Journal of Water Research in Agriculture
Year:2016 | Volume:30 | Issue:1|Papers Count:11

In order to determine the effects of deficit irrigation on qualitative and quantitative characteristics of wheat cv. Hamoon, an experiment was conducted with two irrigation treatments including closed-end border with cut back and corrugation method (as the main plots) and three amounts of irrigation treatments (in subplots) including full irrigation (T1), 75% of full irrigation (T2), and 55% of full irrigation (T3). The experimental design was a randomized complete block in a split plot arrangement in three replicates and was conducted at Zabol Research Station for 2 years. The measured parameters included height of plant and spike, number of seeds per spike, number of spikes per m2, weight of 1000 seeds, biological yield, seed yield, and water use efficiency. Results showed that irrigation methods did not have any significant effect on the abovementioned characters, but amount of irrigation treatment had significant effect on growth factors of plant. The mean of water use in full irrigation (T1), T2, and T3 were 4473, 3505, and 2730 m3/ha, respectively, and water use efficiency was obtained in the range of 0.95- 1.17 kg/m3. In general, the treatment of 75% of full irrigation in border method with water use efficiency of 1.15 kg/m3 and yield of 4040 kg/ha is recommended for deficit irrigation in Sistan region.

Today, even in humid areas, the water crisis is a major problem for agriculture and increasing the efficiency of water use is also one of the requirements for sustainable development. Regarding this, the use of plant growth simulation models as a tool for managing water crisis seems useful. In this study, WOFOST model to simulate the performance of two soybean cultivars (DPX and SEPIDEH) under deficit irrigation was used in the Gorgan region. Using the measured plant yield and simulated water balance components from the model, the average productivity of evapotranspiration (WPET), based on seed yield, was obtained as 0.72 kg m-3. With increasing water stress, water use efficiency based on irrigation and precipitation series (WPI+R) and water use efficiency based on irrigation (WPI) increased in both cultivars, but the DPX water use efficiency under drought stress was higher than the SEPIDEH cultivar. According to the results and accuracy of WOFOST model, index of relative root mean square errors of seed yield and total biomass in both cultivars was less than 10%, the index of the coefficient of residual mass (CRM) was close to zero, the performance factor (EF) was 0.89, the coefficient of determination (R2) equaled 0.93, and the index of Willmott agreement (IOA) was about 0.89. Overall, based on the findings of this study, favorable performance of the model to simulate the growth process and water impact on soybean seed yield and water efficiency is confirmed and cultivar DPX is recommended for cultivation in the Golestan province.

To study the effects of irrigation water (50%, 75%, and 100% of plant water requirement) and potassium fertilizer (0, 50%, and 100% required potassium fertilizer based on soil test) on the dynamics of root, yield, and shoots of sorghum varieties (Pegah, Karaj, and Speedfeed), a research was conducted in the Agricultural Research Center of Semnan province (Shahrood) in 2014. This research was conducted in pots and in field experiment. The experimental variables were irrigation water, potassium fertilizer, and varieties of forage sorghum. The treatments were arranged as split plots based on a randomized complete block design with three replications. In the pot experiment, 243 plastic pots with diameter of 30 and height of 60 cm were used. Irrigation water was calculated with Penman-Monteith method. Drip irrigation was used as irrigation system. Sampling was carried out from the roots in three phases during the season. The root volume was determined by immersion in water method. Shoots parameters such as leaf area, leaf dry weight, stem dry weight, and shoot weight were measured. The results showed that the effects of irrigation water, potassium fertilizer, and sorghum varieties were significant on the forage yield, root volume, and dry weight of roots and shoots of the plants. The highest yield was obtained from the W100K100 treatment (102.8 ton/ha). Pegha variety showed the maximum yield. The maximum water use efficiency was obtained from the W75K100 treatment (20.5 kg/m3/ha). The W75K100Vp treatment was introduced as a superior treatment. Potassium fertilizer could compensate the loss of yield. The mathematical equations expressing root volume and dry weight with time were determined during the season. The relationships between some parameters of the shoots and roots were determined.

More than 90 percent of Iranian pistachio orchards are irrigated using surface methods, thus, changing or improvement of irrigation systems is necessary considering the declining water resources. The present research was carried out to investigation the effect of changing irrigation system from surface to drip on mature pistachio orchards (cultivar Ahmad Aghaei) in 2013 and 2014 in Zarandiye region of Saveh, Iran. The experiment was performed as factorial in a completely randomized block design (CRBD) with irrigation methods (surface and drip irrigation) and years of the experiment implementation as the second level variable, in three replications. Some quantitative and qualitative parameters of pistachio yield as well as growth of annual branch and water use efficiency were measured during the experiment. The results showed that irrigation system change of mature pistachio trees from surface to drip was possible. Irrigation system change was significant in dry yield, number of seed in ounce, percent of blankness, growth of annual branch, leaf area, and the 100 seed weight of pistachio at P£0.05. In the first year experiment, a reduction in performance and quality of yield was observed in drip irrigation compared to surface irrigation, but, in the second year, enhancing of performance and improvement in quality of pistachio in drip irrigation in comparison to surface irrigation showed adaptability of pistachio trees to change of irrigation system. The 2-year means of dry yield, water consumption, and the amount of water use efficiency in surface and drip methods were obtained at 739 and 927 kg per ha, 6375 and 4110 m3 per ha, and 125 and 190 g of dry yield per m3 of water, respectively. Because of alternative bearing, it is recommended to perform these tests for four successive years, so that the results would be more reliable for recommendation purposes.

Using simulation models is a strategy in agricultural water use management and in predicting effect of saline water on crop yield and soil salinity. In this study, soil salinity and forage maize yield were evaluated under alternating application of saline water with fresh water using SWAP and SALTMED models. For this purpose, field experiments were carried out under different treatments of fixed and cyclic use of saline (salinity levels of 3.5 and 5.7 dS.m-1) and non-saline water (non-saline water application in every one, three, and five saline water application) in Karaj region. Electrical conductivity of the non-saline water was 0.4 dS.m-1. Crop yield and soil salinity were simulated via both models and compared with their corresponding measured values. In SWAP model, coefficient of determination (R2) values were 0.754 and 0.587 for soil salinity and crop yield, respectively, while these values were 0.758 and 0.846, respectively, for SALTMED model. Absolute Relative error (|RE|) of SWAP model varied between 1.7% and 26.3% in crop yield estimation and varied between 2.5% and 32.4% in soil salinity estimation. Also, |RE| of SALTMED model ranged from 0.9% to 24.7% in estimation of crop yield, and ranged from 2.2% to 38.2% in case of soil salinity estimation.

In order to investigate the effect of different levels of salinity on physiological traits in fenugreek, an experiment was conducted at the greenhouse of Ferdowsi University of Mashhad, using Completely Randomized Design with 10 replications. Treatments included irrigation water salinities of 0, 60, 120, and 180 mM sodium chloride. The results showed that different levels of salinity had negative effects on physiological characteristics at 60, 120, and 180 mM sodium chloride and reduced shoot biomass by 37%, 50%, and 53%; fruit biomass by 8%, 34%, and 45%; and 16% of chlorophyll index and 0, 4%, and 27% chlorophyll a/b, respectively, compared with 0 mM sodium chloride.

Evapotranspiration is one of the most important components in the optimization of water use in agriculture and water resources management. In recent years, artificial intelligence methods and wavelet based hybrid model have been used for forecasting of hydrological parameters. In the present study, applications of the adaptive network-based fuzzy inference system (ANFIS) and Wavelet-ANFIS models to forecast weekly reference evapotranspiration at the synoptic stations of Tabriz, Ahvaz, Bandar Abbas, and Ramsar were investigated. For this purpose, a 20-year statistical period (1990-2009) was considered: 15 years (1990-2004) for training and the final five years (2005-2009) for testing the various models. Various combinations of input data (various lag times) and different kinds of mother wavelets were evaluated. Results showed that, compared to the ANFIS model, the hybrid model Wavelet-ANFIS had greater ability and accuracy in forecasting weekly evapotranspiration at all of the four synoptic stations. Moreover, the use of yearly lag times in the ANFIS model increased its accuracy. However, in the Wavelet-ANFIS, yearly lags not only did not increase the accuracy of the Wavelet-ANFIS model, but also reduced its accuracy in some cases. Investigation of various kinds of mother wavelets also indicated that the Meyer wavelet was the most suitable mother wavelet for forecasting weekly reference evapotranspiration. Results of this study can also be used for irrigation scheduling in the studied regions.

When good quality water is scarce, application of unconventional water resources is considered in agriculture. One of these sources is treated urban wastewater (TUW). In this research, in which plants were grown in medium-size pots, effect of irrigation with wastewater was evaluated on accumulation and distribution in soil profile of heavy metals (iron, manganese, zinc, copper, arsenic, cadmium, lead, and nickel) under greenhouse conditions of the University of Kurdistan. The factorial experiments were conducted according to complete randomized design with three replications. Also, the effect off three irrigation treatments consisting of TUW, alternating TUW- ordinary water, and ordinary water on the accumulation of heavy metals in the soil cultivated with corn and tomato plant were investigated. Soil samples were taken from four different depths and three horizontal distances from the plant. The results showed that TUW had significantly greater amounts of heavy metals in comparison with ordinary water. Also, the maximum and minimum amounts of heavy metal were observed in TUW and ordinary water, respectively. From the findings, it can be concluded that concentration of heavy metals decreased with increasing depth and horizontal distance from the plant location. Manganese (7.3 mg/kg) had the highest concentration in the soil. Also, Arsenic (5.41 mg/kg), iron (4.21 mg/kg), zinc (3.93 mg/kg) and copper (3.3 mg/kg) ranked from the second to fifth, respectively. Type of plants had a significant effect on the accumulation of manganese, zinc, and arsenic. According to the results of this study, there is a threat to human health of heavy metals contamination in plants such as corn and tomatoes. Therefore, it can recommended that irrigation with treated wastewater is to be limited to non-food crops.

Emitter clogging is the main problem in the use of wastewaters in drip irrigation systems which reduces the emitter discharge, emission uniformity, irrigation efficiency and increases maintenance costs. Aquaculture effluents contain appropriate nutrients (nitrogen and phosphorus) that can be used by plants. Hence, the aim of this study was to evaluate the effects of aquaculture effluent on hydraulic performance of Netafim and Microflopper emitters with different discharges. For this purpose, two drip irrigation systems were established to use inflow water and wastewater of a fish farm in Kurdistan province. Also, adding a management treatment, the effect of drip irrigation laterals discharge at the end of each irrigation event was studied when using this type of waste. The relative discharge, emission uniformity, Christiansen Uniformity Coefficient, statistical uniformity and discharge reduction rate were used to compare the hydraulic performance of the emitters. The results showed that in both fresh water and wastewater cases, the hydraulic performance of Netafim 4 l/hr and Netafim 8 l/hr emitters were better than the Microflopper 4 l/hr, Microflopper 8 l/hr and Netafim 12 l/hr emitters, respectively. Also, Netafim 4 l/hr emitters had the least dependence and sensitivity to water quality and irrigation management compared to the other studied emitters. In addition, the use of management treatment, for lateral pipe flushout, has a great impact on improving the performance of Netafim 12 l/hr and Microflopper 8 l/hr emitters.

Drip irrigation has a priority in selecting an appropriate irrigation method in arid and semi-arid regions because of its potential of precisely applying water and chemicals both in quantity and position. Proper design and management of a drip fertigation system is, to some extent, dependent upon a better understanding of wetting patterns and water and solute distributions in soil under different combinations of soil type and layering, emitter application rate, volume applied and fertigation concentration. In this study, experiments were carried out in a transparent plexiglass tank (0.5 x 1.22 x 3 m) using three different soil textures (light, heavy, and medium). The emitter outflows were considered 2.4, 4, and 6 lit/hr with irrigation duration of 6 hr. The fertigation treatments included treatments with nitrate concentrations of 125, 250, and 375 mg/L. Urea fertilizer (CH4N2O) (46% nitrogen) was used in the fertigation treatments. Then, using the p theorem of Buckingham and Dimension Analysis (DA), equations were developed to estimate the pattern of nitrate distribution pattern (horizontal and vertical) in the three soil textures. The equations developed were functions of initial soil nitrate content, nitrate concentrations in fertigation, initial moisture, radial distance of points, applied water volume, hydraulic conductivity, and emitter outflows. The results of the comparisons between simulated and observed values showed that the equations were capable of predicting the pattern of moisture distribution in different directions. The averages of Root Mean Square Error (RMSE) values in clay soil and for emitter outflows 2.4, 4, and 6 lit/hr were 0.025, 0.105 and 0.093, respectively. These values for loamy soil were 0.032, 0.052, and 0.05, respectively, and for sandy soil were 0.023, 0.038, and 0.035, respectively. Considering these equations in designing surface drip irrigation systems could improve system performance.

In areas facing water shortage, increasing water productivity is the key to overcome the greatest challenge in the agricultural sector. The present field experiment aimed to evaluate the effect of different irrigation water depths and salinity of magnetized and non-magnetized water on grain yield, biomass, height, protein, and oil content of soybean variety DPX. The experiment was performed as factorial based on randomized complete block design with three replications in Aliabad, Golestan province, in 2013. The treatments consisted of three levels of water volume (100%, 75% and 50% of soybean water requirement) and three salinity levels (0.7, 5, and 10 dS/m). The results showed that magnetized water caused irrigation water quality to be improved. Therefore, magnetization of irrigation water resulted in the highly significant increase in the grain yield, biomass, height, protein, and oil content of plant under water deficit and salinity stress treatments (p<0.001). The average decrease of yield in water salinity of 5 dS/m was equal to 8.44 percent, and for water salinity of 10 dS/m was equal to 24.68 percent as compared to the control treatment. Furthermore, the average decrease of yield in 75% irrigation level was equal to 30.68 percent, and for 50% irrigation level was equal to 44.40 percent as compared to the control treatment. In general, the highest grain yield was 5.5 tons per hectare for plants treated with magnetized water and provision of 100% crop water requirement.