مجله پژوهش آب در کشاورزی
سال بیست و هشتم شماره 4 (زمستان 1393)

Nowadays، mycorrhizal fungi are widely used due to their symbiosis relation with roots of so many plants. By facilitating absorption of some plant minerals and water، these fungi have a key role in all ecosystems. In this research، the effects of mycorrhizal fungi and different levels of phosphorous chemical fertilizers on some yield components and macro elements uptake of Zea mays L. under different levels of irrigation water were studied. The experiment was performed in completely randomized block as a split factorial design with four replications using different irrigation levels (A1=60، A2=120، A3=180 mm of evaporation from class A pan) as the main plots and different P levels (P1=0، P2=60 and P3=120 kg P/ha on the basis of P2O5) and mycorrhizal fungi (at two levels: un-inoculated and inoculated with 6 g of mycorrhizal inoculant placed 3 cm under each seed) in the subplots. The results indicated that the effects of Mycorrhizal inoculation were significant and positive on measured indices. Among triple interactions i. e. irrigation/ chemical phosphorus/ mycorrhizal inoculation، significant effects (p<0. 05) on grain yield (maximum 5045 kg/ha) and 1000 seed weight (157. 75 g) and also on P concentration (p<0. 01) were observed in treatments with proper amount of water and fertilizer P and mycorrhizal inoculation (A1P2G2). Under water stress، the highest grain yield، 1000 seed weight، fresh forage، and P concentration were obtained in treatment with moderate water stress and proper amount of chemical P (60g/kg) and mycorrhizal inoculation (A2P2G2). Also، the highest plant height (242. 87 cm) was obtained in the same treatment. Results showed that in moderate water stress، using proper amount of chemical P and mycorrhizal inoculation can compensate decrease in grain yield، while under high level of drought stress، grain yield decreased.

Several mathematical models exist that represent plant response to salinity. These models consider salinity of the soil saturation extract (ECe) for plant response to salinity in the root zone. A considerable step would be taken towards applying such models، if irrigation water salinity can be used instead of ECe، because under field conditions، irrigation water salinity measurement is much easier than determining soil salinity. The objectives of this study were to quantify basil response to irrigation water salinity، to estimate its yield salinity threshold value and to investigate efficiency of available mathematical models for estimating its yield based on irrigation water salinity. Consequently، a large experiment was conducted with 13 water salinity levels including 1. 175 (control treatment)، 1. 8، 2، 2. 2، 2. 5، 2. 8، 3، 3. 5، 4، 5، 6، 8، and 10 dSm-1. The designated salinity treatments were performed by diluting the Shoor River saline water with adequate quantity of fresh water. In order to quantify the salinity effect on basil yield، seven mathematical models were selected. The results indicated that basil yield reduction threshold value based on irrigation water salinity was 1. 7 dSm-1 with yield reduction gradient of 8. 1% per dSm-1. The mathematical model of Homaee et al. (2002) provided more accuracy than the other models in simulating basil yield reduction function based on irrigation water salinity. Overall، the results of this research indicated that root water uptake models of Homaee et al. (2002)، van Genuchten and Hoffman (1984) and two statistical models of Steppuhn et al. (2005) provide reasonable results for simulating basil yield response to irrigation water salinity، respectively (the least nRMSE and ME). The results further indicated that when enough leaching was applied، there would not be significant differences between the ECe-based models and those obtained based on irrigation water salinity.

Estimation of seepage from water channels are necessary in evaluating water productivity in agricultural sector as affected by floodwater spreading on plains and artificial recharge of groundwater. Several empirical seepage equations have been developed for this purpose. Previous research results in Iran have shown lots of variation in the coefficients and the empirical equations change in different areas and regions. It appears that locally calibrated theoretical equations could give satisfactory results for different conditions. For this purpose، actual measured seepage from earth channels (in the Roodasht region in Isfahan province) and Ingham empirical equation were used and compared with Wedernikow theoretical method. Differences between the measured values and estimated values of seepage in July and August were compared using RRMSE and MAE statistical indexes. The results showed that the average RRMSE and MAE statistics were 0. 275 and 0. 01 for the Ingham Method. But، these values were 0. 145 and 0. 005 for Wedernikow theoretical method. These indexes showed that Wedernikow theoretical equation gave the best result of seepage estimated values compared with empirical equations in Roodasht region channels. Moreover، the other advantage of the theoretical equation is that it can be developed and extended to various areas.

Water distribution method based on the type of water conduits can be divided into two groups، namely، open and closed systems، while on the basis of the energy of the water flow، the two groups are gravity flow and pressurized flow. Open channel type conveyance and distribution is achieved by gravity and includes channels made by embankment construction، excavation، or construction of prefabricated sections، as well as the use of underground pipes or closed ducts in which water flows by gravity (no pumping). If the required pressure for the flow of water is less than 10 meters، the conveyance and distribution method is grouped as low-pressure. In this research، the irrigation and drainage network of Sistan، which is a strategic region in east parts of Iran facing severe water shortage، was studied to suggest proper strategies. Three crops، namely، wheat، barley، and alfalfa were studied for economic analysis. The results showed that using a piped conveyance system would increase the net income and the gross benefits of the wheat and alfalfa growing farmers compared to open channel systems، but the area of barley should decrease. Furthermore، due to high costs of construction and low irrigation efficiency and poor water management، the net benefits of farmers under the two conveyance systems would not be significantly different. Thus، by using pressurized water conveyance systems from Chah-Nimeh reservoirs، the existing efficiency of 20%، would rise to 90%. Results revealed that the main problems in the network were deterioration of canals lining، poor performance of the regulating and distribution structures، and low efficiency of the network. Overall، the economic analysis of the project showed that water conveyance by pipe was economically more justified than open channels.

Realization of development، specially rural and agricultural development، as well as soil and water resources efficiency enhancement and irrigation networks management improvement depend on the beneficiaries’ participation. Therefore، it is necessary to have macro planning and to be aware of the factors influencing the beneficiaries'' active participation in irrigation networks management. Accordingly، this research was executed to investigate how irrigation and drainage networks could be developed based on the beneficiaries’ participatory strategies. The research area was in the Bozhan River، Neyshabour County، Iran. Research method was descriptive by using survey technique. The research instrument included a questionnaire. All the network beneficiaries were included in the research statistical population. Stratified random sampling was used to collect data from 254 beneficiaries. Findings revealed that among all variables of the research، ten variables including «referral of other farmers to a beneficiary (water user)»، «visiting demonstration farms»، «contact with extension agents»، «access to funds and facilities»، «educational background»، «accessible amount of water»، «cultivation area»، «awareness of advantages and disadvantages of participation»، «conflict background with Jihad Keshavarzi Organization» and «job satisfaction» could anticipate a total of 60 percent of the variation of the dependent variable of ‘beneficiaries’ participation’ in developing secondary and tertiary irrigation and drainage networks.

Irrigation management transfer to farmers is one of the important and necessary issues for irrigation planners globally. Irrigation management transfer or participatory irrigation management by water users’ associations (WUA) is a widespread strategy in the world and a good way to remove the country''s irrigation and drainage systems problems. The main objective of this research was responsibility analysis and barriers survey of water user association’s from the viewpoint of stakeholders. Population of study included all farmers of Feyzabad water supply network in the Fars Province (192 farmers). Sample size as estimated by stratified random sampling method was 127. A questionnaire was used to collect data whose face validity was confirmed by a panel of experts and pilot test was performed to evaluate its reliability، with the Cronbach''s alpha values for responsibilities and barriers of 0. 79 and 0. 86، respectively. The results revealed that the responsibilities of WUAs from the viewpoint of stakeholders were categorized in four groups: protection of irrigation networks، institutional responsibilities and agronomic responsibility، while for the barriers of WUAs، the four categorize were: social، organizational، awareness and knowledge، and farmers’ management barriers. Protection and operation of the irrigation network were the main responsibilities from the viewpoint of stakeholders. Therefore، it is recommended that، firstly، the responsibility of the irrigation network protection and exploitation be handed over to WUA، then، after capacity building and empowering of the stakeholders، the other responsibilities could be transferred to them.

For the proper use of water resources in agriculture، it is necessary to provide appropriate irrigation system to supply crop water requirement. In the present research، using a hierarchical analysis، different types of irrigation systems were evaluated and prioritized on 1150 hectares of agricultural land of Etka Organization ​​ located in Dorud، Iran. Hierarchical analysis process is one of the multi-criteria decision making techniques that can be used in different sciences. This method can enter effective qualitative and quantitative factors systematically into the decision-making model. At the first step of this research، the structure of the decision problem was designed and then different options were compared based on the criteria in decision making. Finally، the irrigation methods were prioritized. The results showed that in the case of furrow، sprinkler، and drip irrigation systems، sprinkler systems had priority over the other methods. At the end of the study، zoning of sprinkler system in the study area was designed and shown in maps.

Studying the effects of irrigation and drainage network on water table fluctuations is one of the important issues for management of ground water resources. In this study، the effects of establishing Gavoshan dam''s irrigation and drainage network on groundwater of Miandarband plain was investigated using conceptual، mathematical model GMS 6. 5. The first step to simulate this flood plain is investigating Miandarband''s climatological، geological، hydrological and hydrogeological parameters. Using the logs of observation wells، the stratification of layers was identified. The model was run under unsteady flow and calibrated by comparing the simulated water table depth with the depths measured in the piezometric wells for the time interval between May، 2005 and March، 2006. The model validation by using data of hydraulic head of March، 2008 showed an R2 of 0. 997. The model was used for exploitation time of irrigation and drainage network. After calibration and evaluation of the model، the effect of exploitation of the Gavoshan dam’s irrigation and drainage network on Miandarband groundwater 1، 5، and 10 years after operation was found to be 1. 8، 3. 2، and 5. 2 m rise in water table. Also، one year after the network operation، 6. 59% of the lands would be waterlogged، while this area increases to 37. 9% and 56. 28% in five and 10 years after operation of the network.

Soil water retention curve (SWRC) is important in the studies of soil and water relationship، soil conservation، irrigation scheduling، drainage، solute transport، plant growth and crop water stress. The performance of 10 models (Simons et al.، Libardy et al.، Campbell، Farrell and Larson، van Genuchten، Brooks and Corey، Driessen، Exponential Bruce-Luxmore، Power Bruce-Luxmore، and Rogowski) were evaluated using SWRC 3. 0 software. After statistical evaluation of the results، appropriate models were identified. Seventy three soil samples of tea fields in Lahijan city in Gilan province were selected and separated into soil textural classes. The soil moisture content at eight different matric potentials were measured. Using the statistical index of Root Mean Square Error (RMSE)، Akaike Index (AIC) and coefficient of determination (R2)، the accuracy of each model quality was identified. Results showed that in all textural classes the Simons et al. Model with a minimum RMSE (0. 0136 to 0. 0307 cm3 cm-3)، the lowest value of AIC (-1280)، and the highest coefficient of determination (0. 96 to 0. 98) had the best performance، while the power Bruce–Luxmor Model with the maximum RMSE (0. 0372 to 0. 0881 cm3 cm-3)، the highest value of AIC (-879)، and the minimum value of R2 coefficient (from 0. 81 to 0. 92) had the weakest performance. Libardi Model after Simons et al. Model had acceptable performance and better results than the other models. Overall، the Simons et al. and Libardi et al. models were recommend for determination of SWRC in Lahijan area soils.

In management of surface irrigation، infiltration function is important. Quantitative understanding of this phenomenon is essential in preventing soil erosion and water losses. The main objective of this study was to estimate the coefficients of infiltration equations (Kostiakov-Lewis، Philip، and Horton) and evaluate the sensitivity and performance of these equations under various initial (initial soil moisture) and boundary conditions (water head on soil surface). Therefore، two-dimensional infiltration for furrow irrigation were simulated by changing the initial soil moisture (before irrigation) and water head on soil surface (during irrigation) using the solution of the Richards’ equation (HYDRUS model). To determine the coefficients of infiltration equations، outputs of the HYDRUS model (cumulative infiltration over time) were fitted. Evaluating the performance of infiltration equations via statistical evaluation indicators showed that infiltration empirical equations (Kostiakov-Lewis and Horton) had better performance than the physical equation (Philip) to estimate the cumulative infiltration under various initial and boundary conditions. Kostiakov-Lewis equation ranked the first in all cases of estimating infiltration by simulations، followed by Horton and Philip equations. Sensitivity assessment of the coefficients of the equations showed the power coefficient (b) of Kostiakov-Lewis equation as the most sensitive coefficient، while the final infiltration rate coefficient (15ff«>) in Horton equation was the least sensitive. The results also showed that Horton equation was the most sensitive equation in evaluation of infiltration equations sensitivity.