Managing agricultural production in different agro ecological regions

Traditional Technology in Sri Lankan Agriculture
Course code: AS 3210
Faculty of Agriculture, Rajarata University of Sri Lanka,
Puliyankulama, Sri Lanka
• P.B. Dharmasena, 0777 - 613234, 0717 – 613234
• dharmasenapb@ymail.com , dharmasenapb@gmail.com
• Links to My Documents:
https://independent.academia.edu/PunchiBandageDharmasena
https://www.researchgate.net/profile/Punchi_Bandage_Dharmasena/contributions
http://www.slideshare.net/DharmasenaPb
https://scholar.google.com/citations?user=pjuU1GkAAAAJ&hl=en
https://www.youtube.com/channel/UC_PFqwl0OqsrxH1wTm_jZeg
Guest Lecture Two – 2 hrs
Technological variations for managing agricultural production in different agro
ecological regions
At 10.30 am- 12.30 pm, 25.01.2023

CONTENT
• Agro-ecological zones of Sri Lanka
• Rainfall variation within the Agro-ecological Zone
• Impact of droughts on agricultural production
• Impact of floods on agricultural production
• Problems and technological solutions for rain-fed upland
farming
• Problems and technological solutions for lowland farming
under minor irrigation
• Issues of home gardening

Basic factors affecting agricultural production
Climate Factors Soil Factors Crop Factors
1. Precipitation
(quantity,
distribution)
2. Air temperature
3. Relative humidity
4. Light (quantity,
intensity, duration)
5. Altitude/ latitude
6. Wind (velocity,
distribution)
7. CO2 concentration
1. Organic matter
2. Texture
3. Structure
4. Cation Exchange
Capacity
5. Base saturation
6. Slope and
topography
7. Soil temperature
8. Soil management
factors (tillage,
drainage, others)
9. Depth (root zone)
1. Crop species/
Variety
2. Planting date
3. Seeding rate and
geometry (row
spacing)
4. Seed quality
5. Evapo-
transpiration
6. Water availability
7. Nutrition
8. Pests (insects,
diseases, weeds)
9. Harvest efficiency

Three topographic zones:
• The central highlands
(South-central part;
750-2500 m)
• The plains (125-750
m),
• The coastal belt (0-
125m)
• Sixteen principal rivers
(longer than 100 km)
• 12 rivers carry about 75 %
of the mean river discharge
of the country
• The longest river:
Mahaweli Ganga (335 km).
CLIMATE

Weather vs. Climate
Weather and Climate
are not the same
• Weather - The
conditions of the
atmosphere at a
particular place
and time.
• Climate - Average
conditions of a
certain place over a
long period of time

Climatic Seasons in Sri Lanka
• First Inter-Monsoon (FIM) – March & April
• Southwest Monsoon (SWM)- May – September
• Second Inter-Monsoon (SIM)- October &
November
• Northeast Monsoon (NEM) – December -
February

Climatic zones of Sri Lanka
Rainfall
below 1,750 mm - Dry zone
1,750 - 2,500 mm - Inter mediate
zone
above 2,500 mm - Wet zone
NE monsoonal wind
SW monsoonal wind

Agro-Ecological Zones of Sri Lanka
• 24 agro-ecological zones
(RF & Altitude),
combined with effects of
soil, land form and land
use (agricultural
activities)
• DL 1-5 = 5
• IL 1-3, IM 1-3, IU 1-3 = 9
• WL 1-4, WM 1-3, WU 1-3 =
10
• 48 sub-zones
• WZ – 15
• IZ – 20
• DZ - 13
DRY
ZONE
INTERMEDIATE
ZONE
WET
ZONE

Sub zoning
• Each AER is denoted by a 4-character code consisting of letters and
a number; (eg:.DL1a)
• Three major rainfall zones are indicated by the first upper case letter of the code (W, I
and D);
• Three categories of elevation are noted by the second upper case letter of the code (L,
M and U);
• The numerical character in the third place of the code represents the degree of wetness
on the scale of 1  5 where 1 represents the most favorable
• The lower case letter in the fourth place indicates a sub-region as determined by rainfall
and other physical environmental factors. The degree of wetness decreases from a  f .

W
L1a
W
L1b
W
L2a
W
L2b
W
L3
W
M
1a
W
M
1b
W
M
2a
W
M
2b
W
M
3a
W
M
3b
W
U
1
W
U
2a
W
U
2b
W
U
3
WET ZONE CLIMATE

IL1a
IL1b
IL1c
IL2
IL3
IM
1a
IM
1b
IM
1c
IM
2a
IM
2b
IM
3a
IM
3b
IM
3c
IU1
IU2
IU3a
IU3b
IU3c
IU3d
IU3e
INTERMEDIATE ZONE CLIMATE

DL1a
DL1b
DL1c
DL1d
DL1e
DL1f
DL2&DL3
DL2a
DL2b
DL3
DL3&DL4
DL4
DL5
DRY ZONE CLIMATE

Climate of Sri Lanka in Brief
• The climate of Sri Lanka is tropical with distinct wet and dry zones
(northwestern and southeastern). The mean annual rainfall varies from < 900
mm in the dry zone to > 5 000 mm in the wet zone.
• The central part of Sri Lanka is characterized by the Central Highlands – a
series of well-defined high plains and plateaus rimmed by high mountain
peaks and ridges reaching elevations of 910–2 524 m.
• Rainfall in Sri Lanka can be monsoonal, convectional or depressional.
Monsoonal rainfall follows a bimodal pattern. The northeast monsoon brings
more rain to the dry zone and the southwest monsoon to the wet zone.
Between the two main monsoons, there is inter-monsoonal precipitation which
occurs in all coastal regions.
• The main agricultural season (Maha) starts with the northeast monsoon in
September and ends in March. The minor agricultural season (Yala) starts with
the southwest monsoon in May and ends in August.

• Distinct yala season
• Rain-fed yala is possible with
short duration (<3 months) crops
– sesame, meneri, mungbean
• Annual rainfall expectancy –
1,100 mm
• Inadequate yala rainfall
• Rain-fed yala cultivation is not
possible
• Annual rainfall expectancy – 650 mm
Rainfall Variation within the AE Zone
Low Country Dry Zone – 3 AE zones and 13 AE sub zones
Districts: Puttalam, Mannar, Vavuniya, Anuradhapura, Malaithivu, Kilinochchi,
Jaffna, Trincomalee, Batticaloa, Hambantota, Polonnaruwa, parts of Kurunegala,
Mathale, Ampara, Moneragala

• Distinct yala season
• Rain-fed yala is possible
• Perennials and plantation crops
1,400 mm
• Rain-fed yala is possible with short
duration (<3 months) crops – sesame,
meneri, mungbean
• Annual rainfall expectancy – 1200
mm
Low Country Intermediate Zone – 3 AE zones and 5 AE sub zones
Districts: Parts of Puttalam, Kurunegala, Mathale, Badulla, Moneragala, Hambantota, Ratnapura and
Matara

• Uni-modal rainfall pattern
2,000 mm
• Annual rainfall expectancy – 1,100
mm
Mid Country Intermediate Zone – 3 AE zones and 8 AE sub zones
Districts: Parts of Matale, Kandy, Nuwara Eliya, Badulla, Moneragala, Ratnapura

2,400 mm
mm
Up Country Intermediate Zone – 3 AE zones and 7 AE sub zones
Districts: Parts of Badulla, Kandy, Nuwara Eliya

• Distinct uni-modal rainfall pattern
3,100 mm
mm
Up Country Wet Zone – 3 AE zones and 4 AE sub zones
Districts: Parts of Kandy, Nuwara Eliya, Ratnapura

• Distinct uni-modal rainfall
pattern
3,300 mm
mm
Mid Country Wet Zone – 3 AE zones and 6 AE sub zones
Districts: Parts of Kandy, Matara. Ratnapura, Kegalle

• Distinct uni-modal rainfall
pattern
3,200 mm
mm
Low Country Wet Zone – 4 AE zones and 5 AE sub zones
Districts: Parts of Galle, Kaluthara, Ratnapura, Kegalle, Colombo, Gampaha

What is climate variability ?
“Climate variability” refers to changes in
climate from one year to another.
It can be caused by changes in ocean
conditions far away, which can affect climate
all over the world (for ex: el Niño)
Climate variability is natural and occurs on a
regular basis.

Climate change involves both
natural changes and changes
caused by people.
What is climate change ?
Climate change is the change in climate over a time
period from 10 to 100s of years.

What is Climate Change?
 Climate is the average weather at a given point and
time of year, over a long period (typically 30
years).
 We expect the weather to change a lot from day to
day, but we expect the climate to remain relatively
constant.
 If the climate doesn’t remain constant, we call it
climate change.
 The key question is what is a significant change –
and this depends upon the underlying level of
climate variability
 Crucial to understand difference between climate
change and climate variability…

Observed changes in the climate

Dry Zone Rain-fed Agriculture – Maize – sesame
cropping system
Months J F M A M J J A S O N D
Season
dry season yala season dry season maha season...
Traditional
crop system
Sesame Maize
CSA
crop system
Sesame Maize
Sun Hemp Groundnut
High rainfall
Low rainfall
Dry period with no rainfall
Maize
Groundnut
Sun Hemp
Sesame
Maize and Ground nut Residue

Groundnut in dry and intermediate zones
• In the dry and intermediate zones, groundnut is grown in upland areas
under rain-fed conditions in the Maha season and in paddy lands under
irrigation during the Yala season.
• It is grown mainly in Monaragala, Kurunegala, Ampara, Badulla, Puttalam
and Ratnapura districts. An average of 20 000 ha are cultivated with
groundnut, harvesting an average yield of 25 000 tons. To reach national
demand, a further 10 000 tons of groundnut are imported.
• Groundnut is a self-pollinated tropical legume crop.
• It grows best in well-drained loose, friable medium-textured soils.
• Excessive moisture severely affects plant health and lack of oxygen in the
soil limits the activity of the N-fixing bacteria. This limitation results in an
unhealthy growth pattern and yellowing of the leaves, which in case of
inundation, will cause mortality in 2–4 days.
• Groundnut is considered to be moderately drought tolerant, because during
the growing season it can withstand dry periods of 10–12 days before
yields are affected.

Drought Prone Map of Sri Lanka

Impacts of droughts on agriculture
Impacts due to soil moisture stress
• In dry soils which occur under
drought conditions, the water has a
low potential energy and
consequently it is strongly bounded
by capillary and absorptive forces to
the soil matrix, and is less easily
extracted by the crop. When the
potential energy of the soil water
drops below a threshold value, the
crop is said to be water stressed.
• Meanwhile, under drought
conditions, evapotranspiration losses
are extremely high due to increased
atmospheric demand for water and
thus, it will further aggravate the
water stress conditions

• The main consequence of moisture stress is decreased
plant growth and development caused by reduced
photosynthesis. Photosynthesis is the process in which
plants combine water and carbon dioxide to synthesize
carbohydrates using sunlight as the energy source
• Crops will have higher vulnerability to pest infestation
due to several reasons.
• Higher temperature regimes during drought
conditions will have a shorter life cycle of insect
pests with a fast growth rate resulting higher pest
population in a given time.
• Meanwhile, water stress-plants that are grown
under drought conditions tend to secrete metabolic
compounds with high sugar contents. It will attract
more insect pests resulting enhanced pest attacks
than that of a normal season.
Impacts due to soil moisture stress

Degree of damage to the crops caused by the drought
depends on the stage of crop development
Effect of delayed rains and early season droughts
• Delay in field operations
• Delay in sowing or untimely sowing of seeds
• Poor germination
• Low crop stand
• Weak seedlings
• Increased susceptibility to pests
Effect of mid-season droughts
This is the vegetative phase of the crop growth. The most obvious effect of
water stress attributed to drought conditions during this period is the
reduced leaf expansion. Visible injury of water stress is seen in the form of
wilting. Paleness and dryness of leaves is also seen in prolonged drought
conditions. Leaf abscission is often noticed due to the accumulation of
Abscissic acid under prolonged drought conditions. Reduced growth of
crops can also be seen due to the reduction in cell volume and water
potential. In addition, poor seed/ pod/ fruit settings will also be observed.

Effect of late season or
terminal droughts
• Poor seed/ pod/ fruit
settings
• Low crop yields
• Low quality produce
• Increased susceptibility to
pests
Degree of damage to the crops caused by the drought
depends on the stage of crop development

Drought Causes Land Degradation
• Land degradation is a process of decaying the land’s physical and
biological resources
• Under drought conditions which usually associate with high
temperature regime speeds up the decaying of organic matter in
soil causing destruction of soil structure.
• This will lead to reduction of land’s productivity due to enhanced
soil erosion and poor physical, chemical and biological properties
of the soil.
• In areas where the groundwater is inherently saline, high
evaporation rates during drought conditions bring dissolved salts
of groundwater to the soil surface
• Water will immediately evaporates into the atmosphere under high
evaporative demand of the atmosphere leaving salts on surface
layer of soil.
• If the subsequent rains after the drought are not sufficient to wash
away these salts, the process will continue until the land becomes
completely unproductive due to salinization.

Impact of droughts on soil microbial activity and
fertility in the soil
• The health of the soil is dependent upon many factors including
fertility, pH and adequate moisture to support microorganisms,
mainly bacteria, fungi and actinomycetes.
• It is a well known fact that drought or soil moisture stress will
negatively affect the soil micro-organisms.
• Soil microorganisms number is nearly a trillion in each pound of
root-zone soil. Over 98% of them are labeled “the decomposers.”
• Their functions include formation of soil aggregates to improve air
and water movement; decomposition of organic matter including
thatch to humus and solubilizing insoluble mineral nutrients such
as phosphates, sulfates and potassium, calcium and magnesium
oxides to plant available forms.
• Hence, reduction in microbial activities due to drought may hinder
all those processes with subsequent reduction of overall soil
fertility.

Increased threat of invasive species on native species
• Invasive species are non-indigenous species, plants or animals that
adversely affect the habitats they invade economically,
environmentally or ecologically.
• Under drought conditions where water stress and high ambient
temperature is a common feature, any plant or animal species that can
outcompete with available resources will survive and reproduce fast.
• It is also believed that many highly adaptable invasive plants and
animals will out-compete less adaptable native species in the stressful
conditions of a drought.
• Generally, endemic species have several natural enemies and hence,
they are unable to outcompete non-indigenous species under stress
environment of a drought resulting propagation of non-indigenous
invasive species at an un-controllable rate.
• Droughts that kill native plants can leave gaps in vegetation that may
be quickly occupied by invasive species. Therefore, threat of invasive
species will be inevitable in a drought prone areas.

Flood Prone Areas of Sri Lanka
Very high flood prone
districts
• Galle
• Kaluthara
• Colombo
• Rathnapura
High flood prone districts
• Gampaha
• Kegalle
• Kandy
• Matara
• Puttalam
• Batticaloa

Impact of floods on Agriculture
Crops and cropping systems vulnerable for flood hazard
• As the flood water is moving away from sloping terrain, it will remain in
flood plains for a few days depending on how flat the terrain and state of
its associated drainage network.
• Hence, crops that are grown in the flood plains can be severely affected
depending on the number of days that they are submerged and rate at
which flood water moves away from the area.
• These crops are mainly, paddy, vegetables grown on paddy lands and
occasionally some home gardens trees and crops.
• Tree crops such as coconut palms and fruit trees will have hardly any
impact by flood unless fast moving flood water would up-root them.
• Damage to the annual crops will have greater variability from recoverable
damages to complete crop devastation depending on the type of crops and
the age at which submergence occurred.
• If it is a complete washing away of crops, farmers are compelled to find
seed materials for the next attempt.

Sand filling
• After the flood water is drained off naturally, it is a common picture in
the paddy tracts in the flood plains of Sri Lanka to observe piled up
sand and silts along with large quantity of debris. Before the re-start of
the cultivation, these materials have to be removed with a high cost of
labour.
Damages to infrastructure
• Apart from damages to community infrastructure such as bridges,
buildings and roads, there is a strong threat to agricultural
infrastructures being damaged under flood situations.
• This may range from washing away of dikes in paddy tracts and
damage to canals in irrigation systems, anicuts in diversion schemes to
breaching of earth filled dams of both minor and major tank categories.
• This will be an additional burden for farmers and the government as a
whole. This could results some lands to leave behind from agriculture
for several seasons until the rehabilitation works are completed.

Loss of added fertilizer
• Irrespective of the magnitude of the flood, any added fertilizers will
wash away from the agricultural fields with moving flood water,
especially from paddy tracts.
• This will lead to increase the cost of cultivation of the crop as farmer
has to re-apply it.
• Meanwhile, some paddy tracts are to be benefited from minor scale
floods as they will deposit very fertile silts in these paddy tracts.
Reduced seed paddy production
• One of the most significant impacts of floods in rice growing areas is
the reduction of seed paddy production for the following season. If the
harvesting time of the crop coincides with unusual rain spells, seed
paddy production can not be done. It will not only affect the farmers’
current income but also leads into severe shortage of seed material for
the next season too with a subsequent web of negative impacts.

Problems and technological solutions for rain-fed
upland farming
Problem Technology
1 Lengthy land
preparation operation
increases time, labour
and cost
Replacing broadcasting in ploughed soil with no-
till seeding in undisturbed, mulched soil reverses
the trend of soil degradation.
2 Soil erosion and soil
organic carbon depletion
due to soil tillage, heavy
rains and failure to apply
nutrients
Mulching crop residues and using cover crops
• Minimize soil erosion
• Maintain soil moisture
• Increase soil fertility
3 Multiplication of weeds
during Yala fallow
period
Crop intensification
• Growing pulses as intercrop with maize
• Sowing cover crops (e.g. sunn hemp) as
intercrops a few days before planting maize
• Sowing cover crops (e.g. pigeon pea or sunn
hemp) as the sole crop soon after the harvesting
of maize in February .

Problems and technological solutions for lowland
farming under minor irrigation systems
Problem Technology
1 Low water productivity
Grown in continuously
flooded paddies, rice
requires 2–3 times more
water than other irrigated
cereals, despite the similar
transpiration rate.
Timely planting operations – Advance the
commencement of cultivation
Initiating Maha land preparation at the beginning of the
rainy season (with the onset of the second inter-
monsoonal rains late in September to early October) will
reduce water use by 20 percent.
Alternate wetting and drying (AWD)
AWD is an irrigation method involving periodic
application of water followed by aeration of the soil. The
period between irrigations is 1–10 days, depending on
soil type, weather and crop growth stage.
This method reduces water withdrawal by 10–20 percent
as well as methane emissions.

Problem Technology
2 Greenhouse gas
emissions
Agriculture releases
to the atmosphere
significant amounts
of CO2, CH4 and
N2O. CO2 is released
largely from
microbial decay or
burning of plant litter
and soil organic
matter. CH4 is
produced when
organic materials
decompose in
oxygen-deprived
conditions, such as
when rice is grown
under flooded
conditions.
Selecting adapted rice varieties - Rice varietal differences in
methane emission are noticeable. Selecting low emission
varieties (such as Bg 300 and Bg 352) can increase the climate
change mitigation potential of rice production systems.
Improving fertilizer management
• Instead of spreading basal fertilizer (TSP) over the open
fields, application in nursery trays can reduce fertilizer
requirements by approximately 40–45 percent from 55
kg/ha to 30 kg/ ha.
• TSP doses can be targeted for each plot based on laboratory
soil tests
• Doses of urea can be calculated using leaf colour charts
so that the nitrogen needs of the crop can be addressed at
each stage and the amount of urea reduced by
approximately 20 percent without compromising the yield.
Improving water management – Alternative Wetting and
Drying (AWD)
Rice straw management - Burning the straw is banned in
Sri Lanka. Retaining the straw on the field is an important
factor in controlling GHG emissions from paddy fields.

Problem Technology
3 Low
productivity
due to
Weed
competition
emerged
from poor
seed quality
and
broadcasting
practice
1. Adopting integrated weed management
• Preventing weed seed production in farmers’ fields as well as in
neighbouring bunds, on fallow land and in irrigation canals to
deplete the weed seed bank;
• promoting seed decay of non-persistent (vulnerable) weeds;
• stimulating fatal germination of weed seeds (e.g. stale (old) seed
bed); and
• preventing weed germination and emergence through mulching.
2. Using quality seeds
3. Planting with line seeder (drum seeder)
4. Planting with parachute method
5. Planting with mechanical transplanter
6. Growing drought-tolerant rice varieties during the Yala season
7. Growing a short-duration pulse crop between the Maha and Yala
seasons

Issues in home gardening
Characteristic General practice
Species density High
Species type Staples, vegetables, fruits, medicinal plants
Production objective Home consumption
Labor source Family (women, elderly, children)
Labor requirements Part-time
Harvest frequency Daily, seasonal
Space utilization Horizontal and vertical
Location Near dwelling
Cropping pattern Irregular and row
Technology Simple hand tools
Input-cost Low
Distribution Rural and urban areas
Skills Gardening and horticultural skills
The key characteristics of a typical home garden

• Improved food security
• Increased availability of food and
better nutrition through food diversity
• Income and enhanced rural
employment through additional or
off-season production
• Decreased risk through
diversification;
• Environmental benefits from
recycling water and waste nutrients,
controlling shade, dust and erosion,
and maintaining or increasing local
biodiversity
The key benefits of home gardening

The key constraints of home gardening
Limited access to inputs such as seeds, planting material, tools, and capital
Shortage of land and lack of land tenure security
Inadequate access to water
Damage due to insect pests, diseases, animals, and theft
Poor environmental conditions
Lack of knowledge, information, and advisory services
Shortage of family or hired labor
Poor soil fertility and soil erosion
Limited access to quality livestock breeds
Limited marketing opportunities
Excessive post-harvest losses
Inadequate research and development on home gardens
Social and cultural Barriers
Lack of information on nutritional benefits of home gardening

Some conclusions on home gardening
• Home gardens should be considered as an eco-friendly sustainable
agricultural practice to improve food security and enhance
economic growth.
• The anatomy, functions, and contributions of home gardens vary
in geographic regions especially due to climate and soil.
• Home gardens fulfill social, cultural and economic needs, while
providing a number of ecosystem services.
• Recognizing the value and potential of home gardens for
enhancing food security and livelihoods, numerous initiatives
have been launched by governmental, non-governmental, and
international organizations that are providing support and building
local capacity to enhance the productivity and also for scaling up
home garden activities.
• GHG emission can be greatly reduced and carbon sequestration
can be enhanced through home gardens

Managing agricultural production in different agro ecological regions

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