مجله پژوهش آب در کشاورزی
سال سی‌ام شماره 3 (پاییز 1395)

Salt accumulation in the root zone and yield declining are the main problems in using saline water for irrigation in arid areas. So, this study was performed with the aim of investigating the effect of different management of wheat residues on maize (Mobin variety) yield and its components and soil salinity under irrigation with saline water. Therefore, a factorial experiment in a randomized complete block design was carried out in the Agricultural Farm of Shahid Chamran University, in one crop season. The first studied factor was different management use of wheat residues (M1: without use of crop residues, M2: use of crop residues on the soil surface as mulch, and M3: mix of crop residues with surface soil layer to 30 cm depth) and the second factor was irrigation water salinity (S1: Karun river water salinity: 2 dS/m , S2: 4.5 dS/m and S3: 7 dS/m). Management of crop residues as mulch and mixed with soil, compared with non- use of residues, decreased the salinity of surface layer on average by 16.1% and 7.8%, respectively, and transported the salts to lower layer. The effect of salinity and crop residues management on evapotranspiration, yield, and yield components was significant, but their interaction effect was significant only on evapotranspiration, grain yield, biomass, and ear length. So, the maximum effect of crop residues on adjusting the reduction of grain yield (14.6%) and biomass (19.8%) compared to the control was obtained in M2 and S2 treatments. Therefore, the use of crop residues as mulch can be recommended as an effective solution to reduce the negative effect of using saline water in agriculture.

In order to evaluate the role of a limited irrigation and agronomic management scenarios on improving yield and rain water productivity (WP) of rainfed wheat, a field study was conducted at multiple farms of Honam (Lorestan Province) in the upper Karkheh River Basin (KRB), Iran. The calibrated and validated AquaCrop model was used to define the best management scenario in order to enhance yield and WP of rainfed wheat in upper KRB in 2013-2014. In the next step, the best management scenarios were carried out in three research fields of rainfed wheat in 2014-2015. In field experiments, the treatments included two main management (traditional and advanced management) and two levels of limited irrigation (rainfed, single irrigation of 60 mm at spring time). According to the best scenario of AquaCrop model, spring single irrigation with constant depth of 60 mm was applied at three times (the first, middle and end of flowering period). The result shows that under rainfed conditions, by using the advanced management, rain water productivity of wheat increased by 36% as compared to traditional management. The results of this study showed that a single irrigation application at spring time (during flowering stage) increased the average total water productivity of wheat to 0.70 kg m-3, an increase of 74% as compared to the traditional management. The optimum program was obtained by a combination of advanced agronomic management package with single irrigation of 60 mm at the middle of flowering stage, which increased yield and WP of rainfed wheat to 176% and 134%, respectively, as compared to traditional management. Results of field experiments were in good agreement with the proposed scenarios by AquaCrop model.

Due to its biological nature and high dependence on regional condition, agriculture is the largest consumer of water resources in many countries. Hence, today, agricultural water management plays an important role in the use of water resources of these countries. The present study used Genetic Algorithm to optimize cultivation area, allocate irrigation water, and maximize profits gained from the cultivation of some crops under various weather conditions in Qazvin Plain (located in the north west of the central plateau of Iran), where some of the required water is obtained from Taleghan dam. In this study, different probability levels of rainfall, evaporation, and input flow of optimization were combined under four different weather conditions. The results showed that in normal, wet, dry, and hot - dry weather conditions, the profit earned from the new cultivation pattern introduced by the model was much more than that of the current pattern. Moreover, following this new pattern could mostly result in lower water consumption in this sector, such that the volume of water stored in the dam reservoir at the end of the operation in wet, normal, dry, and hot-dry conditions would increase by, respectively, 262045.2, 2862686.6, 273089 and 955542 m3. The results showed that the cultivation area of sugar beet in every of the four different condition was reduced (over 80%) because of its high water requirement and low yield, therefore, its cultivation is not recommended under any weather conditions in the studied area. Following the new cropping pattern delivered by this model, the farmers’ profit in wet, normal, dry, and hot-dry conditions would increase by, respectively, 2.81%, 2.62%, 1.34%, and 1.53% compared to the prevailing pattern.

Climate change will affect rice water requirement through changes in rice physiology and phenology, soil water balance, evapotranspiration, and green water. Adapting with this major environmental challenge is necessary to maintain or improve the current level of rice production in the future. Considering the vital role of Mazandaran province in supplying rice demand of Iran, this study was conducted to quantify the effects of climate change and different cropping calendars on irrigation water requirement and amounts of green water of the province during rice growing season. Using climatic data of Babolsar, Ghaemshahr, Noshahr, and Ramsar for the base period (1980- 2010) and LARS-WG downscaling model, the weather data of 2011- 2100 were generated under different climate scenarios. Based on the minimum and maximum temperatures, the same cultivation period between current and future periods was selected. Rice water requirement was determined by Neuro-fuzzy inference system. Performance evaluation of LARS-WG model using different statistics indicated suitability of the model to simulate future climate conditions in the region. Under climate change, rice cultivation can start 2 to 23 days earlier and the number of days to physiological maturity will be reduced by one to 20 days. Despite shortening the growing period, due to the negative effects of high temperature and decrease in green water, late planting dates will increase irrigation water requirement. However, suitable cultivation time will reduce rice water requirement of the future up to 681 m3 ha-1. The results demonstrated that management of rice cultivation calendar can be an effective way to achieve sustainable agriculture under future climate condition in Mazandaran province.

In order to estimate the production function of canola and Indian mustard under low irrigation, a factorial experiment was conducted based on completely random blocks in three replications during two growing seasons, 2013 and 2014, in the Agriculture and Natural Resources Research Station of Zahak, Sistan and Baluchistan province , Iran. The tested factors were the irrigation regime at three levels (irrigation after 50%, 70%, and 90% of soil moisture depletion by the plant, SWD); potassium rate at three levels of application (0, 150, and 250 kg potassium sulfate/ha), and their interaction effect on two species of the Brassica genus including oilseed rape (Hyola hybrid 401) and mustard (the native cultivar of India). In this paper, the effects of low irrigation on production functions, costs, profits, and revenue of both Hindi Rape and mustard were investigated. Four tyip types of production function were considered including Quadratic, Traonlog, Cobb-Douglas and Leontieof. And by using econometric tests, the best form of function in terms of its processing fitness in rape and mustard was identified as the quadratic function. The economic analysis results showed that 70% SWD treatment and 90% SWD with application of 250 kg potassium sulfate fertilizer, respectively, had the highest profit in terms of the consumed water and the benefit to cost ratio, so, they were introduced as the superior treatments in production of canola and mustard.

Crop models are suitable for simulation of crop yield by different scenarios of deficit irrigation and salinity. In this research, the AquaCrop model was evaluated to simulate the soybean grain yield and biomass under different levels of salinity and deficit irrigation in Gorgan County during 2011 and 2012 growing seasons. The model was calibrated by experimental data of 2011 and validated with data of 2012. The experiment included three irrigation levels of 100%, 75% and 55% water requirement and three salinity levels of 0.7, 5 and 10 dS/m. Statistical indices of the results of validated model including RMSE, E, and d for grain yield were 0.225 ton/ha, 0.88 and 0.97, respectively, and for biomass, they were 0.718 ton/ha, 0.77 and 0.95, respectively. Results showed that grain yield decreased with decrease in the amount of irrigation water and increase in salinity level. Further analysis showed that the sensitivity of AquaCrop model to the canopy decline coefficient (CDC) was more than the other parameters at senescence and maximum canopy cover stages.

In order to investigate the effect of salinity on morphological, physiological and biochemical characteristics of Lisianthus, a pot experiment was conducted hydroponically in sand. Two Lisianthus varieties (‘Champagne’ and ‘Pure White’) and four NaCl concentrations (0, 20, 40, 60 mM) were combined factorially based on a complete randomized design with four replications. The result showed that as salinity increased plant height and fresh and dry weights decreased. Also, chlorophyll a content, photosynthesis rate, and relative water content of plants treated with 60 mM NaCl were, respectively, 31%, 62%, and 20%, lower than the controls. In addition, root length increased with increasing salinity, so that in plants treated with 60 mM NaCl root length was 43% larger than the controls. Further, electrolyte leakage and Malondialdehyde (MDA) content increased with increasing salinity. Results revealed that dry weight, plant height, and photosynthesis rate in ‘Pure White’ were, respectively, 47%, 27%, and 31% higher than in ‘Champagne’. Moreover, under salinity stress, ‘Pure White’ could maintain better morphological and physiological characteristics, i.e. plant height, dry weight, relative water content and cell wall stability compared with ‘Champagne’.

Evapotranspiration of orchard crops is often determined by indirect method and based on meteorological data due to the difficulties inherent in direct measurement instruments such as installation of large lysimeters or precision equipment, and long growing seasons of tree crops. Evapotranspiration estimation with sufficient accuracy is not feasible due to spatial variability of meteorological parameters and, sometimes, due to inappropriate distribution of meteorological stations. Therefore, using methods based on remote sensing, which account for these variations, is much more desirable. In this research, evapotranspiration of olive trees at different phonologic stages was measured using direct and indirect methods in Tarom district of Zanjan Province. In the direct method, actual evapotranspiration was determined by measuring moisture balance components, whilst in the indirect one, it was specified with the help of satellite imagery, the SEBAL algorithms, and Penman-Monteith equation. Olive crop coefficient was subsequently calculated and evaluated by determining reference crop evapotranspiration. The results indicated that evapotranspiration calculated by the remote sensing method at different stages of the growth had acceptable conformity with soil moisture balance data and evapotranspiration values obtained from the Penman–Monteith equation (the respective correlation coefficients were 0.95 and 0.88) and both evapotranspiration curves along the growing season had a similar increasing and decreasing trend. Moreover, crop coefficient obtained by the SEBAL algorithm and the water balance methods were well correlated (R2=0.86) and the remote sensing method with the aforementioned advantages can be used in predicting evapotranspiration.

Beneficiarie's satisfaction plays a key role in the effectiveness of water users’ associations (WUAs). Any purposeful planning in order to empower these organizations, as well as sustainable management of water resources, requires knowledge of the farmers’ satisfactions. The aim of this correlational- descriptive study was to investigate effective factors on beneficiary’s satisfaction. Research tool was a researcher-made questionnaire whose validity was confirmed by experts and its reliability was approved by conducting a pilot study and calculation of Cronbach's alpha coefficient higher than 0.7 for the composite indicators. The statistical population consisted of all members of six WUAs in Sahand Dam Basin (N= 270) and, based on Krejci and Morgan sampling table, 155 were selected by using randomized stratified sampling method. Data was collected by personal interview and analyzed through software SPSS18. The results showed that 86.2 percent of the beneficiaries had a medium level of satisfaction and their satisfaction had a significant positive correlation with personal, social, and educational-information variables. Regression analysis showed that three variables, namely, social trust, households’ number, and income from the second job explained 44.3 percent of the satisfaction variance. Training courses in accordance with the principles of adult education can increase member's awareness of association, build trust among members, and increase their satisfaction.

Reuse of treated municipal wastewater in agriculture and artificial recharge of aquifers in arid and semi-arid regions are of great interest to water resources specialists. In the use of treated wastewater for artificial recharge operations, the fate of substances added to the soil by wastewater transmission of pollutants to the aquifer depth and movement is very important, because they may cause contamination of soil and groundwater resources. In this study, an L-shaped cylindrical column, made of PVC with a diameter of 30 cm was used to simulate the vertical movement of water and its movement in the shallow groundwater layer during artificial recharge operations. Horizontal sections along the vertical length were 300 cm and 250 cm. The column was filled with a sandy loam soil and the treated wastewater of Mahdasht treatment plant located in Alborz Province was used for artificial recharge operations. During the test period, the effect of management strategy of permanent water logging for 40 days and a dry period for the removal of wastewater pollutants in the soil column were examined. Values ​of BOD5, COD, EC, coliform, fecal coliform, phosphorus and nitrate in water samples collected from the inlet and the path length were measured at one meter intervals. The results indicated the high efficiency of removing pollutants in the soil column, while the nitrate removal efficiency and EC changes were low. The values ​of BOD5, COD, EC, coliform, fecal coliform, phosphorus and nitrate in the best of cases were 96.4%, 91.8%, 15.4%, 99.3%, 99.4%, 92.4% and 17.2%, respectively. A comparison with National Guides of Iranian Environmental Protection Agency shows that the outflow of artificial recharge system can be used for irrigation of agricultural crops. However, it is to be noted that, generally, use of wastewater for irrigation of food crops is not recommended.

Food security, drought, environment protection, and industrial development have made efficient water resources management necessary. The concept of (virtual) water footprint (WF) has a considerable potential to help improve water resources management, especially in agriculture. In this research, WF of barley production in 15 major barley-producing provinces of Iran was estimated. WF consists of green (effective precipitation), blue (net irrigation requirements), gray (to dilute pollutants to the maximum acceptable concentration level) and white (irrigation losses) components. The results show that the average total WF in Iran’s national barley production for the period 2005-2011 is around 9172 MCM/year, of which the share of green, blue, gray and white WF were 37%, 19%, 17%, and 27 percent, respectively. Nearly 44 percent of total WF was related to the gray and white components, which is a considerable amount. Around 85 percent of the total WF in barley production is consumed in 15 major barley-producing provinces. Khorasan, Isfahan, and Fars provinces have the highest values of total WF in barley production, with 2364, 518 and 489 MCM/year, respectively. Among the 15 selected provinces, the average total WF in irrigated lands was estimated at around 3209 m3/ton with the contribution of green, blue, gray, and white components being 20%, 26%, 18%, and 36 percent, respectively. For rainfed lands, the average total WF was 2594 m3/ton with 89% and 11 percent of green and gray WF, respectively.