This presentation of a part of Induction training programme conducted for the field staff of EU-SDDP Project of FAO implemented during 2013 - 2016

1. Soil and Water ConservationSoil and Water Conservation
Induction Training for EU - SDDP staff November 2013
Dr. P.B. Dharmasena – National Consultant/ Agriculture and
Water Management
Dr. P.B. Dharmasena – National Consultant/ Agriculture and
Water Management

2. Climate Change & SoilClimate Change & Soil
Resource ProductivityResource Productivity
Climate
change
Soil
productivity
decline
Deforestation
Mis-management of
land
Mis-practices of agriculture

3. Land development plan under theLand development plan under the
projectproject
Ampara: 40 ha
Vavuniya: 260 ha
Mannar: 260 ha
Anuradhapura: 40 ha
Moneragala: 40 ha
Total: 640 ha
3
Implementation Partner: Department of Agriculture

4. Human population growth, forest decline and green revolution
0
5
10
15
20
25
30
1870 1890 1910 1930 1950 1970 1990 2010 2030
0
10
20
30
40
50
60
70
80
90
Forest
PopulationSri Lankan trend

5. GreenGreen
RevolutionRevolution
High yielding varieties
Mechanized agriculture
Chemical fertilizer and agro-
chemicals
Commercialized agriculture

6. ImpactsImpacts
High yielding varieties – High input
requirements, susceptible to pest and
diseases, drought, salinity etc.
Mechanization - soil environment –
physically disturbed
◦ Soil erosion, nutrient loss, water loss, weed
problem
Chemical fertilizer and agro-chemicals –
soil acidity, heavy metals, micro-nutrients
deficiency, health hazards etc.

7. Accelerated erosionAccelerated erosion
Highly erosive rainfalls occur in low lying areas –
Dharmasena (1992)
Elevation in m (amsl)
Erosivity
(t.m/ha)

8. Location
Potential annual soil loss (mt./ha)
Land slope (%)
2 4 6
Anuradhapura
Galgamuwa
Horowpothana
Kantale
Mahailluppallama
Maradankadawala
Polonnaruwa
27
26
31
34
25
28
33
52
51
61
66
48
53
64
84
83
99
108
78
87
104
Potential erosion in selected locations of
the central dry zone
Source: Dharmasena, 1992
Erosion from dry zone agricultural lands can not be
over-looked

9. Tank Year Capacity
(ha.m)
Sedimentation
Volume
(ha.m)
% Rate
(ha.m/year)
Paindikulama
Siwalagala
Marikaragama
1984
1987
1990
1990
1986
1990
30.2
28.0
25.8
19.9
36.2
35.3
9.7
11.9
14.1
8.6
9.6
10.5
24.3
29.8
35.3
30.2
21.0
22.9
0.73
0.73
0.23
Source: Dharmasena, 1992

10. Major Problems in the DryMajor Problems in the Dry
Zone Upland FarmingZone Upland Farming
Erosion of fertile
top soil
Emergence of
obnoxious
weeds
Declining soil
fertility
Difficulty of land
preparation

11. Process of Soil ErosionProcess of Soil Erosion
Disaggregation
of soil
Transport of soil
particle by
water
Deposition in
depressions,
streams, rivers
and reservoirs

12. Types of Soil erosionTypes of Soil erosion
Splash erosion
Vertical erosion
Inter-rill erosion
Rill erosion
Gully erosion
Stream bank
erosion

13. • Erosion of fertile top
soil
• Reduction of soil
moisture holding capacity
• Gradual decline of the
suitable arable lands
• Gully formation and
land slides
• Sedimentation of low
lying areas and
reservoirs
Consequences of soil erosion

14. Soil Erosion
Tank
Sedimentation
Rain-fed
Farming
Tank Capacity
Tank Irrigated
Farming
Vicious circle in tank-village farmingVicious circle in tank-village farming
Population
Pressure

15. Land
slope
(%)
Spacing
(m)
Runoff
(m3
/hr)
Bund
height
(cm)
Drain
Depth
(cm)
Top width
(cm)
< 2
2 – 4
4 – 6
6 – 8
8 - 10
15
10
7
6
5
165
100
75
60
50
30
25
25
20
20
15
10
10
10
10
70
50
50
40
40
Recommendations for soil conservation bunds
Drain depth
Bund bottom width
Bund height
Drain top width
Dharmasena,1998

16. Contour drains Lock & Spill
Contour bunds Stone bunds

17. Contour
cropping
Mulching
Cover crops
Mixed cropping

18. Strip cropping Minimum tillage
Crop residues Alley cropping

19. Alley cropping

20. W
ellDrained,
RBE,<30cmWellDrained,
RBE,30-60cmWellDrained,RBE
>60cm
ModeratelyDrained,
RBE,>60cmImperfectlyDrained
RBE
PoorlyDrained
LHG
Land Use Model Cross SectionLand Use Model Cross Section
Recommended for RBE – LHGRecommended for RBE – LHG
combinationcombination
Village
Forest
Fruit
Forest Rain-fed/
homestead
Irrigated
upland
Irrigated
lowland

21. 50 m
60 m
50 m
35 m
LAND USE MODEL
ALONG CATENA
Home Garden
Irrigated Upland
Farm tract
Village road
Fruit Forest
Village Forest
Irrigated Lowland
Irrigation canal
35 m

22. Storm water diversion drain
Diversionbundanddrain
Common drain
Cultivated land
Cultivated land

23. Main irrigation canal
Natural drainage
Irrigable land
Homestead
Other field crops
Village forest
Main road
Village road
Farm tract
Communal
lands
Tank
Lower Canal
Upper Canal
Fruit forest gardens
Upstream reservation
Downstream reservation

24. How we conserve soil?
• A = RKLSCP
• A = RK (LS)max Ec., where,
• A = Soil loss (mt/ha), R = Erosivity (mt.m/ha), K
= Erodibility
• (LS)max = Maximum slope - length factor one
can achieve by manipulating land slope and
length in a given piece of land and
• Ec = soil and crop management factor termed
as Erosion Coefficient.

25. How we
conserve soil?
1. Increase soil cover
– Leave all the crop
residues in the field,
– Conservation tillage
that leaves the residues
on the soil surface,
– Apply organic materials
as manures or mulch,
– Adopt inter-cropping
and relay cropping,
– Leave the weed
residues on the surface

26. How we conserve soil?
2. Increase soil
organic matter
content
– Apply compost,
– Add green
manure,
– Add liquid
fertilizer,
– Apply straw
mulch

27. How we conserve soil?
3. Increase water infiltration
and moisture retention
capacity
– Maintain a protective
cover of residues over the
soil,
– Reduce wind velocity by
installing wind breaks,
– Create surface roughness
between the crop rows,
– Keep fallow periods
between cropping,
– Apply organic fertilizer,
Adopt contour ridging,
– Reduce the land slope by
terracing

28. How we conserve soil?
4. Reduce runoff
– Collect the runoff in
structures within
which the water can
infiltrate
– Construct structures
that collect and lead
the runoff away from
the field
– Establish permeable
barriers along the
lines of contour to
reduce runoff velocity

29. How we conserve soil?
5. Improve rooting
conditions
– Loosen the soil
around plants to
reduce compaction
and increase porosity
– Improve drainage by
placing drainage
channels where soils
are poorly or
imperfectly drained
– Make furrows or
raised beds