Doi: 10. 1016/j agwat
Participation in training programs, land ownership, soil analysis
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Participation in training programs, land ownership, soil analysis and investment in water conservation influence a farm’s technical efficiency level ( Table 6 ). IWUE in these systems is also positively affected by the participation in training programs, the realization of investments in water conservation and the use of fertigation techniques. However, IWUE is significantly and negatively affected by the proportion of total land area allocated to greenhouses. Thus, IWUE decreases when farmers specialize to a greater extent in the production of greenhouse crops. It is also negatively, (although not significantly), affected by the presence of a well as an alternative irrigation source on the farm. 4. Discussion and implications The average IWUE in the greenhouse production systems of Teboulba region is 41.8%, which is very low, particularly for a semi-arid country, such as Tunisia, with limited water resources. This implies that the observed quantity of marketable fruit and vegetables produced in greenhouses could be maintained by using the observed values of other inputs whilst using 58.2% less irrigation water. Substantial water inefficiencies in Tunisia (47%) were reported also by Dhehibi et al. (2007) for irrigated citrus production in Cap Bon (this region is the primary consumer of irrigation water in Tunisia). Albouchi et al. (2005) found that IWUE in the Kairouan region (the main agricultural area in the central part of Tunisia) was approximately 53%. Chebil et al. (2007) , using the same sample of Teboulba farmers as we use in our study, found that farmers are willing to pay higher prices for irrigation water if this would improve distribution and delivery services. Thus, Tunisia still has much to do to improve the use Table 4 Average efficiencies for selected farm groups, given the assumption of constant returns to scale. Average technical efficiency Average irrigation water use efficiency Group 1 (75% < TE < 100%) 92.5% 79.9% Group 2 (50% <= TE < 75%) 63.3% 30.4% Group 3 (0 <= TE < 50%) 45.0% 11.4% TE denotes technical efficiency. Fig. 3. Cumulative efficiency distribution for both technical and irrigation water use efficiencies. Table 5 Results of correlation test «pairwise correlation» between technical efficiency and irrigation water use efficiency. TE-CRS TE-VRS IWUE-CRS IWUE-VRS TE-CRS 1.000 TE-VRS 0.858 1.000 IWUE-CRS 0.845 0.704 1.000 IWUE-VRS 0.821 0.935 0.754 1.000 All of the correlation coefficients are significant at the 1% level. TE and IWUE denote, respectively, technical efficiency and irrigation water use efficiency. CRS denotes constant returns to scale, while VRS denotes variable returns to scale. Table 6 Factors affecting technical and water use efficiencies: tobit model results, given the constant returns to scale assumption. Explanatory variable Explained variable Technical efficiency Irrigation water use efficiency Estimate P-value Estimate P-value Farmers characteristics Age of the manager 0.233 0.136 Training program ** 11.708 0.013 *** 22.965 0.000 Land ownership ** 12.069 0.012 5.322 0.401 Experience 0.173 0.232 0.091 0.592 Technological characteristics Soil analysis ** 12.691 0.012 Investment in water saving *** 21.570 0.005 *** 26.231 0.010 Fertigation 3.838 0.626 *** 33.083 0.001 Farm characteristics Farm size 0.587 0.657 0.336 0.848 Proportion of greenhouses 0.241 0.313 ** 0.661 0.048 Well 3.203 0.517 Constant *** 47.068 0.000 ** 18.451 0.045 s 11.311 a 1.346 15.468 1.905 Pseudo R 2 0.181 0.194 Log-likelihood 153.348 163.017 LR b 68.190 0.000 78.490 0.000 ** Significant at 5% level. *** Significant at 1% level. a For s and LR the standard error is reported instead of the P-value. b Likelihood ratio statistic. A. Frija et al. / Agricultural Water Management 96 (2009) 1509–1516 1514 and sustainability of its water resources, starting at the farm level. As shown in Table 5 , the technical efficiency of farms in our sample is positively and highly correlated to the IWUE at the farm level. Thus, apart from the impact on sustainability, efforts made to rationalize water use will also have an important impact on the sector’s productivity. In addition our results demonstrate that potential exists to improve IWUE, both on farms with a high technical efficiency level and those with low efficiency ( Table 4 ). Many factors affect technical efficiency and IWUE. Involvement in technical training is highly significant in both of our regression models, and positively affects both types of efficiency. Dhehibi et al. (2007) obtained similar results regarding the positive impact of agricultural training on IWUE in Tunisia. In accordance with these authors, we recommend that policy makers focus on enhancing farmers’ knowledge regarding specific technologies in greenhouse crop production and efficient water management methods via the provision of better extension services and training packages. Information regarding optimal doses and timing of water applications to different crops is also needed in the study area. Providing such information could reduce the variability in IWUE among the 80% of farmers who use the same irrigation technology. As expected, investment in new water saving methods (dummy variable in the tobit model) can improve IWUE ( Table 6 ). The choice of water saving technology affects not only the IWUE but also greenhouse crop production. Farmers using drip irrigation are much more efficient, both in terms of the production process and regarding irrigation water use ( Table 7 ). However, farmers using water saving technology, in some cases, are less efficient than those who do not use any such methods (see minimum and maximum scores for each irrigation system). The ‘‘National Irrigation Water Saving Program’’, introduced in 1995 to encourage irrigators to invest in water saving technologies, generated higher measures of IWUE and improved farmers’ incomes in Tunisia ( Al Atiri, 2004 ). This program, which provides subsidies ranging from 40 to 60% of the purchase price of modern irrigation equipment, has encouraged many farmers to invest in water saving technologies ( Ministe`re d’Agriculture et des Ressources Hydrauliques, 2004 ). However, in 2004 the areas equipped with water saving technologies in Tunisia represented only about 75% of the total irrigated area ( Agency of Agricultural Investments Promotion, 2004a,b ). An effort should be made to encourage farmers with limited resources to adopt these techniques. In addition, more research is needed to evaluate related policies that could enhance the effects of technology adoption. Our results suggest that IWUE is negatively correlated with the level of specialization (i.e. the proportion of farm land area allocated to greenhouses). Given the small scale of farms in our sample, the most specialized ones are those with only sufficient land to install a small number of greenhouses (the 10 more specialized farms in our sample have an average farm size of 0.6 ha. The average size of the other farms is about 1.71 ha). Generally these farms have resource constraints and limited marketing alternatives, which could indirectly affect their level of IWUE (see Wichelns, 2003 ). Establishing secure property rights (land ownership) also is helpful in enhancing technical efficiency. In many areas, land rights are closely linked to farm-level investment decisions. In addition, farmer knowledge regarding soil fertility (through soil analysis) also significantly increases technical efficiency scores by enabling farmers to optimize the use of water and fertilizers. Such practices should be encouraged with the help of extension services. 5. Conclusion Many reforms have been made in Tunisia in the last two decades to improve irrigation water use efficiency. Our research, which measures irrigation water use efficiency at the farm level, shows that the results of these reforms are not always guaranteed. In our study area, characterized by small scale agricultural systems, very high water prices (covering both the operation and management costs in addition to a proportion of the fixed costs of irrigation), and government subsidies for water saving technologies, the calculated irrigation water use effi- ciency is still low and does not reflect the water-saving orientated policies that have been applied. Significant water saving could be achieved if irrigation management in the studied system could be improved. The potential returns to scale for both technical and irrigation water use efficiencies are high, indicating that farmers are operating near the optimal scale. Also, irrigation water use efficiency and the technical efficiency of the greenhouse crop production process are highly correlated. Hence the efficient use of water matters not only in terms of the sustainability of the resource, but also in achieving productivity improvements and increasing the competitiveness of agricul- tural systems. Farmer participation in technical training, investment in water conservation, and the use of fertigation significantly increase the level of irrigation water use efficiency. However, the proportion of total farmland area allocated to greenhouse crop production has a negative and significant impact on the efficiency of the irrigation water use at the farm level. In addition we recommend enhancing farmers’ knowledge through better extension services and training packages. Further research is needed also to understand the negative correlation between farmers’ specialization and irrigation water use efficiency. Table 7 Variability of technical and water use efficiencies by irrigation system. Irrigation system Fertigation unit connected with a drip irrigation network Plastic water pipes irrigation 85% a 15% a Average Minimum Maximum Average Minimum Maximum TE CRS 71.5 42.7 100.0 43.7 26.8 53.0 VRS 79.8 45.0 100.0 52.1 42.7 62.4 IWUE CRS 47.3 6.1 100.0 10.7 3.6 14.2 VRS 58.0 9.3 100.0 21.6 5.0 45.0 TE and IWUE denote, respectively, technical efficiency and irrigation water use efficiency. CRS denotes constant returns to scale, while VRS denotes variable returns to scale. a Proportion of farmers. A. Frija et al. / Agricultural Water Management 96 (2009) 1509–1516 1515 References Al Atiri, R. 2004. 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