فصلنامه علوم و مهندسی آبیاری
سال چهل و ششم شماره 4 (Winter 2024)

In open channel flow, determining the boundary shear stress and its distribution over the wetted perimeter is a significant problem. The shear stress distribution (SSD) is primarily affected by secondary flows, sediment transport rate, erosion or sedimentation, and geometry of the channels. The presented research uses Shannon entropy and support vector regression (SVR) approach to predict the SSD in rectangular channels (RCs). First, the entropy technique proposed by Sterling and Knight, (2002) is used to construct the probability density function of transverse SSD, and the constant coefficients of density are obtained by comparing experimental results in various aspect ratios. Second, to estimate the transverse SSD in a smooth RC, SVR methods have been used. According to the results of the sensitivity analysis, the aspect ratio B/H is the most essential parameter for SSD estimation. The SVR model performed better when the (b/B), (z/H), and (B/H) parameters were also used as input. For the aspect ratios (B/H) 2.86, 4.51, 7.14, and 13.95, the SVR model, with an average MAE of 0.044 in bed and 0.053 in wall, gives higher accuracy than the Shannon entropy, which has an average MAE of 0.062 in bed and 0.073 in wall for all flow depths. The Shannon entropy overestimates shear stress as compared to SVR. As a result, the costs of construction of channels may be significant.

This study assesses the use of drainage water in agriculture by mixing irrigation water and agricultural drainage water to examine the effects of the mixture on soil properties and the yield of tomatoes in Moghan Plain, Iran. The experimental design was completely random, conducted with three irrigation treatments and four replications for two years. The treatments were the control treatment (only irrigation water) (T0), 50% drainage water +50% irrigation water treatment (T1), and only agricultural drainage water treatment (T2). The results showed the treatments had significant differences (p≤0.05) in terms of the microbial population, basal respiration, and substrate-induced respiration. There were also significant differences among the treatments in terms of soil pH and EC (p≤0.01). However, the soil organic matter, yield, bulk density, and chlorophyll content of tomatoes showed no significant differences among the treatments. The treatments did not differ significantly in terms of the saturated hydraulic conductivity (Ks</sub>) in the first year, whereas the Ks</sub> for the drainage water treatment differed significantly (p≤0.05) in the second year. No significant differences were observed in the parameters of van Genuchten (θs</sub>, θr</sub>, and α) among the treatments. Whereas the statistical results showed that there was a significant difference (p≤0.01) in the parameters of van Genuchten (n</em>) between T0 with T1 and T2 treatments, there was no significant difference between T1 and T2 treatments. It can be concluded that the use of drainage water negatively affected soil pH, salinity, and biological properties; but it did not decrease the plant yield.

The present study investigated the effects of engineered sugarcane bagasse hydrochar on the soil properties of sandy loam and the growth parameters of bean plants. After preparing the optimal hydrochar, its physicochemical properties were determined through various analyses. The effects of different rates of hydrochar (0%, 1%, 2%, and 5% w/w) were then investigated on the bulk density, porosity, pH, organic carbon, nitrogen, and phosphorus content of the soil, as well as on plant height, lateral branch number, leaf number, and dry weight of aerial parts and roots. The results show that the addition of engineered sugarcane bagasse hydrochar at all levels improved the soil properties of sandy loam. However, an inverse effect was observed for the electrical conductivity (EC) parameter. The 5% hydrochar treatment resulted in a significant increase of 78.4% in organic carbon, while a minimal decrease of 0.4% was observed in pH. Regarding the growth parameters of bean plants, only the 1% engineered hydrochar treatment showed a positive effect on growth parameters.

One of the greatest challenges currently facing society is the production of high-yield and high-quality foods due to population growth and the need to increase food production. In this study, the effect of two hydroponic systems on water productivity,</strong> </strong>nutrient use efficiency yield and fruit quality </strong>of three greenhouse cucumber cultivars have been investigated. This experiment is in the form of split plots in a randomized complete block design, with the treatment of cucumber cultivars (</strong>Strong, Yalda, and RY) and type of hydroponic cultivation system (open and combined </strong>closed) in which 3 replicates were implemented at Shahid Chamran University of Ahvaz.</strong> The studied traits included water productivity,</strong> </strong>nutrient use efficiency, crop yield, </strong>fruit length and diameter, fruit volume, fruit firmness, fruit dry weight, fruit carotenoids, phenolic compounds, total soluble solids, titratable acidity were measured. The highest fruit length, fruit diameter, yield, water productivity and nutrient use efficiency were obtained in the combined closed system. The highest fruit firmness, total soluble solids, phenolic compounds were obtained in the open system. The combined closed system increased crop yield, water productivity and nutrient use efficiency by 22.63%, 80.81% and 81.92 % respectively, as compared to the open system. The highest phenolic compounds, fruit length, yield and water productivity were calculated in the RY cultivar. The RY cultivar increased phenolic compounds by 56.30% and 71.98% respectively, as compared to the Strong and Yalda cultivars. Based on the results, Fruit diameter had a significant correlation with fruit length (0.47*</sup>) and crop yield (0.55*</sup>). According to the results of this study, combined closed system and RY cultivar have the highest quality characteristics of fruit and yield, therefore they can be recommended for greenhouse production.</strong>

AquaCrop model was developed to simulate crop response to water consumption and irrigation management. The model is easy to use, works with limited input, and has acceptable accuracy. On the other hand, there are different methods for estimating evapotranspiration, whose performance is different in various climatic conditions. The purpose of this research is to investigate the effect of different methods to estimate evapotranspiration of the reference plant in various climates of Iran on estimating the yield of maize and wheat using AquaCrop. To fulfil the experiment, 40-year meteorological data (1980-2020) of five cities of the country (Urmia, Mashhad, Rasht, Qazvin, and Yazd) were used. First, evapotranspiration was estimated using the FAO-56 and five temperature and radiation methods daily. Then, the yield value of these two plants was simulated by AquaCrop and compared with the FAO-56 by error statistical criteria determination coefficient (R2</sup>), normal root means square error (NRMSE) and Nash-Sutcliffe index (NS). According to the results, among the two temperature methods Blaney-Criddle method with the NRMSE is in the range of 0-20%, R2 </sup>and Nash-Sutcliffe are, close to the optimal value of one for maize and wheat in parameter simulation are acceptable. About radiation methods, the Priestley-Taylor and the Turc methods in simulation of maize yield. Also about radiation methods for wheat, the Turc and the Makkink method for simulation of yield are desirable.

Tillage practices have been widely acknowledged to play a critical role in optimizing water use efficiency (WUE) for winter wheat production in the Northern China Plain (NCP) where drought is a critical limiting factor. Therefore, the WUE of wheat as influenced by annual rotational tillage under the corn–wheat cropping system during 2016–2018 has determined. The tillage regimes in the corn season were either N: no–tillage or SR: sub–soiling with rotary tillage). One of three regimes, sTR: strip rotary tillage; R: rotary tillage; and SR: sub–soiling with rotary tillage) were the tillage practices in the wheat seasons. Thus, making a total of 6 treatments. N–SR markedly decreased the penetration resistance, while the soil water storage was enhanced in the 60-100 cm layer during the wheat season, over both years. On the other hand, the use of SR during the wheat-growing season increased evapotranspiration. Compared with other tillage practices, the photosynthesis rate enhanced under the N–SR. As a result, the highest yield and WUE of wheat were recorded in the N–SR regime. Our findings suggest that no–tillage in the corn season and sub–soiling with rotary tillage in the succeeding wheat season can improve wheat yield by promoting deep soil water, enhancing the leaves photosynthesis rate and increasing WUE.

The intensification of drought and water stress caused by climate change is a major factor in yield and productivity reduction in the agricultural sector in arid and semi-arid environments. Agricultural lands are often sorely affected by water tension caused by scarce and low precipitation. This research evaluated the effect of different amounts of water, vermicompost and hydrogel used to save the soil water content on wheat grain and biomass yield. Hence, an experiment was conducted at the research farm of Kashmar higher education institute to evaluate the effects of different amounts of hydrogel and vermicompost on wheat biomass and grain yield. Experimental treatments were included: four levels of A200</sub> hydrogel (i.e. 0(S0</sub>), 0.1(S1</sub>), 0.2 (S2</sub>) and 0.3 (S3</sub>) wt. %) plus four levels of vermicompost (0(V0</sub>), 7(V1</sub>), 10(V2</sub>) and 15(V3</sub>) tons per hectare) and three levels of irrigation water (60(W1</sub>), 80(W2</sub>) and 100(W3</sub>) percent of wheat water requirement). The experiment was carried out in a randomized completely block design (RCBD) in a factorial arrangement as a pot experiment in 144 pots. The results showed that the highest amount of biomass and grain yield was obtained in S3</sub>V3</sub>W3</sub> treatment amounting of 81.7 and 35 grams per pot, respectively. Also, the lowest biomass and grain yield was achieved in S0</sub>V0</sub>W1</sub> treatment at the rate of 35 and 10.2 gram per pot, respectively. Furthermore, grain and biomass yield were significantly affected (P ≤ 0.05) by different amounts of hydrogel and vermicompost under varying irrigation water levels. However, application of hydrogel and vermicompost compounds was not significant on the wheat yields. Overall, the best economic value for achieving the highest amount of grain yield was observed in (S2</sub>, 0.2%) of A200</sub> hydrogel and (V2</sub>, 10 ton/ha) of Vermicompost. Similarly, the highest amount of biomass was obtained in the (S3</sub>, 0.3%) treatment of A200</sub> hydrogels and 15 ton/ha (V3</sub>) of vermicompost. Based on the results, the application of moisture absorbents can be effective in increasing wheat yield in water deficit conditions in the arid and semi-arid environment.

Maroon River is a valuable aquatic ecosystem in Iran. The purpose of this research was to investigate the lasting impacts of the Maroon dam on river water quality (RWQ), particularly downstream, and determine those factors affecting the optimal management of the RWQ. The modified Mann-Kendall and Sen's slope estimator tests were employed to investigate the variation trend of qualitative parameters. Then, multivariate statistical analyses, including correlation assessment, cluster analysis, T-test, and factor analysis of spatiotemporal pattern, are applied to recognize factors affecting the effects of dam construction. Results showed that the total hardness and the calcium, chlorine, and sulfate concentrations significantly increased in downstream at a level of 5%</em> confidence. The cluster analysis indicated that dam construction probably did not affect the upstream; however, the increased dissolution rates of calcium and sulfates downstream illustrated the presence of the Gachsaran formation in the river path and the dissolution of rock gypsum in the water. The factor analysis determined three and two main components before and after dam construction with 84.8%</em> and 71.6%</em> variances, respectively. These components and the correlation between chloride-sodium and calcium-sulfate ions could show the Sodium Chloride  dissolution and the effects of the dissolution of gypsum mid-layers from the Gachsaran formation after the dam construction. The strong relationship between the magnesium and chlorine contents in the Cham Nezam station might result from the salt/detergent-contained household and urban wastes entering the river. According to the results of various tests, the dam has changed the quality of the river downstream. Still, Wilcox and Schoeller's indices demonstrated that dam construction did not significantly affect the RWQ used for drinking and agriculture.