Special Reports/Organic Farming
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Organic
matter status of Pakistan soils and its management
Shahzada Sohail
Ijaz
Soil organic matter affects so many soil properties and
processes that a complete discussion of the topic is beyond
the scope. Often one effect leads to another, so that a
complex chain of multiple benefits results from the addition
of organic matter to soils. For example, adding organic
mulch to the soil surface encourages earthworm activity,
which in turn leads to the production of burrows and other
biopores, which in turn increases the infiltration of water
and decreases its loss as runoff, a result that finally
leads to less pollution of streams and lakes.
In Pakistan, the soils are very poor in organic matter than
the desirable level. A soil having 1.29 % C is considered to
be sufficient in organic matter, but Pakistan soils are
having less than that. In a survey conducted by
Farooq-e-Azam it is reported that the range of soil carbon
in Pakistan soils is 0.52 to 1.38% in different soil series.
Most of them have less than 1%.
Reasons For Low Organic Matter Content of Pakistan Soils
The low organic matter content of Pakistan soils can be
attributed to the following reasons.
Climatic Conditions
The mean annual temperature influences the processes of
decomposition of organic matter. At high temperatures the
decomposition proceeds very quickly. That is why high
temperatures prevailing in Pakistan are conducive for a
rapid decomposition and loss of organic matter.
Soil Orders
The differences of organic matter content among soil orders
also play key role in determining the potential of a soil to
keep a certain level of organic matter. The largest soil
orders in Pakistan are Aridisol and Entisol, which are known
to have lowest organic matter content among all the soil
orders. So our soils naturally have lesser capacity to hold
higher organic matter content.
Use of Mineral Fertilizers
Before the advent of mineral fertilizers and green
revolution the farmers used to replenish their soils by the
application of organic wastes. With the availability of
cheap and easy to handle mineral fertilizers the farmers
were able to get higher yields only with the application of
mineral fertilizers. Thereby the use of organic wastes
reduced drastically. The increasing price of mineral
fertilizers and soil degradation concerns have forced people
to reconsider the organic sources in agriculture.
Poor Economic Conditions of Farmers
The miserable economic condition of our farmers is another
reason for less application of the organic wastes back to
soils. Almost no crop residues are left in the soil after
harvest. The straw and other crop residues are used as
fodder for the farm animals and the animal dung is used as
fuel. About 50% of animal droppings are not collected, about
half of the collected is burnt as fuel and only one fourth
is available for field application. Green manuring is not
adopted by our farmers because it does not give short term
economic returns.
Intensive Tillage
Another culprit for the lower organic matter content of our
soils is the practice of intensive soil tillage. Soil
tillage aerates the soil and breaks up the organic residues,
making them accessible to microbial decomposition thereby
reducing the organic matter content of the soil. The slogan
“Dab Kay Wah Tay Raj Kay Khah” (Plow more, earn more) has
played a considerable role in the organic matter losses.
Different Organic Sources Available for Improving Soil
Organic Matter in Pakistan
There is a large contingent of organic sources available in
the country to be used for improving the organic matter
content of our soils. Some of them are discussed here under.
Farmyard manure
Farmyard manure is decomposed mixture of the dung and urine
of cattle of other livestock with the straw and litter used
as bedding and residues from the fodder fed to them. It has
been estimated that about 1.5 million tones of nutrients are
available from farmyard manure in Pakistan. About 50 per
cent of the dung in Pakistan remains uncollected. Out of
collected animals dung about 50 per cent is used as fuel in
the from dried cake, locally called “Pathi”. Whatever is
collected for manuring is usually heaped on the ground
surface with residues from fodder and other house sweepings.
The nitrogen in the manure is subject to volatilization and
leaching losses and the material that finally will be spread
on the field may have low nitrogen content. The application
of well-decomposed manure is more desirable than using fresh
materials.
Poultry manure
Poultry manure has a higher nutrient content than livestock
manure. According to the estimates the poultry manure
available in the country can contribute about 101 thousand
tones of nitrogen, 58 thousand tones of phosphorous and 26
thousand tones of potash.
Crop residues
Crop residues include straw, husk, leave, vegetable and
fruit waste, grass cuttings, weeds, sawdust etc. In
Pakistan, most of the crop residues such as wheat straw,
sugarcane tops/trash, cotton sticks, rice husk etc are used
as fodder for animals and as a fuel. But other waste
materials can be converted into useful compost manures by
conserving and subjecting them to a controlled process of
decomposition.
Green manure
Green manuring refers to the practice of growing crops,
preferably legumes and ploughing them under, when they reach
maximum production of green tops. Legumes are preferred as
they have the ability to fix atmospheric nitrogen. The
amount of N fixed varies from crop to crop and may be about
20-40 kg/ha. In Pakistan Dhancha, Guar and Sunhemp are
suitable crops for green manuring.
Filter cake and silage
According to an estimate Pakistan sugar industry is
producing about 1.2 million tones of filter cake every year,
which is a rich source of organic matter, micro and
macronutrients. Some sugar mils have molasses based
distillery plants, which produce silage containing nutrients
specially potassium. In case, all these materials are
recycled by composting back to soil, it will also be a good
source of essential plant nutrients for crop growth.
Slaughter house waste
Slaughter house wastes such as dried blood, meat meal, hoof
and horn meal; have a high N content and are essentially
concentrated organic manures, fairly quick acting, safe to
use and effective on all crops. Slaughter houses are wide
spread throughout Pakistan and largely their by-products are
left outside, in one appraisal, it was shown that about 8000
tons blood meal could be produced annually for manorial use
containing essential nutrients.
Other solid and liquid based materials
The other solid and liquid based materials available include
sewage and sludge, fishpond effluent, city refuse and some
waste of food processing industries. All these materials
cannot be used directly as source of plant nutrients.
However, after proper processing and removal of heavy metals
and undesirable materials, these can prove good source of
plant nutrients.
Compost
Composting is the process of decomposing (through the action
of micro-organisms in the soil) plant residues in a heap or
pit with a view to converting the nutrients contained in the
residue in more readily available form.
In rural areas crop residues, stubbles, weeds, fallen
leaves, remnants of fodder and green manure, etc. can be
collected and stored in heap or pit. In this way, as the
last pit is filled, the compost in the first pit is ready
for application. Municipal/industrial wastes comprising
mainly town refuse and human excreta can also be composted.
The preparation of urban compost on a large scale is being
done in many countries. Some plants are also installed in
Pakistan. Quite sophisticated machinery may be required for
this purpose.
Biogas compost
This is a process by which organic material are biologically
decomposed to yield energy in the form of combustible gases.
The residual material provides valuable manure. Cattle dung
which should be used for improving soil productivity is
generally burnt as fuel. Biogas technology reconciles both
these objectives: anaerobic decomposition of the cattle dung
yield both fuel (biogas) and organic fertilizer (sludge).
Biogas, popularly known as “gobargas”, is composed mainly of
methane (CH4), about 60 percent; thus 1000 cubic feet biogas
is equivalent to 600 cubic feet of natural gas, 5.2 gallons
of gasoline and 4.6 gallons of diesel oil. A small family of
four would require 150 cubic feet of biogas per day, for
cooking and lighting an amount which can be generated from
the family’s night soil and the dung of three cows.
Strategies For Improving Organic Matter Content of
Pakistan Soils
Integrated Plant Nutrition Management System
Organic source (farm yard manure, crop residues), in
addition to providing nutrients, improve the physical
condition of the soil. Nevertheless, organic materials
release plant nutrients slowly. Crops require an instant
flow of nutrients at special growth stages to ensure higher
yield, which cannot be supplied by natural weathering of
minerals and organic materials. Biological sources have
their own limitations of being crop specific. Fertilizers,
which have all the nutrients in available form, can provide
sufficient plant nutrient flow to the corps. Fertilizers are
the quickest and surest way of boosting crop production but
their cost and constraints frequently deter farmers from
using them in the recommended quantities and balanced
proportions. The limitations associates with either source
of plant nutrients are often overcome when they are used in
judicious combinations providing a mixture, which in the
long-term, is not only complementary but also synergistic.
At present in Pakistan during a survey by NFDC it was found
out that 49 per cent farmers use the FYM. The cultivation of
sesbania as green manure crop in normal as well as
marginally salt effected soils is being practiced by some
farmers and its worth has been proved in many studies. Among
the crop residues the practice of ploughing of cotton sticks
is picking up among the farmers. Pakistan Agriculture
Research Council (PARC), National Institute of Biotechnology
and Genetic Engineering (NIBGE) and Provincial Agricultural
Research Institute are carrying out work on biological
fertilization. Pakistan Agriculture Research Council in
collaboration with Engro Chemical Pakistan Limited
commercialized rhizobium specific for chickpea in the name
of Biozot. NIBGE is also marketing its bio-fertilizer for
rice in the brand name as Biopower. Provincial Research
Institutes are also providing inoculums to the farmers
formers for leguminous and non leguminous crops.
Zero/ Minimum Tillage System
Zero tillage is a system in which the soil is left
undisturbed. The only soil disturbance is of a narrow band
by soil engaging components of the planter or drill.
Reduction in soil disturbance from conventional, highly
disturbed tillage methods to minimum or zero tillage
produces slower carbon losses and may even increase the
amount of C stored in a soil. Long-term experiments
conducted in developed countries support this conclusion.
Other benefits of zero tillage to farmers include: Less
labour, reduced machinery wear and tear, high soil moisture,
improved soil tilth, reduced soil erosion and reduced
production cost.
In Pakistan, the zero tillage has proved excellent for
rice-wheat cropping system. It allows utilization and
conservation of antecedent soil moisture, time saving due to
early planting, and minimize yield losses attributed to soil
structural break down under continuous cropping practices.
Adoption of zero tillage system for all the agro ecological
zones of Pakistan still needs a lot of experimentation and
research work.
Weed control through chemicals is one of the drawbacks of
this system. Because of being costly and environmentally
hazardous it is desirable to use some cheaper and
environmentally safe chemicals. It is also possible that
instead of keeping the field completely free of weeds, we
can keep them to a safe threshold level and only till when
weeds exceed threshold level. Increasing the cropping
intensity is excellent way-out to reduce weeds.
However, under our conditions, minimum tillage system seems
to be more promising than zero tillage. Cultivation can be
done only when ever it is inevitable, for example at seedbed
preparation or when weeds exceed the threshold level. This
would also help reduce the use of chemicals for control of
weeds and insects. Thereby reducing the input costs and
environmental concerns.
References
Azam, F., M. M Iqbal, C. Inayatullah and K. A. Malik. 2001.
Technologies for sustainable agriculture. Nuclear Institute
for Agriculture and Biology, Faisalabad.
Ahmed, N. and M. Rahid. 2003. Fertilizers and Their Use in
Pakistan. National Fertilizer Development Center. Islamabad.
Brady, N.C. and R. R. Weil. 2002. Nature and Properties of
Soils 12th Ed. Pearson Education inc. Delhi, India.
Khan, S. R.A. 2001. Crop Management in Pakistan with Focus
on Soil and Water. Directorate of Agricultural Information,
Punjab, Lahore.
Shahzada Sohail Ijaz
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