Mitigating soil erosion through farm-level adoption of soil and water conservation measures in Samanalawewa Watershed, Sri Lanka

Figures & data

Figure 1.  Location map of the study area.

Table I. Hypothesized determinants for the adoption of SWC measures.

Variable name	Measurement	Hypothesized influence
X 1 .Farmer's perception of soil erosion problems	Dummy	+
X 2 .Educational level of the HH head	Dummy	+
X 3 .Age of the HH head	Continuous	−
X 4 .Family size	Discrete	+
X 5 . Gender of the HH head	Dummy	+
X 6 .Past awareness about SWC measures	Dummy	+
X 7 .Security of tenure	Dummy	+
X 8 . Size of land under crop	Continuous	+
X 9 .Off-farm income	Continuous	+/−
X 10 .Dependency ratio	Continuous	−
X 11 . Size of rented land	Continuous	−
X 12 .Training on SWC	Dummy	+
X 13 .Membership in SWC committees	Dummy	+
X 14 .Advice from extension officers	Discrete	+
X 15 .Assistance in soil conservation practice	Dummy	+
Note:+means positive influence,-means negative influence and +/− positive or negative influence.

Figure 2.  Schematic representation of the research procedure of the assessment of soil erosion and farm-level adoption of SWC measures.

Figure 3.  Soil erosion map of the study area.

Table II. Status of soil erosion in Samanalawewa Watershed, 2008.

Soil erosion status	Range (t ha^−1 yr^−1)	% area
Very low	0–4	55.3
Low	4–8	30.2
Moderately high	8–12	10.1
High	12–16	2.9
Very high	16–20	0.9
Extremely high	20–289	0.6
Note: Total area was 536 km^2.

Table III. Summary of sample respondents and variables used in the regression model.

Variable name	Unit or type	% with a value 1	Average
			All	Adoption	Non-adoption
X 3 .Age of the HH head	Years		54.29	55.52	58.38
X 4 .Family size	Number		4.09	4.49	3.49
X 8 . Size of land under crop	Hectare		1.78	1.78	1.78
X 9 .Off-farm income	US$/yr		778.59	1256.20	57.00
X 10 .Dependency ratio	Ratio		0.41	0.37	0.47
X 11 . Size of rented lands	Hectare		0.44	0.33	0.36
X 14 .Advice from extension officers	Number/yr		2.91	3.36	2.21
X 1 .Farmer's perception of soil erosion problem	Dummy	63.7
X 2 .Educational level of the HH head	Dummy	64.2
X 5 . Gender of the HH head	Dummy	65.7
X 6 .Past awareness about SWC measures	Dummy	61.2
X 7 .Security of tenure	Dummy	68.7
X 12 .Training on SWC	Dummy	59.7
X 13 .Membership in SWC committees	Dummy	71.6
X 15 .Assistance in soil conservation practice	Dummy	70.5

Table IV. Parameter estimates of the variables included in the binary-logistic model.

Variable name	B	Wald	p	Odds ratio, Exp (B)
X 1 .Farmers’ perception of soil erosion problems	7.785	6.728	0.009	2403.103
X 5 . Gender of the HH head	7.953	7.249	0.007	2844.404
X 6 . Past awareness about SWC measures	3.997	5.903	0.015	54.437
X 9 .Off-farm income	0.001	3.659	0.049	1.000
X 12 .Training on SWC	6.259	9.485	0.002	522.954
X 14 .Advice from the extension officers	1.759	6.674	0.010	5.809
Constant	−19.474	9.426	0.002	0.001
Note: B = Coefficients of the regression model, Wald=(B/s.e)^2, s.e.=Standard error.

Table V. Impacts of adoption of SWC measures for soil erosion in Samanalawewa Watershed.

Adoption of SWC measures (Years)	% (n)	Average SWC cost US$ ha^−1yr^−1	Average rate of soil erosion t ha^−1 yr^−1 (s.d.)	Human-induced soil erosion vs natural soil erosion
< 5	24.8 (30)	85.5	10.5 (5.7)	48
5–10	18.2 (22)	75.5	7.8 (5.2)	35
10–15	24.8 (30)	66.5	3.5 (0.8)	16
15–20	12.4 (15)	45.7	2.5 (0.7)	11
> 20	19.8 (24)	30.8	1.8 (0.5)	8
Note: n = Number of HHs according to years of soil and water conservation (SWC) measures adopted,% = Percentage, US$ = United States dollar, s.d.=Standard deviation.