مجله پژوهش آب در کشاورزی
سال سی و دوم شماره 1 (بهار 1397)

In rice cultivation, mid-season and end-season drainage at harvest time are two important operations of water management which, respectively, increase yield and provide better conditions for harvesting rice. Due to the unique conditions of paddy fields of Guilan province, making decisions about the spacing and depth of drains and proper equation to determine the drainage spacing in paddy field requires research on the mid-season and end-season drainage. Therefore, in this research, the efficiency of drains spacing (L) and depth (D) of subsurface drainage in controlling water table and also accuracy of the steady and non-steady equations were evaluated at mid-season and end-season drainage stages in Guilan’s rice fields. Drainage treatments included six conventional subsurface drainage systems with rice husk envelope including drainage system with drain depth of 0.8 m and drain spacing of 7.5 m (L7.5 D0.8), (L10 D0.8), (L15 D0.8), (L7.5 D1), (L10 D1), and (L15 D1). All drain lines were 40 m long and made of PVC corrugated pipes with a diameter of 125 mm. Results showed that subsurface drainage with spacing of 15 m and depth of 80 cm (due to the proper water table depth and higher yield) and subsurface drainage with distance of 10 m and depth of 80 cm (due to the highest resistance to pentrometer penetration and the lowest soil moisture content) are recommended as the best drainage treatment for mid-season and end-season drainage, respectively. Dagan, Hooghoudt and Bouwer & Van Schilfgaarde equations combined with Hooghoudt equation were suitable equations for determining drainage spacing at mid-season drainage stage. Hooghoudt, Kirkham, Dagan, Bouwer & Van Schilfgaarde equations combined with Hooghoudt equation and Glover-Dumm equation were selected as suitable formulas for determining the spacing of subsurface drains for end-season drainage.

Individual effects of conservation tillage and irrigation methods on corn yield and water productivity have been adequately investigated so far, but simultaneous effects of these treatments on corn production have not received enough attention. Therefore, in this research, effect of conservation tillage and irrigation methods on soil properties, water productivity, and corn yield was evaluated using a split plot experimental design with nine treatments and three replications. Main plots were allocated to irrigation methods including surface irrigation (gated pipe), tape irrigation, and sprinkler irrigation. Tillage methods including zero tillage (direct drilling), reduced tillage, and conventional tillage were in the sub plots. Soil bulk density, forage moisture content, water consumption, corn yield, and water productivity were measured in different tillage and irrigation treatments. Results showed that no-till increased soil bulk density at soil depth of 0-10 cm compared to the reduced and conventional tillage methods (9 and 4%, respectively); while, irrigation method had no significant effect on soil bulk density. Irrigation method had a significant effect on corn grain yield so that pressurized irrigation methods had the maximum corn yield, while the minimum corn yield was obtained from the surface irrigation. However, corn yield was not affected by tillage method. The maximum water consumption occurred in surface irrigation, and drip irrigation had the minimum. Drip irrigation saved 34% and 57% water compared to the sprinkler and surface irrigation methods, respectively. Water productivity in corn was significantly affected by irrigation methods; while, tillage methods had no significant effect on water productivity. The maximum water productivity (1.22 kg/m3 on average) was obtained in drip irrigation and the minimum water productivity (0.34 kg/m3 on average) belonged to the surface irrigation.

Kashmar plain is located in an arid region and recent consecutive drought events have attracted serious attention to water use management. In this research, the effects of four levels of super absorbent polymer A200 (0(V0), 0.1% (V1), 0.2% (V2) and 0.3% (V3) wt%), four levels of vermicompost (0(V0), 7(V1), 10(V2) and 15(V3) tons per hectare), and three levels of irrigation (60%(W1), 80%(W2) and 100%(W3) of water requirement) were evaluated on water use efficiency (Irrigation water and rain) (WUE) and irrigation water use (WUEi) of wheat. The study was conducted in research farm of Kashmar Higher Education Institute. Factorial experiment was performed using a completely randomized design with 144 pots. The results showed the highest WUE and WUEi in S3V3W3 treatment as 1.49 kg/m3/ha and 2.26 kg/m3/ha, respectively. The lowest WUE and WUEi were observed in S0V0W1 treatment and were 1.03 kg/m3/ha and 1.56 kg/m3/ha, respectively. Totally, it can be concluded that superabsorbent and vermicompost increased the WUE and WUEi. Under the conditions of this experiment, according to the analysis of variance, the combined application of superabsorbent and vermicompost was not significant. Also, according to the comparison of means at 5% significance level, in separate application of superabsorbent and vermicompost, the best value for achieving maximum WUE and WUEi is 0.2% (weight percent) superabsorbent or 10 ton/ha of vermicompost. By using the maximum superabsorbent and vermicompost and increasing water application from 60% to 80% and from 80% to 100%, WUEi increased by 6.5 percent and 19.7 percent, respectively.

Improvement of water productivity is very essential for achieving water and food security. One of the basic strategies in this field is determination of crop yield gap and water productivity gap, which is the difference between the present actual situation and the potential situation. This research was carried out for wheat in Qazvin province according to GYGA protocols, which is an international methodology. At first, the map of climatic zones of the province was prepared based on Emberger method by using GIS. Then potential yield gap of wheat was estimated according to calibration and simulation of version 5 of Aqua crop model. Results showed that yield gap in various climate zones of the province was between 4502-6271 kg/ha, evapotranspiration water productivity gap was between 0.56-0.66 kg/m3 and water (irrigation and effective rain) productivity gap was between 0.57-0.71 kg/m3. Results showed that actual wheat yield in Qazvin province is 37 percent of the potential yield. Also, relative evapotranspiration water productivity index was 0.47 and relative water productivity index was 0.31. These indices show the ratio of the actual to potential productivities. Based on this research results, the extent of gap between optimum and current condition of yield and water productivity is very wide. Yield gap is 63% of potential yield and water productivity gap is 69% of potential water productivity. This issue represents the considerable weakness existing in management of agricultural production and irrigation and reflects the potential opportunities for strengthening these operation, improving water productivity, decreasing the pressure on water resources, and increasing food security.

The inputs of water and fertilizer are important in agricultural production, with a shortage of each one reducing the yield of the product. The role and importance of each of the factors of water and fertilizer separately can be effective in increasing yield. The purpose of this study was to evaluate the effect of irrigation and nitrogen fertilizer on production function and water productivity in peanut plant in Guil cultivar. The experiment was conducted as a split plot based on randomized complete block design with 3 replications, in 2009 in Astaneh Ashrafiyeh. The main treatments included: without irrigation (control) and irrigation with intervals of 6, 12, and 18 days, while the sub treatments were nitrogen fertilizer rates of 0, 30, 60, and 90 kg ha-1. A quadratic equation was used to estimate the water-fertilizer production function. The results of production function estimation indicated that seed yield increased with nitrogen fertilizer up to 60 kg ha-1. But, with a gradual increase in nitrogen fertilizer, yield was reduced. Increasing nitrogen fertilizer from 60 kg ha-1 in different amounts of water consumed had no effect on yield increase. Water productivity and the water utilization rate in the irrigation interval of 6 days, with consumption of 328 mm, was the highest. In the irrigation interval of 6 days and consumption of 60 kg N-fertilizer ha-1, the maximum amount of water productivity was 0.96 kg m-3.

In arid and semi-arid regions, such as Iran, it is inevitable to use wastewater for irrigation. In this regard, the present research was conducted using a completely randomized block design with three replications and five irrigation treatments. The study included well water (control):T1, municipal wastewater of Torbat Heydarieh city:T2, combining 50% well water and 50% wastewater: T3, alternative irrigation with well water and wastewater: T4, and the combination of 34% well water and 66% wastewater (used farmers) T5. Based on the results obtained from the mean square of the traits, effect of the type of irrigation water was significant on yield, number of boll per plant, number of leaves, and plant height at a probability level of 1% (P

One of the most important parameters in designing, managing, and operating surface and subsurface drip irrigation systems is the advance velocity of the wetting (moisture) front in soil, which enormously affects the performance of these systems. Emitter discharge, soil type (soil texture and structure) and initial moisture content are the main factors affecting advance velocity under drip irrigation. Experiments were carried out in a transparent plexiglass tank (0.5 m*1.22 m*3 m) using three different soil textures (light, heavy, and medium). The drippers were installed at 4 different soil depths (surface, 15 cm, 30 cm, and 45 cm). The emitter outflows were considered 2.4, 4, and 6 L/hr. A simulation model was developed using artificial neural network (ANN) for predicting advance velocity of the wetting front (horizontal, downward, and upward direction) under point sources in surface and subsurface drip irrigation. The variables affecting wetting pattern included emitter discharge, emitter installation depth, application time, saturated hydraulic conductivity, soil bulk density, initial soil moisture content, and the proportions of sand, silt and clay in the soil. The results of the comparisons between the simulated and measured values showed that the ANN model was capable of predicting the advance velocity of the wetting front in different directions with high accuracy. The values of Root Mean Square Error (RMSE) varied from 0.09 to 0.35, from 0.02 to 0.17, and from 0.08 to 0.25 cm/min for horizontal, downward and upward velocity, respectively. Also, the values of Mean Absolute Error (MAE) varied from 0.06 to 0.27, from 0.02 to 0.07, and from 0.05 to 0.12 cm/min for horizontal, downward, and upward velocity, respectively. Using these models in designing and operating surface and subsurface drip irrigation systems could improve system performance.

Evaluation of soil moisture transfer between two subsurface drains and water drainage from the roots is very important. In this regard, application of conservation of mass equations by HYDRUS-2D software, in addition to reducing costs, could speed up access to the results. In this study, a subsurface drainage systems with drain depth of 0.9 m, drain spacing of 30 m, and groundwater depth of 50 cm was studied during one growing season of canola in paddy fields located in Sari region. Soil profile was considered from the surface to a depth of two meters and six layers of soil were defined. Soil saturated hydraulic conductivity (K) for each of the 6 layers of the soil was calculated by Piezometric method and using Kirkham equation. The K values for the surface layer down to the layer at the depth of 2 m were, respectively, 0.8, 0.11, 0.29, 0.16, 0.38 and 0.083 m/day. Other input parameters of HYDRUS-2D model were measured every day including precipitation, water table depth, and soil moisture. Observed data and simulated water tables between the two drain pipes were compared and the model was calibrated in saturated period. The performance of the model was evaluated by statistical approaches considering root mean square error (RMSE), the coefficient of determination (R2), the average deviation (AD) percent error (PE) and the modeling efficiency (EF), which were 0.0214 cm3/cm3, 0.932, 0.0407 cm3/cm3, 0.079, and 0.525, respectively. The results showed that simulation was considerably satisfactory.

In order to study the effect of biofertilizers, chemical fertilizers, and water deficit stress on biological yield, lawsone content, and root colonization with mycorrhiza in henna[1] an experiment was conducted at research greenhouse of Bam University in 2014 and 2015 growing seasons. The treatments included fertilizers (without any fertilizer (), humic acid (), application of mycorrhizae and vermicompost (), vermicompost (), and chemical fertilizer () and water deficit levels (100% water requirement (I1), 80% W.R (I2), and 60% (I3). The treatments were arranged as factorial in a randomized complete blocks design with fifteen treatments and three replications. Results showed that the highest weight of dry leaf, no. of leaves, and biological yield were obtained with application of mycorrhizae and vermicompost treatment under full irrigation (). With increasing stress severity, the highest weight of dry leaf (0.153g), no. of leaves (171), and plant height (120.33 cm) were obtained in , largest number of nodules (63) in (), and maximum biological yield (5.21 g/plant), total lawsone content (69.6 mg/g), and colonization with roots (82.2%) was obtained with application of mycorrhizae and vermicompost treatment under 60% water requirement i.e. treatment. It seems that biofertilizers can be considered as a replacement for chemical fertilizers in henna medicinal plant production.

Rice is the second most important staple food after wheat in the world, and Iran has an annual production of 2 M tons. Due to water scarcity problems and high water consumption in paddy fields and the need to increase irrigation water productivity, a lot of paddy fields are consolidated in the Northern provinces of Iran every year. In consolidation projects, soil is displaced by leveling practice, and then the content of soil chemical elements will be changed. This study was aimed to investigate the role of consolidation projects in paddy fields on soil and drainage water quality. The research was conducted in Astaneh Ashrafiyeh in Guilan Province on traditional and consolidated paddy fields in 3 situations (upland, middle land, and lowland) with 5 replication, in 2016. The soil and outlet/drainage water chemical properties were analyzed based on split plot design with Tucke’s mean analysis method. The soil physical and chemical characteristics results showed that the amount of SAR, Cl, NO ­3 and SO 4 in consolidated fields were significantly different than that in traditional fields. The amount of SP and OC of soil in consolidated fields were, respectively, 22% and 11%, more than that in traditional fields, and available potassium was 2% less than traditional farms. Also, the amount of SAR and Cl and NO 3 of outlet water in consolidated fields were, respectively, 14%, 23%, and 49%, more than that in traditional fields. All soil mineral components, other than clay, land had less uniformity in levelled lands than traditional lands. Uniform distribution of mineral components in levelled lands can be effective in improving irrigation and nutrition management of plants. In addition to infrastructural changes, the leveling of rice paddies also causes changes in physical and chemical conditions of the soil, as well as changes in the quality of drainage water, which should be considered in agricultural management and reuse of outlet drainage water in downstream farms.

One of the main components of sustainable water management is attraction of farmers’ participation in management and maintenance of water networks. Moreover, attraction of farmers’ participation in the process of planning, designing, building, and exploitation of the projects (based on popular organizations and groups) can impact optimal water management. The purpose of this case study was to investigate the effect of participatory management on optimal water use in Payvand Production Cooperative of Aqqala County, Golestan province, Iran. Survey method and questionnaire was used to collect the required data. Target population included 400 farmers of cooperative members in 7 villages with participatory irrigation management project in Aqqala County. Using Cochran formula, 196 farmers were selected with random sampling method. Validity of research questionnaires was confirmed based on view of experts and its reliability was verified by calculation of Cronbache's alpha coefficients for scale of optimal management, (0.8) satisfaction of project, (0.77) participatory project management, (0.83) and awareness of the current situation (0.73). The comparison of the optimal water management, before and after the implementation of the project by using of Wilcoxon test showed that there was significant difference in means ranking. The result of path analysis showed that the highest impact on final dependent variables of optimal water management was related to “awareness of the present situation of irrigation system”. The variables of level of participation and satisfaction with implementation of the project, background of membership in the cooperative, access to farm road, type of irrigation method, and education were in the next ranks, respectively. In contrast, having a second job had negative effect on optimal water management.

Considering the limited water resources in arid and semi-arid climate of Iran, deficit irrigation is one of the strategies for efficient use of water and increasing water use efficiency in agricultural districts. In order to study the effects of deficit irrigation on the quantitative traits of Thymus vulgaris L., an experiment was conducted in Kerman Municipality seedling production station in 2016. The experimental treatments were arranged as randomized complete block design with three replications. The irrigation regimes consisted of full irrigation (FI-100), regulated deficit (RDI75% and RDI55%) and partial root zone drying irrigation (PRD75% and PRD55%). The results showed that the highest herbage dry weight (1670.6 kg/ha) and leaf area index in different stages of growth were produced by full irrigation treatment, while no significant difference between this treatment and PRD75 was observed. Also, the highest number of shoots (64.4) and plant height (39.4 cm) were produced by full irrigation treatment and there was significant difference between this treatment and other treatments. However, the highest water use efficiency (0.66 kg/m3), root fresh weight (4.5 g), root depth (15.8 cm) and root volume (2.8 cm3 per plant) appeared in PRD75. Therefore, 75 percent water replacement in partial root zone drying irrigation treatments, in addition to saving water consumption, provides better use of soil moisture and sunlight. Thus, this treatment can be considered as suitable approach to cope with the water crisis and achieve a sustainable agriculture.