ECHO Asia Notes
Edited by Rick and Ellen Burnette
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ECHO Agricultural Conference 2010
Dec. 7-9
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The Amazing Effects of Rice Straw: Recycling Crop Residues
to Improve the Soil
By Winfried Scheewe, German Development Service
(DED), Center for Studies and Development of Cambodian
Agriculture (CEDAC)
Editor: Winfried Scheewe represents DED, a leading European
development service for personnel cooperation, serving as the Marketing Advisor
to CEDAC http://www.cedac.org.kh/home.asp based in Phnom Penh.
From 1990 until 2006, he helped several NGOs in the Philippines, promoting sustainable
agricultural practices. He is also the author of 'Nurturing the Soil - Feeding
the People.'
An
earlier version of this article was published in Philippine Agriculture Monthly
(October 2004). Winfried also offered a presentation on the effects of
recycling rice straw at the September 2009 ECHO Asia Agricultural Conference.
How the recycling of
crop residues improves the soil
 Does rice straw have any value? Looking at the practices of
most farmers, it seems not! The burning of rice straw is a common sight during
the harvest period in many parts of Asia. Yet a number of farmers think
otherwise. One of them is Isidro Prado from Alba in the municipality
of Tago, Surigao del Sur, Philippines.
He does not consider rice straw as trash to be disposed of in the easiest way. Instead
he recognizes rice straw as essential for maintaining the fertility of his rice
field. About eight years ago, he learned that returning the rice straw could
help to overcome the problem of zinc deficiency that was prevalent in his rice
field at that time.
Prado, now 69 years old, started cultivating the rice field
he inherited from his parents in 1969. For
about 15 years he cultivated his rice field like most farmers: using high
yielding varieties (HYV), fertilizers and pesticides. Although he considered a yield of about 40 cavans (one cavan equals 50 kg or 110 lbs.) from his 0.38 hectare (0.94 acre) field
acceptable, he felt lucky to have even five sacks of palay (unhusked rice) left over for consumption; barely enough to
last his family a few months. Unfortunately, most of his produce went to the money
lender who asked up to 10 cavans as
payment for each 1,000 Philippine pesos (1 US dollar = P 47.2) of borrowed
capital.
A zinc deficiency became apparent in Prado's fields during the
early nineties. Within a couple of years yield went down to 12 to 17 sacks, an
equivalent of about 30 cavans per
hectare. During that time the rice plants always looked somewhat sickly, but
the worst result was that most seed heads were not filled with grain.
The condition of his land improved when in 1996 he joined a
farmers' group served by the Tago Center for Sustainable Agriculture (TCSAI), a
newly formed NGO. The NGO workers encouraged Prado to return rice straw to his
field after each harvest. They also introduced
several traditional and newly bred lines of rice from the MASIPAG network (Magsasaka
at Siyentipiko para sa Pag-unlad ng Agrikultura - Farmer Scientist Partnership
for Development, Incorporated). These rice varieties grew well and brought
about yields comparable to the HYVs, although Prado no longer applied chemical fertilizers.
Within two years (or four croppings) the yield of his rice
crops was back to normal. The signs of zinc deficiency were gone. He soon realized
another big advantage: because he no longer needed to buy fertilizers and
pesticides, he needed less capital. Now, Prado needs to borrow only P 2,000.00 per
cropping, for which he has to pay an equivalent of seven sacks of palay. Thus he is able to keep most of
his rice for consumption. He covers most of his cash needs by selling copra (dried
meat or kernel of coconut) and banana.
Due to this experience, Prado keeps on spreading the rice
straw in his field after every harvest. He says it is best to do it immediately
after harvest. "If you wait longer, the straw becomes hot and it is more
difficult to broadcast it," he explains. Besides, the straw starts to develop
molds which cover the straw with an unpleasant dust. Once a year, he adds about
20 sacks of rice hulls from the nearby rice mill as additional soil conditioner.
Many farmers are reluctant to scatter rice straw in the
field, because they expect problems during land preparation. "Not so," says Prado,
"but you have to let the rice straw decompose for about one month on the
surface." An extension worker once told him that this way microbes involved in
the decomposition process will even add nitrogen to the soil. "If you
incorporate the rice straw immediately and plant again, the microbes that decay
the straw would take away nitrogen from the young crop. Besides, methane gas will
be released which disturbs the young rice plants."
In addition to the reduced expenses as well as the more
filled and tastier grains, Prado realized another important benefit. He no
longer has to work with farm chemicals. Before, whenever he had to spray
pesticides he felt very exhausted and even sickly afterwards. Even though
several of his neighbors continue to use pesticides, pests do not seriously
affect his rice.
To be sure of a good harvest, Prado usually plants at least
three different rice varieties. At the time of writing, he was testing two varieties
in smaller plots. In another small portion he was planting a glutinous rice variety
called Tapol, which his family uses for special occasions.
Asked what he would recommend to other farmers, Prado replies
that it would be good if farmers could stop burning the straw and utilize it
instead on their farms. "Considering that the straw of an average harvest
contains 25 to 40 kg (55 to 88 lbs.) of nitrogen, they are really burning money,"
he reasons.
What may be even more important than the nitrogen is the
energy (carbon) contained in the straw. Soil microbes convert most of the
carbon into humus, which ensures the supply of nutrients to the next crop. Energy
from the straw also enables soil organisms to better contribute to the
maintenance of good soil structure, allowing for better aeration and enabling
the soil to absorb and hold more water. Thus, Prado considers recycling of rice
straw an essential step towards reducing the costs of rice farming and improving
the situation of farmers.
The value of rice straw
Per metric ton, rice straw
typically contains 5 to 8 kg (11 to 17.6 lbs.) nitrogen, 0.7 to 1.2 kg (1.4 to
2.64 lbs.) phosphorous, 12 to 17 kg (26.4 to 37.4 lbs.) of potassium and 40 to
70 kg (88 to 154 lbs.) silica. When the straw is burned, the carbon, which
comprises 40 percent of the straw, goes immediately into the atmosphere and
increases the CO2 content, thus contributing to the problem of
global warming. Otherwise, it could have supplied soil organisms with energy.
Likewise, 93 percent of the
nitrogen content is lost. Therefore, on
average about 30 to 40 kg (66 to 88 lbs.) of nitrogen per hectare is unnecessarily
released into the atmosphere. In addition, 25 percent of the phosphorous and 21
percent of the potassium are lost during the burning. Heat also renders the
silica in the ash less soluble than in fresh straw.
Where does the soil nitrogen
come from?
For eight years,
Isidro Prado has no longer applied nitrogen fertilizer to his fields. Yet, on
average, he obtains between 4,000 and 4,500 kg (8,800 to 9,900 lbs) of palay per hectare.Assuming that one metric ton (2,200 lbs.) of harvested rice contains
about 12.5 kg (27.5 lbs.) nitrogen, the cereals harvested from one hectare (2.47
acres) remove about 54 kg (118.8 lbs.) of nitrogen. The straw left in the field
contains around 30 kg (66 lbs.) of nitrogen. Thus, the harvest from one hectare
represents about 84 kg (184.8 lbs) of nitrogen. But with the retention of the
rice straw, probably most of the 30 kg (66 lbs.) nitrogen in the straw from the
previous harvest will have been reincorporated into the soil.
Additionally,
soil scientists claim that biological nitrogen fixation related to the
decomposition of the straw can potentially supply an additional 20 to 25 kg (44
to 55 lbs.) of nitrogen. There remains a gap of 25 to 30 kg (55 to 66 lbs.),
from the nitrogen that is removed with the crop (i.e., grains and straw) during
harvest. Although a small part of this nitrogen comes with rainwater, this is
strong evidence that various nitrogen-fixing microorganisms in the paddies
supply most of the balance.
 This is made possible through the association of bacteria
living on the surface of roots, giving rice plants (as well as various other
grasses) access to nitrogen that certain bacteria fix from the air. [Editor: Choudhury and Kennedy cite the role of plant growth-promoting
rhizobacteria (PGPR) such as Azotobacter,
Clostridium, Azospirillum, Herbaspirillum, Burkholderia and Rhizobium, in improving the
ability of the rice plant to assimilate soil N]. It is essential that the soil be well aerated for such
bacteria to thrive. Therefore, if the situation allows, rice fields should be
flooded and drained alternatively. Additionally, these bacteria require sources
of energy, such as straw, to function efficiently. If the soil is deprived of straw
and other types of organic matter, nitrogen-fixation processes cannot occur.
These effects were obvious on Isidro Prado's farm when he
transitioned away from several years of intensive application of synthetic
fertilizers. With his rice field losing
fertility and the crop suffering severely from zinc deficiency, it was not
until he began to recycle the rice straw that conditions improved. Now Prado
regularly returns the straw to the field to enhance the fertility of his rice
field.
References
Choudhury, ATMA and I. R. Kennedy. 2004. Prospects and potentials for systems of
biological nitrogen fixation in sustainable rice production, Biology and Fertility of Soils (2004)
39:219-227.
Dobermann, Achim, and Thomas Fairhurst. 2000. Rice:
Nutrient Disorders & Nutrient Management. Los Baņos: IRRI.
Ponnamperuma, F.N.
1984. "Straw as a source of nutrients for wetland rice" in Organic Matter and Rice.
Los Baņos: IRRI.
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Preserving Bamboo with Borates
By Thomas Singer, the Rain Tree Foundation, Chiang
Mai, Thailand
Working together with Thai Care, the children's
ministry of the Rain Tree Foundation, Meribah Ram Pump is engaged in various
community development projects in northern Thailand. A major focus is to make simple, sustainable
technology, such as ram pumps and bio sand water filters, available to those
who have limited access to water and electricity.
 Bamboo plays a key role in our work as
well. Meribah enhances local livelihood opportunities
by promoting the production and sale of bamboo products such as handicrafts, and
has also constructed a coffee shop almost entirely out of bamboo.
Bamboo is widely available in the area
and local people understand its use, including for the construction of
traditional homes. But because of damage from bamboo pests, such as borer
beetles and fungi, such homes must be rebuilt nearly every two years.
A related problem includes the scarcity
of bamboo due to overharvesting. Unfortunately,
as those who can afford it rebuild their homes with concrete, skills for constructing
traditional bamboo houses are likely to be lost.
In
response, we have determined that bamboo treatment and preservation offers an
opportunity to help: -
prevent
over harvesting of bamboo and create sustainable bamboo utilization;
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preserve
traditional building techniques;
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offer
durable bamboo housing and products; and
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encourage
the production of bamboo handicrafts and other marketable products.
 With information
from the EBF manual, we were able to utilize the boric acid/borax formula and
replicate other key steps. We have also
improvised certain variations of our own, including the use of a solution bath
in which culms (bamboo poles) are soaked horizontally as opposed to having the
solution injected into them vertically.
Having successfully adapted EBF's bamboo
preservation technique to our work in Thailand, the following is an
overview of key materials and steps, including our own observations and
adaptations.
Required facilities and tools for bamboo
preservation with borates
- A watertight vat, trough or pool
(protected from the sun and rain) for soaking the bamboo in borate solutions. The size of treatment containers may vary according
to the demands. Our vat, measuring 6 m (19.7
ft.) long x 1.5 m (4.9 ft.) wide x 1 m (3.3 ft.) high, is designed to handle
large amounts of bamboo to be used for construction purposes.
-
Metal grate that can be placed atop the
soaking vat.
-
Eye protection.
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Rubber gloves and boots.
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Water.
-
200 liter (52.8 gallon) plastic
container for mixing and storing the solution.
-
Dye.
-
Plastic containers for mixing and
measuring materials.
-
Handsaw.
-
Iron T-bar with a spearhead welded to
the end (length depending on the bamboo to be treated).
-
Wooden stick for mixing solution.
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Hydrometer (an instrument used to
measure the specific gravity or relative density of liquids).
-
Brushes (or coconut husks) for cleaning.
-
A piece of cloth stretched over a frame,
used for skimming debris off the surface of the solution.
-
Tim-Bor [Editor: Tim-Bor is a commercial wood preservative that works as an insecticide and fungicide, utilizing disodium
octaborate tetrahydrate, a natural borate compound, as the active ingredient] or boric acid and borax
(used
in combination as a substitute for Tim-Bor).
-
Well-ventilated
space unexposed to sun or rain, for drying the bamboo poles.
Harvest of Culms
The EBF manual stresses that the
best season to harvest culms is the period immediately after the rainy
season when starch content in the bamboo sap is low (starch is a favorite
food for bamboo pests). This season occurs in November and December in northern
Thailand.
Conversely, it is not a good
idea to harvest poles during the period that shoots are being produced, when
starch content is at its peak.
The EBF manual also recommends
using 3- to 5-year-old bamboo. Younger culms are too weak, while poles older
than five years tend to be too hard, having inner culm walls that may be
impermeable to the treatment solution.
Instead of using a machete to cut
the culms, we have discovered that cutting bamboo cleanly with a saw will
keep capillaries in the wood open, allowing the solution to penetrate better.
Preparing the solution
- If Tim-Bor is available, mix 25 kg (one bag) with 225 liters
of water to produce a "10% weight for weight solution."
-
Instead of
purchasing Tim-Bor, our
large batches of borate solution are
made by slowly adding 50 kg of boric acid and 75 kg of borax to 700
liters of water while stirring the solution. Based on this
ratio of boric acid, borax and
water, depending upon the amount of solution needed per situation, the
amount of borates mixed proportionately with water can be adjusted. When all
crystals are dissolved, you will have a 17% boric acid/borax weight (or mass) solution
that is equivalent, in borate concentration, to a 10% Tim-Bor weight solution.
Editor: EBF's bamboo treatment manual offers limited
information about the availability of Tim-Bor in Indonesia and Thailand. Related to the comparative expense of using
either Tim-Bor or the boric acid/borax mixture to treat bamboo, depending upon
the location in Thailand,
Tim-Bor costs approximately 85 baht ($2.58 US) per kg or 2,125 baht ($64.39 US)
for a 25 kg bag. A 25 kg bag of boric
acid costs approximately 1,500 baht ($45.45 US) and a bag of borax of equal
weight costs approximately 950 baht ($28.78 US).
To
better manage the composition of the solution, it is easier to mix smaller
volumes of higher concentrated solution in a container (e.g. 200 l) and then
pour the solution into the pool, adding the volume of water needed to attain
the correct concentration of the Tim-Bor or borax/boric acid solution.
Editor: The EBF describes Tim-Bor
as "more environmentally friendly than other wood preservatives currently used"
and superior to boric acid "because it diffuses and penetrates bamboo or wood
better and faster." However, the Tim-Bor
label prescribes caution in the use of the product, specifically warning
against ingesting or inhaling the material and cautioning users to avoid
contact with eyes or clothing. The same precautions should be applied to all
borate solutions.
In our
experience, adding warm water to the container aids in dissolving Tim-Bor or
boric acid/borax powder. However, before
checking the composition of the solution in the pool with a hydrometer (see
below), the liquid must have cooled down completely.
Tinting the solution
While mixing the solution in the
container or vat, add adequate amounts of dye, such as red or green, for easier
identification of treated
poles.
Measuring the solution
To monitor the level of borates
in the treatment solution, the EBF  manual recommends using a salt measuring
hydrometer "under normal temperatures of your region" as opposed to
measuring during either extreme hot or cold weather conditions. We have found that the optimum air
temperature range to measure the solution is 20-25 degrees C (68-77 degrees Fahrenheit).
To test with a hydrometer, slowly
add the borate solution to a test container (bucket, etc.), so that you avoid air
bubbles in the solution prior to lowering the hydrometer into the solution. Before releasing the instrument, allowing it
to partially float, give the hydrometer a quick twirl by spinning its top
shaft. This action will help deflect air bubbles which can accumulate around the
hydrometer, affecting its buoyancy and resulting in a false reading.
A hydrometer is read similar to a
thermometer. Note number where the
solution crosses the scale. A
well-calibrated hydrometer should have a reading of 1.045 (plus or minus 0.005).
Preparing the bamboo poles for the
treatment
The EBF manual
recommends the following:
-
Thoroughly
clean the outside of the bamboo culms with either water and brushes, coconut
husks and sand, or a product similar to Scotch Brite.
-
Prepare
a long rod with a spear head welded to one end. The spear head should be approximately 10 cm
long with a diameter of 2-3 cm at the base (depending on the width of the
bamboo poles). This modified iron rod can be used to punch holes easily through
the node diaphragms separating the internodes.
[Editor: see adjoining
illustration of a cut-away view demonstrating technique for hollowing bamboo
culms]. Piercing the diaphragms will
prevent clogging from inside of the culm and allow the solution to move freely
throughout the interior. Larger diameter holes are recommended to prevent air
bubbles from forming during the filling procedure. Fortunately, larger holes will not diminish
the strength of the culm.
-
To
facilitate the hollowing process, place one end of the bamboo against a sturdy wall
and force the iron rod into the other end, punching holes through all of the
nodes.
Treatment
The
EBF injects borate solution into culms arranged in a vertical position.
However, for convenience, we prefer to use the following soaking method: -
Add
borate solution to the soaking vat. We have found it best to add enough
solution to fill the vat approximately 1/3 full. Then arrange the bamboo poles into the
container until the displaced solution rises almost to the top of the vat.
-
While
placing poles into the vat, be careful to displace as many air bubbles as possible. Also, keep the culms submerged by placing weights
on top of the poles. Several 50-liter containers full of water
work well as weights.
-
Allow
the bamboo to soak for at least two weeks.
Removing
the poles and reusing the solution
-
To save the borate solution for reuse,
remove the bamboo poles before placing a metal grate on top of the vat. Immediately stand the freshly treated bamboo
on top of the grate for at least one hour, to allow as much solution as
possible to drain out of the poles back into the vat.
-
Use a simple screen to remove debris and
other materials suspended in the solution. A screen can be made from cloth,
such as an old tee-shirt, stretched across a small frame.
-
The borate solution can be used over and
over. [Editor: according to the Tim-Bor label, wastes resulting from the use
of the product may be disposed of on site or at an approved waste disposal
facility. However, the pesticide is
toxic to fish and wildlife. Tim-Bor or
Tim-Bor solutions that are spilled or applied to plants or cropland may kill or
seriously retard plant growth. The label
also warns against applying the product or solutions directly to surface water and
discharging the effluent into streams, ponds or other bodies of water or into
sewer systems].
-
Before reusing a batch of solution, check
the borate level with a hydrometer. If
the reading is less than 1.040, add more solution. Should
the scale show a reading more than 1.050, add more water, checking and adding water until the optimum
concentration is reached.
Drying
and storing
In a
well ventilated, covered area, allow the bamboo to dry in a prone position for
4-6 weeks (length of time depending on the humidity). This must be
done in the shade, as direct exposure to hot sun while drying can split the culms.
Testing
A simple way to test the success
of the treatment is to capture some bamboo borers and place them into a closed
(but not airtight) container along with two pieces of bamboo; one treated and
the other untreated. After a few days
any untreated bamboo will show obvious signs of infestation. This is the
simplest, most effective means of monitoring the efficacy of the treatments and
should be repeated with each finished batch.
Occasionally we find a few holes made by
borers in treated wood. However, we have
learned that this results from a few remaining bugs which are actually dying
from the borax treatment. Fortunately,
there will be no additional infestation as the treated bamboo remains
unpalatable to the pests.
Summary
Our method is only one of many
techniques that can be used to preserve bamboo.
Other approaches include the vertical injection method recommended by
EBF; pressure treatment; and smoking.
With borate treatments, bamboo can
reportedly last 15 to 20 years or longer.
Over the past two years we have implemented the borate soaking method to
treat bamboo used to build two houses as well as to produce furniture and handicrafts. As the work remains pest free, we invite
others to see for themselves how such treated bamboo lasts longer.
References
Chomwarangkhana Veerachot
(Chemical Fareast, Chiang Mai), telephone conversation. December 11, 2009.
NumchaiLoyritthiwuthikri (Chieng
Thai Trading, Bangkok), telephone conversation, December 15, 2009.
Oberg, Ralf (Rain Tree
Foundation), e-mail communication. December 16, 2009.
Sobel, Christi. Bamboo cut-away illustration. Submitted January 21, 2010.
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ECHO Agricultural Conference
for Northeast India
The
ECHO Agricultural Conference for Northeast India, the first of its kind
in the region, will be hosted by NEICORD (North East India Committee on Relief
and Development) in collaboration with the ECHO Asia Regional Office.
The
conference, organized for those engaged in agriculture development in Northeast
India, will focus on sharing among participants, particularly with regard to
improvement of hill cultivation, eco-forestry, SRI and preserving the environment.
The conference will include plenary sessions on important issues provided by excellent
resource persons. Participants will be able to network and exchange skills and
knowledge.
Date:
6-8 October 2010
Venue:
CBCNEI (Baptist Centre) Guwahati
For
more information contact:
Joshi
Tuisum
Phone
- +919436102076
Email
- jtuisum2003@yahoo.com, charity@neicord.org
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The ECHO Asia Regional Office operates under ECHO, a non-profit, Christian organization that helps you help the poor to produce food in the developing world .
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