus (P) and have the advantage of forming stress-resistant in plants.
According to Umar et al (2016), Fusarium enhanced root enlargement. Fusarium
also facilitated the development of tap and lateral roots in the plant (Yigit and Dikilitas, 2008) which
means for a crop like cassava, Fusarium will
facilitate an increase in the number of roots and enlarge root size which are key components of yield determination. Hence,
for crops like cassava in which the root is the major economic need, the
presence of Fusarium which was introduced by the
application of the microbial soil enhancer, will improve yield. Staphylococcus
checks and balances the growth and multiplication of other microbes. According
to Jacquemyn et
al (2013), Staphylococcus has been found to be a nectar-
inhibiting/preventing microbes. Staphylococcus is associated with
inorganic fertilizers. And its multiplication is favored at a lower rate or an
average quantity of fertilizer applied. Hence, when microbial soil enhancer is
applied with 50% rate of fertilizer that is supposed to be applied to a soil,
it provides an atmosphere where the microbes are generated in a moderate rate,
not becoming overpopulated to cause harm to the soil but an average population
whose activities, will enhance the soil structure, texture, bulk density and
improve the soil organic matter and fertility, through immobilisation
and mineralisation. In the treatment where only
microbial soil enhancer was applied, the microbial soil enhancer eradicated
staphylococcus, likewise where 100% fertilizer was applied staphylococcus was
eradicated. In other words, excess nutrients prohibit staphylococcus and this
may lead to an excess multiplication of microbes, or accumulation of not utilised synthetic substances, that might turn to be
disastrous to plant and the environment instead of its main purpose, of
sustaining soil for better productivity and agricultural continuity.
8.2 Microbes and Plant Protection
Beneficial microbes
also known as rhizospheric microorganisms suppress
diseases in the soil (Grotz, 2014; Hoorman, 2016). They reside in the rhizosphere
of the soil, and participate in active plant growth, by inducing root exudation,
enhancing the availability of nutrients to plants, and releasing growth
regulators, and help in soil-borne disease suppression or control. Many soil
bacteria produce antibodies that protect plants from disease-causing organisms
and plant pathogens. Different types of bacteria compete for the same soil
nutrients, and water which tends to balance the system by reducing the
population of disease-causing organisms, since the population of pro-bacteria
are more than the pathogenic bacteria population. Actinomycetes
produce more than 50 different antibiotics, to protect plants from pathogenic
bacteria (Sylvia et al, 2005). They
have large filaments or hyphae, and act similar to fungus in processing soil
organic remains, which are difficult to decompose (Chitin, lignin, etc.). When actinomycetes die, maybe during processing the land through
tillage, they release "geosmin" which is
the cause of smell as a characteristic of newly plowed soil (Hoorman, 2016). According to Ingham (2009), Actinomycetes are more active and decompose many substances
at high soil pH levels. Actinomycetes play an
important role in forming stable humus, which enhances soil structure, improves
nutrient storage, and increase water holding capacity of the soil (Hoorman, 2016). Many photosynthetic bacteria colonize the soil, recycle N, C, P, and other soil nutrients to produce
organic matter.
Pseudomonas species
are a group of pro-bacteria required for biological control of pathogens and
bioremediation (Ganeshan and Kumar, 2007). They
promote growth in a plant, protect and reduce severity in plant fungal diseases
(Hoffland et al,
1996; Wei et al, 1996). O'Sullivan
and O'Gara (1992), also reported that pseudomonas control pathogens, by the
secretion of some secondary metabolites (antibodies, siderophores
and hydrogen cyanides). They also produce urease. Bacillus spp. and Klebsiella aerogens are good in
urea production and for environmental soil bioremediation.
8.3 Microbial soil enhancer and
Bioremediation
Many agricultural lands are lost to
pollution. They are contaminated or polluted with compounds that are difficult
to decompose (recalcitrant). But with the use of microbial soil enhancer that
introduces many microbes, such lands can be remediated. Microbes like Actinomycetes have the ability to break down such hard to
decompose compounds (Hoorman, 2016). Mucors are good in loosing bonds of many hard compounds
that are hazardous to the environment. Ane et al (2013),
reported that fungi like Aspergillus, mucor spp. and Fusarium are good
in degrading synthetic substances like herbicides, organophosphate compounds
like glyphosate, and developing in culture media containing herbicides mainly
as a source of carbon and phosphorus. They said that the degradation occurs by
glyphosate oxidoreductase which breaks off the
glyphosate C-N bond to produce aminomethylphosphonic
acid and glyoxylate. Mucor rouxii can be used for the stereoselective
reduction of β-keto-esters. Hence, mucor is a good bioremediation source. Rhizopus aryzae is capable of exhibiting
versatility in the transformation of a wide range of xenobiotics
as steroids, terpenes and aromatic compounds (Dijksterhius and Samson, 2006).
8.4 Microbial Soil Enhancer and Cost
Management
The use of microbial soil enhancer will
reduce the cost of labor. It will reduce the cost of nutrients sources like
fertilizers and solid organic nutrients sources like manure, poultry droppings,
cow dungs, etc. The transportation of microbial soil enhancer to farm or
location to be used is very easy compared to other nutrients sources. Only one
person can carry the whole microbial soil enhancer to be used in a whole
hectare of farmland with ease, but fertilizers, manure, poultry droppings and
cow dungs to be used in a hectare will involve more labors. The use of
microbial soil enhancer for bioremediation will not involve labor and cost as
an ex-situ bioremediation process will.
9 CONCLUSION
To maintain high productivity and sustain the
soil health for sustainable production and agricultural continuity, the use of
microbial soil enhancer should be encouraged. For effective utilisation
of microbial soil enhancer and to prevent disaster, microbial soil enhancer
should not be used in a virgin soil or a fertile soil. It can be used from the
second or third time of cultivating on that same piece of land depending on the
crop planted and the level of nutrients removed. Supplementing
it with inorganic fertilizer at lower rate gives a better result.
Microbial soil enhancer should be encouraged, because it is also good for
bioremediation. And it will help to reclaim more agricultural lands lost to
pollution, which in turn will increase the available arable land.
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