a. r. sepaskhah

 This article presents a study of the evolution of the water-energy-food (WEF) nexus since its rise to prominence in policy and development discourses in 2011. Drawing from an extensive review of published literature, the article presents various interpretations of the concept while also considering the novelty of the WEF nexus. Various criticisms levelled at the WEF nexus, such as the neglect of livelihoods and the environment in assessments, are noted, together with governance considerations associated with this framework. Finally, the potential of the WEF nexus to contribute to the achievement of the sustainable development goals is reviewed. In terms of possible weaknesses associated with the WEF nexus, a concern identified in the literature is that livelihoods, social justice and the environment are often omitted from these assessments. So far, WEF nexus studies have focused on global macro-scale resources security. This was not the intention when the concept was first promoted. For this framework to gain traction, particularly in light of the sustainable development goals, it must be utilized to achieve adequate resource security for all groups. It must simultaneously acknowledge and protect the environment as the irreplaceable foundation of the nexus. The challenge of integrating and optimizing the components of this multi-centric nexus is examined, with six international case studies and seven national case studies being presented and discussed.

In recent decades, Iran has witnessed a noteworthy surge in agricultural water consumption due to population growth, economic development accompanied by irrigated agricultural lands, and changes in dietary habits. Unfortunately, the ratio of consumption to renewable water has consistently exceeded four times the threshold of water stress for several decades.  A recent analysis of annual groundwater depletion using the GRACE satellite observations was estimated to be about 15.9 BCM/year, significantly higher than the previously estimated value of 4.7 BCM/year obtained using the conventional estimation methods. In fact, this research estimated that the accumulated depletion of groundwater supply in 2021 could be more than 350 BCM, contrary to the reported amount of 143 BCM. Despite the severity of the situation, water consumption in Iran has not been adequately reduced to balance the low recharge rate of its water resources.  In fact, by building many dams and digging many wells, more water than the share of the environment has been consumed. To prevent environmental severe water stress or consumption of 60% of renewable water, a 44% reduction in agricultural water consumption is necessary. However, achieving this significant reduction in agricultural water consumption, it poses several social and economic challenges, such as gaining the consent and cooperation of farmers to participate in reducing water usage, ensuring accurate measurement of water delivery, securing sufficient foreign currency for importing agricultural products, creating alternative job opportunities for farmers, and leading to a significant increase in the price of agricultural products.

Plant growth and yield are influenced by many production parameters such as the amount of irrigation water, fertilization, plant density, etc. Due to the limitation of resources and agricultural inputs, increased production costs, food demand, population growth, and environmental problems, the development of scheduling approaches to use production parameters is necessary. In this study, firstly, crop yield and net benefit responses to variation of production parameters and secondly, economic-mathematical analysis of production parameters such as irrigation water were reviewed. Presented analyses in this study were categorized into four cases including 1) constant or variable crop price, 2) single, two, or multiple variables production functions, 3) limited land area and water or not limited, and 4) variable water price. The economic-mathematical analysis presented about deficit irrigation in this study was extended to determine the optimum value of other production parameters such as fertilizer rate, plant density, seed density, corm planting intensity, etc.

Inefficient use of limited water resources, along with increasing population and increasing water demand for food production has severely threatened agricultural water resources. One way to overcome this problem is to improve water productivity by introducing new crops that tolerate water stresses such as quinoa. In this study, the effect of water stress at different stages of plant growth (vegetative, flowering, and grain filling) was studied on plant parameters, yield, and water productivity of quinoa (cv. Titicaca). This study was conducted under field conditions and the treatments were performed as a block experiment in a completely randomized design with four replications. Experimental factors were: treatment without water stress or full irrigation (F) and water stress treatment (D) at 50% of the need for full irrigation at different stages of quinoa growth. The application of deficit irrigation during different stages of plant growth decreased stomatal conductance, leaf area index, leaf water potential, seed yield, and water productivity, while deficit irrigation increased the green canopy temperature. According to the results of the present study, the flowering stage of quinoa was very sensitive to water stress leading to produce lower yield compared with the amount of yield obtained when vegetative and or grain filling stages are under water stress conditions.

Innovative and sustainable agricultural water management is critical in adaptation programs to climate variability and change, and emerging, eco-friendly irrigation technologies are expected to play a key role in the world's future water and food security. The current study was carried out with the aim of discussing pros and cons of new irrigation and agricultural water technologies in the world, and the possibility of application of these technologies in Iran. These techniques are classified into seven categories: smart technology, nanotechnology, greenhouse technology, superabsorbent technology, cloud seeding technology, deep water technology, and seawater desalination technology. These technologies are analyzed in terms of economics, water and energy usage, and certain environmental factors (such as toxicity and greenhouse gas emissions). The state-of-the-art of modern irrigation and agricultural water technologies in Iran is examined, and the issue of their domestic application is matched with the country’s potentials. According to documentary studies, our country is at the beginning of the road in terms of intelligent technologies for agricultural water management and nanotechnology, and further study is required to employ these technologies. However, intelligent irrigation management utilizing crop growth and yield models, mobile phone applications, and micro-irrigation implementation was proposed as a feasible solution. The use of silver nanoparticles was suggested for the disinfection of water in remote areas, and the use of titanium dioxide for areas that do not have power supply problems. Employing the vertical farming is not recommended in the country due to the problems of electrical power supply and air pollution and presence of unlimited arable land. The technology of artificial light and solar panels has been adopted in Iran and more research is needed to justify their applications in greenhouses. Cloud seeding, deep water, and seawater desalination technologies have become indigenous to Iran. Cloud seeding is ineffective to alleviating droughts and strengthening aquifers. Because of the environmental consequences, the employment of deep-water technologies is not recommended. Employing of seawater desalination technologies for drinking and industrial (not agricultural) uses is cost effective.

Iran with a long-term mean annual precipitation of 254 mm (210 mm in short-term of drought period), mean annual potential evaporation of more than 2000 mm, and dominance of arid and semi-arid climates over 85% of its area is located in one of the driest regions of the world. These factors have led to the dependence of most agricultural productions in Iran on the surface water and groundwater. In this article, based on the statistics and documents collected from the reliable sources, the current situation of agricultural water resources and uses in the country has been studied and analyzed. In addition, the adequacy of agricultural water resources under the current and future conditions, the position of the country in terms of water resources and uses in the world, pathology and solutions to get out of the current situation have been studied and analyzed. Examination of available documents shows that despite the increase in irrigation water efficiency and productivity in the field in recent years, lack of attention to climatic and water resources potentials and unplanned development of agricultural lands to meet the food needs of the country's growing population have led to overexploiting the surface water and groundwater resources, and hence, the destruction of aquifers. Reducing water use in agriculture along with increasing agricultural water productivity and implementing groundwater balance plans have been proposed as the key solutions to the existing challenges.

In the present study, the effects of different levels of irrigation, organic mulch and planting method on the mungbean yield in Badjgah were investigated. The experimental plan in the first year was full randomized block, while in the second year, it was full randomized split-split plot block design, in three repetitions. The results showed that in the FI treatments, the yield was increased up to 2% for the first year and 5% for the second year by changing the planting method from on over-ridge planting method to the in-furrow planting one. Also, the results of the first year showed that there was no significant difference between the yield in the fully-irrigated treatments without mulch and the treatment with mulch and 0.75 FI. The amount of the irrigation water could be decreased up to 25% by adding organic mulch in both planting methods, as compared to the fully-irrigated treatments without mulch. The maximum water productivity equal to 0.4 kg/m3 was observed in 0.5 FI, in-furrow planting method with mulch treatment. It can be, therefore, concluded that the water productivity may be maximized with the application of both deficit irrigation and mulching strategies.

Due to the limited water resources and growing population, food security and environmental protection have become a global problem. Increasing water productivity of agricultural products is one of the main solutions to cope with the difficulties. By optimizing applied water and nitrogen fertilizer, the pollution of groundwater could be deceased and the water productivity could be increased. The aim of this research was to determine the relationships between water productivity (IRWP) and water use efficiency (WUE) and different amounts of applied water (irrigation + rain fed) and nitrogen (applied and residual). This study was conducted on wheat (Triticum aestivum L., cv. Shiraz) in Shiraz University School of Agriculture, based on a split-plot design with three replications, in 2009-2010 and 2010-2011 periods. Irrigation treatments varied from zero to 120% of full irrigation depth, and nitrogen fertilizer treatments varied from zero to 138 kg ha-1 under basin irrigation system. The experimental data of the first and second years were used for the calibration and validation of the proposed relationships, respectively. The calibrated equations using the dimensionless ratios of irrigation depth plus rainfall, actual evapotranspiration and nitrogen fertilizer plus soil residual nitrogen to their amounts in full irrigation and maximum fertilizer amounts were appropriate for the estimation of water productivity and water use efficiency. The values of the determination coefficient (R2) for water productivity and water use efficiency (0.88 and 0.93, respectively), and the values of their normalized root mean square error (NRMSE) (0.2 and 0.13, respectively) showed a good accuracy for the estimation of IRWP and WUE.

The changes in Root Length Density (RLD) of rainfed fig trees due to supplemental irrigation were studied during two growing seasons in Estahban, southern Iran, with objective of finding out the optimum position, time, and amount of supplemental irrigation. Irrigation position treatments were: (1) In a micro-catchment close to tree trunks; (2) Inside the tree canopies (1-1.1 m from tree trunks); and (3) Outside the tree canopies (2.1-2.2 m from tree trunks). Irrigation time treatments included: (a) In early spring and (b) In mid-summer; and the treatments of irrigation amount were: (i) No supplemental irrigation (control), (ii) 1,000, and (iii) 2,000 L per tree. Results showed that the highest RLD in different irrigation amounts occurred at 15-45 cm depth during late winter and late spring. However, during summers, the high RLD occurred 15 cm lower at 30-60 cm depth. Irrigation water treatments of 1,000 and 2,000 L per tree increased RLD values by 11.3 and 19.3%, respectively, in late spring and 10.5% and 14.7%, respectively, in late summer, compared with the rainfed treatment. Whereas this increase generally occurred in the wetted area; supplemental irrigation out of tree canopy could develop the root horizontal extension to a greater distance. Lower temporal variation in RLD profile was obtained for depths deeper than 75 cm, which was in agreement with soil water content variations. Supplemental irrigation applied out of tree canopy with 2,000 L per tree (200 m3 ha-1) during early spring is recommended to improve root development of fig trees in drought prone rainfed areas.

Harvest index (HI), ratio of seed yield to aboveground dry matter, is a very important parameter for estimating seed yield in several crop models. In this study, the importance, definition, variability and estimation methods of HI in crop models were discussed. HI estimation methods are categorized into two groups including: (i) complex methods that estimate HI from the beginning of seed growth to crop maturity, dynamically and (ii) simple methods that estimate the final HI at crop maturity. HI is a trait that is affected by many environmental parameters and the genotype of a crop. Soil water content or soil water suction during growing season, soil nutrient, groundwater depth, high air temperature, plant population and irrigation water salinity are some environmental factors affecting the HI. Therefore, in all models that used HI to estimate crop yield, either complex (e.g., AquaCrop model) or simple method, the harvest index estimating equations should be calibrated by changing the genotypes or cultivars, environmental and non-environmental parameters.

Infiltration rate is one of the most important parameters used in irrigation water management. Direct measurement of infiltration process is laborious, time consuming and expensive. Therefore, in this study application of some indirect methods such as artificial neural networks (ANNs) for prediction of this phenomenon was investigated. Different ANNs structures including two training algorithms (TrainLM and TrainBR), two transfer functions (Tansig and Logsig), and different combinations of the input variables such as sand, silt, and clay fractions, bulk density (BD), soil organic matter (SOM), cumulative infiltration (CI) and elapsed time were used to predict sorption coefficient (S) and hydraulic conductivity (A) in Philip equation (I=S*t0.5+A*t), which corresponded to 30 soil samples from study areas located in the Agricultural College, Shiraz University, (Bajgah). A two-hidden layer ANNs with two and three neurons in the hidden layers, respectively and TrainLM algorithm performed the best in predicting S when Logsig and Tansig were used. Silt+ clay+ sand+ time+ CI combination was the most basic influential variables for the S prediction. Furthermore, a two-hidden layer ANNs with two and three neurons in the hidden layers, respectively and TrainBR algorithm performed the best in predicting A when Tansig and Tansig were used. Silt +clay +sand +BD + OM+ time+ CI combination was the most basic influential variables for A prediction. Results showed that increasing the hidden layers and input variables significantly improved the ANNs performance. The coefficient of determination (R2) confirmed that the ANNs predictions for A (84.6 %) fit data better than S (77.5 %).

The amount of water used to produce a product or service is called virtual water. Trade of products and services between countries is called virtual water trade. Virtual water for a given product is an index of environmental degradation that occurred by the product production. Usually, there are misinterpretation in virtual water concepts that makes its applicability for substitution of a product with others questionable. Therefore, the planning concepts for virtual water trade should be taken into consideration. In this survey, first the potential of the concepts of virtual water trade were investigated. In applicability of the concepts of virtual water trade, the regional context and conscious choice should be considered. The effective factors in proper applicability of the virtual water concepts to food trade are food security, food self-sufficiency, food safety, food sovereignty, and environmental conservation. Furthermore, in this regards, the employment and poverty in a country should be considered. Also, in applicability of the virtual water trade, the geo-politics, pricing and subsidies for agricultural products, investments in infrastructure instead of virtual water trade, and changing diets should be considered. For reduction in the virtual water trade, the value of water in agricultural products and food production methods should be changed. Although the methods of calculating the virtual water of agricultural products are not well established, these uncertainties should not be emphasized very much; rather, the policy makers should be familiarized with the concepts of the virtual water trade in order to make conscious choices.

Nowadays, due to limited water resources and low soil fertility, especially in arid and semi-arid regions, the use of water with low quality (such as saline water) and soil amendments such as biochar is essential. Biochar is a kind of charcoal produced from plant residue and animal manure, which improves soil physical and chemical properties due to its porous structure. Therefore, the current research was conducted to investigate the effect of different levels of saline irrigation water and biochar on soil chemical properties under faba bean cultivation. Four saline irrigation water treatments having EC values of 0.5, 2.5, 5 and 7.5 dS m-1 and four levels of biochar including 0, 1.25, 2.5 and 3.75 % w/w were applied based on completely randomized design with three replications. Chemical properties such as potassium, calcium, and sodium ions concentration, sodium adsorption ratio, and electrical conductivity of saturated extract were measured in two depths of 0-10 and 10-20 cm. The results showed that increase in salinity and biochar levels increased the amount of sodium, potassium, and calcium ions and also soil electrical conductivity. Further, all ions concentration, sodium adsorption ratio, and electrical conductivity in the depth of 0-10 cm were higher than 10-20 cm depth, due to soil evaporation and water and solute movement towards upper layer. According to the results obtained in this study, it can be concluded that the use of biochar as a rich source of plant nutrients can greatly increase availability of nutrients such as calcium and potassium in soil, but, the negative effects of biochar application, such as increasing salinity, should be considered.

Total renewable water resources in Iran is about 105 billion m3 that is about 0.3% of the world total fresh water; whereas, the land area and population of Iran is 1.1% of the world. Furthermore, the per capita water resources in Iran is about 1300 m3 that is lower than that in many other countries in the world. Therefore, shortage of water resources in Iran is higher than that for other countries. The total capacity of dam reservoirs in Iran is about 48 billion m3 from which about 34 billion m3 is regulated water and may be used for agriculture, industry and domestic. Due to dry air and high air temperature the evaporation water loss from the dam reservoirs is high; therefore, it should be reduced to save the stored water resources. In this study it is shown that the magnitude of evaporated water is important (4.2%-14.3% of total capacity of the stored water in dams). The amount of evaporated water, on average (10%) is 4, 8 billion m3 that should be reduced in drought and water crisis conditions and the saved water should be used in agriculture, industry and domestic. Different methods for reduction of water evaporation from reservoirs are used in the world, among which emulsion and powder chemicals and covering water surface are suitable ones that can be used in Iran. Application of emulsion and powder on the water surface produces monolayers that cover the water surface to reduce the evaporation losses. However, wind and water wave disrupt the monolayer and reduce its effects on the evaporation reduction; therefore, it should be applied continuously by 1-2 day intervals. One of the evaporation reduction chemicals in the world is “Watersaver” that its use is safe for environment. Application of this chemical can reduce the water evaporation by 40%. Covering materials that can be used are floating white Styrofoam or floating light hollow concrete blocks that reduce the evaporation loss by 80%. Economic analysis indicated that evaporation reduction and water conservation by these chemical and materials are compatible to fresh water production by desalinization of saline sea water and wastewater treatment.

One of the principal methods to improve water productivity in irrigation network is to use the suitable distribution of water. In this research، the distribution of water in Doroodzan dam irrigation network was evaluated using 14 years of data (1996-2010). This irrigation network is located in northwest of Fars province and distributes stored water in Droodzan dam. Distribution of water between Hamoon، Ordibehesht، Left side Principal and Abarj canals was studied. Monthly distribution of water showed that in April and May، inflow in canals are high، in November they are low and in February there is no water in canals. The index of delivered water per unit area of land must be equal between canals. The lowest amount of this index was 0. 19 (l. s-1. ha-1) for Hamoon canal and the highest amount was 0. 37 (l. s-1. ha-1) for Abraj canal. The results showed that Hamon canal compared to others received less water per unit area and Abarj canal، received the highest amount of water per unit area. It was recommended that the water must be distributed between canals by equal amounts per unit area on volumetric basis based on crop water requirements.

Wheat is one of the most important product in Fars province and accurate irrigationscheduling causes to increase irrigation efficiency and optimal use of water resources. Because، most of rain events occurs during wheat growing period in Fars province، irrigation of winter wheat is important. Therefore، in this study، a simple daily rainfall generator model with two components was used. Stochastic output of this model coupled to a water balance model that used average deterministic ETp values. Irrigation dates and amountsat 32 climatologically stations in Fars province were determined. The model was based on daily water balance approach and used crop and soil data as input. In the next step، a predictive irrigation schedule at selected probability level for irrigation dates developed with Arc GIS. Finally، spatial maps of simulated values under same probability level was drawn. Because wheat is most sensitive to water stress during critical stages of booting and two weeks before pollination، predictive scheduling does not lead to water stress. The results showed that number of irrigation in southern، west southern and east southern stations in Fars province is higher. Under 75 probability also the highest irrigation requirement was predicted in southern and east southern station. Analyzing the result of model according to certain risk level، is helpful in determining irrigation requirement ofwinter wheat and water resources strategies in Fars province.

Water and fertilizer applications management should be improved due to scarce resources and environmental protection aspects. An analysis of crop yield production and profit maximization was conducted to determine the optimal water and nitrogen allocation. In this study, maize grain yields were predicted for 25 different amounts of irrigation water (350-1700 mm) and 46 different rates of nitrogen application (0-450 kg N/ha) were predicted using MSM (Maize Simulation Model) model. Irrigation water was distributed in growth period based on maize evapotranspiration. 30% and 70% nitrogen fertilization was used 19 and 50 days after planting date, respectively. Based on field operational costs and present market value in Fars province, optimal amounts of applied water and nitrogen were determined in different conditions of maximum yield (Wm and Nm, respectively), maximum profit under limited land (WL and NL, respectively) and maximum profit under limited water (Ww and Nw, respectively). At present market value ( 88 Rls m-3 for water, 1946 Rls kg-1 for nitrogen and 1570 Rls kg-1 for maize grain), the amounts of Wm, WL and Ww were 1336, 1008, 844 mm, respectively, and the amounts of Nm, NL and Nw were 450 kg N ha-1. Because of the low price of nitrogen, the optimum amounts of nitrogen in the analyzed conditions were similar. If the price of nitrogen and water are increased (i.e. 30000 Rls kg-1 N and 1000 Rls m-3 water), the optimum amounts of applied nitrogen and water in the analyzed conditions are changed to 450, 120 and 210 kg N ha-1, and 1336, 899 and 874 mm, respectively.

Microirrigation has the potential to minimize water droplet evaporation and wind drift losses associated with sprinkler irrigation, improving the irrigation control by frequent applications, providing the needed nutrients for crops through the system, minimizing deep percolation and improving crop yield. This study was conducted to evaluate sugar beet yield under conventional and alternate tape and furrow irrigation. The sugar beet pp22 was cultivated with 0.3 m row spacing. There were four treatments of tape irrigation (tapes from Iranian and foreign manufacturers) and two treatments of furrow irrigation. In each treatment four rows of sugar beet were grown. Alternate and every row irrigation was applied for both tape and furrow irrigation treatments. The amount of water used, irrigation application efficiency (Ea), water use efficiency (WUE), coefficient of uniformity (CU) of applied water and fertilizer in tape irrigation, white sugar percentage, gross sugar percentage, root yield, white sugar yield, gross sugar yield, the WUE of root yield, and the WUE of white sugar and gross sugar were assessed in a field experiment near the College of Agriculture of Shiraz University. The results showed that the amount of water used in tape irrigation treatments was 50 percent less than furrow irrigation treatments. The average Ea of tape and furrow irrigation was 90.7% and 52%, respectively. The CU of Iranian and foreign tape was 97% and 98%, while the CU of applied fertilizer was 97.5% and 94.5%, respectively. The highest white sugar percentage was found in alternate tape irrigation; however, the highest gross sugar percentage belonged to alternate furrow irrigation treatment. The highest root yield was obtained from Iranian tape irrigation treatment of all rows. The highest gross sugar yield was found in furrow irrigation; however, there was no significant difference among all treatments for white sugar yield. The amount of water used in tape irrigation was 58% of furrow irrigation, while the highest WUE of root yield, white sugar yield and gross sugar yield was found in the alternate tape irrigation. These values were the least for conventional furrow irrigation.

Optimal crop water requirement is needed for precise irrigation scheduling. Prediction of crop water requirements is a basic factor to achieve this goal. In this study, maize potential evapotranspiration (ETp) was prediced by maize simulation model (MSM). Then, it was evaluated and validated using experimental field data obtained in Agricultural Research Station of Shiraz University (Bajghah, Fars province) during 2003 and 2004. Comparison of measured volumetric soil water content with predicted values by MSM model in 2003 and 2004 indicated that this subroutine (prediction of maize evapotranspiration) did not need modification. Also, daily potential evapotranspiration of maize was estimated by using Penman-Monteith equation considering single and dual crop coefficients. Comparison between the results of predicted ETp by MSM model, calculated ETp by Penman-Monteith, and measured irrigation water and soil water content indicated that the prediction of ETp by MSM model was satisfactory. Model prediction of seasonal ETp, potential transpiration (Tp) and soil evaporation (E) were 831, 536 and 329 mm, respectively, in 2003, and 832, 518 and 314 mm, respectively, in 2004. The values of ETp, Tp and E calculated by Penman-Monteith method using dual crop coefficients were 693, 489 and 205 mm, respectively, in 2003, and 700, 487 and 213, respectively in 2004. Maximum rate of predicted potential ETp, Tp and E were 11.1, 8.2 and 5.1 mm d-1, respectively in 2003 and 13.0, 9.0 and 4.0 mm d-1, respectively in 2004. The values of calculated seasonal ETp by Penman-Monteith method using single crop coefficient were 615 and 632 mm in 2003, and 2004, respectively. Comparison between the results of predicted ETp by MSM model, calculated ETp by Penman-Monteith equation with single and dual crop coefficients (FAO-56) and measured values of irrigation water and soil water contents of root depth indicated that FAO-56 methods underestimated the ETp.

Irrigation water Scarcity is the major limiting factor for crop production in irrigated farming. Therefore, optimal use of water is influenced by seasonal rainfall especially where the water price is high. Nitrogen also plays a key role in plant nutrition. In this study, wheat grain yield production as a function of applied water (irrigation plus seasonal rainfall) and nitrogen fertilizer (applied plus soil residual nitrogen) using existing data of a field experiment, were used. This function was obtained based on the data from the Maraghah Agricultural Experiment station. Based on this production function, maximum attainable yield can be 8.12 t/ha obtained by the consumption of 1.56 m of water (irrigation plus rainfall) and 193 kg/ha of nitrogen. An economic analysis based on the Iso-Quant curve was conducted to optimize the application rates of production inputs (water and nitrogen). When land is limited, the optimum water and nitrogen use will be based on maximizing net returns from land unit area. The optimal levels of these inputs were determined on the basis of farmer ability for paying the costs of water and nitrogen. Furthermore, optimum amounts of water and nitrogen were determined for different levels of wheat yield. The results indicated that despite low price of irrigation water and nitrogen fertilizer, at present market value, optimum values of water were more variable than those of nitrogen, for its high effective role in wheat production. The results also indicated that when there is no limitation of the source and use of water and nitrogen, and farmers are also able to pay their costs, application of 1.47 m of water (irrigation plus rainfall) and 190 kg/ha of nitrogen (applied plus soil residual) will produce maximum profit per hectare, reaching Rls 12,207,506. When water is limited, optimum levels of water and nitrogen will be based on the maximizing profit per unit of water. In this analysis, the use of 0.556 m of water (irrigation plus rainfall) and 190 kg/ha of nitrogen (applied plus soil residual) resulted in maximum net income per unit of applied water (irrigation plus rainfall) amounting to Rls/m3 1203. This amount of water use, which is 64.4 % lower than its amount under maximum yield condition, resulted in 181 % increase of cultivated area. Graphic expansion path on the isolines of yield showed more dependence of wheat production on water than nitrogen. Therefore, the optimum amounts of nitrogen in the three mentioned conditions are close to each other due to its subsidized price and lower effect on wheat production relative to water.

Agricultural investigations use computer models for simulation of crop growth and field water management. By using these models, the effects of plant growth parameters on crop yields are simulated, hence, the experimental costs are reduced. In this paper, the model of MSM (Maize Simulation Model) was calibrated and validated for the prediction of maize forage production at Agricultural College, Shiraz University in 1382 and 1383 by using maize forage yield under furrow irrigation with four irrigation and three nitrogen treatments. Irrigation treatments were I4, I3, I2, and I1, with the depth of water 20% greater than, equal to, 20% and 40% less than potential crop water requirements, respectively. Nitrogen treatments were N3, N2, and N1, with the application of N as urea equal to 300, 150, and 0 kg N ha-1, respectively. After calibration and validation of MSM, it was used to estimate suitable planting dates, forage yield and net requirement of water discharge for planting at different dates. The results indicated that the net requirement of water discharge was reduced by gradual planting at different planting dates. By considering different planting dates for maize, from Ordibehest 20th to Tir 10th, the planting area might be increased 17.9%, compared with single planting date on Ordibehesht 30th under a given farm water discharge and full irrigation.

In the present research, for the development of Fars province minimum temperature atlas, minimum daily temperature data of 20 evaporative stations of Fars Regional Water Organization and five synoptic stations of Fars Meteorological Organization were used. At first, two starting times were selected for all of the stations. The first was the first day of Farvardin for analyzing the spring frost and the secend was the first day of Mehr for analyzing the autumn and winter frost. Also, the temperature range of 0 to –1.5 was classified as mild frost or freeze, the temperature range of -1.5 to –3 as the moderate frost or freeze and temperature below –3 as severe frost or freeze. The data of minimum temperatures, the first and the last days in which the three temperature ranges occurred and the day of the lowest temperature based on the two starting times were recorded. The selected number of days (dates) were fitted to the distribution functions by SMADA software and the best distribution function was identified using the statistical parameter Root Mean Square. The best fitted distribution functions were Pearson type III and log Pearson type III. Then, based on the fitted distribution function, the number of days for the occurrence of the first and last frost and number of days for the occurrence of the first lowest temperature were determined at 50 and 70% probability levels. Finally, each of these occurrence dates was plotted with Surfer software using the geographical positions of each station (longitude and latitude) for Fars province. Based on these plotted maps, the best days of planting and harvesting of the crops can be determined throughout the Fars province.

Iran with a cultivation area of 45000 ha and production of 150 ton/year is the number one saffron producer in the world. Planting of large size corms will increase flowering, but production of corms (number and size) may be affected by irrigation method or frequency. In this research which is performed in the farm of College of Agriculture, Shiraz University, the effects of method and frequency of irrigation on corm production, and the effect of produced corms on flowering were evaluated in two consecutive years. Two irrigation methods (basin and furrow) with four levels of irrigation frequencies (12, 24 and 36 days and dryland farming) were applied. In August of 2000 sample corm was taken from every plot, and the effect of applied treatment from previous growing period on corm production and the effect of produced corms on future flowering were evaluated and analyzed. Based on the results, in furrow irrigation, total number of corms and total number of corms smaller than 4 gr is significantly higher than basin irrigation. In all of the above cases, irrigation frequencies did not show a meaningful difference between themselves or in comparison with dryland farming treatment. Total weight of corms and number and weight of corms larger than 8 gr in basin irrigation were more than furrow irrigation. This is to the extent that it is considered as the main reason for the difference in the flowering of corms, and has caused the flowering of basin irrigation to be significantly higher than furrow irrigation. In basin irrigation, irrigation frequencies of 12 and 24 days had the highest amount of flowering. No significant difference was observed on average corm production between the treatments in the two irrigation methods. However, irrigation treatments in both irrigation methods showed significant differences when compared with dryland farming treatment. So, basin irrigation with irrigation frequency of 24 days is preferred over furrow irrigation due to lower water consumption and production of larger size corms which is effective in flowering.

Estimation of seepage is essential prior to lining of earth canals. In Iran such investigation has been achieved in some irrigation networks using empirical relationships derived in other countries. Estimation of water loss in canal is required in design, operation and management of water distribution systems. Water seepage may be determind by using empirical equations proposed by F.A.O. These equations are applicable for different soils and hydraulic parameters. However, the appropriate estimating equation should be determined for each region. Therefore, these equations should be calibrated for local usage and different canal vegetation conditions. In this investigation water losses in canals at the Rudast region of Isfahan were measured by inflow and outflow procedure. Different canals reaches were selected in soils of relatively heavy, medium and light textures. The density of vegetation population in canals were low, medium and high. The estimated seepage losses by different empirical equations were not corresponded to those of measured values. Therefore, by using the measured seepage at different soil textures and vegetation densities the empirical coefficients of six empirical equations of F.A.O. (Ingham, Davis and Wilson, Affengendon, Moritz, Molesworth and Yennidumia, Misra) were modified for the study region. The relationships between measured seepage and estimated seepage before and after modification of the empirical equations were determined by regression analysis. These equations estimated the seepage loss much smaller than the measured values. The regression parameters (selope, intercept, and coefficient of determination of regression equation) indicated that after modification, the Ingham and moritz equation with higher slopes (0.91, 1.01), lower intercepts (-0.096, -0.039) and higher coefficient of determination (0.96) estimated the closest seepage values to the measured values respectively. The misra equation was the next best equation for seepage estimation. The results of present investigation indicated that the modified Ingham and Moritz equations were the most appropriate ones for estimation of seepage losses at different soil textures and vegetation densities in the study region.

Hydraulic coefficients of a porous media such as hydraulic conductivity K(θ) and diffusivity D(θ) have a controlling role in the evaluation of groundwater flow and pollutant transport behavior. Therefore, successful porous media flow evaluation depends on the accurate determination of its hydraulic coefficients. But it is hard and time consuming to measure. Values for these coefficients accurately as measurements usually task place at a moisture range close to saturation. This situation justifies the preference for prediction models to be used. One method for evaluation of K(θ) and D(θ) coefficients is to use models which take measured soil moisture characteristic curve data into consideration. For the purposes of the present study, pressure plates apparatus measured the required data to develop soil moisture characteristic curve for nine various soil textures. The volume of instantaneous outgoing water was measured with respect to time and the total volume of water released at the end of each experiment was measured for a given pressure (0.1 to 1.5 Mpa) imposed on undisturbed soil samples. A simple equation based on Richard’s equation is provided for the estimation of K(θ) and D(θ). Application of Mualem, van Genuchten et. al, Burdine, Green and Corey, and Gardner models for estimation of the K(θ) and D(θ) values at a variety of nine varied soil textures under experiment showed a wide range of variation. Therefore, it is hard to simulate the accurate hydraulic conductivity behavior for the given varied soil textures by means of the models available. However, if the minimum and maximum simulated values obtained from the models at respective soil moisture contents are considered to be a permitted range, one may state that the results of the estimated hydraulic coefficients by the proposed method in this study lie within the permitted range or agree with the results of other models considered. Therefore, the proposed method for determination of K(θ) and D(θ) is capable of selecting the best simulation model to estimate hydraulic coefficient values.