1st RDA/ARNOA International Conference
“Development of Basic Standard for Organic Rice Cultivation”
12-15 November 2002, RDA and Dankook Univ. Korea
Enhancing Biodiversity Revolutionizes Crop Protection
in Organic Rice
By G.K.Upawansa
Eco Conservation Organization
Hyneford,Dekinda,Nawalapitiya, Srilanka
ABSTRACT
Package of practices involved in Nawa Kekulama method of rice
cultivation provide opportunity for organic rice production full filling
entire spectrum of requirements on the production process. A main feature
of Nawa Kekulama (NK) is weedy bunds. Maintaining weeds on bunds
through out the year is a measure of total crop protection includin g damage
by crabs, rats and wild boars. This measure can be complemented with
timely cultivation and if it becomes necessary under extreme conditions,
with the use of many botanicals described in this paper. Weedy bunds,
minimal or zero tillage, straw and husk mulch and restricted irrigation are
instrumental in organic rice production. Hence the easiest crop to go
organic is rice if and when the NK innovations mentioned are properly
adopted
Introduction
In conventional rice cultivation biodiversity is completely destroyed before
sowing or transplanting at this stage both pests and predatory insects are
destroyed or driven away. But in Sri Lanka when rice is s own late due to
delay in monsoon rains eg. after 15 th of December in rice tracts of hundred
of acres, attack of thrips within a week of germination can be observed.
Attacks engulf entire tracts. This is due to extremely high rate of
multiplication and more importantly the non availability of predators at the
beginning, to destroy migrating thrips from out side the rice tracks. In the
absence of predator availability, adlib feed supply and favourable weather
condition causative for the sudden multiplication of thrips and destruction
of the crops in entirely.
Similar observation was made with rice brown plats hopper damage BPH
damage is prominent in the month of March. In the development of Nawa
Kekulama method of rice cultivation in order to combat intensi ve
ecological damage cost by conventional rice farming due consideration was
given to enhance biodiversity and maintain it through out the year,
irrespective of hard dry spell during the month of September every year.
Observations were made in farmer fields in several locations and two
experiments were conducted to determine the effects of weeds on bunds.
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1st RDA/ARNOA International Conference
“Development of Basic Standard for Organic Rice Cultivation”
12-15 November 2002, RDA and Dankook Univ. Korea
Observations made in insect pest control.
1. Most recent and striking observation was the managing mite damage to
growing rice. Mite damage was reported for the first time in 1999 from
Polonnaruwa district of North central province of Sri Lanka. Dusting
with sulphur was recommended but the treatment was not effective.
During this periods and afterwards the attack is spreading to other
districts like Puttalam. In all fields cultivated to Nawa Kekulama
method with weedy bunds were not affected.
2. Improvement of predator population number and species wise is
observed. According to experiment conducted Prof. J.M.R.S. Bandara
and the team gives the results in the following table.
Table 1. Increase in parasite, paratisoid predator population per squire
meter in fields after ecological farming (Field : Palitha Morayaya)
Parasites or Predator
Nawa Kekulam
field
Conventionally
farmed field
Damsel fly
(Ischnura spp)
0.3
0
Epilacna beetle
-
0.3
Hymenopterance
16.3
6.3
Dipterance
22.6
7
Oxoipidae spiders
0.6
0
3. In the North East monsoon season of 97/98 island wide infection of
Rice Brown Plant Hopper (BPH) attack occurred. An experiment was
conducted with the faculty of agriculture, university of Peradeniya to
estimate BPH damage to Nawa Kekulama farmed fields. It shows a
significant drop of BPH damage to Nawa Kekulama fields.
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1st RDA/ARNOA International Conference
“Development of Basic Standard for Organic Rice Cultivation”
12-15 November 2002, RDA and Dankook Univ. Korea
Table 2. Summary of group Statistics
Group
(i) Eco Farmers
(ii) Adj. Farmers
(iii)Other farmers
All farmers
N
20
16
27
63
Variables/Mean
NFU
PER
23.7
2.3
97.8
2.9
90.6
2.0
71.2
2.3
EFS
72.5*
12.1
5.9
28.6
BPHI
4.25
28.4
35.7
26.9
YIELD
58.7
45.0
42.5
48.1
Index
EFS - Ecological farming score
BPHI - Brown Plant Hopper
NFU - Nitrogen Fertilizer used ( kg/Ac)
PER - Period of harvest
Yield – bu/Ac
The data in about tables and the general liners models analysis showed that
the three groups were significantly differ according to their ecological
farming score, BPHI, NFU, and Yield. The highest mean yield was
observed in the ecological farmer group(58.7 bu/Ac)
While the lowest was reported by the other farmers (42.5bu/Ac). The
difference in yield between group (i) and (ii) was not signi ficant.
The significantly low nitrogen fertilizer use (23.7kg/Ac) was observed in
the ecological farmer category and the highest was reported by the
adjoining farmers(97.8kg/Ac).The difference in NFU between group (i) and
(ii) was not significant.
Brown Plant Hopper Damage (BPHI) was remarkably low (4.25%) in the
ecological farmer category and was highest in the other farmer group
(35.7%)where the overall mean was 26.9%. The data also indicated that the
NK ecological farmers on average have adopted approx imately 75%
practices introduced and lesser amount of nitrogen fertilizers , indicated the
lesser amount of incidence of BPH damage and received significantly
higher yield than he adjoining and other farmer groups.
4. Occurrence of insect pests in Nawa Kekulama fields was remarkably
reduced. In the experiment mentioned earlier it was shown clearly and
the results were summarised in the table below.
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1st RDA/ARNOA International Conference
“Development of Basic Standard for Organic Rice Cultivation”
12-15 November 2002, RDA and Dankook Univ. Korea
Table 3.Occurrence of pest as mean number per squire meter in rice
ecosystem
Pest
Nawa Kekulam
field
0 – 19.6*
Green leaf hopper
(Nephotettix cincteeps)
Conventionally
farmed field
0 – 112
Grass hopper
(Oxya chinensis)
1-1.6
0.3 – 1.3
Paddy bug
(Leptocoriza acuta)
4.3-0
0 – 1.3
Pentatomid bug
(Nezara spp)
-
0–1
Leaf caterpillar
-
-
Brown Plant Hopper
(Nilapawata legunes)
0 – 82
0 – 257
Zig-zag leaf hopper
(Recillia dorsalis)
0 – 13.3
0 – 16.3
* First figure indicate the values at the sowing and the figure followed by
the dash indicated the values at harvest
5. Crabs normally bore holes to trap feed particles floating on the surface
of water the crabs stays in the holes and pickup feeds particles carried
down by the water running trough hole. When the bunds are weedy feed
particles are trapped by the weedy screen present. Because of this crabs
do not bore holes.
6. When fields are weedy animals and reptiles such as iguana, mongoose,
rat snakes are attracted to the rice fields. These animals predate on rats
and crabs.
7. Wild boars sometimes are a menace for rice fields. They dig bunds in
search of rhizomes of weeds like Panicum repence and earthworms. In
two or three seasons, when bunds are not replastered with fertile soil,
weeds with rhizomes decline and other dwarf hardy weeds appear. The
earthworm population also reduced. When feeds are not available for
wild boars they do not damage the bunds.
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1st RDA/ARNOA International Conference
“Development of Basic Standard for Organic Rice Cultivation”
12-15 November 2002, RDA and Dankook Univ. Korea
8. Over a period of 4 to 5 years, a completely different vegetation on the
bunds appears. Some species that had disappeared due to continuous
removal reappears. Along with this new vegetation some species of
beneficial insects too reappears enhancing further biological insect pest
management.
OTHER MEANS OF INSECT PEST MANAGEMENT
Botanicals
In Sri Lanka around 40 species of plants are used to control, manage and
repel the insect pests. A few commonly used treatments are given below.
(i)
Euphorbia antiquorum L.
For thrips particularly and as a general purpose organic insecticide, a
few pieces of a branch is placed at the point of impounding water to
the field. Alternatively little milky sap mixed with water and added
to irrigation water.
(ii)
Gnidea ercocephala meisn
Whole plant is crushed and about 500 gm of material is placed at
few points of impounding water. This treatment is very effective for
leaf hoppers, plant hoppers and leaf rolling and eating caterpillars.
(iii) Cycus cercinalis
Flower of this cycus is cut in to small pieces and hang in few places
to prevent paddy bug damage. This is a very effective for rice bug
damage.
(iv) Derris scandens
A bundle of 6-7 sticks of the size of a pencil, about 15 inch (40
centimetres) long, tied and placed in irrigation channel. This is good
for all insect pests.
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1st RDA/ARNOA International Conference
“Development of Basic Standard for Organic Rice Cultivation”
12-15 November 2002, RDA and Dankook Univ. Korea
Indigenous practices
For paddy swarming caterpillars
Thirty minutes before sunrise cooked milk rice is placed on few plantain
disks punched to sticks placed in the areas of crop damage. Crows are
attracted to milk rice early in the morning and when they perch on plantain
discs, milk rice fall in to paddy fields. When crows go down to eat milk
rice they come across the caterpillars and feed on them. Other crows and
birds follow the crowing of first visitors and the damage is controlled in
about four hours. These type of treatments are described as Kems. There
are over 600 such Kems used by farmers in Sri Lanka. In Naw a Kekulama
only Kems are advised and even the use of botanicals are discouraged. In
fact when Nawa Kekulama cultivation procedure is adopted properly, no
crop protection measures are required.
Weed management
An integrated approach has been adopted in weed management, it is
involuntary and no specific weed management operation is required. Weed
management takes place in following manner.
(i)
The ants gather weed seeds when the fields are drained off for
harvesting. During the conventional land preparation bunds are
slashed and sods with ants and weed seeds are thrown back to the
fields During ploughing some seeds get buried and some remain on
the surface. Puddling of soil with water is the final land preparation
operation. During this operation weed seeds are dispersed, surfaced
and mixed. When the fields are drained off for sowing or trans
planting optimum condition for weed seed germination occurs.
Under these conditions weed seeds germinate and establishes earlier
then rice crop it self and weed poses a threat. When bunds are kept
weedy the number of ant hills increases as long as weed seeds are
available. The ants collect weed seed and store them in anthills.
Gradually in three to four seasons of not weeding of bunds brings
down the weed population to very low thresh hold level.
(ii)
In Nawa Kekulama method of rice cultivation
eight
centimetres thick rice straw mulch is applied having sown the seed
either dry or germinated. This innovation keeps down the weed
population completely for about three and half month. When the
mulch is less than 5cm thick a lush growth weed can be expected.
Therefore thickness of the mulch is very important
(iii) Land preparation of Nawa Kekulama is conducive for
reducing weed population in two ways. Conventional land
preparation consisting first ploughing, second ploughing and
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1st RDA/ARNOA International Conference
“Development of Basic Standard for Organic Rice Cultivation”
12-15 November 2002, RDA and Dankook Univ. Korea
puddling is avoided. Instead minimal tillage or near zero tillage is
adopted. In the case of minimal tillage a shallow ploughing is done
once and allowed to weather for about 10 days. Then a partial
levelling along with breaking down of big clogs is done before
sowing. In zero tillage only operation is slashing down stubble and
weeds at ground level and well dried before heaping. The dried
weeds and stubble are utilized subsequently to mulch the fields after
sowing. In both cases weeds or even shattered rice seeds are on the
surface and liable to get picked up by ants and birds thus reducing
the amount of germinating seeds. On the other hands when seeds are
on the near surface, rice straw mulch destroys all weeds keeping a
weed free fields
Disease management
Having bunds weedy and mulched with rice straw with a supplement of
charred or raw husk on the surface of mulch is a natural disease
management process. Firstly, the predators dominating in the field
eliminate vectors transmitting pathogens. Secondly, enhancement of soil
microbial population by mulching would re-establish the balance or
equilibrium status among microbes thus not allowing the pathogens to
dominate. Thirdly probably most important is the development of resistance
to insect pest and disease by the rice plant itself owing to the cultural
practises adopted.
Rice plant is greedy for silica. Organic silica is available both in rice straw
and husks. When both these materials are recycled, growing ric e plants
absorb as much as it can and form a strong and abrasive surface which can
resist not only disease but also insect pests.
Rice is an upland crop. It is a miraculous crop. Among many potentials and
abilities it posses living under inundated condition is one. It should not be
forgotten that living in standing water is under stress and is a constraint for
high yields. This concept can easily be observed by counting the number of
dead roots of a clump after tillering stage. The number of dead roots
reaches the level of 75 percent or more particularly when substantial
amount of organic mater undergoes anaerobic putrefaction.
In conventional rice cultivation bunds are well maintained, soil puddled
and levelled to keep a steady level of standing water to control weeds. In
new method weeds are managed by other means and as such keeping
standing water is not necessary.
The mulch in addition to managing weeds keeps the soil temperature
steady; keeps the soil lose, fertile and ventilated; increase microbia l
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1st RDA/ARNOA International Conference
“Development of Basic Standard for Organic Rice Cultivation”
12-15 November 2002, RDA and Dankook Univ. Korea
population number and species wise; earthworm and other soil organisms.
It deepens the foraging depth. Decay of mulch enrich the soil with micro
nutrients and organic compounds for growth. All these contribute to an
extensive root systems which in turn produce the robust, strong, healthy,
and well tillered clump giving a product having a high grain weight and
higher number of seeds per panicle.
In tropics crops often suffer nitrogen deficiencies. Major reason for this is
the action of denitrifying bacteria. These bacteria are very active in
presence of moisture and high ambient temperature (28 0 C to 38 0 C
approximately) and break down the nitrogenous compounds to nitrogen and
other un-absorbable compounds. To avoid such situations 10 Kg Neem
seeds powdered and mixed with 50-100 Kg of compost and added once
prior to sowing and then rice seedlings are one month old. (The effect of
Neem seed as a nitrogen supplement had been observed by the scientists of
IRRI in Philippines as far back as 1986.)
Conclusion
With weeds on bunds, mulch in the field, lush growth due to nitrogen
obtain form Neem seeds may give the rice fields an appearance of a natural
grass land with plenty of fauna and flora. This is one of the main objectives
of organic farming aiming at. Innovations adopted in the organic rice
production are simple and low cost. Yield enhancement is attractive. Hence
it can be concluded that easiest crop to grow organically is rice.
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