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Hossein Parvizi; Amir Parnian; Hadis Hatami; Mohammad Hasan Rahimian
Abstract
The effects of pressure changes and type of emitter on the performance of pistachio orchard’s drip irrigation systems were studied in 21 orchards, under irrigation by saline water. Based on the results, water distribution uniformity in different parts of the orchards (EU) and the average flow of ...
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The effects of pressure changes and type of emitter on the performance of pistachio orchard’s drip irrigation systems were studied in 21 orchards, under irrigation by saline water. Based on the results, water distribution uniformity in different parts of the orchards (EU) and the average flow of emitters ranged from 71% to 95% and 5.5 to 28.8 l hr-1, respectively. Furthermore, the lowest and highest operating pressure of the emitter were 0.1 and 1.8 bar in different pistachio orchards, respectively. The highest (21%) and lowest (3%) values of coefficient of variation (CV) were obtained from the evaluation of orchards number 13 and 4, respectively. Moreover, the minimum (0.6 %) and maximum (26.2 %) deviation values of the measured average flow from the nominal flow were also observed in orchards No. 3 and 18, respectively. The values of CV in orchards No. 3, 4, 10, 11. 12, 19, and 20 were lower than 10% and were excellent. Orchards No. 2, 13, 14, and 15 with values of about 20% showed good and very good CV, and all of the remaining orchards had very good values of CVs between 10% and 20 %. The results showed that the emitters had a low CV and high EU in the orchards with proper supply and distribution of operation pressure (0.5 to 4 bar) without considering their types and brands. However, the two 8 liters per hour emitters including the Eurodrip and Europlast (King model) for soils with low infiltration rate, and the 26.2 liters/hour Eurodrip emitter for supplying high flow rates with an operating pressure of 0.5 to 1 bar can be recommended. Results indicated that, in most orchards, it is vital to modify the irrigation planning (time and frequency). It seems that if the operating pressure is supplied and distributed properly, emitter clogging and, consequently, EU would not be much affected by water salinity.
7
reza saeidi
Abstract
In this research, the effect of salinity stress on the amount of evapotranspiration components of maize were investigated in mini-lysimeters (in the initial, development, mid, and late growth stages). Salinity treatments were applied by water with EC of 0.5(S0), 2.1(S1), 3.5(S2), and 5.7(S3) dS.m-1. ...
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In this research, the effect of salinity stress on the amount of evapotranspiration components of maize were investigated in mini-lysimeters (in the initial, development, mid, and late growth stages). Salinity treatments were applied by water with EC of 0.5(S0), 2.1(S1), 3.5(S2), and 5.7(S3) dS.m-1. The experiment was performed as factorial and in a completely randomized design. For the whole growth period and for S0 to S3 treatments, the values of evapotranspiration, transpiration, and evaporation were measured in the range of 420-320, 285-124, and 135-196 mm, respectively. The share of crop transpiration (T/ETc) decreased by 29% while the share of evaporation (E/ETc) increased by the same value. From S0 to S3 treatment, the values of evapotranspiration, transpiration and evaporation were measured in the range of 420-320, 1 / 285-3 / 124 and 134-7 / 195.9 mm (in the whole growth period), respectively.From S0 to S3 treatments, the values of evapotranspiration, transpiration and evaporation were measured in the range of 79-72, 19-10 and 61-62 mm (initial stage), 202-150, 150-71, and 51-79 mm (development stage), 124-84, 110-39, and 14-45 mm (mid stage), and 15-14, 6-4, and 9-10 mm (the late stage). The shares of crop transpiration decreased in the order of the developmental, mid, initial, and the late stages, while the decreasing order for the shares of evaporation was related to the initial, developmental, mid, and late stages, respectively. The dry biomass yield decreased by salinity stress, and its amount in treatments S0, S1, S2, and S3 was as 12942, 12168, 10872, and 8928 kg.ha-1, respectively. Stress coefficients of evapotranspiration (KS), transpiration (KS-T), and evaporation (KS-E) were calculated in the range of 1-0.76, 1-0.43, and 1-1.45, respectively. The results showed that for 1 dS.m-1 increase in water salinity, the amounts of relative evapotranspiration and relative transpiration decreased by 4.7% and 11.1%, respectively, and the amount of relative evaporation increased by 9%. The results showed that the transpiration component decreased with a greater slope, relative to the evapotranspiration.
yaser hossini; Javad Ramezani Moghaddam; Mohammad Reza Nikpour; Attieh Abdoli
Abstract
Various mathematical models are available for predicting the response of plants to combined water and salinity stress and their share in water uptake. The reduction functions are classified as additive, multiplicative, and conceptual models. In this study, 6 macroscopic reduction functions, namely, Van ...
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Various mathematical models are available for predicting the response of plants to combined water and salinity stress and their share in water uptake. The reduction functions are classified as additive, multiplicative, and conceptual models. In this study, 6 macroscopic reduction functions, namely, Van Genuchten (additive and multiplicative), Dirksen et al., Van Dam et al, Homaee and Skaggs were evaluated in a greenhouse experiment on cherry tomato, var. cherry tomato cluster. This experiment was performed based on a completely randomized design with 3 replicates and 2 levels of salinity (4 and 7 dSm-1). Water stress levels were imposed as matric potential decline during the study at 3 levels of available water depletion (40%, 50%, and 65%). The result of the study indicated that the crop response to water stress and salinity stress was incremental at 4 and 7 dSm-1 salinity levels. Among the multiplicative models, reduction functions of Dirksen model had better fit than others at 4 dSm-1 salinity level (RMSE=0.15 and ME=0.14).However, at 7 dSm-1, Van Dam (RMSE=0.017, ME=0.09) and Skaggs (RMSE=0.018, ME=0.14) had better fit to the measured data.
y h; h b; b kh
Abstract
Various mathematical models are available for estimating the response of plants to combined drought and salinity stress and the share of each component in water uptake. The reduction functions are classified as additive, multiplicative, and conceptual models. In this study, 5 different macroscopic reduction ...
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Various mathematical models are available for estimating the response of plants to combined drought and salinity stress and the share of each component in water uptake. The reduction functions are classified as additive, multiplicative, and conceptual models. In this study, 5 different macroscopic reduction functions, namely, Van Genuchten (additive and multiplicative), Dirksen et al., Van Dam et al, and Homaee, were evaluated in greenhouse conditions using pepper data. This experiment was performed based on a completely randomized design with 3 replicates and 3 levels of salinity (2.5, 4.5, and 6.5 dS/m). Drought levels were carried out as matric potential during the experiment at 3 levels (50%, 60%, and 70% of field capacity). The results of this study indicated that the crop response to drought and salinity stress was additive at low salinity level (2.5 dS/m) and multiplicative at 4.5 and 6.5 dS/m salinity levels. Also, reduction function of Van Genuchten (average RMSE=3%, ME=0.15) had the best fit at low salinity level (2.5 dS/m). Among the multiplicative models, reduction functions of Dirksen model at 4.5 dS/m with average RMSE=5% and ME=0.09 was in better fit to the measured data than the other functions.Homaee (average RMSE=9%, ME=0.12) and Vandam models (average RMSE=9%, ME=0.11) at higher salinity level (6.5 ds/m) were in better fit to the measured data than the other functions.