Farmers’ scheduling patterns in on-demand pressurized irrigation

Irrigation scheduling results from the irrigator's integration of meteorological, environmental and crop information. In this paper, the irrigation scheduling patterns of a group of irrigators in the Candasnos Water Users Association (WUA), located in north-eastern Spain, were analysed. Scheduling sprinkler and drip irrigation in this WUA shows additional complications due to the sharing of a collective pressurized irrigation network and to the need to file water orders two days in advance of its foreseen use. The database created by a remote surveillance and control system was mined to obtain the time evolution of hydrant operation time during the 2004–2008 irrigation seasons. Records were selected for clearly identified crops and irrigation systems, and for verified water allocations. Hydrant operation showed a relationship with meteorology (precipitation, wind speed, relative humidity and air temperature), although this relationship was often not evident when hydrants were individually analysed. Statistical analyses were run to classify irrigator's scheduling practices, leading to the establishment of ten different groups. The adopted classification criteria included the average number of weekly irrigations, the SD of the number of weekly irrigations and the modal range of the irrigation starting time. The irrigation pattern was determined by the irrigator (56%), the irrigation system (33%), and the crop (11%). Only in a fraction of the cases (22%) the time change in the scheduling pattern responded to a clear time trend; in 39% of the cases, changes in time appeared random. Further, 45% of the irrigators used the same irrigation pattern in at least half of their hydrant-years, independently of the crop. Only 14% of the irrigators applied different irrigation scheduling patterns to different crops. Our results suggest that irrigators do not find value or do not have the capacity to develop irrigation patterns more consistent and adapted to the local environment, the crops and the irrigation systems.     

Water savings in irrigated potato production by varying hill-furrow or bed-furrow configuration

Current agronomic practices for potato production in the irrigated areas of southern Alberta involve a hill/furrow configuration that was adopted from elsewhere, and designed to shed rainfall away from the hill and into the furrow. However, the principal intent of supplemental irrigation is to capture as much of the applied water into the hill, where the potato tubers and roots are located, and minimize water accumulating in the furrow. A three-year project began in 2006 to quantify the potential irrigation water savings of altered hill shapes for potato production. The three treatments (standard hill, flat-topped hill, and double-planted wide-bed) were arranged in a randomized strip plot design replicated four times. Soil water in each treatment was generally kept between 60 and 90% of available. A fourth treatment, triple-planted wide bed, was added to the project in 2008. The irrigation requirements to maintain the treatments were 487, 442, and 449 mm for the standard hill, flat-topped hill, and double-planted bed, respectively, in 2006 and 442, 408 and 411 mm for the same treatments in 2007. This translates into approximately 10% less irrigation water required for the flat-topped hill shape compared to the standard hill shape. The flat-topped hill shape required 5.0% more irrigation than the standard hill in 2008, but the double and triple-planted wide beds required 8.0 and 9.9%, respectively, less irrigation water than the standard. Although not always statistically significant, water use efficiency was greater in all years for the altered bed shapes compared to the standard hill geometry. Greater water use efficiency can be interpreted as more of the applied water infiltrated into the hill, where the potato plant could use it for transpiration and tuber development. Total yield was greater in 2006 for both the flat-topped hill (72.3 Mg ha⁻¹) and wide-bed hill (69.2 Mg ha⁻¹) compared to the standard hill (61.4 Mg ha⁻¹); however, the treatments were not significantly different. Significantly greater marketable yield was realized from the flat-topped hill treatment in 2006. This treatment also had a significantly greater number of marketable size tubers. In 2007, there were no significant differences in total yield; however, the standard and flat-topped treatments had a significantly greater number and yield of tubers in the 113-170 g size category. Significant differences in total yield were found in 2008. The triple-planted wide bed had significantly greater yield in the smaller size categories compared to the standard treatment and significantly greater total tuber numbers than the other treatments, but the increase was in the smaller size categories, less than 170 g. There were no significant differences among the treatments in yield or total number of tubers in the size categories greater than 171 g in 2008.     

Implementing irrigation: Water balances and irrigation quality in the Lerma basin (Spain)

The growing necessity to develop more productive agriculture has encouraged the expansion of new irrigated lands. However, water use in agriculture may affect the natural regimes of water systems. This study aims to analyze, for the first time, water use and its dynamics during the creation of a newly irrigated land. Water use was studied through the development of water balances and subsequent application of quality indices for irrigation in two unirrigated years (2004–2005) and three years of gradual implementation of irrigation (2006, 2007 and 2008) in the Lerma basin (752 ha, Spain). Increases in evapotranspiration, drainage and water content in the aquifer were verified during the gradual transformation into irrigated land. Water balances closed adequately, giving consistency to the results and enabling the application of quality indices for irrigation. Irrigation quality analysis showed a use of available water resources equal to 84%. However, the estimated irrigation efficiency presented lower values, mainly due to irrigation drainage (15%) and combined losses by both evaporation and wind drift of sprinkler irrigation systems (13%). The results indicate that the use of water in the Lerma basin is at the same management level of other modern irrigation systems in the Ebro basin, although there is still margin for improvement in irrigation management, such as reducing the irrigation drainage fraction and the evaporation and wind drift losses of sprinkler irrigation systems.     

Low energy consumption seasonal calendar for sectoring operation in pressurized irrigation networks

Pressurized irrigation networks and organized on-demand are usually constrained by the high amounts of energy required for their operation. In this line, sectoring, where farmers are organized in turns, is one of the most efficient measures to reduce their energy consumption. In this work, a methodology for optimal sectoring is developed. Initially it groups similar hydrants in homogeneous groups according to the distance to the pumping station and their elevation, using cluster analysis techniques and certain dimensionless coordinates. Second, an algorithm based on the EPANET engine is implemented to search for the best monthly sectoring strategy that accomplish supplying the actual irrigation demand under minimum energy consumption conditions. This methodology is applied to two Spanish irrigation districts (Fuente Palmera and El Villar). Results showed that organizing the networks in sectors, annual energy savings of 8 and 5% were achieved for Fuente Palmera and El Villar when the theoretic irrigation needs were considered. However, these savings rose up to 27 and 9%, respectively when the local practices, deficit irrigation, were taken into account. Thus, they confirm that water and energy efficiency cannot be optimized independently and need to be considered together.     

Modelling the effects of climate variability and water management on crop water productivity and water balance in the North China Plain

In the North China Plain (NCP), while irrigation using groundwater has maintained a high-level crop productivity of the wheat-maize double cropping systems, it has resulted in rapid depletion of groundwater table. For more efficient and sustainable utilization of the limited water resources, improved understanding of how crop productivity and water balance components respond to climate variations and irrigation is essential. This paper investigates such responses using a modelling approach. The farming systems model APSIM (Agricultural Production Systems Simulator) was first calibrated and validated using 3 years of experimental data. The validated model was then applied to simulate crop yield and field water balance of the wheat-maize rotation in the NCP. Simulated dryland crop yield ranged from 0 to 4.5 t ha⁻¹ for wheat and 0 to 5.0 t ha⁻¹ for maize. Increasing irrigation amount led to increased crop yield, but irrigation required to obtain maximum water productivity (WP) was much less than that required to obtain maximum crop yield. To meet crop water demand, a wide range of irrigation water supply would be needed due to the inter-annual climate variations. The range was simulated to be 140-420 mm for wheat, and 0-170 mm for maize. Such levels of irrigation applications could potentially lead to about 1.5 m year⁻¹ decline in groundwater table when other sources of groundwater recharge were not considered. To achieve maximum WP, one, two and three irrigations (i.e., 70, 150 and 200 mm season⁻¹) were recommended for wheat in wet, medium and dry seasons, respectively. For maize, one irrigation and two irrigations (i.e., 60 and 110 mm season⁻¹) were recommended in medium and dry seasons, while no irrigation was needed in wet season.     

Impact of irrigation with treated low quality water on the heavy metal contents of a soil-crop system in Serbia

Water availability for irrigation is a limiting factor for agriculture in Mediterranean countries. An upcoming strategy for increasing water supply is to use treated wastewater for irrigation. A principal drawback of irrigating with wastewater is the potential heavy metal accumulation in soil and foodstuff.Accumulation of heavy metals in soil and potato plants (Solanum tuberosum L.) irrigated with treated low quality surface water was studied in a three years experiment. The low quality surface water used for irrigation experiments contained a significant proportion of urban sewage and was spiked with selected heavy metals (Cd, Cr, Cu, Pb) and arsenic before treatment for years 2 and 3.The experiments were carried out during the growing seasons of 2006, 2007 and 2008 on a humogley soil of a commercial vegetable farm, 10 km north of Belgrade, Serbia. The growing seasons started in April/May and finished in August. Irrigation water was treated using (1) a conventional sand filter treatment, and (2) a sand filter combined with a specific filter for heavy metal removal treatment.Irrigation water composition was highly variable and cases both of enrichment and depletion of the measured inorganic trace elements were observed in the treated water, compared to the low quality feed water.In spite of this variability of the irrigation water composition, the soil contents in inorganic elements at the end of the three irrigation years are similar to the initial state. After the third harvest, no impact of the irrigation water on potato quality could be detected except for total sugar and sugar in total solids. Statistical tests (ANOVA) were performed to assess similarities between the different set of samples.The principal conclusion of this investigation is that, when appropriately treated, low quality feed waters with high heavy metal contents can be used for irrigation over several years without significant degradation of soil and produces. Even though, long-term cumulative effects in other pedologic and hydroclimatic settings, irrigation and cropping conditions cannot be excluded.     

Determination of comprehensive quality index for tomato and its response to different irrigation treatments

In order to investigate better irrigation scheduling with the compromise between yield and quality of greenhouse-grown tomato under limit water supply, two experiments of different irrigation treatments were conducted in the arid region of northwest China during spring to summer in 2008 (2008 season) and winter in 2008 to summer in 2009 (2008-2009 season). After measuring single quality attributes, the analysis hierarchy process (AHP) and technique for order preference by similarity to an ideal solution (TOPSIS) were used to determine the weight of single quality attributes and comprehensive quality index, respectively. The results show that the rank of comprehensive quality index had good fitness to that of single quality attributes, indicating that the comprehensive quality index was reliable. Compared to full irrigation, applying 1/3 or 2/3 of full irrigation amount at the seedling stage had slight improvement of comprehensive quality and limit water saving. Applying 1/3 or 2/3 of full irrigation amount at the fruit maturation and harvesting stage decreased the yield by 23.0-40.9%, but had the best comprehensive quality. However, applying 1/3 of full irrigation amount at the flowering and fruit development stage significantly reduced crop water consumption and had obvious improvement of comprehensive quality, but did not decrease the yield significantly and water use efficiency in the 2008 season. And applying 2/3 of full irrigation amount at the flowering and fruit development stage significantly decreased crop water consumption and slightly improved the comprehensive quality, but did not decrease the yield significantly in the 2008-2009 season. Considering the water saving amount, yield and comprehensive quality, applying 1/3 or 2/3 of full irrigation amount at the flowering and fruit development stage and no water stress in other growth stages appears to be a better irrigation scheduling with the compromise between yield and quality of greenhouse-grown tomato, which can be recommended for the spring to summer and winter to summer seasons in the arid region of northwest China.     

Withholding of drip irrigation between transplanting and flowering increases the yield of field-grown tomato under plastic mulch

Experiments were conducted in summer of 2003 and 2004 to study the effect of withholding irrigation on tomato growth and yield in a drip irrigated, plasticulture system. Irrigation treatments were initiated at tomato planting (S0), after transplant establishment (S1), at first flower (S2), at first fruit (S3), or at fruit ripening (S4). An additional treatment received only enough water to apply fertigation (FT). Withholding drip irrigation for a short period (S2–S3) increased tomato marketable yield by 8–15%, fruit number by 12–14% while reducing amount of irrigation water by 20% compared to the S0 treatment. Withholding drip irrigation also increased irrigation water use efficiency (IWUE). Similar trends were observed in 2003 and 2004 despite large differences in rainfall, heat units, and tomato yield between years. This suggests that if soil moisture is adequate at transplanting, subsequent withholding of irrigation for 1–2 weeks after tomato transplanting may increase yield while reducing the amount of irrigation water.     

Rice growth, yield and water productivity responses to irrigation scheduling prior to the delayed application of continuous flooding in south-east Australia

The majority of rice grown in south-east Australia is continuously flooded for much of its growing season, but reduced irrigation water availability brought about by a combination of drought and environmental flow legislation has presented a need to maintain (or even increase) rice production with less irrigation water. Delaying the application of continuous flooding until prior to panicle initiation can increase input water productivity by reducing non-beneficial evaporation losses from free water and the soil. A field experiment was conducted over two growing seasons, 2008/9 and 2009/10, comparing a conventional dry seeded treatment (the control - continuous flooding from the 3 leaf stage) with delayed continuous flooding (10-20 days prior to panicle initiation) with several irrigation scheduling treatments prior to flooding commencement. In the first year, the delayed water treatments were irrigated at intervals of 40, 80 and 160 mm of cumulative reference evapotranspiration (ETo) prior to delayed continuous flooding, thereby imposing differing degrees of crop water stress. In year 2, the 80 and 160 mm treatments were modified by use of a crop factor (Kc) when the plants were small and the 40 mm treatment was replaced with a continuously flooded treatment throughout the crop duration.Decreases in net water input (irrigation + rain − surface drainage) and increases in input water productivity were achieved by reducing the flush irrigation frequency during the pre-flood period. Savings of 150 and 230 mm (10 and 15%) were achieved in Year 1 from the 80 and 160 mm cumulative ETo irrigation frequency treatments, respectively, in comparison to the control. In the second year, net water input savings of 230 and 330 mm (15 and 22%) were achieved with the 80/Kc and 160/Kc mm treatments, respectively. Input water productivity of the 160 mm treatment was 0.06 kg/m³ (8%) higher than the control in Year 1, while in Year 2 a 0.15 kg/m³ (17%) increase in input water productivity above the control was achieved by the 160/Kc mm treatment. Delaying the application of continuous flooding in the second year greatly extended the period of crop growth suggesting the need for earlier sowing (by 7-10 days) to ensure pollen microspore still occurs at the best time to minimise yield loss due to cold damage. Nitrogen fertiliser management is an important issue when delaying continuous flooding, and nitrogen losses appeared to increase with the frequency of irrigation prior to continuous flooding. This was likely due to increased denitrification from alternate wetting and drying of the soil. Further research is required to determine the most appropriate nitrogen management strategies, and to also better define the optimal pre-flood irrigation frequency.     

The effects of irrigation methods with effluent and irrigation scheduling on water use efficiency and corn yields in an arid region

A great challenge for the agricultural sector is to produce more food from less water, particularly in arid and semi-arid regions which suffer from water scarcity. A study was conducted to evaluate the effect of three irrigation methods, using effluent versus fresh water, on water savings, yields and irrigation water use efficiency (IWUE). The irrigation scheduling was based on soil moisture and rooting depth monitoring. The experimental design was a split plot with three main treatments, namely subsurface drip (SSD), surface drip (SD) and furrow irrigation (FI) and two sub-treatments effluent and fresh water, which were applied with three replications. The experiment was conducted at the Marvdasht city (Southern Iran) wastewater treatment plant during 2005 and 2006. The experimental results indicated that the average water applied in the irrigation treatments with monitoring was much less than that using the conventional irrigation method (using furrows but based on a constant irrigation interval, without moisture monitoring). The maximum water saving was obtained using SSD with 5907 m³ ha⁻¹ water applied, and the minimum water saving was obtained using FI with 6822 m³ ha⁻¹. The predicted irrigation water requirements using the Penman-Monteith equation (considering 85% irrigation efficiency for the FI method) was 10,743 m³ ha⁻¹. The pressure irrigation systems (SSD and SD) led to a greater yield compared to the surface method (FI). The highest yield (12.11 × 10³ kg ha⁻¹) was obtained with SSD and the lowest was obtained with the FI method (9.75 × 10³ kg ha⁻¹). The irrigation methods indicated a highly significant difference in irrigation water use efficiency. The maximum IWUE was obtained with the SSD (2.12 kg m⁻³) and the minimum was obtained with the FI method (1.43 kg m⁻³). Irrigation with effluent led to a greater IWUE compared to fresh water, but the difference was not statistically significant.     

Irrigation scheduling strategies for cotton to cope with water scarcity in the Fergana Valley, Central Asia

The Central Asian countries face high water scarcity due to aridity and desertification but excess water is often applied to the main irrigated crops. This over-irrigation contributes to aggravate water scarcity problems. Improved water saving irrigation is therefore required, mainly through appropriate irrigation scheduling. To provide for it, after being previously calibrated and validated for cotton in the Fergana region, the irrigation scheduling simulation model ISAREG was explored to simulate improved irrigation scheduling alternatives. Results show that using the present irrigation scheduling a large part of the applied water, averaging 20%, percolates out of the root zone. Several irrigation strategies were analyzed, including full irrigation and various levels of deficit irrigation. The analysis focused a three-year period when experiments for calibration and validation of the model were carried out, and a longer period of 33 years that provided for an analysis considering the probabilities of the demand for irrigation water. The first concerned a wet period while the second includes a variety of climatic demand conditions that provided for analyzing alternative schedules for average, high and very high climatic demand. Results have shown the importance of the groundwater contribution, mainly when deficit irrigation is applied. Analyzing several deficit irrigation strategies through the respective potential water saving, relative yield losses, water productivity and economic water productivity, it could be concluded that relative mild deficits may be adopted. Contrarily, the adoption of high water deficit that produce high water savings would lead to yield losses that may be economically not acceptable.     

Evaluating drip irrigation in commercial tea production in Tanzania

This paper evaluates the performance of the first drip irrigation scheme in commercial tea production in Tanzania with a view to making recommendations for improved management and providing data for investment decisions. Uniformity, efficiency and adequacy of irrigation were calculated and the scheduling of irrigation water was reviewed. Operators were interviewed to highlight the main benefits and problems of the system. Investment and recurrent costs of drip and overhead sprinkler systems were quantified and compared. Root development was assessed qualitatively using excavation pits. Irrigation uniformity DU and efficiency ranged between 88 and 95% in the 10 out of 14 irrigation blocks where endline pressures were at least 0.5 bars, and between 77 and 89% in the four blocks were endline pressure was less than 0.5 bars. Scheduling drip irrigation using tensiometers offered potential water savings of 26% in comparison to a water balance schedule, but these are not currently realised. Gross marginal income was very sensitive to tea price and yield. Economically optimal fertilizer rates vary in dependence of tea price and yield and appear to be lower than the current level of 300 kg N ha⁻¹. The higher costs under drip, compared to overhead sprinklers, were mainly for purchase and installation and fertilizer. The costs of labour for applying water and fertilizer were reduced by nearly 50%. At average 2002 tea prices of 1.31 US$ kg⁻¹, drip irrigation would improve the grower’s gross margin if an additional yield of at least 411 kg ha⁻¹ was achieved. The main threats to drip system performance are discussed. Future research efforts should aim at establishing the yield response of tea to water and fertilizer under drip irrigation.     

The effect of an intelligent surface drip irrigation method on sorghum biomass, energy and water savings

Over the last few decades, precipitation has decreased as a result of climate change. This change increases crop water requirements, while irrigation water is wasted because of improper irrigation scheduling. Soil moisture sensors could be used to improve irrigation scheduling and save both water and energy. The objective was to study the energy and water savings, and the gross margin achieved, when using an intelligent surface drip irrigation method on sorghum bicolor (L.) Moench. In the years 2008 and 2009, a study was conducted at the farm of the University of Thessaly, Central Greece. A Class A evaporation pan and an automated frequency domain reflectometry soil moisture sensor were used for irrigation scheduling. Two treatments in four replications were organized in a randomized complete block design: (1) pan surface drip irrigation (PSDI100) and amount of water equal to 100 % of the daily evapotranspiration (ETd), as determined by a Class A evaporation pan, and (2) automated surface drip irrigation (ASDI100) and amount of water equal to 100 % of the ETd, as determined by an automated soil moisture sensor. The mean dry biomass production and the gross margin were greater in the PSDI100 treatment. The fully automated treatment remained profitable despite the high first costs. The mean water saving was 12.5 %, while the mean energy saving was 12.4 %, and the irrigation water-use efficiency was higher in the ASDI100 treatment.     

On-farm labour allocation and irrigation water use: case studies among smallholder systems in arid regions

On-farm measurements and observations of water flow, water costs and irrigation labour inputs at the individual parcel level were made in case studies of smallholder irrigation systems in sub-Saharan Africa and south-eastern Arabia. The systems, in which the water source supplied either single or multiple users, were analysed to address the fundamental issues of labour allocation for on-farm water management as this has important consequences for the success of such systems. Results show that the costs associated with accessing water influenced labour input, because when they were low the farmers tended to increase the irrigation rate and reduce the amount of time they spent distributing the water within their parcels. Conversely when water costs were high, lower flow rates and more time spent in water distribution were observed, and this resulted in more uniform irrigation and higher irrigation efficiency. Also, opportunities and demands for farmers to use their labour for activities other than irrigation can lead them to modify operational or physical aspects of the system so that they can reduce the time they spend distributing water within the parcels, particularly when the water is relatively cheap. Awareness and better understanding of how farmers may allocate their labour for water management will lead to more effective planning, design and management of smallholder irrigation systems.     

农业节水措施对地下水涵养的作用及其敏感性分析

以北京市大兴区为研究区,利用经校验的水平衡模型,通过调整灌溉满足率和灌溉水利用系数,探讨了不同农业节水措施对增加地下水补给量和减少地下水开采量的作用及其敏感性。结果表明,不同水文年型下,降低灌溉满足率及提高灌溉水利用系数都能减少地下水开采量,且降低灌溉满足率对减少地下净开采量的作用更为显著,有利于区域地下水涵养。在参数取值范围内,地下水净开采量对灌溉满足率的敏感性较大,而地下水补给量对灌溉水利用系数的敏感性较高。与提高灌溉水利用系数相比,对资源性缺水区域,采用先进节水技术,适度降低区域灌溉满足率,对促进水资源持续有效利用及加大地下水涵养具有更显著的效果。     

Are landscapes over-irrigated in Southwest Florida? A spatial�Ctemporal analysis of observed data

Monthly water billing records for eleven cities in Hillsborough County Florida were available from 2001 through 2007. Irrigation was estimated from total water use based on two different methods to estimate basic indoor water use and assumed impervious areas. Estimated irrigation use was compared with a calculated irrigation requirement by a water balance to test if homeowners were over-irrigating. Results showed that on average, the mean estimated irrigation was lower than the calculated irrigation requirements in most of the cities and years given the uncertainties in this analysis. The calculated irrigation ranged from 612 to 744 mm year⁻¹, whereas the average estimated irrigation ranged from 264 to 684 mm year⁻¹. However, there were some homeowners that greatly exceeded the calculated irrigation requirement. The estimated irrigation increased temporarily in areas under urban development, which was evidenced by built landscape expansion. Good correlation was found between the annual estimated irrigation and the annual calculated irrigation requirements, when the per capita method was used, but not between the annual estimated irrigation and the annual rainfall. Future conservation programs can use this methodology to identify users where substantial opportunity for water savings exists.     

Farmers’ incentives to save water with new irrigation systems and water taxation—A case study of Serbian potato production

Drip irrigation systems and irrigation strategies like deficit irrigation (DI) and partial root drying (PRD) are potential water saving irrigation systems and strategies. This paper analyses the Serbian farmer's economic incentive to use these water saving systems and strategies instead of the present sprinkler irrigation. The analysis is a partial budgeting analysis, based on irrigation application efficiency from the literature, standard figures for power requirements, pumping efficiency and friction losses for various sources of water and pressure requirements, yields and water use from recent Serbian field experiments, as well as prices and cost structures for potatoes collected in the Belgrade region. The analysis shows that changing the present system and strategy can save a significant amount of water (almost 50%). At the same time, however, irrigation costs are also significantly increased (more than doubled), and the total production costs are increased by 10% (deficit drip irrigation) and 23% (PRD). Increased taxes on water, investment subsidies, increased energy prices, and an increased yield or yield quality may provide incentives for farmers to change to new systems and strategies. The analysis indicates that a 0.80 to 1.97 € m⁻³ water tax is needed to make deficit drip irrigation and PRD profitable. The socioeconomic cost of providing water for irrigation and the alternative value of saved water are probably not that high. Thus, water taxation may not be a socioeconomic efficient means to improve the irrigation water productivity of Serbian potato production. Drip irrigation and PRD may, however, also increase the yield quality, and a 10-23% quality premium (price increase) is needed to make deficit drip irrigation and PRD profitable.     

Strategy for Efficient Energy Management to solve energy problems in modernized irrigation: analysis of the Spanish case

While the modernization of irrigation techniques in recent years has improved water use efficiency, the substitution of open channels by pressurized pipes led to a substantial increase in the energy used in irrigated agriculture. Given the concern for energy savings and sustainability, official administrations have promoted several initiatives to improve energy efficiency in irrigated agriculture, and researchers have developed different tools for the same. Although energy audits have been conducted in irrigation networks managed by Water Users’ Associations, the implementation of energy conservation measures proposed in these audits has not been always successful. This paper, which reviews the energy aspects of irrigation systems modernized in recent decades in Spain and in other countries, considers the characteristics and special features of Water Users’ Associations and proposes an energy management system (EMS) for the same. The stages of the EMS are described, beginning with the definition of energy policy and the establishment, implementation and verification of energy plans, the essential conditions to guarantee the success of the EMS are described, in which energy audits are just a part of a process of continual improvement of energy efficiency. A Strategy for Efficient Energy Management has been implemented in a Water Users’ Association in southeast Spain. The improvement measures proposed in the first energy plan were implemented, and an increase from 60 to 65 % in average energy efficiency was achieved.     

Soil water storage and drainage under cotton-based cropping systems in a furrow-irrigated Vertisol

Comparative studies of drainage and leaching under tillage systems in irrigated tropical and sub-tropical Vertisols are sparse. The objective of this study was to quantify drainage under cotton-based cropping systems sown on permanent beds in an irrigated Vertisol. Drainage and soil water storage were measured with the chloride mass balance method and neutron moisture meter, respectively, during the 2002-03, 2004-05, 2006-07 and 2008-09 cotton seasons in an on-going experiment in a Vertisol in NW NSW. The experimental treatments were: cotton monoculture sown either after conventional tillage or on permanent beds, and a cotton-wheat rotation on permanent beds where the wheat stubble was retained as in situ mulch into which the following cotton crop was sown. Subject to in-crop rainfall, irrigation frequency varied between 7 and 14 days for cotton and 2-3 months for wheat. In 2005, a split-plot design was superimposed on the existing experiment such that the main-plot treatments were irrigation frequency (“frequent”, 7-14-day irrigation interval; “infrequent”, 14-21-day irrigation interval), and sub-plot treatments were the historical tillage system/crop rotation combinations. In comparison with cotton monoculture sown either after conventional tillage or on permanent beds, soil water storage, particularly during the early part of growing season when rainfall provided the major proportion of crop water requirements, and drainage were greatest when a cotton-wheat rotation was sown on permanent beds. Seasonal drainage out of the 1.2 m depth, averaged among all seasons, was of the order of 25 mm, 33 mm and 70 mm with cotton monoculture sown either after conventional tillage or on permanent beds, and a cotton-wheat rotation on permanent beds, respectively. Soil water storage and drainage were also greater when irrigation frequency was greater. Seasonal drainage out of the 1.2 m depth, averaged between the 2006-07 and 2008-09 seasons, was 54 mm with “frequent irrigation”, and 28 mm with “infrequent” irrigation. Infiltration was less in management systems which resulted in wetter soil; viz. frequent irrigation or a cotton-wheat rotation on permanent beds with in situ stubble retention. Drainage water losses in a furrow-irrigated Vertisol may be reduced and soil water storage increased (i.e. water conservation improved) by sowing a cotton-wheat rotation with in situ stubble retention under less frequent irrigation.     

Water balance of centre pivot irrigated pasture in northern Victoria, Australia

The irrigated dairy industry in Australia depends on pasture as a low-cost source of fodder for milk production. The industry is under increasing pressure to use limited water resources more efficiently. Pasture is commonly irrigated using border-check but there is growing interest amongst dairy irrigators to explore the potential for overhead sprinklers to save water and/or increase productivity. This paper reports on a detailed water balance study that evaluated the effectiveness of centre pivot irrigation for pasture production. The study was conducted between 2004/2005 and 2005/2006 on a commercial dairy farm in the Shepparton Irrigation Region in northern Victoria. More than 90% of supplied water (irrigation plus rainfall) was utilized for pasture growth. Deep drainage of respectively 90 and 93 mm was recorded for the two observation seasons. During the 2004/2005 season, deep drainage resulted from large unseasonal summer rainfall events. Over the 2005/2006 season, deep drainage resulted from excess irrigation. The cumulative pasture dry matter (DM) production was 15.5 and 11.3 tonnes DM ha⁻¹ for the two irrigation seasons, with an agronomic water use efficiency (WUE) of 16 and 12 kg DM ha⁻¹ mm⁻¹ respectively. The farmer's intuitive irrigation scheduling was found to be very effective; the pattern of irrigation application closely matched measured pasture water use, prevented water stress and resulted in high irrigation efficiency.