Irrig Sci (2011) 29:311–319 DOI 10.1007/s00271-010-0235-3
ORIGINAL PAPER
Improving on-farm water management through an irrigation scheduling service A. Montoro • P. Lo´pez-Fuster • E. Fereres
Received: 20 April 2010 / Accepted: 22 September 2010 / Published online: 8 October 2010 Ó Springer-Verlag 2010
Abstract Irrigation scheduling services (ISS) provide farmers with recommendations on timing and amount of irrigation, thus contributing to improving on-farm water management. There are wide variations in the level of services, from providing regional water use guidelines to local, on-farm advisory services. An ISS (ISS-ITAP) was created in 1988 in Albacete, Central Spain, a province encompassing 100,000 ha which are irrigated mostly with groundwater. The ISS-ITAP first offered general information on crop water requirements (ET), and after 1994 fieldspecific scheduling services were provided to growers. By 2005 the ISS-ITAP had expanded its services to over 33,500 ha, corresponding to about 30% of the irrigable area. The evolution of irrigation performance in a number of individual farms was followed over 10 years, and it was found that the proportion of fields which were adequately irrigated increased from 50 to over 70% in that period. Meanwhile, the proportion of deficit-irrigated fields declined from 20 to 10%, while the proportion of overirrigated fields which also had initially decreased from 20 to 10%, went back to 20% at the end of the study period. To assess the benefits and costs of the ISS-ITAP, a comparison of the yields achieved in the scheduled farms against those obtained in the rest of the province was carried out. When the Service was evaluated in economic
Communicated by J. Kijne. A. Montoro (&) P. Lo´pez-Fuster Instituto Te´cnico Agrono´mico Provincial (ITAP), C/Gregorio Arcos, s/n Apdo. 451, 02080 Albacete, Spain e-mail:
[email protected] E. Fereres IAS-CSIC and University of Co´rdoba, Apdo. 4084, 14080 Co´rdoba, Spain
terms, using information from 2003, the pay-back was 2 years and the internal rate of return was 59.1%, highlighting the high returns on the public funds invested by ISS-ITAP to provide irrigation advisory service to growers in the Albacete province.
Introduction In most of the world, irrigated agriculture has been faced with increased limitations in water supply over the last few decades. Additionally, higher energy and water costs and lower product prices are all leading to efficiency improvements and cost reductions, for which adoption of advanced technologies is mandatory. Among those technologies, technical irrigation scheduling, by which the precise timing and amount of irrigation are determined, has long been advocated as an improved water management technique (Jensen 1981). In fact, since the early 70s or even earlier, significant efforts were devoted to develop irrigation scheduling services (ISS) in several areas (Shearer and Vomocil 1981). These ISS programs had diverse objectives such as the conservation of water and energy (Shearer and Vomocil 1981; Dockter 1996; Alam et al. 1996), improvement of crop yield and quality (Lyford and Schild 1981; Silva and Marouelli 1996; Tacker et al. 1996), reduction of non-point pollution (Boesch et al. 1981; Klocke et al. 1996; Nguyen et al. 1996), or generally improving the irrigation management of an area (Ortega et al. 2005). Smith and Mun˜oz (2002) carried out a review of the different ISS to date and found a significant number of ISS around the world which went from providing information on general crop water requirements (ET), to specific on-farm advice on timing and amount of irrigation. After
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the early efforts in the 70s that emphasized on-farm advisory services (Lyford and Schild 1981; Silva and Marouelli 1996; Tacker et al. 1996), there was a tendency to generate ET information by government agencies that could be taken up by growers and consultants alike to develop sitespecific recommendations (Fereres 1996). One of the early efforts that provided regional ET information was the California Irrigation Management Information System (CIMIS) which started in 1981, and where the number of users grew at an annual rate of 20% until 2001 (Eching 2002). By the time the survey was conducted, the number of direct users was 4,700, of which 26% were farmers and the rest were irrigation consultants providing information to growers, for a total number of farms of about 15,000 (Eching 2002). Since the establishment of CIMIS, numerous agricultural weather station networks have been established in irrigated areas with the purpose of providing ET information (Smith and Mun˜oz 2002). One big advantage of this type of regional ISS is its low cost relative to those that include providing site-specific advice and field checks (Fereres 1996). The major problem with the provision of ISS that was identified early on was that of adoption (Shearer and Vomocil 1981). One reason was the lack of motivation on the part of the farmer to conserve water, but the costs of the ISS relative to the perceived benefits were an even greater barrier (Fereres 1996). When the ISS were provided for free, the uptake of this technology was quick and increased the irrigation management skills of growers, but, in the past, when the ISS programs were discontinued due to lack of funding, they were not generally demanded by growers who were not ready to cover the costs. While the emphasis of many ISS was to conserve water, it should be noted that the primary goal for adopting new irrigation technologies is to increase yields, not to save water. In fact, the use of more efficient technologies often increases, rather than decreases, water consumption (Whittlesey 2003; English et al. 2002). A recent survey undertaken in Alberta (Canada) to determine the uptake of improved irrigation technologies and management practices showed that the major drivers of adoption were to ensure water supply during droughts, to increase crop yields and quality, and to reduce costs, while the major impediments were related to financial constraints (Bjornlund et al. 2009). It is therefore important to assess the benefits and costs of ISS so as to promote them in areas where they can improve irrigation management practices. Few studies on the impact and benefits of ISS have been carried out. In addition to that of CIMIS (Eching 2002), Leib et al. (2002) described an ISS where nine private consultants were contracted to provide growers with irrigation scheduling information on nearly 120,000 ha per year in the state of Washington. A survey carried out which also covered different programs indicated an adoption rate
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of the ISS of 18% of the growers, a substantial proportion relative to other programs. In the province of Albacete, (Spain) about 92% of the irrigated area is supplied with groundwater, and pumping costs provide an incentive for improved irrigation management. Also, groundwater overdraft has been a problem at time and some aquifers within the province have been overexploited. The irrigation development in the province has been significant, with approximately 80,000 ha developed in the last three decades, almost exclusively from groundwater. As a result, irrigation water consumption has increased from 150 hm3 to near 500 hm3 with the consequent decline in the depth of the water table of about 28 m over 25 years (Montoro and Lo´pez Fuster 2005a). Farms are relatively large in size (average around 100 ha), mostly devoted to herbaceous crops, and mechanized sprinkler systems are used in over 85% of the area. Considering the need for sustainable management of the groundwater resources, and given the groundwater overdraft problems, the provincial government developed a service in 1988 for helping farmers to improve irrigation management, and to deal with future water scarcity. Since that time, the service evolved into an ISS (hereafter named ISS-ITAP) that provided recommendations on irrigation timing and amounts. With time, the ISS-ITAP included field checks and irrigation monitoring and systems performance assessment (Montoro et al. 2002). In this paper we summarize the results of 10 years of the ISS-ITAP, describing its evolution, operational guidelines, and its performance until 2005. An economic assessment of the benefits and costs of the service is presented, and the impact of the ISS-ITAP is evaluated.
Methods According to the UNESCO classification, the climate of Albacete is semiarid; average annual precipitation is 325 mm, and the average annual reference ET (ETo) (Penman–Monteith equation; Allen et al. 1998) is 1,280 mm (Montoro and Lo´pez Fuster 2005b). Soils are classified as Petrocalcic Calcixerepts (Soil Survey Staff 2006). Average soil depth is 40 cm, and is limited by the development of a more or less fragmented petrocalcic horizon. Texture is silty–clay–loam. The Irrigation scheduling service of ITAP From 1988 to 1994, the ISS-ITAP was centered on disseminating crop water requirements information through the press and local radio for the major crops of the province (Martı´n de Santa Olalla et al. 1999). For that purpose, the ET values were calculated following FAO methodology
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(Doorenbos and Pruitt 1977) to calculate ETo and crop coefficients (Kc). Seven agrometeorological weather stations are located around the province and the data collected were used for the determination of ETo. Specific advice to commercial farms started about that time, but only after 1996 the number of farms and fields was significant and the collected on-farm data were fully reliable. After 1994 the Penman–Monteith equation (Allen et al. 1998) was used for the calculation of ETo, after it had been checked with data from a weighing lysimeter (Lo´pez Urrea 2004). The ISS-ITAP provided growers weekly predictions of crop water requirements tailored to each of their fields. For every field, the crop development characteristics and the actual irrigation amounts applied to every field were recorded by technicians in periodic field visits throughout the season. Generic distribution of information is provided for by the ISS-ITAP though the local press, answering phone calls, farm visits, irrigation district meetings, and its website. The most intensive efforts are made in the followup of the farms using the Service; a technician from ISSITAP is in charge of visiting a certain number of sites normally once a week during the irrigation season. In that visit, the technician records the crop developmental stage, irrigation dates and amounts, effective rainfall, and makes an assessment of the irrigation performance. The results presented below summarize the highlights of the programme, which have been described in more detail by Montoro (2008). To evaluate irrigation performance, the relative water supply (RWS) (Malano and Burton 2001) for each field in the Service was calculated as the ratio of the water supply (irrigation plus effective precipitation) to the net water requirements as: RWS ¼ ðAIW þ PeÞ=ET
ð1Þ
where AIW is irrigation water; Pe is effective precipitation, and ET is crop evapotranspiration. The information on AIW was collected by the Service every week from the farmer. The effective precipitation was determined from rainfall data either from the farmer himself or from the agroclimatic station closest to each field. The method used to calculate Pe from rainfall data was that of the U.S. Bureau of Reclamation (Stamm 1967). Given the inherent uncertainties in the RWS values, the RWS data from all fields of any single crop were arbitrarily classified into three levels; if the RWS values fell within 15% of unity, the fields were considered adequately irrigated; otherwise, RWS values outside that interval were considered an indication of insufficient or excessive irrigation according to the following criterion: if, RWS(%) [ 115%, is named over-irrigated field (OI); if, RWS (%) \ 85%, under-irrigated field (UI), and if, 115 C RWS (%) C 85%, adequately irrigated (AI).
To determine the relationship between yield and water supply, data for 6 years (2000–2005) for wheat, opium poppy (grown in the area for medicinal purposes and under strict control from a corporation) and maize were collected and plotted and an envelope curve over the highest yield points for different levels of water supply was drawn by hand. The crop yield ratio (CYR) (Malano and Burton 2001) was calculated as: CYR ¼ CYA x CYP1
ð2Þ
where CYR is crop yield ratio; CYA is actual crop yield (kg ha-1); CYP is potential crop yield (kg ha-1). The yield potential was estimated from highest yield values recorded in the fields of yield versus water supply. Water productivity (WP) defined as kg per m3 and € per m3 was determined from the data collected by the Service for the 2000–2005 period. Product price information was obtained from the local wholesale market. Subsidies received for each crop from the Common Agricultural Policy of the European Union were included in the calculations of economic WP. To evaluate the impact of the ISS-ITAP, an assessment of the costs and benefits of the Service was carried out (Montoro 2008). It was not possible to compare water use records from users and non-users, thus a yield comparison was performed. Average yield data for the ISS-ITAP fields for the year 2003 were compared to the average provincial yields on irrigated area of that year (MAPA 2004). The comparison was performed only for the main five crops, wheat, barley, maize, sugar beet, and potato for which there were reported provincial yields (MAPA 2004). For the economic analysis, the benefits derived from the use of ISS-ITAP were calculated as the difference in income between the average field yield and the average provincial yield for the five selected crops. The higher yields of the scheduled fields may be attributed to the use of the ISS-ITAP, but they may be attributed to other factors as well. Farmers using the Service may have better agronomy than average, in terms of planting dates, densities, soil management, etc. They may also have better fertility and pest management programs than the average farmer. Since none of these other factors influencing yield were quantified in this study, it was conservatively assumed that only 10% of the yield increase could be attributed to the ISS-ITAP. The operating and total annual costs of the Service are computed in detail in Montoro (2008), consisting of direct and indirect costs. Direct costs include those derived directly from conducting the advisory work, namely personnel and consumables. The indirect costs included the share of maintenance and general costs of offices, vehicles,
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Results Adoption of the ISS-ITAP Figure 1 presents the evolution of the number of farmers and the area advised by the ISS-ITAP. Starting in 1994, and after an initial interest, the area covered by the ISSITAP levelled off in 1998 (Fig. 1). Subsequently, the ISSITAP expanded both in area and number of growers to reach 33,500 ha and 160 farms in 2005. The total number of farms in the Province is around 1,080. At present, the ISS-ITAP continues to serve about the same number of farms and acreage, as the financial resources allocated to the Service have not changed since 2005.
Improving performance through ISS-ITAP Irrigation performance assessment was evaluated for the different crops through the evolution of the RWS with time. As indicated above, the performance of the different fields was classified into three categories; those where the RWS was between 85 and 115% were assumed to be AI; those with RWS \ 85% were considered UI and those with RWS [ 115% were OI. Figure 2a presents the evolution of the percentage of AI, UI and OI fields for the wheat crop between 1997 and 2005. In the first year, only 44% of the fields were AI, and more than 30% were UI. After seven years of ISS-ITAP, the proportion of AI fields increased to over 60%, while the UI fields were down to 20% of total. At first, there was a substantial reduction in the proportion of OI fields (from 24% to less than 10% in 2001), and then it increased after that year, its proportion reaching 18% in 2005. In the case of maize, there was substantial over-irrigation in 1997, at the start of this assessment (Fig. 2b). Nevertheless, after the first three years the proportion of AI fields increased from 50 to 75%, while that of OI fields decreased drastically, from almost 40% to about 10%. The proportion of UI fields went from 15 to about 5% in 2001, while in recent years, there has been a slow increase in the proportion of OI fields, reaching 17% in 2005 (Fig. 2b). The evolution of the RWS with time for the other crops showed a general improvement in irrigation management
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etc. administration and general services, both totalling € 220,100.00 for the year 2003. Pay-back, net present value (NPV), and internal rate of return (IRR), were calculated for 2003. Payback period refers to the period of time required for the return on an investment to repay the sum of the original investment, and it was calculated with algorithm that reduces to the calculation of cumulative cash flow and the moment in which it turns to positive from negative. NPV is a standard method for using the time value of money to appraise long-term projects and it is defined as the sum of the present values of the individual cash flows. IRR is a rate of return used in capital budgeting to measure and compare the profitability of investments, and is defined as the annualized effective compounded return rate or discount rate that makes the net present value of all cash flows (both positive and negative) from a particular investment equal to zero. The analysis was carried out under the assumption that only 10% of the benefits may be attributed to the ISS-ITAP. Such an estimate may be too low but it provides a base for the assessment of the benefits of this ISS. More details on the economic analysis may be found in Montoro (2008).
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Fig. 1 Evolution since 1994–2005 of the area and number of farms was advised by ISS-ITAP
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Fig. 2 Evolution since 1997–2005 of the percentage of adequately irrigated (AI), under-irrigated (UI) and over- irrigated (OI) fields for wheat and maize crop. Every value is the average of two consecutive years
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following somewhat different trends (Montoro 2008) and the results are summarized in Fig. 3 for the whole service area, and the 11 crops studied. In 1997, 44% of the fields were AI, 27% were OI, and 19% were UI. By 2001, the proportion of AI had gone up to 71% while the OI and UI fields were around 15% each (Fig. 3). After that year, the trend changed and by 2005, the OI fields had gone up to 26% while the UI were down to 11%, and the proportion of AI fields had decreased somewhat to 63% (Fig. 3). The impact of the ISS in absolute terms was significant; for instance in wheat, the AI area doubled from 500 ha in 1,997 to 1,000 ha in 2005, while in maize the AI area went from less than 500 ha in 1997 to over 1,200 ha in 2005 (Montoro 2008). Likewise, the absolute reduction in UI fields was significant, and by 2005, only 170 ha of wheat and less than 50 ha of maize were UI. In horticultural crops the effects of the ISS-ITAP were also notable; for instance the AI area in onions tripled from less than 100 ha in 1997 to 300 ha in 2005 (Montoro 2008). Since there had not been major changes in irrigation systems over the period of study (center pivots were used since the 1980s) or, until very recently, changes in irrigation pumping costs, one may assume that only changes in irrigation management (irrigation timing and amounts) were induced by the ISSITAP recommendations. Relations between yield and water supply
level slightly under 400 mm but, as the supply is reduced, the yield declines more sharply than in wheat. Again, the variation in yield (1–3 0t/ha) and in water supply (200–575 mm) is quite large. Finally, Fig. 4c depicts the yield-water supply relationship for maize. Here, maximum yields of about 16 t/ha were achieved with a water supply just under 700 mm. There was significantly less variation in actual yields relative to wheat and opium poppy, as most fields yielded between 11 and 16 t/ha. Also variation in water supply was less, with the exception of a few fields grossly over-irrigated (Fig. 4c). The variation among the three crops of Fig. 4 in management is clearly depicted in Fig. 5 which represents the cumulative frequency of the crop yield ratio (CYR). It can inferred from Fig. 5 that, in the case of wheat, 85% of the fields had yields that were less than 70% of the maximum observed in the survey. For opium poppy, 55% of the fields had yields below 70% of maximum (Fig. 5). However, for maize, only 6% of all fields had yields which were less than 70% of the maximum observed. Water productivity Water productivity measured in agronomic and economic terms, increased since the beginning of the study, but
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SDyield=1,373 SDwater=96 (***) p
