Measuring the willingness of farmers to pay for groundwater in the highland areas of Jordan

The main objective of this paper is to estimate the willingness of farmers to pay for groundwater resources under different conditions of water supply regimes. Information available on water supplies, areas under irrigation and market conditions were the basis of the calculations. In order to identify solutions that maximize the total net income subject to resource restraints, parametric linear programming models were used to derive farmers’ willingness to pay for irrigation water. Results showed that there is potential to decrease water consumption and to reallocate it in an optimal way. Optimal reallocation increased the net agricultural income in the study area. The water demand for agriculture reacts to increasing water prices in a quite elastic manner over a long interval, whereas it reacts inelastic in the case of a decrease of the overall water supply by 15%. Farmers are willing to pay two and a half times the prevailing price of groundwater. The results show that the water values in the region are underestimated and the decision makers can impose a price level for groundwater from US$ 0.14 to 0.35/m³ without having any impact on the cropping pattern or the planted area.     

Analysis of water application costs with a centre pivot system for irrigation of crops in Spain

The aim of this study was to present a methodology to analyse the main factors that influence annual water application costs in centre pivot irrigation systems and to determine the most cost-effective centre pivot design, given the variables of machine length, lateral pipe diameter, sprinkler type (LEPA and fixed and rotating spray plate sprinklers (FSPS and RSPS)), system capacity, application efficiency, and water and energy costs for the irrigation of crops such as maize under conditions in Spain. Annual water application costs were calculated as the sum of the investment (Ca), energy (Ce), water (Cw), and equipment maintenance costs (Cm). Parameters used to assess the influences on pivot design were system capacity S _c = 1.25 L s^?1 ha^?1; application efficiency Ea = 80% for FSPS, Ea = 85% for RSPS, and Ea = 90% for LEPA; water price P _w = 0.06 € m^?3 (0.081 US dollars); energy price En_e = 0.10 € kWh^?1 (0.135 US dollars); net annual crop irrigation water requirement N _n = 7,000 m³ ha^?1 year^?1; and net daily peak crop water requirement N _nmax = 7.63 mm d^?1 for maize. Results indicate that for plots smaller than 30 ha, the recommended pipeline diameter is 127.0 mm (5 in); for 30–40 ha, 168.3 mm (6 5/8 in); for 40–75 ha, 219.1 mm (8 5/8 in); and for 75–100 ha, 254.0 mm (10 in). A multidiameter pipe solution only slightly reduced water application costs in most cases studied. It was also determined that water costs and irrigation efficiency have a major influence on the total annual cost of water application; however, system capacity and energy price did not strongly affect total cost. For this reason, water application uniformity is very important and can be accomplished using a proper nozzle package and regular maintenance. The paper helps farmers determine the most cost-effective centre pivot design and management.     

The contribution of shallow groundwater by safflower (Carthamus tinctorius L.) under high water table conditions, with and without supplementary irrigation

Lysimetric experiments were conducted to determine the contribution made by groundwater to the overall water requirements of safflower (Carthamus tinctorius L.). The plants were grown in 24 columns, each having a diameter of 0.40 m and packed with silty clay soil. The four replicate randomized complete block factorial experiments were carried out using different treatment combinations. Six treatments were applied during each experiment by maintaining groundwater, with an EC of 1 dS m^?1, at three different water table levels (0.6, 0.8 and 1.10 m) with and without supplementary irrigation. The uptake of groundwater as a part of crop evapotranspiration was measured by taking daily readings of the water levels found in Mariotte tubes. The supplementary irrigation requirement for each treatment was applied by adding water (EC of 1 dS m^?1). The average percentage contribution from groundwater for the treatments (with and without supplementary irrigation under water table levels of 0.6, 0.8 and 1.10 m) were found to be 65, 59, 38% and 72, 70, 47% of the average annual safflower water requirement (6,466 m³ ha^?1). The increase in groundwater depths under supplementary irrigation treatments from 0.6 to 0.80 and 1.10 m caused seed and oil yield reductions of (7, 23.10%) and (48.23, 65.40%), respectively.     

Wheat yield response to line source sprinkler irrigation and soil management practices on medium-textured shallow soils of arid environment

A field experiment was conducted for 3 years to evaluate the effect of deficit irrigation under different soil management practices on biomass production, grain yield, yield components and water productivity of spring wheat (Triticum estivum L.). Soil management practices consisted of tillage (conventional and deep tillage) and Farmyard manure (0 and 10 t ha^?1 FYM). Line source sprinkler laterals were used to generate one full- (ETm) and four deficit irrigation treatments that were 88, 75, 62 and 46 % of ETm, and designated as ETd₁, ETd₂, ETd₃, and ETd₄. Deep tillage significantly enhanced grain yield (14–18 %) and water productivity (1.27–1.34 kg m^?3) over conventional tillage. Similarly, application of FYM at 10 t ha^?1 significantly improved grain yield (10–13 %) and water productivity (1.25–1.31 kg m^?3) in comparison with no FYM. Grain yield response to irrigation varied significantly (5,281–2,704 kg ha^?1) due to differences in soil water contents. Water productivity varied from 1.05 to 1.34 kg m^?3, among the treatments in 3 years. The interactive effect of irrigation × tillage practices and irrigation × FYM on grain yield was significant. Yield performance proved that deficit irrigation (ETd₂) subjected to 75 % soil water deficit had the smallest yield decline with significant water saving would be the most appropriate irrigation level for wheat production in arid regions.     

Critical points: interactions between on-farm irrigation systems and water distribution network

In this work, a new model useful to analyze interactions between the on-farm irrigation system supplied by critical points and the water supply network management was developed. The model evaluates the impacts of changes in the pressure head and demand simultaneity (number of open hydrants at a given time) on the irrigation system and evaluates emitter discharge and uniformity. It also estimates the potential reductions in crop yield due to decreased emission uniformity. The methodology is applied in the Bembézar Irrigation District (Southern Spain). Results show that the additional cost required for providing maximum pressure to the critical field does not offset the increase in crop yield. Hence, an increment from 91.7 to 92.1 % in yield in the critical field would represent increases in energy consumption from 0.15 to 0.17 kWh m^?3 of water. Also, the unit energy cost could be reduced by up to 0.11 kWh m^?3 without implying significant reductions in crop yield. The importance of a good selection of emitters in the critical fields (fields that are supplied by the critical hydrants) was also evaluated.     

Evaluation of surface irrigation as a function of water infiltration in cultivated soils in the Nile Delta

As sources of irrigation water are decreasing, efficient use of surface irrigation is essential. The purpose of this study is to determine if partially-wetted furrow irrigation has more efficient water storage and infiltration than traditional border irrigation in an alluvial clay soil under cultivated grape production. The two irrigation components considered were wet (WT) and dry (DT) treatments, at which water was applied when available soil water reached 65 % and 50 %, and the traditional border irrigation control. Empirical power form equations were obtained for measured advance and recession times along the furrow length during the irrigation stages of advance, storage, depletion and recession. Coefficient of variation (CV) was 5.2 and 9.5 % for WT and DT under furrow irrigation system comparing with 7.8 % in border, respectively. Water was deeply percolated as 11.9 and 19.2 % for wet and dry furrow treatments respectively, compared with 12.8 % for control, with no deficit in the irrigated area. Partially-wetted furrow irrigation had greater water-efficiency and grape yield than dry furrow and traditional border irrigation, where application efficiency achieved as 88.1 % for wet furrow irrigation that achieved high grape fruit yield (30.71 Mg /ha). The infiltration (cumulative depth, Z and rate, I) was functioned to opportunity time (t ₀ ) in minute for WT and DT treatments as: Z _WT ?=?0.528?t ₀ ^0.6, Z _DT ?=?1.2?t ₀ ^0.501, I _WT ?=?19?t ₀ ^?0.4, I _DT ?=?36?t ₀ ^?0.498. Empirical power form equations were obtained for measured advance and recession times along the furrow length during the irrigation stages of advance, storage, depletion and recession. The irrigation parameters and coefficients, and soil water distribution have been also evaluated.     

Combining hydrological modeling and GIS approaches to determine the spatial distribution of groundwater recharge in an arid irrigation scheme

Accurate quantification of the rate of groundwater (GW) recharge, a pre-requisite for the sustainable management of GW resources, needs to capture complex processes, such as the upward flow of water under shallow GW conditions, which are often disregarded when estimating recharge at a larger scale. This paper provides (1) a method to determine GW recharge at the field level, (2) a consequent procedure for up-scaling these findings from field to irrigation scheme level and (3) an assessment of the impacts of improved irrigation efficiency on the rate of GW recharge. The study is based on field data from the 2007 growing season in a Water Users Association (WUA Shomakhulum) in Khorezm district of Uzbekistan, Central Asia, an arid region that is characterized by a predominance of cotton, wheat and rice under irrigation. Previous qualitative studies in the region reported irrigation water supplies far above the crop water requirements, which cause GW recharge. A field water balance model was adapted to the local irrigation scheme; recharge was considered to be a fraction of the irrigation water losses, determined as the difference between net and gross irrigation requirements. Capillary rise contribution from shallow GW levels was determined with the HYDRUS-1D model. Six hydrological response units (HRUs) were created based on GW levels and soil texture using GIS and remote sensing techniques. Recharge calculated at the field level was up-scaled first to these HRUs and then to the whole WUA. To quantify the impact of improved irrigation efficiency on recharge rates, four improved irrigation efficiency scenarios were developed. The area under cotton had the second highest recharge (895 mm) in the peak irrigation period, after rice with 2,514 mm. But with a low area share of rice in the WUA of <1 %, rice impacted the total recharge only marginally. Due to the higher recharge rates of cotton, which is grown on about 40 % of the cropped area, HRUs with a higher share of cotton showed higher recharge (9.6 mm day^?1 during August) than those with a lower share of cotton (4.4 mm day^?1). The high recharge rates in the cotton fields were caused by its water requirements and the special treatment given to this crop by water management planners due to its strategic importance in the country. The scenario simulations showed that seasonal recharge under improved irrigation efficiency could potentially be reduced from 4 mm day^?1 (business-as-usual scenario) to 1.4 mm day^?1 (scenario with maximum achievable efficiency). The combination of field-level modeling/monitoring and GIS approaches improved recharge estimates because spatial variability was accounted for, which can assist water managers to assess the impact of improved irrigation efficiencies on groundwater recharge. This impact assessment enables managers to identify options for a recharge policy, which is an important component of integrated management of surface and groundwater resources.     

Mapping the total volumetric irrigation water requirements in England and Wales

The net volumetric (m³) irrigation water requirements for the main crop categories currently irrigated in England and Wales have been calculated and mapped within a geographic information system (GIS). The procedure developed by Knox et al. (1996, Agric. Water Manage., 31: 1–15) for maincrop potatoes (Solanum tuberosum) was extended to cater for the other crops currently irrigated. The annual irrigation needs (mm) for the eight major irrigated crop categories, grown on three contrasting soil types at 11 representative weather stations, were determined using a daily water balance irrigation scheduling model. The results were correlated with existing national datasets of climate, current land use, soils and irrigation practice, to generate volumetric (m³) irrigation water requirement maps at 2 km resolution.The total net volumetric irrigation water requirements for a UK ‘design’ dry year (defined as the requirement with a 20% probability of exceedance) are estimated to be 140 × 10⁶ m³ for the eight main crop categories currently irrigated and the 1994 cropping pattern. Previous theoretical dry year demand estimates, using scheduling models and large agroclimatic areas, were 109 × 10⁶ m³ and 222 × 10⁶ m³. The irrigation demand for other crops grown in the open would typically add another 4%.The procedure has been validated nationally, by comparing the calculated dry year demand for 1990 against government irrigation survey returns for 1990, for each crop category, and regionally against National Rivers Authority (NRA) abstraction records for 1990, for each NRA Region. The estimates obtained agree well with the reported distribution between crops and between regions.The most recent actual ‘dry’ year for which comparative data are available is 1990. It is estimated that the dry year requirements for the 1990 land use would have been 148 × 10⁶ m³. Although farmer demand, actual abstractions and crop requirements are not necessarily the same, irrigation survey returns to the Government indicated that 134 × 10⁶ m³ were actually applied, and the NRA estimated from meter returns that 138 × 10⁶ m³ were abstracted. It is noted, however, that some abstraction restrictions were in force, the scope of the data is slightly different and all figures contain inaccuracies. Potential applications for improving irrigation demand management and water conservation at regional and catchment levels are discussed with reference to two contrasting regions.     

Effect of amount and timing of subsurface drip irrigation on corn yield

A field study was conducted at North Platte, Nebraska in 2007–2009, imposing eight irrigation treatments, ranging from dryland to fully irrigated. Four of the eight treatments allowed for various degrees of water stress only after tasseling and silking. In 2007, corn yield ranged from 8.9 Mg ha^?1 with a season total of 41 mm of irrigation water to 11.5 Mg ha^?1 for the fully irrigated treatment (264 mm of irrigation water). The treatment with the greatest reduction in irrigation water after tasseling and silking (158 mm) had a mean yield of 10.9 Mg ha^?1, only 0.6 Mg ha^?1 less than the fully irrigated treatment. In 2009, yields ranged from 12.6 to 13.5 Mg ha^?1. There were no significant yield differences between the irrigation treatments for several possible reasons: more in-season precipitation and cooler weather required less irrigation water; much of the irrigation water was applied after the most water-stress sensitive stages of tasseling and silking; and lower atmospheric demand allowed for soil water contents well below 50 % management allowed depletion (MAD) not to cause any yield losses.     

Water saving and economic impacts of land leveling: the case study of cotton production in Tajikistan

Water conservation is essential to prevent salinity and land degradation in Central Asia. Therefore, field-testing and evaluation of water conservation methods, i.e. laser land leveling in new farming systems of Central Asia is important task. This in mind the International Water Management Institute (IWMI) and its regional partner on IWRM FV (IWRM FV project – Integrated Water Resources Management in Ferghana Valley project is funded by Swiss Development Cooperation (SDC) and conducted jointly with IWMI and Scientific Information Center of Interstate Coordination Water Commission (SIC ICWC) in the Ferghana Valley of Central Asia) project SIC ICWC have conducted 3 year study of impacts of the Laser leveled land leveling on water use, productivity and crop yields in northern Tajikistan. The major research question was laser land leveling an effective water saving tool in the new context of land use and ownership on smaller private plots. Can farmers afford the costs of laser land leveling and how economically viable is it? These research questions were studied in 5 ha laser leveled and neighboring non-leveled (control) fields for 2004–2006. The results showed that laser land leveling can reduce the water application rate in 2004 by 593 M³/ha, in 2005 by 1509 M³/ha and in 2006 by 333 M³/ha in comparison with the unleveled field, located in the similar agro-ecological conditions. The deep percolation was 8% lower and run off 24% less than in non-leveled field. The average annual net income from the laser field was 22% higher than that from the control field. The gross margin from the laser-leveled field were 16. 88 and 171% higher compared to that from the control field for 2004, 2005 and 2006, and on average was 92% higher. In spite of these positive results, there are hindrances on wide application of laser land leveling in Tajikistan. These are absence of initial capital of farmers and scattered land location.     

Net irrigation requirements for Florida turfgrasses

A long-term (30 year) historical analysis of turfgrass monthly net irrigation requirements for southeast USA is analyzed and discussed in this paper. The process involved gathering weather data for ten locations in Florida plus one in Alabama, from 1980 through 2009, and data quality. Available weather data included maximum and minimum temperature, maximum and minimum relative humidity, wind speed, and rainfall. Solar radiation was estimated using the Hargreaves–Samani equation, and coefficients were calibrated for every location. Reference evapotranspiration (ET_os) was calculated using the ASCE-EWRI standardized reference evapotranspiration equation. Net irrigation was estimated using a daily soil–water balance. Variability in soil types and root depth was taken into account during the simulations, and three sets of monthly K _c values from the literature were applied from north through south Florida. Results showed that the calibrated Hargreaves–Samani adjustment coefficients varied from 0.14 in Tallahassee to 0.24 in Key West, with an inland average value of 0.15, and a coastal average value of 0.18. The calculated ET_os ranged from 1,296 mm year^?1 in Tallahassee to 1,658 mm year^?1 in Miami. The estimated net irrigation ranged from 423 mm year^?1 in Mobile, AL, to 1,063 mm year^?1 in Key West, FL. The number of irrigation events per year varied from 25 in Mobile to 161 in Key West. May and December were the months with the highest and lowest net irrigation requirements, respectively.     

Increasing water productivity of irrigated crops under limited water supply at field scale

Borkhar district is located in an arid to semi-arid region in Iran and regularly faces widespread drought. Given current water scarcity, the limited available water should be used as efficient and productive as possible. To explore on-farm strategies which result in higher economic gains and water productivity (WP), a physically based agrohydrological model, Soil Water Atmosphere Plant (SWAP), was calibrated and validated using intensive measured data at eight selected farmer fields (wheat, fodder maize, sunflower and sugar beet) in the Borkhar district, Iran during the agricultural year 2004-2005. The WP values for the main crops were computed using the SWAP simulated water balance components, i.e. transpiration T, evapotranspiration ET, irrigation I, and the marketable yield Y_M in terms in terms of Y_MT⁻¹, Y_M ET⁻¹ and Y_M I⁻¹.The average WP, expressed as $ T⁻¹ (US $ m⁻³) was 0.19 for wheat, 0.5 for fodder maize, 0.06 for sunflower and 0.38 for sugar beet. This indicated that fodder maize provides the highest economic benefit in the Borkhar irrigation district. Soil evaporation caused the average WP values, expressed as Y_M ET⁻¹ (kg m⁻³), to be significantly lower than the average WP, expressed as Y_MT⁻¹, i.e. about 27% for wheat, 11% for fodder maize, 12% for sunflower and 0.18 for sugar beet. Furthermore, due to percolation from root zone and stored moisture content in the root zone, the average WP values, expressed as Y_MI⁻¹ (kg m⁻³), had a 24-42% reduction as compared with WP, expressed as Y_M ET⁻¹.The results indicated that during the limited water supply period, on-farm strategies like deficit irrigation scheduling and reduction of the cultivated area can result in higher economic gains. Improved irrigation practices in terms of irrigation timing and amount, increased WP in terms of Y_MI⁻¹ (kg m⁻³) by a factor of 1.5 for wheat and maize, 1.3 for sunflower and 1.1 for sugar beet. Under water shortage conditions, reduction of the cultivated area yielded higher water productivity values as compared to deficit irrigation.     

Distribution and dynamics of soil water and salt under different drip irrigation regimes in northwest China

A 2-year experiment was carried out to investigate the effects of different drip irrigation regimes on distribution and dynamics of soil water and salt in north Xinjiang, China. Five treatments—F7 (0.24 dS m^?1 + Once every 7 days), B7 (4.68 dS m^?1 + Once every 7 days), S7 (7.42 dS m^?1 + Once every 7 days), F10 (0.24 dS m^?1 + Once every 10 days) and F3 (0.24 dS m^?1 + Once every 3 days)—were designed. For all treatments, additional 150-mm fresh water was applied on 10th November in 2009 (winter irrigation) to leach the accumulated salt. The results revealed that irrigation frequency and water quality had significant effects on the spatial distribution and change of soil water content, soil salt and the crop water consumption rate, but had a limited impact on the seasonal accumulative water consumption, and the cotton yield decreased with the decrease in irrigation frequency and water quality on the whole. During the cotton growing season, results showed that the salt mainly accumulated in the 0- to 60-cm soil layer, while the soil salt in 60- to 100-cm layer changed slightly, indicating that the drip irrigation could not leach the soil salt out of the root zone under the irrigation regimes. Therefore, salt leaching was necessary to maintain the soil water–salt balance and to prevent excessive salt accumulation in the root zone. After the 150-mm winter irrigation and subsequent thawing, soil salts were leached into the deeper layers (below 60 cm), and the soil salt content (SSC) (EC_1:5) in root zone in the next year was about 0.2 dS m^?1. Moreover, compared to 2009 season, the SSC within the root zone did not increase even the EC of the irrigation water was up to 7.42 dS m^?1. Additionally, it is important to note that the results were concluded based on the data of the 2-year experiment; further studies are need to optimize winter irrigation amount and assess the sustainability of saline water irrigation since long-term utilization of saline water may lead to soil degradation.     

Evaluation of mulched drip irrigation for cotton in arid Northwest China

Field experiments were conducted in arid Southern Xinjiang, Northwest China, for 3 years to evaluate sustainable irrigation regimes for cotton. The experiments involved mulched drip irrigation during the growing season and flood irrigation afterward. The drip irrigation experiments included control experiments, experiments with deficit irrigation during one crop growth stage, and alternative irrigation schemes in which freshwater was used during one growth stage and relatively saline water in the others. The average cotton yield over 3 years varied between 3,575 and 5,095 kg/ha, and the irrigation water productivity between 0.91 and 1.16 kg/m³. Crop sensitivities to water stress during the different growth stages ranged from early flowering-belling (most sensitive) > seedling > budding > late flowering-belling (least sensitive), while sensitivities to salt stress ranged from late flowering-belling > budding > seedling > early flowering-belling. Although mulched drip irrigation during the growing season caused an increase in salinity in the root zone, flood irrigation after harvesting leached the accumulated salts to below background levels. Numerical simulations, based on the 3-year experiments and extended by another 20 years, suggest that mulched drip irrigation using alternatively fresh and brackish water during the growing season and flood irrigation with freshwater after harvesting is a sustainable irrigation practice that should not lead to soil salinization.     

Yield and water productivity of five chickpea varieties under supplemental irrigation in contrasting years

Chickpea (Cicer arietinum L.) is one of the most important pulse crops in the world, cultivated on a wide range of environments. In Mediterranean regions, it is traditionally grown as a spring-sown rainfed crop, very dependent on rainfall. In this situation, supplemental irrigation can improve significantly the crop yield. The objective of this study was to evaluate the improvement on chickpea crop yield and water productivity (WP) of five chickpea varieties with supplemental irrigation, in the Mediterranean conditions, with both dry and wet years. Field tests were carried out over two cropping seasons, in Southern Portugal, using three kabuli-type and two desi-type chickpea varieties and four irrigation treatments, corresponding to 100, 50, 25 % of crop irrigation requirements (IR) and rainfed. The results show that all chickpea varieties responded to supplemental irrigation with the increase in grain and biomass yield. However, the magnitude of individual chickpea response depends on the year and the genotype. In 2009, a dry year, the highest WP values were attained at the 50 % IR treatment, whereas in 2010, a wet year, it was the rainfed treatment that showed the highest WP values. The Elixir variety showed the best grain yields and water productivity.     

Modeling soil water dynamics in a drip-irrigated intercropping field under plastic mulch

Intercropping, drip irrigation, and the use of plastic mulch are important management practices, which can, when utilized simultaneously, increase crop production and save irrigation water. Investigating soil water dynamics in the root zone of the intercropping field under such conditions is essential in order to understand the combined effects of these practices and to promote their wider use. However, not much work has been done to investigate soil water dynamics in the root zone of drip-irrigated, strip intercropping fields under plastic mulch. Three field experiments with different irrigation treatments (high T1, moderate T2, and low T3) were conducted to evaluate soil water contents (SWC) at different locations, for different irrigation treatments, and with respect to dripper lines and plants (corn and tomatoes). Experimental data were then used to calibrate the HYDRUS (2D/3D) model. Comparison between experimental data and model simulations showed that HYDRUS (2D/3D) described different irrigation events and SWC in the root zone well, with average relative errors of 10.8, 9.5, and 11.6 % for irrigation treatments T1, T2, and T3, respectively, and with corresponding root mean square errors of 0.043, 0.035, and 0.040 cm³ cm^?3, respectively. The results showed that the SWC in the shallow root zone (0–40 cm) was lower under non-mulched locations than under mulched locations, irrespective of the irrigation treatment, while no significant differences in the SWC were observed in the deeper root zone (40–100 cm). The SWC in the shallow root zone was significantly higher for the high irrigation treatment (T1) than for the low irrigation treatment, while, again, no differences were observed in the deeper root zone. Simulations of two-dimensional SWC distributions revealed that the low irrigation treatment (T3) produced serious severe water stress (with SWCs near the wilting point) in the 30–40 cm part of the root zone, and that using separate drip emitter lines for each crop is well suited for producing the optimal soil water distribution pattern in the root zone of the intercropping field. The results of this study can be very useful in designing an optimal irrigation plan for intercropped fields.     

Irrigation water prices for farmer-managed irrigation systems in Tanzania: a case study of Lower Moshi irrigation scheme

A computer program model for pricing irrigation water among beneficiaries was developed and tested. The data used for the purpose was collected from Lower Moshi farmer-managed irrigation scheme (FMIS) in northern part of Tanzania as a case study. The scheme has two intakes; namely Rau and Mabogini irrigation systems. Allam's mathematical model for allocating irrigation water price which was developed in Egypt (Allam, 1987) was adopted and adapted for the purpose. The results indicate that the irrigation water price depends on a number of structures serving the area, their installation costs, amount of water received by each tertiary block and water rights. The prices differ between different tertiary blocks within the same system and also between two systems that exist in Lower Moshi Irrigation Scheme (LMIS). This indicates that the model can be used as a tool by designers and planners for selecting the best designed irrigation system that farmers can afford to pay for its operation, maintenance and management. The mean irrigation water price value for Mabogini is Tshs. 12 151/-¹ while that of the Rau system is 10 414/-. To maintain uniformity of irrigation water price in the scheme, it is recommended that a mean value of Tshs. 11 283/- is used. Generally, farmers in Tanzania are used to contribute one bag of paddy which costs about Tshs. 10 000/- for maintenance works. Therefore, the irrigation water price derived from the model is reasonable and one the farmers can afford.     

Evaluation on the potential of improving border irrigation performance through border dimensions optimization: a case study on the irrigation districts along the lower Yellow River

In the Yucheng region along the lower reach of the Yellow River, current border irrigation systems in all three irrigation districts have low irrigation performances with the applied depth per irrigation event >150 mm, and application efficiency <65 %. It is often difficult to change irrigation practices, and rates of adoption are usually slow for China’s small-scale farmers. This study emphasizes the feasibility of optimizing border dimensions in border irrigation taking into consideration the existing irrigation conditions and farmers’ methods of irrigation practice. The performances of current border irrigation systems and improved systems were evaluated using agricultural irrigation survey data, field experimental data, and a simulation model. The irrigation conditions, that is, inflow rate, border dimensions, and relative cutoff distance, in the irrigation districts were found to be diverse. However, after border dimensions were optimized through simulation and field testing, it was determined that the applied depth per irrigation event could be decreased by an average of 49 mm, and the application efficiency could be increased on average by 26.7 % in the three irrigation districts. The annual potential amount of water savings among the three districts was calculated to be approximately 5,551 × 10⁴ m³ in the Yucheng region. Optimizing border dimensions is a practical technology for small-scale farming practices in the irrigation districts along the lower Yellow River.     

Isohydrodynamic behavior in deficit-irrigated Cabernet Sauvignon and Malbec and its relationship between yield and berry composition

Cabernet Sauvignon and Malbec grapevines were irrigated at 70 or 23 % of estimated crop evapotranspiration throughout berry development over four growing seasons. Stomatal behavior was characterized by relating predawn leaf water potential and mid-morning stomatal conductance to mid-morning leaf water potential. Seasonal average weekly midday leaf water potential was lower in Cabernet Sauvignon than Malbec despite similar irrigation amounts. Both cultivars exhibited anisohydric behavior with midday leaf water potential decreasing linearly with declining predawn leaf water potential (r ² = 0.51) and stomatal conductance (r ² = 0.42). However, both cultivars utilized hydrodynamic mechanisms to maintain a soil-to-leaf water potential gradient of ?0.62 (±0.03) MPa under standard irrigation and ?0.75 (±0.04) MPa under reduced irrigation. Berry fresh weight and titratable acidity decreased, and the concentration of total anthocyanins increased in both cultivars in response to decreases in midday leaf water potential. The slope of regression equations for seasonal mean midday leaf water potential was used to estimate cultivar-specific levels of water stress associated with changes in berry weight and berry composition at fruit maturity.     

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.