Agricultural Research & Technology: Open Access Journal - Juniper Publishers
Soil is an unsolidified entity in which microbes are
diverse, having mutualistic, antagonistic, synergistic relationships
with plants and provides a base for living. The synthetic inputs
(fertilizers and pesticides) and anthropogenic practices aimed at
agricultural production dramatically enhance the soil chemical
reactions. Inorganic chemical reactions that occur in soil pollute the
environment after entering into four major environmental compartments
including water and air. Presence of radioactive gases in the atmosphere
may cause significant changes in the earth's environment, including
changes in precipitation and temperature along with increase in the
regional and global runoff that causes ecosystem degradation and human
health related issues through acid rain. It is a burning topic in
today’s context since it is vital to conserve the ecosystem in a
sustainable manner and as a result it decides whether global food
production is increasing or decreasing. Management of these chemical
processes by different methods is essential which could be a viable
choice for the reduction of environmental emissions and improving growth
and yield attributes of agricultural commodities. Among all the
strategies, microbial adaptation in synthesizing reactions is crucial as
it reduces ecosystem effects and increases the global food production
for the growing population.
Keywords: Soil; Environment; Synthetic inputs; Microbiology; Sustainability
Soil provides a basis for agricultural crop
production and microbial functioning in the ecosystem has a crucial role
to play in improving soil health for healthy crop growth because
microorganisms function as a complex link among soil-plant continuum.
Microorganisms in soil are a dynamic component of the soil system and
they perform vast beneficial functions in the system. Microbes aid in
different biological transformations such as organic matter
decomposition and Biological Nitrogen Fixation (BNF). Moreover, they
enhance the availability of nutrients to the plants [1]. Almost all the
things that are present in universe are dependent on the soil as it
provides basic food, fiber, shelter to humans and to other living
organisms for their survival. It is the end product of minerals, gases,
organic matter and liquids which is the habitation for mankind and
animals [2]. They interact with the plants in many different forms
including synergetic, antagonistic and mutualistic relationship
depending upon the plant to microorganism and microorganism to plant
contact. Therefore, the microbes develop the plant community structure
by specific interaction [3, 4, 5] and support growth of flora in many
ways that leads it to take part in different processes. The nature of
soil is heterogeneous, and its study is very complex. For instance, soil
chemical, biological and physical studies are important for enhancing
increase in production from limited resources [6] and thus, have various
direct and indirect consequences on different ecosystems in which soil
biodiversity, resilience and quality in extreme conditions are very
sensitive [7]. Synthetic inputs such as inorganic fertilizers,
insecticides and other agrochemicals are being used to meet the needs of
global food scarcity. These agricultural inputs not only disturb the
soil quality, health and microbial communities but also affect the other
systems directly and indirectly. The presence of carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O)
to the surroundings, for example it affects the entire community, which
is generated as a result of decaying, denitrification and
methanogenesis. The production of agrochemicals requires energy for
manufacturing. In any energy system, it is extensively accredited,
having an environmental impact with its consequences. Over last few
decades, energy-related environmental concerns have evolved from
regional local or primarily issues to universal and international
situations of major energy-related environmental issues [8].
Environmental issues are especially evident in developing or recently
mechanized republics, where energy demands progress charges are usually
too high and ecological administration is not still entirely
incorporated into a frame [9]. Anthropogenic or human induced activities
are very well known for having a remarkable influence on the
surroundings or environment. It significantly contributes to land use
and its composition is nearly about total of 38 percent of global
portion of soil, food sector that is considered as the most important
sector among all other production sectors [10], use of freshwater
approximately about 70 percent of all human use [11]. Anthropogenic
activities have an impact on marine life/ecosystem as well [12], causing
environmental problems. Air is primarily polluted by four gases, namely
sulphur dioxide (SO2), nitrogen oxides (NOx: NO, NO2), carbon dioxide (CO2), and ozone (O3),
in accordance with their historical significance, concentrations, and
its impact on animals, plants and humans. Sulfur dioxide and nitric
oxide are the primary contributors [13]. Hydrogen (H) along with carbon
(C) in various ratios combines to form fossil fuel, which can be liquid,
gaseous or even solid. Carbon and hydrogen both tend to react with
oxygen during the combustion process producing CO2 and water (H2O).
When the combustion process is incomplete or other substances (such as
sulphur, nitrogen, organic compounds and heavy metals) are present in
the fuel, other compounds are also formed chemically instead of CO2 and H2O.
If the concentration of these chemical composites in the air goes
beyond a certain threshold, it will undoubtedly endanger human life and
the environment [14]. When there is much more tax on fertilizer it leads
to application of manures at a great level. Manures are used as an
alternate for expensive fertilizers but as compare to fertilizers they
results in slow release of nutrients for plant and crop growth and yield
attributes. The farming communities discourage the use of manure due to
its slow reaction and benefit [15]. Cultivation based on synthetically
produced fertilizers is more intensive as it entirely declines the whole
system of the soil and quality of the environment. Organic amendments
basically improve soil physical, chemical and biological properties in
the tropical region [16]. There are a large number of literatures
related to the management of environment to make the agricultural
farming system sustainable. Agricultural productivity is mainly
determined by the environment as the agricultural systems are chiefly
dependent on environmental sustainability. Climate change has a
significant impact on agricultural fabrication, which is improved by
greenhouse gas discharges; conversely, high rates of fertilizer
application to soils are a key source of emissions [17].
Impacts of Agricultural Inputs on Soil Chemical Behavior
Inputs that are used for production of crops
externally like chemical fertilizers, organic amendments, microbe
inoculants and synthetic pesticides for getting the higher yield and
economic return, but some of these have adverse impacts on the soil and
these are usually neglected. The objective of this study is to summarize
how these inputs (used for production of crops) influence the condition
of soil (physical, chemical and biological). Chemical fertilizers have
little effect on soil physical properties, while organic additions
improve soil biological properties by increasing system productivity,
crop residue return and organic matter in soil. Some indirect effects
like use of nitrogen fertilizer cause acidification in soil that affects
the health of soil adversely, for example, total number, action and
diversity of soil organisms. Organic amendments are considered as the
main C reservoir for organisms in soil and secondary source of C for the
growth of plants and plant residue return. These organic amendments are
manures, different composts, bio-solids and some other humic
substances. Influence of non-target application of microbial inoculants
is small. Herbicides have shown effects on the health of topsoil
considerably, amongst all other kind of pesticides. Negative impacts of
other pesticides like insecticide and the fungicides are most common and
so they are applied under strict regulations [18].
According to inhabitants around the globe are
expected to increase about 9-10 billion in near future (2050), so
production of food is the prime goal of nearly all countries over the
world. The rate of population growth in developing countries is
approximately 3 percent per year, and food demand is increasing at a
rate of 3.8 percent per year. But production of food is increasing at
very fast speed i.e. 1.2 percent per annum. Whereas the production of
food across the world needs to be increased by 70 percent in order to
fulfill the food requirements of the growing global population [19]. The
production of food is linked to many challenges, among which the most
important is the area for the farming of food crops which is limited
[20]. The soil fertility of most of developing countries has totally
been deteriorated [21], infestations by pest are also at alarm [22].
Farming systems are bearing a huge pressure because of ever increasing
world food demand along with certain additional provocations to meet the
need of food which differ from different assets i.e. land and water
etc. [23]. To meet the global food demand, production of crops must be
increased and for this process some inputs of crop production in a
proper recommendation like pesticides and chemical fertilizers along
which organics must be used in a balanced rate without hindering any
system [24].
When nitrogen is lost from soil or plant surface, it
not only decreases the production of crops and negatively impacts on
potency of soils but also has a huge impact on its surrounding. When
nitrogen ammonia form is emitted into air it contributes with water and
forms acid rain and is considered as an in-direct source of Greenhouse
Gas (GHG) release in nitrous oxide form. When nitrous oxide is emitted
into the air, it causes ozone depletion that contributes significantly
towards climate change. The soil cation exchange reaction
electrostatically attracts ammonium ions to the surface of clay and
organic matter. As ammonium is deposited in soil through this mechanism,
the concentration of ammonium in soil solution substantially declines. A
soil with higher cation exchange capacity (CEC- clayey soils) have
lower potential to volatilize ammonia as compare to soil with lower CEC
like sandy soils [25]. Soil with calcareous environment has higher soil
pH that can easily lead to loss in huge amounts of ammonia gas, whereas a
significant quantity of ammonia gas from soils with neutral or acidic
pH is lost when animal urine or urea is applied [26,27]. When the
nitrification process begins, the soil pH decreases significantly,
resulting in lower rates of volatilization. Dropping level of phosphorus
(P) from agricultural lands may raise the productiveness of natural
waters which may accelerate the development of algae and other marine
plant species. P is typically the nutrient that regulates the
eutrophication process in renewed waters. The United States
Environmental Protection Agency (USEPA) has recommended a governing
limit for eutrophication of 0.05 ppm for total P in streams that arrive
into the lakes and 0.1 ppm for total P in flowing streams. P is removed
from the soil through the following processes:
a. runoff and erosion;
b. crop uptake and removal; and
c. leaching. From the field and soil harvested crops P
removal takes place. Concentrations of P in plant cells usually vary
between 0.1 to 0.5 percent on a basis of dry biomass and maximum plant
take up and consumption of about 20 and 90 pounds of P2O5 every year.
Moreover, the inorganic sewage sludge phase is predominantly composed of
P2O5 and SiO2 oxides. The extra oxides Fe2O3, CaO, Al2O3, K2O and Na2O
are present in lesser amounts depending on the sludge origin. The high
behavior of temperature, the liquid or solid transitions of this
inorganic combination and the phosphorus volatilization are serious
operating restrictions, but they remain poorly identified. The P2O5
present in the biomass affects the liquid manufacturing of inorganic
phase and in the inorganic formation of vapors disturbing the wear of
lining refractory, the degradation of metallic assemblies and the high
temperature of the gasification reactor. During thermo-chemical
conversion, thermodynamic controls at altered temperatures help us fix
the biomass behavior [28]. Longer greenhouse gas emission results in
higher concentrations in the atmosphere. Concentrations of greenhouse
gas are measured in parts per million (ppm), parts per billion (ppb),
and even Parts Per Trillion (ppt). One ppm is the same as one drop of
diluted water into about 13 gallons of liquid (approximately the fuel
tank of a dense car). CO2 is emitted through soil respiration
from the land, which comprises three biological procedures, i.e.,
microbial respiration, faunal respiration and root respiration mainly on
the soil surface [29]. Micro-flora within the soil adds 99 percent of
the CO2 rising from the decay of organic matter [30] as
compared to the contribution of soil fauna which is much lower [31].
However, root respiration accounts for half of total respiration. Sewage
sludge incineration generates a number of secondary pollutants,
including heavy metals volatilization, metal-chemical complexes
volatilization and nitrogen oxides. Between these pollutants, release of
heavy metal cannot be efficiently declined by drain gas cleaning
devices [32].
The most frequently defined attribute is Soil Organic
Carbon (SOC) and is chosen as the utmost significant soil quality
indicator and agricultural sustainability. In this manuscript, we
precised in what way crop alternation, cultivation, tillage and residue
managing, monoculture and fertilization influence on the features of
soil, C transformation and SOM. The outcomes ratify that SOM is a sink
for sequestration of C and also a source of C. Tillage and cultivation
may decrease SOC content and results in the degradation of soil.
Cultivation has a significant impact on C and N distribution, as well as
the rates of Organic Matter (OM) decomposition and N mineralization.
Crop rotation can help to maintain, improve the quality and amount of OM
in the soil, as well as improve the physical and chemical properties of
the soil. Proper application of fertilizers in conjunction with
Farmyard Manure (FYM) can improve soil nutrients and SOC content. Crop
residue or manure only cannot be sufficient to maintain SOC levels
[33,34]. Tillage is also used to ventilate and blend the soil, as well
as to incorporate crop cover, crop residue, manure, pesticides, and
fertilizers into the rhizosphere [35]. Tillage management in soil can
influence soil respiration controlling factors such as substrate
accessibility, soil temperature, water content, oxidation-reduction
potential, pH, number and type of microorganisms, and soil ecology [36,
37]. Second, crop rotation may have a significant impact on soil health
due to the development of soil environmental processes and connections
over time. These include increasing soil structural stability and
nutrient use efficiency, increasing crop water use efficiency and SOM
levels, providing better weed and disease control and disrupting insect
life cycles [38, 39]. Crop rotation can also increase yields and
nitrogen availability when nitrogen-fixing legumes are included [40,41].
Additionally, in crop production, fertilization is one of the most
important practices for improving soil nutrient availability. According
to [42], fertilizer uses significantly higher concentrations of P and K
in the soil and the concentrations of SOC and N, P, K were higher in the
plough layer than in the subsoil. As proper plant growth and
improvement are inextricably linked to nutrient sources. Several
nutrients affect biochemical processes in the plant's body and play an
important role in soil fertility making it more useful for plant growth
[43].
Microorganisms have extended the ecosystem where they
reside in, through acquiring enzymes that enable them to metabolize
various anthropogenic manufacturing compounds (xenobiotics) [44]. The
usage of microbes or microbial mechanisms for inactivating and
deteriorating the ecological pollutants is known as bioremediation. Over
many years, microbes have been used for regular treatment and
alteration of waste materials [45]. Microorganisms that degrade the
wastelands that enter the treatment plan rely on the metabolic processes
of fixed-film and activated sludge treatment systems. Many such waste
management plants are specialized with designated and accustomed
microbial species that are frequently used to tackle industrial
wastewater. Microorganisms can even be catalyzed by a variety of metal
transforms which can help with waste management. Oxidation, reduction,
and alkylation interactions are the examples of these transformations.
Fungi, bacteria, algae Soetan 113, and protozoa may store manganese and
ferrous ions during oxidation processes. Geobacter metallireducens is a
bacterium that eliminates uranium, a radioactive waste, from mined
groundwater sources and contaminated water. For oil extraction,
prevention of pollution, mineral leaching and restoration,
microorganisms may now be genetically modified using rDNA techniques.
Microbes may also be genetically modified to manufacture compounds
effective in enhanced oil recovery mostly in petrochemical industries
[46]. Oil spill cleanup may be delegated to genetically modified
bacteria in the future [47]. Microbes with improved leaching capacity
may be engineered for use in the mining industry. Metals may bind to the
microorganism surfaces and be concentrated internally.
Agricultural land is an essential component for food
production, shelter and fiber for mankind [48]. In the economic growth
of several developing countries farming plays a dynamic role and also
provides self-employment opportunities [49]. Many plant physiologists
believe that soil is the primary source of plant nutrients; however,
good soil quality is required for agricultural production, and quality
is improved by soil bacteria, fungi, and protists [50]. The microscopic
biosphere is the major pool of biodiversity on earth [51]. In other
words, microorganisms can be considered as soil machinery in recycling
of the nutrients [52]. The quality of soil and its conservation can be
improved by soil microbes within the soil system. Soil microorganisms
will allow the breakdown of OM such as animal and plant remains, as well
as the formation of soil structure and the rate of biogeochemical
cycling [53]. Improvement in soil quality, plant nutrition and
maintenance of plant health is a fundamental function of soil
microorganisms in agriculture [54]. Generally, people think that
microbes are disease-causing agents. The decomposition of organic matter
will be done through the help of these microorganisms in the soil [55].
Interactions between Plant and Soil Microbes along with Stressed Agriculture
According to [23] plant-soil microbe relationship
affects crop growth and competitive capacity which is critical for the
structure of terrestrial ecosystems. Abiotic factors such as nutrient
concentrations or environmental stress have been shown in several
studies that change the course and extent between the interactions of
plant and microbes. Considering this frame of reference, it's likely
that the consequences of changing climate, such as altering the
availability of water might alter the consequence of plant-microbe
interaction that could influence plant species interaction. They used a
managed greenhouse experiment on 3 species of plants: Plantago
lanceolata, Schizachyrium scoparium and Rudbeckia hirta, to see
whether the availability of water regulated the influence of soil
microbes on pair-wise plant interactions throughout the Texas coastal
prairie. Plants were grownup under living or germ-free soil treatments
including high, medium, and least availability of water to see whether
there was an association amongst water availability and soil organisms.
They discovered that the existence of soil microbes enhanced
intra-specific competitiveness in comparison to inter-specific
competition, and therefore this impact was dependent on water
availability. With the presence of microorganisms, the intensity of
intraspecific competition rose as the availability of water lowered.
Their findings indicate that the soil microbial communities,
particularly in drier environment can perform a key function in
stabilizing co-occurrence by raising conspecific negative density
dependency. Changing microbial composition of the land community or the
plant-microbial interactions can results in alteration in the structure
of the plant community. Legate effects of drought and rainfall have been
observed to reduce native biomass in soil microbial species, but have
no impact on non-native biomass. While availability of water affects
interaction between plant-plant and plant-soil, limited studies explored
if the availability of water controls soil microbe effects on plant
collaborations. If water deficit reduces the diversity of microorganisms
in soil, so they can be estimated to perform poorer in modulating plant
interactions than wet environments under dry conditions. Conversely, as
the impact of soil microorganisms on plant output increases with dry
conditions, then soil microorganisms might also perform a better role in
facilitating plant interaction under desiccated conditions. This might
be crucial to recognize how specific groups of soil microorganisms react
to accessibility of water to improve our power to foresee how
plant-microbial contacts alters with the alteration in environment [56].
According to [57], the estimated increase in heat and reduced rate of
precipitation due to alteration in climate and undiminished human
activities supplement to agricultural industry complications and
uncertainties. The world is constantly investigating the effects in
terms of food safety, the soil nutrient imbalances, poorly managed use
of pesticides, high temperatures, floods, or drought, soil salinity and
heavy metal pollutants. They explain the importance of
soil-plant-microbe associations with organic manure for all the
solutions of troubled problems in agriculture. Plant-associated
advantageous microorganisms are believed to enhance plant growth and
increase resistance mechanisms of plants to biotic (diseases) and
abiotic stresses like (salinity, drought, waste etc.). The Plant Growth
Promoting Rhizobacteria (PGPR) and mycorrhizae are crucial elements of
the microbial communities and have the vital function in maintaining
plant fitness and soil health in extreme circumstances. Addition of
organic manures to strained soil together with appropriate bacterial
strains may further improve plant-microbe contact and enhance
agricultural crop productivity. A mixture of plant, stress resistant
microbe and organic modification is the tripartite association that
provides hospitable environmental conditions for the propagation of
advantageous rhizospheric microorganisms which in turn improve the
growth output of plants in a disrupted agro-ecosystem. The agricultural
soil-used patterns, with plant microbe interactions properly and using
appropriate advantageous microbial agents is perhaps one of the most
successful management technique in the agricultural land concerns
[58,59].
Soil is a necessary basic need towards agricultural
crop production and microbe’s activity in the system has a unique and
essential role to play as in improving soil health in a sustainable
manner for healthy crop growth due its complex link among the soil-plant
continuum. Microbes have an intrinsic role to play in different
biological transformations such as organic matter decomposition,
biological nitrogen fixation and enhancement of the availability of
nutrients to the plants for its growth and development. Several inputs
that are used for crop production purposes like chemical fertilizers,
organic amendments, microbe inoculants and synthetic pesticides in order
to attain the required yield and economic return all have adverse
effect on the soil and these are usually neglected by most of the
countries. Synthetic fertilizers have little effect on soil physical
properties whereas organics improve soil biological properties by
increasing system productivity, crop residue return and organic matter
in soil. The use of nitrogen fertilizer leads to acidification in soil
that affects the health of soil. Soil organic carbon is regarded as the
utmost significant soil quality indicator and agricultural
sustainability. Soil organic matter is a sink for the sequestration of
carbon and also a source of carbon. The quality of soil and its
conservation can be improved by soil microbes within the soil system.
Soil microorganisms allow the decomposition of organics such as animal
and plant remains, as well as the formation of soil structure, supply
plant nutrients and the control the rate of biogeochemical cycles.
Improving soil health, plant nutrition and maintenance of plant health
is a fundamental function of that is controlled by the soil
microorganisms in the field of agriculture. Plant-soil microbe
relationship affects crop growth and competitive capacity which is
critical for the structure of terrestrial ecosystems. Abiotic factors
change the course and extent between interaction of plant and microbial
biomass. It is necessary to understand the dynamics between microbes and
its environment especially its processes in relation to agriculture and
soil health.
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