Modeling the role of irrigation in winter wheat yield,crop water productivity,and production in China

Irrigation plays an important role in increasing food production in China. The impact of irrigation on crop yield (Y), crop water productivity (CWP), and production has not been quantified systematically across regions covering the whole country. In this study, a GIS-based EPIC model (GEPIC) was applied to simulate Y and CWP for winter wheat (Triticum aestivum L.) in China at a grid resolution of 5 arc-minutes and to analyze the impacts of reducing irrigation water on wheat production. The findings show that irrigation is especially important in improving CWP of winter wheat in the North China Plain (NCP), the “bread basket” of China. On average, the provincial aggregate CWP was 56% higher under the irrigated than that under the rainfed conditions. The intensification of water stress and the associated increase in environmental problems in much of the NCP require critical thoughts about reducing water allocation for irrigated winter wheat. Two scenarios for irrigation reduction in the NCP provinces are presented: reducing irrigation depth (S1), and replacing irrigated winter wheat by rainfed winter wheat (S2). The simulation results show that S1 and S2 have similar effects on wheat production when the reduction in irrigation water supply is below 20% of the current level. Above this percentage, S2 appears to be a better scenario since it leads to less reduction in wheat production with the same amount of water saving.     

Integrated management of irrigation water and fertilizers for wheat crop using field experiments and simulation modeling

The reported study aimed at developing an integrated management strategy for irrigation water and fertilizers in case of wheat crop in a sub-tropical sub-humid region. Field experiments were conducted on wheat crop (cultivar Sonalika) during the years 2002–2003, 2003–2004 and 2004–2005. Each experiment included four fertilizer treatments and three irrigation treatments during the wheat growth period. During the experiment, the irrigation treatments considered were I₁ = 10% maximum allowable depletion (MAD) of available soil water (ASW); I₂ = 40% MAD of ASW; I₃ = 60% MAD of ASW. The fertilizer treatments considered in the experiments were F₁ = control treatment with N:P₂O₅:K₂O as 0:0:0 kg ha⁻¹, F₂ = fertilizer application of N:P₂O₅:K₂O as 80:40:40 kg ha⁻¹; F₃ = fertilizer application of N:P₂O₅:K₂O as 120:60:60 kg ha⁻¹ and F₄ = fertilizer application of N:P₂O₅:K₂O as 160:80:80 kg ha⁻¹. In this study CERES-wheat crop growth model of the DSSAT v4.0 was used to simulate the growth, development and yield of wheat crop using soil, daily weather and management inputs, to aid farmers and decision makers in developing strategies for effective management of inputs. The results of the investigation revealed that magnitudes of grain yield, straw yield and maximum LAI of wheat crop were higher in low volume high frequency irrigation (I₁) than the high volume low frequency irrigation (I₃). The grain yield, straw yield and maximum LAI increased with increase in fertilization rate for the wheat crop. The results also revealed that increase in level of fertilization increased water use efficiency (WUE) considerably. However, WUE of the I₂ irrigation schedule was comparatively higher than the I₁ and I₃ irrigation schedules due to higher grain yield per unit use of water. Therefore, irrigation schedule with 40% maximum allowable depletion of available soil water (I₂) could safely be maintained during the non-critical stages to save water without sacrificing the crop yield. Increase in level of fertilization increases the WUE but it will cause environmental problem beyond certain limit. The calibrated CERES-wheat model could predict the grain yield, straw yield and maximum LAI of wheat crop with considerable accuracy and therefore can be recommended for decision-making in similar regions.     

Temporal variability in water quality of agricultural tailwaters: Implications for water quality monitoring

Accurate assessments of non-point source pollution and the associated evaluation of mitigation strategies depend on effective water quality monitoring programs. Intensive irrigation season water quality monitoring was conducted on three agricultural drains (6 h to daily sampling) along with analysis of decade long records from two larger agricultural drains (biweekly to monthly sampling) in the San Joaquin Valley, California. Analyses revealed significant temporal variability in concentrations of nutrients, salts, and turbidity over short time-scales (<1 day), as well as significant differences in monthly and annual mean concentrations. Statistical techniques were used to evaluate the sampling intensity required to meet rigorous confidence and accuracy criteria, as well as to evaluate the efficacy of different sampling strategies (e.g. grab samples versus composite samples). The number of samples required to determine mean constituent concentrations within 20% of the mean at a 95% confidence level ranged from 2 to 39 samples per month (SPM) for total phosphorus, 1-16 SPM for total nitrogen, 5-25 SPM for turbidity, and 1-3 SPM for electrical conductivity. Using a daily composite sample (4 subsamples per composite) instead of discrete samples was shown to maintain the same accuracy and confidence standards, while reducing the required sample number by up to 50%. This study emphasizes the value of a statistical approach for evaluating water quality monitoring strategies, and provides a framework through which cost-benefit analysis can be implemented in the development of monitoring plans.     

Tuber yield, water and fertilizer productivity in early potato as affected by a combination of irrigation and fertilization

Excessive amounts of irrigation water and fertilizers are often utilized for early potato cultivation in the Mediterranean basin. Given that water is expensive and limited in the semi-arid areas and that fertilizers above a threshold level often prove inefficacious for production purposes but still risk nitrate and phosphorous pollution of groundwater, it is crucial to provide an adequate irrigation and fertilization management. With the aim of achieving an appropriate combination of irrigation water and nutrient application in cultivation management of a potato crop in a Mediterranean environment, a 2-year experiment was conducted in Sicily (South Italy). The combined effects of 3 levels of irrigation (irrigation only at plant emergence, 50% and 100% of the maximum evapotranspiration - ETM) and 3 levels of mineral fertilization (low: 50, 25 and 75 kg ha⁻¹, medium: 100, 50 and 150 kg ha⁻¹ and high: 300, 100 and 450 kg ha⁻¹ of N, P₂O₅ and K₂O) were studied on the tuber yield and yield components, on both water irrigation and fertilizer productivity and on the plant source/sink (canopy/tubers dry weight) ratio. The results show a marked interaction between level of irrigation and level of fertilization on tuber yield, on Irrigation Water Productivity and on fertilizer productivity of the potato crop. We found that the treatments based on 50% ETM and a medium level of fertilization represent a valid compromise in early potato cultivation management. Compared to the high combination levels of irrigation and fertilization, this treatment entails a negligible reduction in tuber yield to save 90 mm ha⁻¹ year⁻¹ of irrigation water and 200, 50 and 300 kg ha⁻¹ year⁻¹ of N, P₂O₅ and K₂O, respectively, with notable economic savings for farmers compared to the spendings that are usually made.     

Fresh tomato production for the Sydney market: An evaluation of options to reduce freshwater scarcity from agricultural water use

In response to the growing concerns of freshwater scarcity, two metrics are considered for assessing the impacts of consumptive water use of a kg of fresh tomato supplied to the Sydney market. The first is the water use efficiency (WUE)—commonly used by agronomists which considers the absolute volumes of water consumed, and second, a recently developed method for water footprints based on Life Cycle Assessment (LCA) which describes the impacts in terms of contributing to freshwater scarcity. The results indicated that although a kg of tomato supplied from within Sydney had the highest water use efficiency (38 L for a kg of tomato as compared to 39-78 L from other regions of Australia), it had the biggest LCA-based water footprint (16 L for a kg of tomato as compared to 1.9-2.2 L from other regions of Australia). WUE as an indicator of agriculture water use is inappropriate to indicate the potential to contribute to local freshwater scarcity; potential stress on local and regional water resources, estimated using LCA-based water footprints, provide useful dimension to assess consumptive water use. Having both metrics will enable to achieve short term benefits at the farm level for saving water (through water use efficiency), while also recognising that longer term changes are required for alleviating freshwater scarcity (through LCA-based water footprints). Scenario modelling indicated relocation of production away from Sydney or modernisation of Sydney tomato greenhouse industry as a priority for reducing freshwater scarcity. The latter may be the best long term option to reduce additional emissions from transport and to take advantage of recycled water sources from Sydney's wastewater.     

A package of water management practices for sustainable growth and improved production of vegetable crop in labour and water scarce Sub-Saharan Africa

A package of water management practices including pitcher irrigation method and water conserving techniques of manure application and mulching is experimented for sustainable growth and improved production of cucumber crop in Makanya village in North Eastern Tanzania. The increase in total yield due to package of water management practices is 203 per cent and water use efficiency obtained is 12.06 kg m⁻³. The seasonal water requirement of cucumber crop under package of water management practices ranges from 146.30 to 198.10 mm, which is on an average 4.19 times less as compared to control treatment of can irrigation. The irrigation interval in package of water management practices is 4.9 times higher than the can irrigation method. The water and labour uses are reduced by 75.9 and 73 per cent, respectively in package of water management practices. The results showed that the self-regulative nature of pitchers and moisture retention by water conserving techniques is helpful in mitigating water stress in crop root zone. The moisture retention period in soil is increased assisting reduction of labour hours required in irrigation. In local context, the water management practices included in the package are easy to understand, adopt, operate and maintain.     

Evaluation of options for increasing yield and water productivity of wheat in Punjab, India using the DSSAT-CSM-CERES-Wheat model

The DSSAT-CSM-CERES-Wheat V4.0 model was calibrated for yield and irrigation scheduling of wheat with 2004–2005 data and validated with 13 independent data sets from experiments conducted during 2002–2006 at the Punjab Agricultural University (PAU) farm, Ludhiana, and in a farmer's field near PAU at Phillaur, Punjab, India. Subsequently, the validated model was used to estimate long-term mean and variability of potential yield (Y_p), drainage, runoff, evapo-transpiration (ET), crop water productivity (CWP), and irrigation water productivity (IWP) of wheat cv. PBW343 using 36 years (1970–1971 to 2005–2006) of historical weather data from Ludhiana. Seven sowing dates in fortnightly intervals, ranging from early October to early January, and three irrigation scheduling methods [soil water deficit (SWD)-based, growth stage-based, and ET-based] were evaluated. For the SWD-based scheduling, irrigation management depth was set to 75 cm with irrigation scheduled when SWD reached 50% to replace 100% of the deficit. For growth stage-based scheduling, irrigation was applied either only once at one of the key growth stages [crown root initiation (CRI), booting, flowering, and grain filling], twice (two stages in various combinations), thrice (three stages in various combinations), or four times (all four stages). For ET-driven irrigation, irrigations were scheduled based on cumulative net ETo (ETo-rain) since the previous irrigation, for a range of net ETo (25, 75, 125, 150, and 175 mm). Five main irrigation schedules (SWD-based, ET-driven with irrigation applied after accumulation of either 75 or 125 mm of ETo, i.e., ET75 or ET125, and growth stage-based with irrigation applied at CRI plus booting, or at CRI plus booting plus flowering stage) were chosen for detailed analysis of yield, water balance, and CWP and IWP. Nitrogen was non-limiting in all the simulations.Mean Y_p across 36 years ranged from 5.2 t ha⁻¹ (10 October sowing) to 6.4 t ha⁻¹ (10 November sowing), with yield variations due to seasonal weather greater than variations across sowing dates. Yields under different irrigation scheduling, CWP and IWP were highest for 10 November sowing. Yields and CWP were higher for SWD and ET75-based irrigations on both soils, but IWP was higher for ET75-based irrigation on sandy loam and for ET150-based irrigation on loam. Simulation results suggest that yields, CWP, and IWP of PBW343 would be highest for sowing between late October and mid-November in the Indian Punjab. It is recommended that sowing be done within this planting period and that irrigation be applied based on the atmospheric demand and soil water status and not on the growth stage. Despite the potential limitations recognised with simulation results, we can conclude that DSSAT-CSM-CERES-Wheat V4.0 is a useful decision support system to help farmers to optimally schedule and manage irrigation in wheat grown in coarse-textured soils under declining groundwater table situations of the Indian Punjab. Further, the validated model and the simulation results can also be extrapolated to other areas with similar climatic and soil environments in Asia where crop, soil, weather, and management data are available.     

Magnetic treatment of irrigation water: Its effects on vegetable crop yield and water productivity

This study examines whether there are any beneficial effects of magnetic treatment of different irrigation water types on water productivity and yield of snow pea, celery and pea plants. Replicated pot experiments involving magnetically treated and non-magnetically treated potable water (tap water), recycled water and saline water (500 ppm and 1000 ppm NaCl for snow peas; 1500 ppm and 3000 ppm for celery and peas) were conducted in glasshouse under controlled environmental conditions during April 2007 to December 2008 period at University of Western Sydney, Richmond Campus (Australia). A magnetic treatment device with its magnetic field in the range of 3.5-136 mT was used for the magnetic treatment of irrigation water. The analysis of the data collected during the study suggests that the effects of magnetic treatment varied with plant type and the type of irrigation water used, and there were statistically significant increases in plant yield and water productivity (kg of fresh or dry produce per kL of water used). In particular, the magnetic treatment of recycled water and 3000 ppm saline water respectively increased celery yield by 12% and 23% and water productivity by 12% and 24%. For snow peas, there were 7.8%, 5.9% and 6.0% increases in pod yield with magnetically treated potable water, recycled water and 1000 ppm saline water, respectively. The water productivity of snow peas increased by 12%, 7.5% and 13% respectively for magnetically treated potable water, recycled water and 1000 ppm saline water. On the other hand, there was no beneficial effect of magnetically treated irrigation water on the yield and water productivity of peas. There was also non-significant effect of magnetic treatment of water on the total water used by any of the three types of vegetable plants tested in this study. As to soil properties after plant harvest, the use of magnetically treated irrigation water reduced soil pH but increased soil EC and available P in celery and snow pea. Overall, the results indicate some beneficial effect of magnetically treated irrigation water, particularly for saline water and recycled water, on the yield and water productivity of celery and snow pea plants under controlled environmental conditions. While the findings of this glasshouse study are interesting, the potential of the magnetic treatment of irrigation water for crop production needs to be further tested under field conditions to demonstrate clearly its beneficial effects on the yield and water productivity.     

Effects of irrigation regimes on yield and water productivity of safflower (Carthamus tinctorius L.) under Mediterranean climatic conditions

A field study was carried out in order to determine the effect of deficit irrigation regimes on grain yield and seasonal evapotranspiration of safflower (Carthamus tinctorius L.) in Thrace Region of Turkey. The field trials were conducted on a loam Entisol soil, on Dincer, the most popular variety in the research area. A randomised complete block design with three replications was used. Combination of four well-known growth stages of the plant, namely vegetative (V_a), late vegetative (V_b), flowering (F) and yield formation (Y) were considered to form a total of 16 (including rain fed) irrigation treatments. The effect of irrigation and water stress at any stage of development on grain yield per hectare and 1000 kernels weight was evaluated. Results showed that safflower was significantly affected by water stress during the sensitive late vegetative stage. The highest yield was obtained in V_aV_bFY treatment. Seasonal irrigation water use and evapotranspiration were 501 and 721 mm, respectively, for the non-stressed treatment. Safflower grain yield of this treatment was 5.22 Mg ha⁻¹ and weight of 1000 kernels was 55 g. The seasonal yield-water response factor value was 0.87. The total water use efficiency was 7.2 kg ha⁻¹ mm⁻¹. Irrigation schedule of the non-stressed treatment may be as follows: the first irrigation is at the vegetative stage, when after 40-50 days from sowing/elongation and branching stage, that is the end of May; the second irrigation is at the late vegetative stage, after 70-80 days from sowing/heading stage, that is in the middle of June; the third irrigation is at the flowering stage, approximately 50% level, that is the first half of July; and the fourth irrigation is at the yield formation stage, seed filling, that is the last week of July.     

Performance evaluation and calibration of soil water content and potential sensors for agricultural soils in eastern Colorado

This study evaluated the performance of three soil water content sensors (CS616/625, Campbell Scientific, Inc., Logan, UT; TDT, Acclima, Inc., Meridian, ID; 5TE, Decagon Devices, Inc., Pullman, WA) and a soil water potential sensor (Watermark 200SS, Irrometer Company, Inc., Riverside, CA) in laboratory and field conditions. Soil water content/potential values measured by the sensors were compared with corresponding volumetric water content (θ_v, m³ m⁻³) values derived from gravimetric samples, ranging approximately from the permanent wilting point (PWP) to field capacity (FC) volumetric water contents. Under laboratory and field conditions, the factory-based calibrations of θ_v did not consistently achieve the required accuracy for any sensor in the sandy clay loam, loamy sand, and clay loam soils of eastern Colorado. Salt (calcium chloride dihydrate) added to the soils in the laboratory caused the CS616, TDT, and 5TE sensors to experience errors in their volumetric water content readings with increased bulk soil electrical conductivity (EC; dS m⁻¹). Results from field tests in sandy clay loam and loamy sand soils indicated that a linear calibration (equations provided) for the TDT, CS616 and 5TE sensors (and a logarithmic calibration for the Watermark sensors) could reduce the errors of the factory calibration of θ_v to less than 0.02 ± 0.035 m³ m⁻³. Furthermore, the performance evaluation tests confirmed that each individual sensor needed a unique calibration equation for every soil type and location in the field. In addition, the calibrated van Genuchten (1980) equation was as accurate as the calibrated logarithmic equation and can be used to convert soil water potential (kPa) to volumetric soil water content (m³ m⁻³). Finally, analysis of the θ_v field data indicated that the CS616, 5TE and Watermark sensor readings were influenced by diurnal fluctuations in soil temperature, while the TDT was not influenced. Therefore, it is recommended that the soil temperature be considered in the calibration process of the CS616, 5TE, and Watermark sensors. Further research will be aimed towards determining the need of sensor calibration for every agricultural season.     

Accounting for water use: Terminology and implications for saving water and increasing production

Scarcity and competition for water are matters of increasing concern, as are potential shortages of food. These issues intersect both within the agricultural sector and across all water using sectors. Irrigation is by far the largest user of water in most water-scarce countries, and is under pressure to reduce utilisation (to release water to other sectors, including the environment) and use water more productively to meet demands for food and fibre.The terminology for such intra- and inter-sectoral analysis must be unambiguous across sectors so that interventions and their impacts are properly understood. Such terminology, based on previous work and debate, is set out. Implications for a better understanding of the scope for improved productivity of water in agriculture are traced, and some examples are given using data from recent research submissions, demonstrating the benefits of precise water accounting.     

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.     

Deficit irrigation in maize for reducing agricultural water use in a Mediterranean environment

Research on crop response to deficit irrigation is important to reduce agricultural water use in areas where water is a limited resource. Two field experiments were conducted on a loam soil in northeast Spain to characterize the response of maize (Zea mays L.) to deficit irrigation under surface irrigation. The growing season was divided into three phases: vegetative, flowering and grain filling. The irrigation treatments consisted of all possible combinations of full irrigation or limited irrigation in the three phases. Limited irrigation was applied by increasing the interval between irrigations. Soil water status, crop growth, above-ground biomass, yield and its components were measured. Results showed that flowering was the most sensitive stage to water deficit, with reductions in biomass, yield and harvest index. Average grain yield of treatments with deficit irrigation around flowering (691 g m⁻²) was significantly lower than that of the well-irrigated treatments (1069 g m⁽²). Yield reduction was mainly due to a lower number of grains per square metre. Deficit irrigation or higher interval between irrigations during the grain filling phase did not significantly affect crop growth and yield. It was possible to maintain relatively high yields in maize if small water deficits caused by increasing the interval between irrigations were limited to periods other than the flowering stage. Irrigation water use efficiency (IWUE) was higher in treatments fully irrigated around flowering.     

Water harvesting and supplemental irrigation for improved water productivity of dry farming systems in West Asia and North Africa

In the dry areas, water, not land, is the most limiting resource for improved agricultural production. Maximizing water productivity, and not yield per unit of land, is therefore a better strategy for dry farming systems. Under such conditions, more efficient water management techniques must be adopted. Supplemental irrigation (SI) is a highly efficient practice with great potential for increasing agricultural production and improving livelihoods in the dry rainfed areas. In the drier environments, most of the rainwater is lost by evaporation; therefore the rainwater productivity is extremely low. Water harvesting can improve agriculture by directing and concentrating rainwater through runoff to the plants and other beneficial uses. It was found that over 50% of lost water can be recovered at a very little cost. However, socioeconomic and environmental benefits of this practice are far more important than increasing agricultural water productivity. This paper highlights the major research findings regarding improving water productivity in the dry rainfed region of West Asia and North Africa. It shows that substantial and sustainable improvements in water productivity can only be achieved through integrated farm resources management. On-farm water-productive techniques if coupled with improved irrigation management options, better crop selection and appropriate cultural practices, improved genetic make-up, and timely socioeconomic interventions will help to achieve this objective. Conventional water management guidelines should be revised to ensure maximum water productivity instead of land productivity.     

Management trends and responses to water scarcity in an irrigation scheme of Southern Spain

Improvement of irrigation management in areas subjected to periods of water scarcity requires good knowledge of system performance over long time periods. We have conducted a study aimed at characterizing the behaviour of an irrigated area encompassing over 7000 ha in Southern Spain, since its inception in 1991. Detailed cropping pattern and plot water use records allowed the assessment of irrigation scheme performance using a simulation model that computed maximum irrigation requirements for every plot during the first 15 years of system operations. The ratio of irrigation water used to maximum irrigation requirements (Annual Relative Irrigation Supply, ARIS) was well below 1 and oscillated around 0.6 in the 12 years that there were no water supply restrictions in the district. The ARIS values varied among crops, however, from values between 0.2 and 0.3 for sunflower and wheat, to values approaching 1 for cotton and sugar beet. Farmer interviews revealed some of the causes for the low irrigation water usage which were mainly associated with the attempt to balance profitability and stability, and with the lack of incentives to achieve maximum yields in crops subsidized by the Common Agricultural Policy (CAP) of the European Union. The response to water scarcity was also documented through interviews and demonstrated that the change in crop choice is the primary reaction to an anticipated constraint in water supply. Water productivity (value of production divided by the volume of irrigation water delivered; WP) in the district was moderate and highly variable (around 2€ m⁻³) and did not increase with time. Irrigation water productivity (increase in production value due to irrigation divided by irrigation water delivered) was much lower (0.65€ m⁻³) and also, it did not increase with time. The lack of improvement in WP, the low irrigation water usage, and the changes in cropping patterns over the first 15 years of operation indicate that performance trends in irrigated agriculture are determined by a complex mix of technical, economic, and socio-cultural factors, as those that characterized the behaviour of the Genil-Cabra irrigation scheme.     

Effects of saline water irrigation on soil salinity and yield of winter wheat–maize in North China Plain

Drought and fresh water shortage are in the way of sustainable agriculture development in the North China Plain. The scarcity of fresh water forces farmers to use shallow saline ground water, which helps to overcome drought and increase crop yields but also increases the risk of soil salinization. This paper describes salt regimes and crop responses to saline irrigation water based on field experiments conducted from October 1997 to September 2005. It was found that use of saline water causes the ECe of the topsoil (0–100 cm, Cv: 0.196∼0.330) to be higher and more variable than the subsoil (100–180 cm, Cv: 0.133∼0.219). The salt load rapidly increased, notably in the upper 80 cm and especially during the season of October 1999 to June 2000. It was concluded that the maximum soil depth to which the soil was leached during the wet season was about 150 cm. The relative yields of winter wheat could be ranked Fresh Sufficient (FS, 100%) > Fresh Limited (FL, 91.80%) > Saline Sufficient (SS, 91.63%) > Saline Limited (SL, 88.28%) > Control (C, 69.58%) and for maize FS (100%) > FL (96.37%) > SS (93.05%) > SL (90.04%)> C (89.81%). The best irrigation regime was Saline Limited for winter wheat and maize, provided rainfall is sufficient. The experiments confirm that saline irrigation water appears to be economically attractive to farmers in the short term and ecological hazards can still be controlled with proper leaching.     

Farmer participation in irrigation management: The case of Doroodzan Dam Irrigation Network, Iran

The importance of farmer participation in system design and management has been emphasized in previous studies. The purpose of this study was to identify the factors affecting farmer participation in irrigation management using survey research. The study was conducted in Doroodzan Dam Irrigation Network in Fars province, Iran. Multistage stratified random sampling was used to collect data from 270 farmers as the research sample. Results reveal that farmers’ attitudes toward participation in irrigation management, attitudes toward personnel of the State Water Authority and the Agricultural Extension Service Centers (AESCs), family size, the problem perception, dependence on the dam for water, and educational background have influenced their participation in irrigation management. By contrast, contact with information sources, animal units, sociability, age and agricultural experience did not affect farmers’ participation. Moreover, based on farmers’ perspectives, unequal water distribution among farms, dissatisfaction with Water Authority operators and high water fees and charges were the main problems and obstacles toward farmer participation in irrigation management.     

Effects of different emitter space and water stress on yield and quality of processing tomato under semi-arid climate conditions

The objective of the study was to determine the effects of different emitter spaces and water stress on crop yield, such that the tomatoes would be suitable for processing and paste output (Lycopersicon esculentum Mill cv. Shasta). Such variables were also analyzed with respect to crop quality characteristics (e.g., mean fruit weight - MFW, fruit diameter - FD, penetration value of fruit - PV, pH, total soluble solids - TSS, and ascorbic acid contents - AA). The experiment was conducted under ecological conditions typical of the Konya Plain, a semi-arid climate, in 2004 and 2005. Drip irrigation laterals were arranged in such a way that every row had one lateral. Emitters were spaced at 25, 50, and 75 cm intervals in the main plots, while four levels of water supply, irrigation at 7-day intervals with enough water to fill the soil depth of 0-60 cm until capacity was reached (I₁), and 25, 50, and 75% decreased water supply levels were applied as subplots of the experiment. Results of the field experiments showed that yield suitable for processing (68.7-72.7 t ha⁻¹) and paste output (12.2-12.9 t ha⁻¹) were obtainable under conditions of I₁ application (p < 0.01). MFW, FD, PV, and TSS were significantly affected from treatments (p < 0.05). High stress resulted in the highest soluble solids. The total irrigation water amount and water consumptive use of the mentioned application (I₁) were determined as 426 and 525 mm in 2004. In 2005, the total irrigation water amount and water consumptive use of the same treatment were 587 and 619 mm, respectively.     

Investigating water availability for introducing an additional crop yield in dry season on hill land at Rubirizi, Rwanda

The study explores the potential of introducing an additional crop during dry season in Rwanda, comparing the efficiency of in situ soil moisture conservation techniques to sustain rain-fed agriculture. Comparative study of in situ soil moisture conservation techniques in bench terraces and unterraced field with maize crop had been conducted from June 2007 to October 2007. Bench terrace increased the average soil moisture content in 90 cm soil depth by more than 50% than that of unterraced land. Within the bench terraced field compartment bund and ridges and furrows increased soil moisture by 19.5% and 27.9% higher than plain bed. In terms of efficiency of moisture conservation, ridges and furrows performed well with 85.8% followed by compartment bund with 75.9% in terraced field. Unterraced field conserved moisture very poorly with 13.9% efficiency inferring importance of bench terraces for soil moisture conservation. No maize grain yield was recorded in all the techniques because soil water depleted to 60% and above from the beginning of the cropping period inferring the need of supplementary irrigation. Analysis of rainfall, crop water demand and in situ moisture conservation reveals exciting opportunities for water productivity enhancements by integrating components of water management within the context of rain-fed farming through water harvesting and supplemental or microirrigation for dry spell mitigation. Detailed analysis is needed for feasibility of lift irrigation with different crops under different altitudes to derive suitable policy for hill land irrigation.     

Modeling the potential for closing quinoa yield gaps under varying water availability in the Bolivian Altiplano

In the Bolivian Altiplano, the yields of rainfed quinoa are relatively low and highly unstable. We use a validated crop water productivity model to examine the potential of closing quinoa yield gaps in this region. We simulate the expectable yields under rainfed cultivation and under different deficit irrigation (DI) strategies using the AquaCrop model for the Northern, Central and Southern Bolivian Altiplano. Simulated DI scenarios include a reference strategy avoiding stomatal closure during all sensitive growth stages and allowing drought stress during the tolerant growth stages (DI₀) and various restrictive deficit irrigation strategies (DI_i) representing cases when water resources are limited. We obtain a logistic crop water production function for quinoa by plotting the seasonal actual evapotranspiration versus total grain yield. Due to the large scatter, this function only indicatively provides expectable yields. From the scenario analysis, we derive yield probability curves for the 3 agro-climatic regions. DI, without restriction in irrigation water during the drought sensitive growth stages, is able to close the yield gaps in the Northern, Central and Southern Bolivian Altiplano, and would guarantee a high and stable level of water productivity (WP). The yields of quinoa under rainfed cultivation during dry years are only 1.1, 0.5 and 0.2 Mg ha⁻¹ in the Northern, Central and Southern Bolivian Altiplano, whereas under DI₀ they are 2.2, 1.6 and 1.5 Mg ha⁻¹, respectively. Under limited water availability for irrigation, these stable yield levels decrease, most drastically in the Southern Bolivian Altiplano. Below a minimum water availability of 600 m³ per ha and 700 m³ per ha in the Central and Southern Bolivian Altiplano, respectively, the application of DI for quinoa is not significantly effective and should be avoided to save valuable resources. The yield probability curves we derive can serve as input for stochastic economic analysis of DI of quinoa in the Bolivian Altiplano.