This paper provides empirical evidence that improved supplemental irrigation (ISI) can be justified on both environmental and economic grounds. Results of a stochastic frontier model which explicitly and simultaneously accounts for technical inefficiency and production risk applied to data collected from 513 wheat farms in the rainfed areas of Syria show that the typical adopter farmer obtained yield and productive efficiency gains of 6% and 7% respectively. A stochastic dominance criterion also showed that the adopter farmers got 10% and 13% reductions in risk of obtaining yield levels below 4 tons/ha and 3 tons/ha respectively. Given its adoption level of 22.3% in 2010, ISI led to the production of 52 thousand metric tons (6%), more wheat and conservation of 120 million cubic meters of water (10%). ISI has the potential to reduce total irrigation water use by upto 45% and for further increases in yield if accompanied with sprinklers and other improved agronomic practices, thereby enhancing food security and environmental sustainability in the country. An important policy implication of these findings is that wider dissemination of ISI along with other complementary agronomic practices in postwar Syria could be a viable option to be considered by national and international efforts for the restoration and rehabilitation of agriculture in the country.
Agriculture in the dry areas is exposed to a variety of risks which occur with high frequency where the stochastic nature of agricultural production is the major source of risk [
Yield variability is often explained by external factors such as weather, pests, diseases and input and output prices that are outside the control of farmers. However, factors, such as variability in agronomic conditions including levels of inputs applied, which are under the control of farmers, also play important roles [
Farmers in developing countries are generally risk-averse [
Water scarcity is a critical constraint to agriculture in dry areas. This problem is likely to become more severe because of population growth, climate change and deterioration of water quality. Characterized by low average amounts and high variability of rainfall, agricultural production in the dry areas carries substantial risk. In its effort to help farmers in the dry areas, the International Center for Agricultural Research in the Dry Areas (ICARDA) along with the national agricultural research institutions of many countries in the Middle Eastern and North African region has introduced the practice of improved supplemental irrigation (ISI) in predominantly rainfed areas. Improved supplemental irrigation (ISI) is the addition of small amounts of water to essentially rain-fed crops during times when rainfall fails to provide sufficient moisture for normal plant growth, in order to improve and stabilize yields [
The components of the new improved supplemental irrigation technology focused on irrigation scheduling: when to irrigate, how to irrigate, and how much water to use [
Using data from 513 Syrian wheat farmers and the stochastic frontier production function, this paper argues and tries to provide empirical evidence that the adoption of ISI reduces the risks of yield variability and the associated variability in technical efficiency. The findings of this study are expected to be useful to researchers, policy makers, development organizations and extension personnel in their effort to help farmers in the dry areas cope with water scarcity induced by climate change.
Syria is highly vulnerable to climate change. Located in the western part of the Mediterranean basin, Syria has a surface area of 185,518 km2 and 32.2 percent is of this area is cultivable. Total irrigated land has more than doubled in 20 years between 1985 and 2005 [
Wheat is the most important food grain grown in Syria. It is a crop of strategic political importance due to its high potential to enhance food security. In 2011, wheat was cultivated on nearly 1.8 million hectares, with a total production of 4.9 million metric tons [
Water use efficiency (WUE), which is the ratio of the amount of water actually utilized by the crop to the total water pumped, for irrigated agriculture in Syria stands at about 40% - 60% [
Prior to the introduction of the improved supplemental irrigation (ISI) by ICARDA and the Ministry of Agriculture (MoA), all Syrian wheat growers used irrigation techniques that resulted in high water use per unit area. Thus current adoption of improved supplemental irrigation (ISI) technology by 22.3% of Syrian wheat farmers has resulted in water savings and sustained wheat farming systems, generating huge environmental benefits. Applying supplemental irrigation in one or two well-timed applications at heading, anthesis, or milk stage can lead to increased and stabilized yield. To avoid confusion, we make distinction in this paper between improved supplemental irrigation (ISI), in which the recommended water application rates are used and traditional supplemental irrigation (TSI) where farmers use excessive irrigation over the recommended levels1.
Owing to their relatively high share in total rainfed wheat land in the country and also the tremendous scope for ISI, zones 1 and 2 of Syria have been chosen for this study. From among the total of 14 governorates in the country, 12 have areas which fall in zones 1 and 2 out of which, the top three wheat producing governorates (Aleppo, Deraa and Al-Hassakeh) were chosen for this study. These three governorates account for about 66% of total wheat land and 61% of total wheat production in Syria.
Using power analysis, the minimum sample size needed to ensure 95% confidence level for estimating the total number of ISI adopters was calculated to be 513. A stratified sampling procedure was then used to proportionally distribute the sample among the two zones where 241 and 272 households were drawn from Zones 1and 2 respectively. The distribution of these households into the two zones and 26 randomly drawn villages across the three governorates are provided in
The stochastic frontier production function approach has been widely applied to analyze technical efficiency in production [
Aleppo | Dara’a | Al-Hasakeh | Total | |||||
---|---|---|---|---|---|---|---|---|
Z1 | Z2 | Z1 | Z2 | Z1 | Z2 | Z1 | Z2 | |
No. of villages selected | 5 | 4 | 4 | 4 | 4 | 5 | 13 | 13 |
Total number of households in the selected villages | 30,752 | 30,647 | 12,152 | 16,383 | 23,500 | 29,500 | 66,404 | 76,530 |
No. of households selected by zone | 111 | 109 | 45 | 59 | 85 | 104 | 241 | 272 |
irrigation water use technical efficiency with very high variability ranging between 23.9% - 98.63% and 1.6% - 98.87%, respectively. The low estimated mean irrigation water efficiency results show that using the observed values of other inputs and 53% and 47% less irrigation water respectively, the observed quantities of outputs could be produced. The typical stochastic frontier production function can be specified as:
ln ( y i ) = f ( x i , β ) + v i − u i (1)
where y i is a scalar output of production unit I; x i is a vector of N inputs used by producer I; f ( x i , β ) is the deterministic part of the production frontier; β is a vector of technology parameters to be estimated; and v i and u i are noise and inefficiency components which can take a number of forms, depending on specific assumptions. The specification given by (Equation (1)) is consistent with the typical Just-Pope framework [
u i = 0
v i ∼ N ( 0 , σ v i 2 )
σ v i 2 = exp ( z i γ )
where z i is an input vector which may or may not equal x i and γ is a vector of parameters. So the Just-Pope framework takes the form:
y = f ( x i , β ) + h ( z i , γ ) (2)
where the function h ( z i , γ ) represents the output risk function. More recent advances in efficiency analysis showed that stochastic production frontier models can include the technical inefficiency and production risk simultaneously [
v i ∼ N ( 0 , σ v i 2 ) (3)
σ v i 2 = exp ( z i γ )
u i ~ N + ( ū i , σ u i 2 )
ū i = ω i α
Following the conventional specification in the stochastic production frontier model, the random error v i follows a normal distribution with zero mean and variance σ v i 2 , and the inefficiency term u i follows a truncated-normal distribution with mean ū i and variance σ u i 2 . To capture the heterogeneity of the efficiency and risk terms, the mean efficiency and risk functions are determined by exogenous factors. The vector ω i denotes exogenous variables that have influence on the mean value of production inefficiency.
The risk function is assumed to have an exponential functional form with the vector of the exogenous factors z i as explanatory variables [
ln L = constant − 1 2 ∑ i ln [ exp ( z i γ ) + exp ( k i l ) ] + ∑ i ln ϕ ( h i a σ i λ i − ε i λ i σ i ) − 1 2 ∑ i ( ε i + h i α ) 2 σ i 2 (4)
where σ i 2 = σ v i 2 + σ u i 2 ; ε i = y i − x i β ; λ i = [ exp ( k i l − z i r ) ] 0.5
Following [
T E i = f ( X i j , β i j , v i , u i ) f ( X i j , β i j , v i ) (5)
T E = exp ( − u i t ) = exp ( − z i t δ − w i t ) (6)
where, 0 ≤ T E ≤ 1 and the closer the TE score to 1, the higher the efficiency. In this specification, the parameters, β, σ, σu, and δ have been estimated simultaneously using the maximum likelihood method. Thus, the log likelihood ratio (LR), which has a chi-square distribution, is used to test the significance of parameter estimates.
Model results show that wheat area, application rates of Nitrogen and Phosphorus fertilizers, seed rate and quantity of Labor used had positive and significant effect on yield-showing that at their current average application levels, an increase in any of the five inputs leads to yield increase (
Variables | Average value | |||
---|---|---|---|---|
Unit | ISI | TSI | FI | |
Quantity of irrigation water | m3/ha | 1460 | 1615 | 2766.7 |
Wheat area | Ha | 3.7 | 2.8 | 3.4 |
Nitrogen quantity | kg/Ha | 132 | 138 | 148 |
Phosphorus quantity | kg/Ha | 49.4 | 84.3 | 62.7 |
seed quantity | kg/Ha | 250 | 260 | 275 |
Labor | Hour | 32.2 | 38.9 | 57 |
Farmer age | Year | 51.7 | 53.8 | 52.6 |
years of schooling | Year | 8 | 6.8 | 3.7 |
Farm size | Ha | 11.5 | 8.1 | 11 |
Source: survey data.
The insignificance of the linear irrigation water term should not come by surprise as the descriptive statistics from our sample survey show that the typical farmer is applying about 1110 m3/ha in excess of the maximum of the recommended range of 600 - 1800 m3/ha. The profit maximizing level of irrigation water is 2032 m3/ha showing that the typical farmer is producing on the downward slopping part of the total product curve where marginal product of irrigation water is negative.
From the inefficiency model, the negative and significant coefficient on the use of improved supplemental irrigation indicates that improved supplemental irrigation reduce inefficiency-a result that is consistent with the theoretical expectation as improved supplemental irrigation is believed to ensure better utilization of water by plants. The positive and significant coefficient on the soil salinity variable shows that at its current average, an increase in soil salinity would lead to higher inefficiency. The coefficient on the years of schooling is negative and significant. This shows that more farmer education reduces inefficiency, which is consistent with what one can expect.
A closer look at the efficiency figures shows that 11.9% of the farmers who had used ISI have efficiency levels of between 90 to 100 percent. The corresponding figure for farmers who had used full irrigation (FI) and TSI is 0. Regardless of their irrigation method (surface canal or sprinkler), 77.4% of farmers who used ISI have efficiency rates of greater than 70 percent, which is much higher than that of those who had used FI and TSI which exhibit irrigation water efficiency levels of 38% and 52.6% respectively-a clear indication that using ISI leads to improvements in productive efficiency (
In the risk function, the coefficients on improved supplemental irrigation (ISI), Nitrogen fertilizer and, improved wheat variety are negative and significant showing that they contribute to the reduction of production risk. The negative and significant coefficient on ISI is consistent with the theoretical expectation as yield stability is one of the main benefits of ISI. The stochastic dominance
Deterministic frontier | ||
---|---|---|
Inputs/Attributes | Coefficient | Std. err. |
Quantity of irrigation water (m3/ha) | 0.0074 | 0.0055 |
Wheat area (Ha) | 0.0277 | (0.0106)*** |
N (kg/Ha) | 0.1225 | (0.0139) *** |
P (kg/Ha) | 0.0756 | (0.0085)*** |
seed (kg/Ha) | 0.1344 | (0.0297)*** |
Labor (hour) | 0.0702 | (0.0166)*** |
Constant | 6.6405 | (0.1400)*** |
Risk function | ||
Soil salinity (0 = Low and 1 = High) | 0.0934 | (0.0305)*** |
Wheat area (Ha) | −0.0003 | 0.0014 |
N (kg/Ha) | −0.0002 | (0.0001)* |
P (kg/Ha) | 0.0019 | 0.0034 |
Wheat variety (0 = Local and 1 = Improved) | −0.9128 | (0.4970)* |
Labor (hour) | −0.0004 | 0.0037 |
Surface Supplemental irrigation (0 = No and 1 = Yes) | 0.0463 | (0.0261)* |
Improved supplemental irrigation (0 = No and 1 = Yes) | −0.1378 | (0.0400)*** |
Constant | −5.4658 | (0.4840)*** |
Mean function of inefficiency | ||
Farmer age (year) | −0.0007 | 0.0045 |
years of schooling (year) | −0.0786 | (0.0155)*** |
Farm size (Ha) | −0.0030 | 0.0094 |
Soil salinity (0 = Low and 1 = High) | 0.6098 | (0.2246)*** |
Wheat variety (0,1) | −0.0152 | 0.1672 |
Surface Supplemental irrigation (0 = No and 1 = Yes) | −0.3646 | (0.1999)* |
Improved supplemental irrigation (0 = No and 1 = Yes) | −0.9111 | (0.3573)*** |
Constant | −2.4218 | (0.2888)*** |
Log likelihood | 276.8000 |
Dependent Variable: natural logarithm of yield (kg/ha); ***, **,* indicate significance at the 1%, 5%, and 10% levels.
criterion also showed that ISI first degree stochastically dominates TSI and the shift from TSI to ISI led to 10% and 13% reductions in the risk of obtaining yield levels below 4 tons/ha and 3 tons/ha respectively (
The negative and significant coefficients on improved wheat varieties (IVs) are also consistent as the drought tolerance characteristics of IVs is expected to reduce yield variability. However, the negative and significant coefficient on Nitrogen fertilizers is counterintuitive because if the amount of irrigation water
made available to the crop is very low, fertilizers could possibly have burning effect and hence lead to lower yield levels than what is achievable without fertilizers. These results indicate that risk-averse farmers can use ISI, improved wheat varieties and fertilizers in order to reduce the production risk and hence the revenue variability. Further analysis of the data shows that risk-averse farmers are less likely to adopt supplemental irrigation with surface canal because adoption of SI with surface canal (instead of sprinklers) can increase the variability in production.
Using a survey of 513 Syrian wheat farms as case study and a stochastic frontier production function model which explicitly and simultaneously accounts for technical inefficiency and production risk, this paper provided empirical evidence that a shift from both flood irrigation (FI) and traditional supplemental irrigation (TSI) to improved supplemental irrigation (ISI) in rainfed agriculture, particularly in the dry areas, increases technical efficiency and reduces production risk and increases yield, thereby contributing to national food security.
At current average application rate of 1490 m3/ha, the adopters of ISI are using about 1110 m3/ha (43%) irrigation water less than those using TSI. Therefore, at its current adoption level of 22.3%, ISI leads to the conservation of about 120 million m3 (10% of total) irrigation water in the country. This shows that if all farmers in the country were to shift to ISI, it has the potential of cutting the total amount of irrigation water by about 45%. With a negative and significant coefficient in the inefficiency model, the use of improved supplemental irrigation reduces inefficiency―a result that comes without a surprise as improved supplemental irrigation is believed to ensure better utilization of water by plants.
Analysis of estimates from the inefficiency model shows that 11.9% of the farmers who had used ISI have efficiency levels between 90 and 100 percent. The corresponding figure for farmers who had used FI and TSI is 0. Likewise, regardless of the irrigation method used (surface canal vs. sprinklers), 77.4% of farmers who used ISI have efficiency levels greater than 70 percent, which is much higher than that of those who had used FI and TSI (8% and 52.6% respectively)―a clear indication that using ISI helps in the improvement of productive efficiency.
The stochastic dominance criterion also showed that the shift from TSI to ISI led to 10% and 13% reduction in risk of obtaining yield levels below 4 tons/ha and 3 tons/ha respectively. These results all together indicate that investment in improved supplemental irrigation (ISI) helps in the reduction of risk in wheat production. The use of sprinklers, improved wheat varieties particularly those which are drought tolerant, and the use of nitrogen fertilizers along with ISI played an important role in enhancing productive efficiency and hence productivity as well as in reducing income risks for wheat farmers in Syria.
ISI has the potential for enhancing food security and environmental sustainability in the Syria and other countries with dry land agriculture under similar production conditions. An important policy implication of these findings is that wider dissemination of ISI along with other complementary agronomic practices in postwar Syria could be a viable option to be considered by national and international efforts for the restoration and rehabilitation of agriculture in the country.
This study was carried out as a partial fulfillment for a PhD study at Damascus University, Syria. The authors thank the International Center for Agricultural Research in the Dry Areas (ICARDA) and CRP-Wheat for the financial support which made the study and publication of this manuscript possible.
El-Shater, T., Yigezu, Y.A., Shideed, K. and Aw-Hassan, A. (2017) Impacts of Improved Supplemental Irrigation on Farm Income, Productive Efficiency and Risk Management in Dry Areas. Journal of Water Resource and Protection, 9, 1709-1720. https://doi.org/10.4236/jwarp.2017.913106