Tillage has been an essential part
of innovative development in the advancement of agribusiness, specifically in
production. The soil is tilled to achieve a fine tilth for the sowing of seed,
water, and soil preservation, and weed control. Tillage exerts different
physical, chemical and biological impacts on the soil both advantageous and
debasing, contingent upon the suitability of the systems utilized. The physical
impacts, for example, aggregate stability, penetration rate, soil and water
preservation, specifically, have a coordinate effect on soil profitability and
manageability. (FAO. 1993)
However, as the world population
grows at an alarming rate, food production has undergone a decline. This is in
part due to declining levels of soil productivity. Agriculture has to find
innovative ways of producing enough food to meet the demand, especially in vulnerable
regions like Africa and Asia, which are the most food insecure.
Swilling and Annecke state that
there is mounting evidence that the ecosystems that make agriculture possible
are steadily deteriorating as the levels of extraction and exploitation
intensifies (Swilling & Annecke. 2012). Swilling and Annecke directly link
declining yield growth to soil degradation. To achieve food security we have to
find sustainable ways of food production to meet the growing population demand.
Tillage-based crop production system?
Tillage is known as the mechanical
exploitation of the soil with the intention of growing crops. This disturbance
of the soil affects the soil characteristics such as soil water conservation,
soil temperature, transpiration, and evapotranspiration processes. This means
that tillage exerts a footprint on the soil willfully to yield crops;
therefore, damages the environment.
Conventional tillage practice exerts
the most impact on the soil. It is responsible for the loss of soil organic carbon
content, nitrate leaching, greenhouse emissions. Busari, Kukal, Bhatt &
Duluzi claims that soil disturbance by conventional tillage makes the soil
serve as a source rather than a sink of atmospheric pollutants and; thus, is
unsustainable and environmentally friendly.
Busari et al. list conservation
tillage practices as ranging from No-Till (NT), Reduced Tillage (RT), Mulch
Tillage (MT), and Ridge Tillage to Contour Tillage. NT involves land
cultivation with little or no soil disturbance, the only disturbance being
during planting while minimum tillage means a reduced level of manipulation
involving plowing using primary tillage implements (Busari et al. ).
In mulch tillage, they state that
the soil is tilled in a manner that plant residues are left to cover the soil
surface to the highest degree. They explain ridge tilling as the planting of
crops in rows along both sides or on top of the ridges prepared at the
commencement of the cropping season while contour tillage is when tillage is at
right angles to the direction of the slope.
The texture has two important
physical properties when it comes to indicating soil quality; those are
aggregate stability and size distribution. The particle size distribution is an
essential physical property that defines the soil texture and influences the
soil properties the most. These two physical properties mentioned above
reflects the resistance of soil erosion, especially in a no-tillage system,
which is why they are the most important factors when it comes to soil quality.
The soil structure defines which
different types of particles that are stored in the soil and it exerts control
over the physical, biological and chemical processes. It also explains how and
where the particles are located, which is important for how suitable the soil
is for growing crops.
If the soil has a poor structure, it
can affect the nutrient availability and the nutrient uptake negatively and
increase the input energy requirement for tillage, increase the nutrient loss
and the denitrification, which is negative from an environmental point of view.
Organic matter, tillage system, and biological activity matters for the
aggregate structure in the soil.
Soil’s conductivity, which is the
ability of the soil particles to attract nutrients, is influenced by the
presence of organic matter in the soil. Nutrients are spared from leaching in
soils with high organic matter content. With less organic matter content and
leaching of nutrients, over time the soil can become more acidic.
Various studies has proven that
tillage has an impact on soils physical and chemical properties. To ensure soil
water availability, nutrient availability, and proper root development, it must
be ensured there is a very minimal disturbance to the soil.
Environmental effects of tillage
Intensive tillage leads to soil
erosion. Soil erosion is described as the detachment and movement of soil
particles from point of origination through the action of water and wind. Wind
erosion is the more visible, though water erosion is the most devastating. The
loss of natural nutrients and possible fertilizers directly affect crop
emergence and growth. Seeds can be disturbed or removed and pesticides can be
washed off. This means fewer nutrients for plants leading to reduced yields.
Soil water erosion has great environmental and economic implications as eroded
soils can inhibit the growth of seeds, bury seedlings, contribute to road
damage, and even contaminate water sources.
The topsoil typically has more
organic matter and more plant nutrients than the soil deeper in the soil
profile. Associated with the organic matter are billions of soil
microorganisms. Microorganisms are the engine that keeps soil alive and
productive. Numerous scientific studies have shown that soil with fewer
microorganisms or a lower diversity of microorganisms is less productive than
soils with a good balance. Erosion can be made more severe due to man’s
influences. A soil with a higher proportion of clay and humus usually increases
the stability of structure and aggregates. Aggregate stability is characterized
by the sensitivity to external influence. The essence of aggregate stability is
the organic matter because large parts of plants and roots act like a barrier
and prevent aggregates to break into smaller units with help from decomposing
of microorganisms that provide an adhesive effect. With tillage systems,
organic matter is greatly reduced.
Permeability is the soil´s capacity
to drain off the water. The structure of a soil is influenced in both the long
and short term of tillage and cultivation measures, which in turn affects the
soil physical properties. Tillage affects soil quality, structure, stability,
and texture, which in turn affect the holding capacity of the soil referred to
water infiltration rate. This is due to the decrease in soil organic matter and
the subsequent aggregate breakdown.
Tillage causes air to enter the soil
particles. When the soil is more aerated, nitrous oxide escapes into the
atmosphere offsetting the cooling effect of carbon dioxide drawdown. N2O is the
most important agent for stratospheric ozone destruction. The soil is the
largest source of N2O emissions and it is exasperated by tillage and the
ever-increasing use of synthetic nitrogen (N).
(Growingnations.co.za, 2018) describes soil is
one of the most important natural resources farmers have. In the absence of
soil, farmers cannot farm. As with other important resources, it is vital to be
protected or improved for the benefit and sustainability of future generations.
Once soil leaves a farmers field it is lost forever. As soil erodes from
farmer’s fields, the most valuable part of the soil (the topsoil) is gone.
Economic effects of conventional tillage
Tillage operations are generally
conducted to prepare a seedbed, incorporate fertilizers, and cultivate for weed
control. The number of trips required to perform these operations depends on
soil type and condition, the crop, weather conditions, and the type of tillage
system utilized. Excessive tillage operations increase fuel consumption,
operating costs, machinery wear, and time and labor requirements.
Yield reduction reported for
conventional reduced tillage systems due to poor soil quality. This has a
domino effect on farm income, exports, and food security concerns.
Arable land supplies food and it is
therefore important to develop the production and land-use plan in a
sustainable way. To grow crops for food should be both economical and
environmentally sustainable and the soil structure and quality should be taken
into consideration when cultivating the land.
We need to find new approaches to
maintain good soil structure, and minimized tillage systems have many
advantages, including reduced costs for the growing of crops, while leaving
plant material in the fields can reduce erosion and increase the biological
activity and humus content of the soil.
A non-cultivated soil generally has
a better structure due to the higher content of organic matter and less
compaction than a cultivated soil has. Soil structure is influenced by soil and
crop management inputs and has an impact on soil quality. One of the factors
that influence the quality is tillage. This input is an important factor and
relevant to the point of sustainability
Vegetation and recycling of organic
matter contribute to a better structure and physical environment. Soil
cultivation measures do the opposite. If the structure should be improved, the
structure-building measures need to be greater than the structure depleting
measures such a conventional tillage systems.
Adding organic matter can preserve
soil structure and increase the crop safety. Measures to improve the structure
and provide better conditions for the crops is to return crop residues to the
soil, grow cover crops and only apply shallow tillage or no-till, which could
increase the humus content in the top layer. Increased humus content will give
a lower bulk density, increased aggregate stability and increased porosity,
which in turn give soil the increased water holding and infiltration capacity.
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