مجله پژوهش آب در کشاورزی
سال بیست و نهم شماره 3 (پاییز 1394)

Crop growth simulation models have been developed for predicting the effects of water and salinity on grain and biomass yields and water productivity of different crops. These models are calibrated and validated for different regions using the data generated from field. This study was carried in Mashhad for two years (2010 and 2011) in order to evaluate the AquaCrop model under simultaneous salinity and water stress. Calibration was done using the data of 2009-2010 and validation with the data of 2010-2011.Results indicated that AquaCrop successfully simulated yield, biomass, water productivity, harvest index, soil moisture and salinity profiles for spring wheat under salinity and water-limiting treatments with high accuracy, although simulation of harvest index and soil salinity profiles were less accurate. Average value of normalized root mean square error (NRMSE), maximum error (ME), index of agreement (d), coefficient of the residual mass (CRM) and coefficient of determination (R2) in both the calibration and verification were 13.3 %, 36.1 %, 0.95, -0.072, and 0.87, respectively, for grain yield, while these measures were 12.59%, 34.46%, 0.92, 0.057, and 0.77, respectively, for biomass. Also, value of NRMSE, ME, d and CRM were 11.84 %, 25.72 %, 0.93, and 0.032, respectively, for soil moisture, while these measures were 26.25%, 58.5%, 0.91 and -0.12, respectively, for soil salinity. Sensitivity analysis revealed that crop transpiration coefficient (KC-Tr), normalized crop water productivity (WP*), reference harvest index (HIO), volumetric water content at field capacity, soil water content at saturation[S1], and air temperature were the most sensitive parameters. Although the accuracy of the model simulation decreased with increasing salinity and water stress, AquaCrop can be a valuable model for simulating spring wheat yield and soil water content and salinity in Mashhad region, because the model requires few input data which can be readily available or easily collected. [S1]This is probably”initial conditions” and not saturation.

Large areas of Iran are affected by salinity and drought. Due to the tolerance of almond (Prunus dulcis) to water stress, this tree is mainly grown in arid and semi-arid regions, where salinity is commonly another agricultural problem at such areas. Sensitivity of almond trees to salinity calls for special attention to the integrated effect of salinity and water stress on its water relations. This study aimed to evaluate the combined effect of salinity and drought stress on almond water status. The trial was conducted during 2014 based on randomized complete block design with three replications on a loamy sand soil at horticultural station of the Agricultural Research Center of Azarbaijan province. Treatments comprised three irrigation salinity levels viz. 2 (T1), 4 (T2), and 5 (T3) dSm-1. Leaf (Tc) and air (Ta) temperatures, air relative humidity, leaf water potential (LWP) and integrated volumetric soil water content (SWC) at three depths (0˗20, 0˗40, and 0˗70) were measured at midday (12˗14) during the growing season. Results indicated that salinity had significant effect (p<0.0001) on stomatal conductance (gs), Tc, LWP and available water depletion (AWD). Seasonal averages of gs for treatment T1 to T3 were 0.86, 0.59 and 0.44 cm.s-1, respectively, and the corresponding LWP were ˗1.90, ˗1.93 and ˗2.16 MPa. Also, significant correlation was found between gs, LWP, Tc and AWD. Based on the regression equations, threshold value of gs for initiating stress was obtained to be 0.73 cm s-1. Corresponding LWP and AWD for this gs value were ˗1.85 MPa and 64%, respectively. Optimum Tcfor highest gs was determined to be 28.2 oC. Highly significant correlation between Tc and other water status indicators showed that midday canopy temperature may be a useful tool for assessment of water status and irrigation scheduling of almond orchards.

In order to investigate the economics of simultaneous effect of salinity and drought stress on growth and yield of tomato plant (LycopersiconesculentumMill. Cv. Oriental), four levels of irrigation (125% ET, 100%ET, 75%ET and 50%ET) and six levels of salinity (0.1, 1.3, 3, 5, 7, and 9 dS/m) were combined in a factorial and completely randomized design with 3 replication in a greenhouse soilless culture. Economic model of deficit irrigation optimization was extracted and used for growing tomato in a greenhouse under salinity and drought stresses. The results of this model showed that the net profit of full irrigation of tomato in soilless culture in greenhouse using water of 0.1, 1.3, and 3 dS/m was equal to the net profit of deficit irrigation at 36%, 21%, and 24%, respectively. Thus, considering the large number of tomato greenhouses with soilless production and very high price of chemical fertilizers and other costs related to plant nutrition and irrigation, applying approximately 25% deficit irrigation will cause a corresponding reduction in total costs of production, which is economically significant.

Plant yield is a function of root distribution and its activity. Under limited water conditions, adequate root growth and efficiency are essential for crop productivity. To study the relationship between the dynamics of corn (Zea Maize L., variety single cross 704) root growth and soil available water uptake under drip-tape irrigation system, an experiment was conducted in a randomized complete block design with three replications. Experimental variables were three irrigation treatments including: 100% (I1), 80% (I2), and 60% (I3) of the actual plant water requirement calculated by the Penman–Monteith formula using meteorological data. The roots were collected from the beginning to the end of the growing season at four stages including: 25, 55, 85 and 115 days after planting. Samples were taken from 5 depths: 0-10, 10-20, 20-30, 30-40, and 40-50 cm. The results showed that irrigation treatments had significant effect (p=0.01) on root length density at different depths. About 60% of the corn root length density was up to the depth of 20 cm. On the other hand, the surface layers of the soil at this depth lost their moisture rapidly and, therefore, the plant needed to absorb water from the lower layers (below 20 cm) to survive. In low irrigation treatment (60% water requirement) up to the depth of 40 cm, root growth was low and, as a result, water absorption was also low. Higher irrigation had a positive effect on corn yield as the highest yield (7769 kg/ha) was obtained with the irrigation treatment of 100% water requirement.

Drip irrigation is one of the effective ways to conserve water and increase water use efficiency (WUE). Despite the many benefits of drip irrigation system, a substantial amount of irrigation water is wasted through evaporation from the soil and transpiration by weeds growing between the rows. Using mulch between planting rows can maintain soil moisture, reduce evaporation from the soil and transpiration from weeds, reduce irrigation water consumption, and increase crop yield. The purpose of this study was to evaluate irrigation depth and mulching effects on potato yield and water use efficiency in Dehgolan plain of Kurdistan Province. For this propose, a field experiment was conducted in the spring season of 2014, using a split plot scheme based on randomized complete blocks design with three replications. The main plots and subplots included the amount of irrigation water at four levels (60%, 80%, 100%, and 120% of the potato water requirement) and three mulch treatments (without mulch, straw mulch, and plastic mulch), respectively. Results showed that the effect of irrigation water and mulch on yield was significant (P<0.01). The maximum and minimum amounts of potato tuber yield were related to 120% and 60% water requirement, respectively. The results also showed that the effect of mulch on potato WUE was significant (P<0.01). The highest WUE (14.96 kg.m-3) was related to plastic mulch. It is to be noted that the use of plastic mulch compared to the biodegradable straw mulch will lead to environmental problems.

Basil (Ocimumbasilicum L.) is one of the important plants belonging to the genus family Lamiaceae (Labiatae), which is used as herbs, spices, and as well as fresh vegetables. The present study was conducted to investigate the interaction of deficit irrigation, soil texture, and fertilization on yield components and vegetative growth of basil variety Keshkeniluvelou, using a factorial experiment based on randomized complete block design (RCBD) with 18 treatments and 3 replications. Deficit irrigation treatments consisted of three levels of irrigation including I1=100%, I2=75%, and I3=50% of ETc, and soil texture included sandy loam and loamy soil. Also, 3 fertilizer treatments with 100 percent of the recommended rate (including macro- and micronutrients) (F1), 70 percent (F2), and no fertilizer (F3) were applied to each pot. The ANOVA results showed that effect of irrigation was significant, soil texture and fertilizer were not significant, and interaction of soil texture and fertilizer were significant on plant height, leaf area, leaf dry weight, stem dry weight, and fresh weight of basil, respectively. The tallest plant height (31.42cm), leaf area (109.21cm2), leaf dry weight (0.97 gr), stem dry weight (2.24 gr), and fresh weight of leaf (5.12gr) was obtained in S1I1F3 treatment and the lowest in the S1I3F3 treatment. Also, the highest seed weight per plant (2.41gr), number of seeds per plant (1822.3), thousand seed weight (1.447gr), and seed yield (42.13 gr/m2) were obtained in the treatment having loamy soil texture, full irrigation, and 100% of the recommended fertilizer rate (S2I1F1), which showed the effect of fertilizer on improving the yield of basil.

Limited water and energy resources in the world and the increasing demand for water and energy due to population growth and the development of human societies necessitate investigation of the water and energy consumption in irrigation systems. This study aimed to evaluate the water and energy consumption, losses, and efficiency of diesel pumping stations and was conducted in Hamadan Province farms during the period 2009 to 2011. Nebraska Pumping Plant Performance Criteria was applied to compare the performance of irrigation pumping stations. The results showed that the total efficiency varied from 7.2% to 24.3 percent. The average of total efficiency and wasted energy of a diesel pump was calculated at about 14.7 percent and 4.84 liters per hour, respectively. The results showed that in many farms where sprinkler systems were used, the water applied was lower than crop water requirement. Average water use efficiency in alfalfa fields in the furrow and sprinkler systems was 1.7 and 2.7 kg/m3, respectively. The factors influencing decrease in energy efficiency were worn-out pump or motor, inappropriate implementation foundation for the pump engine, and inappropriate selection of engine for the pump.

Development projects, along with their positive impacts, have some direct and indirect impacts on natural and social environment that are potentially negative. There may be some undesired consequences if provisions are not foreseen for mitigating the negative impacts and reinforcing the positive ones. Environmental, social, and economic impacts assessment of irrigation and drainage network projects in Korbal plain based on its beneficiaries’ view point was the main objective of this study. Research method was descriptive; non-experimental toward variables controlling; applied toward its object and the data was collected by survey technique. The statistical population of this study included all of the beneficiaries who were farming the modern irrigation and drainage network in Korbal plain, in Fars province. Totally, 280 beneficiaries were selected as sample groups. A questionnaire was used for data collection and its validity was approved by a panel of specialists and its reliability was examined by conducting a pilot study. Cronbach’s alpha coefficient was about 0.79. Findings revealed that most of the beneficiaries believed that the project had relatively desirable environmental, social, and economic impacts. Among four groups of personal, economic, social, and situational determinants, two groups of personal and social determinants had more effect on beneficiaries’ impact assessment. Besides, regression analysis revealed that four groups of attitudinal variables had the highest effect on beneficiaries’ assessment toward the three types of impacts. Some recommendations are presented at the end of the article in order to improve implementation and benefits of such projects.

Today, use of drip irrigation systems for row crops is widespread. One of these systems is subsurface drip irrigation. Knowing the dimensions of the wetting pattern is essential for drip irrigation system design. To design a proper system, as field experiments are time consuming and expensive, using computer models is recommended. In this regard, the present study examined the performance of three models including empirical Kandelous et al. model, analytical WetUp, and numerical HYDRUS-2D models in subsurface tape irrigation. Treatments included three volumes of water i.e. 10, 15, and 20 liters per meter length of tape and three installation depths of 10, 20, and 30 cm, in three replications. Comparison between the measured and simulated wetting dimensions were made by using four statistical indices i.e. RMSE, nRMSE, CRM, and MAE. RMSE values of horizontal wetting extension for Kandelous et al and HYDRUS-2D models were 0.051 and 0.066 m, respectively, while for vertical wetting extension, the values of RMSE were 0.052 and 0.078 m, respectively. nRMSE values of horizontal wetting extension for Kandelous et al. and HYDRUS-2D models were 15.46% and 19.71 %, respectively, being in class ‘good’. nRMSE values of vertical wetting extension for Kandelous et al and HYDRUS-2D models were 15.99 and 23.74 %, respectively, considered as ‘good’ and ‘fair’, respectively. Statistical indices calculated for WetUp model was not in acceptable range. For horizontal and vertical wetting dimensions, CRM and MAE indices for Kandelous et al model were the lowest values. Overall, the Kandelous et al model had the best estimation.

The technology of magnetic water has been widely studied and adopted in the field of agriculture in many countries. The objective of the present study was to investigate the effect of magnetic water on germination and vegetative growth of two varieties of tomato (lycopercicum esculentum) seeds. A factorial experiment in completely randomized design was carried out using three replications, in 2014. Based on the results, seeds irrigated with magnetic water exhibited marked increases in rate of germination, vegetative growth, vigor index, root length, seedling length, seedling fresh weight and chemical constituents i.e. photosynthetic pigments (chlorophyll a and b and carotenoids), over the control. Percentage of germination for seeds irrigated with magnetized water was 94.6 for the two varieties, while for the control it was 90 and 93 in Sunseed and Sudin, respectively. Results indicated that irrigation with magnetized water induced positive significant effect on all studied parameters. It appears that utilization of magnetized water may lead to improved quantity and quality of tomato production.