Saline Drainage Water Research Articles

Acceptable Salinity Level for Saline Water Irrigation of Tall Wheatgrass in Edaphoclimatic Scenarios of the Coastal Saline–Alkaline Land around Bohai Sea

Saline water irrigation contributes significantly to forage yield. However, the acceptable salinity levels for saline water irrigation of tall wheatgrass remains unclear. In this study, field supplemental irrigations of transplanted-tall wheatgrass with saline drainage waters having salinities of electrical conductivity (ECw) = 2.45, 4.36, 4.42, and 5.42 dS m−1 were conducted to evaluate the effects of saline water irrigation on forage yield and soil salinization. In addition, the effects of plastic film mulching, fertilization, and saline water irrigation on sward establishment of seed-propagated tall wheatgrass were determined. Finally, a pot experiment was carried out to confirm the above field results. The results showed that two irrigations with ECw = 2.45 and 4.36 dS m−1 saline waters produced the highest dry matter yield, followed by one irrigation with ECw = 4.42 or 5.42 dS m−1. After rainfall leaching, the soil EC1:5 was reduced by 41.7–79.3% for the saline water irrigation treatments. In combination with saline water irrigation, plastic film mulching promoted sward establishment and enhanced the plant height and dry matter yield of seed-propagated tall wheatgrass, while fertilization played a marginal role. However, two irrigations with ECw = 7.13 and 4.36 dS m−1 saline waters resulted in rates of 3.2% and 16.0% of dead plants under the mulching and no mulching conditions, respectively. Furthermore, a pot experiment demonstrated that irrigation with ECw = 5.79 dS m−1 saline water led to the lowest reduction in forage yield and the highest crude protein content in leaves. However, the plants irrigated with ECw ≥ 6.31 dS m−1 saline water enhanced soil salinity and reduced the plant height, leaf size, and gas exchange rate. Conclusively, one irrigation with ECw ≤ 5.42 dS m−1 and SAR ≤ 36.31 saline water at the end of April or early May could be acceptable for tall wheatgrass production and minimize the soil salinization risk in the coastal saline–alkaline land around the Bohai Sea.

Leaf production and quality of sea beet (Beta vulgaris subsp. maritima) grown with saline drainage water from recirculating hydroponic or aquaculture systems

The application of greenhouse soilless culture (or hydroponics) and recirculating aquaculture system (RAS) is rapidly growing worldwide as these technologies provide controlled growing conditions for crop plants and aquatic organisms, thus enhancing productivity. The wastewater from RAS and hydroponics is generally rich in many essential plant nutrients and could be reused for crop irrigation, thus reducing the costs for both wastewater treatment and fertilizers. Many wild edible plant species are salt-tolerant glycophytes or halophytes and hence are suitable for cultivation with saline wastewater in cascade cropping systems or decoupled aquaponic systems.The goal of this work was to investigate the effects of drainage water from semi-closed substrate plant culture or saltwater RAS on leaf production and quality of sea beet plants (Beta vulgaris subsp. maritima) grown hydroponically in a greenhouse. Two experiments were conducted in autumn with plants cultivated in a floating raft system to compare five different nutrient solutions: standard nutrient solution (CNS, control; EC 2.80 dS m−1, Na 0.7 mM); the effluent from a semi-closed substrate culture of tomato used as such (tomato effluent 100%, TE100; EC 6.49 dS m−1, Na 34.9 mM) or diluted (50:50) with CNS (tomato effluent 50%, TE50; EC 4.50 dS m−1, Na 17.8 mM); the effluent from a saltwater RAS with gilthead sea bream, used as such (aquaculture effluent 100%, AE100; EC 42.00 dS m−1, Na 408.6 mM) or diluted (50:50) with CNS (aquaculture effluent 50%, AE50; EC 25.40 dS m−1, Na 204.6 mM).In both experiments, leaf production was significantly reduced in plants grown with AE50 (−46.8%, on average) and AE100 (−70.4%, on average) compared to CNS; on the contrary, no or minor differences were found between CNS, TE50 and TE100 plants. The reduction of crop yield was due to the higher salinity and not to abnormal concentration of some mineral nutrients in AE. In the first experiment, the use of TE and AE also resulted in higher leaf antioxidant capacity and concentration (both expressed on a fresh weight basis) of total chlorophylls, carotenoids, flavonoids, and phenols. In both experiments, leaf concentration of Na and oxalate (both total and soluble) significantly increased with the salinity of the nutrient solution. Due to the less favourable light conditions, leaf nitrate concentration was much higher in the second experiment than in the first one, regardless of the nutrient solution.In conclusion, sea beet could be grown using hydroponic wastewater with moderate salinity with no or minor effect on leaf production and quality. In contrast, the use of highly saline aquaculture effluents markedly reduced crop yield and negatively affected leaf quality due to increased concentration of sodium, oxalate, and nitrate. In general, sea beet leaves were high in oxalate and their consumption should be limited.

Effects of salt source and irrigation water salinity on growth, yield and quality parameters of black cumin

AbstractExcess salinity, osmotic stress, toxic ions and ion imbalance negatively affect plant growth. Many crops are classified as salt sensitive. However, there is no information in the literature about the effects of different salt sources (SS) and salinity levels (SLs) on black cumin (Nigella sativa L.). This study was conducted to determine the effects of SL (0.6, 1.5, 2.5 and 5.0 dS/m) prepared separately by different SSs (CaCl2, MgCl2, NaCl, Ca(NO3)2, MgSO4 and Na2SO4) on the evapotranspiration, growth, yield and quality parameters of black cumin. The results showed that the evapotranspiration, soil salinity, plant height, vegetative dry weight and oil content of black cumin were affected only by SL. Both SS and SL have a significant effect on the number of capsules and seed weight. The SS × SL interaction was meaningful on drainage water salinity and the number of seeds. The seed weights under CaCl2, MgCl2, Ca(NO3)2, MgSO4 and Na2SO4 SS were adversely affected even at very low SL. However, the low slope values for these salts reveal that the increase in SL has a limited effect on seed weight. Therefore, it can be recommended to consider both the salt type and SL of irrigation water in black cumin cultivation.

Performance assessment of subsurface drainage systems in the Harran Plain of the South‐East Anatolian region of Turkey

AbstractThe purpose of performance assessment of subsurface drainage systems is to achieve efficient and effective system performance by providing relevant feedback to the management of the drainage system at all levels. Therefore, it assists management in determining whether performance is satisfactory and, if not, what corrective actions need to be taken and where to rectify the situation. In this study, approximately 30% of the drainage systems built in the Harran Plain were monitored during one irrigation season in 2017. The fluctuation of the water table was measured daily at a total of 33 subcentres. In addition, electrical conductivity (EC) and pH values were measured by taking water samples from six collectors once a week. Drain flow measurements were carried out at three collector outlets. According to the SEW30 (sum of excess water at depths less than 30 cm) indicator, 82% of the monitored areas had good, medium‐good drainage and moderate drainage. The seasonal average water table depth of the monitored area was found to be approximately 120 cm. The data show the existence of a drainage system that creates an aerated soil layer suitable for all shallow‐ and deep‐rooted, water‐resistant, and sensitive plants in all of the monitored areas. Generally, the salinity of drainage water is much higher than that of irrigation water. This value was up to 25 times higher in some collector outlets. This finding has raised suspicions that salty groundwater is being pumped into the drainage system.

Bio-Saline Agriculture Modeling, Using Saline Water for Irrigation Purposes

Climate change effects increase the scarcity of irrigation water and deterioration of its quality, which affects the crop water requirements. Researchers were studying the water recycling technique and finding about other possible renewable water resources for irrigation, they conclude that saline water can be used to meet part of the irrigation water needs for many crops under special field management, because there are many crops have a high tolerance to the salinity without decreasing in the yield. The current study aims to evaluate the economic yield of saline drainage water in irrigation. A computer program (Fıuat Ujaj) using Visual Basic language was constructed to use the largest possible amount of drainage water for irrigation after removing the toxic effects and then calculates the relative yield of the selected crops. The Main Outflow Drain (MOD) in Iraq was selected as a saline water resource which has 4.63 dS m-1 Electrical Conductivity (EC). This saline water contained high concentrations of chlorine and sodium ions. MFUP results showed that toxic effect of these ions can be removed by diluting with 35% of the nearby river water. MFUP results showed that the crops with high and medium tolerance to salinity give an acceptable yield ratio when they were irrigated with diluted water (35%) to remove toxicity effects only, while the dilution increases for crops of medium sensitivity, but the acceptable yield of sensitive crops is not achieved except with fresh river water. If the crop production is lower than the economically acceptable limit, another 5% of the river water will be added to mitigate, and the dilution process continues until the percentage of the river water become 80% of the irrigation water. If the required product is not achieved, then the program instructs to irrigate this crop with the river water only.

Reducing the Effect of Agricultural Drainage Water Salinity on Sugar Beet Productivity and Quality by Some Soil Amendments

Reducing the Effect of Agricultural Drainage Water Salinity on Sugar Beet Productivity and Quality by Some Soil Amendments

Guayule as an alternative crop for natural rubber production grown in B- and Se-laden soil in Central California

The potential of growing guayule ( Parthenium argentatum A. Gray) as an alternative crop for saline, boron- and selenium-laden soils in the Westside of central California was evaluated in both greenhouse and drainage sediment field experiments. In the greenhouse experiment, salt and boron (B) tolerance and selenium (Se) accumulation were evaluated in guayule accessions AZ-1 thru AZ-6 grown in saline soil and irrigated with simulated saline drainage water. The guayule accessions AZ1, AZ5, and AZ6 tolerated salinity and B levels better than the others. Consequently, AZ1, AZ5, and AZ6 were then planted in field sediment plots with slight salinity and moderate B levels. In both greenhouse and field studies, concentrations of Se, B, and Na in the leaves were as high as 0.6–8 mg/kg dry weight (DW), 2000 mg/kg DW, and 17,500 mg/kg DW, respectively, in both experiments. In both experiments, concentrations of rubber and resin ranged from 4 to 14 w/w% in the stems, and applied salinity increased rubber and resin production in some accessions. This two-phase study provides additional evidence for guayule accessions (AZ1–6) as a promising rubber-producing crop that tolerates saline irrigation water in poor quality soils. In addition, guayule may be useful in the gentle phytoremediation of Se in poor quality soils or in soils irrigated with Se-laden drainage water. • Guayule AZ accessions grown under saline, B- and S- laden conditions were evaluated. • Guayule’s tolerance to salinity, B, and Se in soil and irrigation varies by accession. • Boron, Se, and Na accumulation mostly takes place in leaf tissue. • Natural rubber and resin were not negatively affected by slight to moderate salinity. • Accession AZ5 was best suited for salinity and B.

Microtopography change of agricultural lands during leaching by establishing internal field canal and drain network for soil salinity control in Sahl El-tina area, Egypt

Despite of supplying recommended leaching fraction, the soil of Sahl El-Tina region in Egypt is moderately saline due to the land systematic irregularity of surface irrigation. The current experiment investigated the effectiveness of changing the land microtopography only during leaching by establishing internal field canals and drains. The baseline measurements showed little salinity of irrigation water, moderate soil salinity and high drainage water being 73 times of irrigation water. Failures were observed in internal canals’ berms attributed to soil salinity and its consequent dispersion and low breaching resistance. Canals’ cross section was maintained weekly until stability was achieved after four weeks, then the daily leaching discharge increased accelerating the salinity removal rate. The results showed strong inverse relationships between leaching water quantity and both drainage water and soil salinities. There was also a strong direct relationship between soil and drainage water salinity in internal field drains. The drainage water salinity and soil salinity decreased to 50% and 23% of initial values, respectively after 64 days with an accumulated water height of 71.4 cm. After 76 days, the drainage salinity decreased to 15% of initial value equivalent to only 10 times of irrigation water salinity and the soil salinity decreased to 17% with an accumulated water height of 104 cm. The experiment ended after 90 days as the drainage salinity became unchanged. The citizen science approach was applied by involving the landowner and farmers in construction, maintenance, measurements, and data analysis.

Optimizing cropping pattern to improve the performance of irrigation network using system dynamics-Powell algorithm.

One of the strategies for agricultural development is the optimal use of irrigation and drainage networks, which leads to higher productivity and economic benefits. In this regard, quantitative and qualitative studies of drainage water from networks are essential for efficient water management. In the present study, we develop a model using a system dynamics approach to simulate the cropping pattern of an irrigation and drainage network as well as the discharge and salinity of drainage water from network farms. We apply the Powell algorithm to optimize the economic profitability of cultivated crops by considering the salinity and discharge of drainage water from the fields. With three aims, i.e., (1) maximizing benefit-cost ratio, (2) minimizing drainage water salinity and discharge of network, and (3) economic and environmental considerations simultaneously, the optimization of cropping pattern within the Kosar irrigation and drainage network is performed. Results based on five consecutive years under different scenarios showed that some crops, such as watermelon, are not economically recommened for production due to high costs, water consumption, and low selling price causes environmental pollution. On the other hand, wheat, grain maize, silage maize, sorghum, and alfalfa have different conditions, and their production is suitable by considering all scenarios. By comparing with experimental data, we find that the proposed model is accurate to simulate and optimize the irrigation network and to detect its cropping pattern.

Assessing the impact of shallow subsurface pipe drainage on soil salinity and crop yield in arid zone.

PurposeSoil salinization is one of the key problems of sustainable development of arid agricultural land. Exploring the use of shallow subsurface pipe drainage to improve soil salinization.MethodsThis study investigates the desalinization effect of shallow subsurface pipe drainage, in combination with drip irrigation under plastic mulch, in an arid region in China. Field data collection was conducted in 2010. Soil salinity at a range of soil depths, water EC and pH of subsurface pipe drainage and crop yield during crop growth stages in salinized farmlands were measured.Results and ConclusionThe results show that soil salinity was reduced significantly on mildly (1–3 dS m−1) and moderately (3–6 dS m−1) salinized farmlands. The highest desalinization rate of mildly and moderately salinized soils was 51% and 91% respectively. The desalinization in upper soil layers, to a depth of 60 cm, was more significant than that in lower soil layers. Drainage water salinity was much higher than irrigation water salinity. Crop yield on mildly and moderately salinized land increased about 25% and 50%, respectively. This indicates that the combination of drip irrigation and shallow subsurface pipe drainage on farmlands is potential feasible to desalt farmlands and to improve crop yield. The study has led to a desalinization of 330 ha year−1 in Xinjiang.

Simulation of real-time variations of saline drainage water: comparing system dynamics with DRAINMOD-S

Abstract Accurate simulations of wastewater quality and quantity, particularly in saline and semi-arid areas, are important in agricultural water management. In this study, a system dynamics (SD) approach was proposed to simulate drainage water and groundwater salinities, water table fluctuation, and drainage discharge at field scale. The results of the SD approach were compared with results from DRAINMOD-S, a computer simulation model. For model validation, earlier experimental data from two field units were used. The field units each contained three rows of piezometers. During irrigation, daily water table fluctuation, drainage discharge, irrigation and drainage water salinity, and the salinity in each piezometer, were measured. The SD approach simulated these parameters more accurately than DRAINMOD-S for both units.

SALEACH: A new web-based soil salinity leaching model for improved irrigation management

Leaching is essential in irrigated croplands where natural precipitation is insufficient to control salinity buildup. Several useful models exist for salinity management; however, leaching requirement (LR) calculations are based on steady-state approaches that only consider salinity tolerance of crops and irrigation water salinity to estimate the LR. In this study, a web-based soil salinity leaching management model (SALEACH) was developed as an online tool to assist growers for better and easier management of soil salinity to sustain agricultural production in irrigated croplands. SALEACH employs the traditional steady-state approach to estimate LRs but improves outputs by not only considering irrigation water salinity (ECiw) and salinity tolerance of specific crops (ECt), but also root water uptake patterns to account for irrigation system differences, and soil types for differences in hydraulic characteristics, as well as water stress and rainfall input. The SALEACH model can calculate the required irrigation water depth by using the estimated LR or any user-specified leaching fraction (LF) values; it can predict the drainage water salinity and soil salinity in the rootzone based on the applied leaching; and it can estimate relative crop yield for a given LF. SALEACH-estimated LRs were assessed in different soil types and irrigation systems by comparing them with LRs, soil water and drainage water salinity values obtained from an existing steady-state model (WATSUIT) and a transient-state model (HYDRUS-1D). Statistical analyses showed that SALEACH-estimated LRs, soil salinity, and drainage water salinity were all in the acceptable ranges of the corresponding values derived from other models. Thus, we conclude SALEACH is reliable and can be employed by practitioners to produce satisfactory estimations of LRs and soil salinity by considering the soil, crop, water quality, and irrigation system. Adoption of the model can improve water use efficiency and reduce groundwater pollution.

Effect of saline drainage water on performance of denitrification bioreactors

Abstract Excessive use of nitrate fertilizers in agriculture causes harm to humans and the environment. The most suitable nitrate removal process is heterotrophic biological denitrification. The purpose of the present study was to evaluate the performance of three shapes of denitrification bioreactors: triangular, rectangular and semicircular. The main element that was used to remove nitrate was beech woodchips. The concentration of inlet nitrate was 75 mg/l and the salinity of the solution was 1 ds/m and 5 ds/m, for a period of six months. The results showed that the efficiency of the triangular bioreactor with a salinity level of 1 ds/m was 90%, which is more efficient than the rectangular and semicircular bioreactors with performances of 55.8% and 53.8%, respectively. The results also indicated that at a salinity level of 5 ds/m, the semicircular bioreactor with a performance of 50.8% inlet nitrate removal was the best of the three shapes of bioreactors tested, the efficiencies of the triangular and rectangular bioreactors were 49.9% and 48.6% respectively. Also, it was observed that at the salinity level of 1 ds/m, a high hydraulic retention time had a high positive effect on denitrification, on the other hand at the salinity level of 5 ds/m, there was better performance of denitrification if the hydraulic retention time was lower.

Comparising and evaluating reaction factor and drainage water quality respect to direction of surface irrigation

This research was carried out to compare the performance of subsurface drainage laterals for four units including two laterals parallel to irrigation direction which are called LP and two laterals perpendicular to irrigation direction which are called LV. In order to study and compare the behaviour of LP and LV, the reaction factors were calculated. The reaction factors were 0.49 and 0.41 in LP and 1.07 and 1.1 in LV. The reaction factor in LV was greater than LP which is implies that the system works properly, and has a quick response to rainfall inputs in LV. Duncan test was used to examine the changes and results showed that there is not a significant difference between different levels of treatment of reaction factor, but there are significant difference between the different treatment levels of outflow and drainage water salinity, and these are dependent on irrigation direction.

Long-term effects of using controlled drainage on: Crop yields and soil salinity in Egypt

ABSTRACT Egypt suffers from a lack of rainwater and hot weather most of the year, which represents a challenge to the current trend to achieve optimum utilization of newly reclaimed land. Egypt’s agriculture depends on irrigation that consumes about 85% of the available water resources. How this problem is managed is the aim of the study, where the controlled drainage (CD) application was evaluated as a water-saving tool and the long-term impacts of using such practice on crop productivity and soil salinity were predicted using DRAINMOD-S for El-Tina plain in the northwestern corner in Sinai. Soil texture of the plain varies between sandy loam to clay. Collected data of wheat and corn as winter and summer crops, respectively, were used to check the model reliability. The water table fluctuations were monitored on a daily basis. At the same time, drains discharges and salinities were also monitored during the whole growing season. The salinities of the topsoil till 1.0 m depth were measured. The obtained results from the model were assessed compared with the observed values of the daily water table fluctuations; lateral discharges, salt concentrations in the soil profile, and relative crop yield during each season. Simulation results satisfactorily matched the data collected from the field. Simulation values obtained for 10 years indicated that the average quantity of drain discharge increased by increasing the managed drainage depth which makes (CD) a promising tool for regulating the draining intensity, a remarkable increase in the soil salinity of the root zone will take place if the irrigation water salinity reaches values above 800 ppm, and consequently the high irrigation water salinity values will badly affect most of the crops that grow normally in the field under study except the high salt tolerance ones as wheat. A noticeable decrease in crop yields will be the inevitable result if both the managed drainage depth and water salinity are increased. The outputs of the study can be considered as guidelines for how to utilize the controlled drainage application under Egyptian conditions.

Drainage water salinity and quality across nested scales in the Nile Delta of Egypt.

Improving water management depends on understanding the functioning of irrigation and drainage systems across different environmental scales. For this purpose, this study in the Nile Delta of Egypt particularly examines the spatial and temporal variation of drainage water salinity from the system to the plot level. A better understanding of this variation across nested scales is crucial to refine the government's drainage reuse strategy and reduce the adverse effects on agricultural productivity, lagoon ecology, and human health. The study investigates the drainage system of the Meet Yazid study area (82,740ha) located in the upper central part of the Nile Delta. The parameters measured were electrical conductivity (EC), dissolved oxygen (DO), pH, and temperature. Results showed that salinity and quality of drainage water in the Nile Delta vary highly with space and time. The secondary drains exhibited the highest variability of salinity compared with main drains and subsurface drainage collectors because they accumulate salts from deeper soil layers and seepage of saline groundwater at the time of low flow discharge. In secondary drains, the salinity increased up to four times that of drainage water coming from the collectors. Moreover, DO values were most of the time not meeting standards for reuse in irrigation, especially at main drains that collect not only agricultural drainage but also untreated household sewage water.

Effect of irrigation with saline water on growth and chemical composition of celery

Celery crop belongs to the family Umbelliferae. The present study aims to understand the physical and chemical changes in celery plants that affected by using saline water in irrigation. A pot experiment was conducted during the two winter seasons of 2017/2018 and 2018/2019 to study the effect of irrigation with agriculture saline drainage water brought from Karoun Lake in El-Fayoum Governorate, Egypt on the growth and chemical contents of celery plants cv. Balady. The used saline water concentrations were 1000, 2000, 3000 and 4000 ppm and tap water at 260 ppm was used as control. The results showed that the plant length, fresh weight and number of leaves were increased significantly at a concentration of 1000 ppm as compared with control. Meanwhile, gradual decrease occurred in these characters with increasing salinity levels. The contents of ascorbic acid, total chlorophyll, carotenoids, nitrogen, phosphorus, potassium and dry weight were significantly increased up to the level of 2000 ppm then gradual decrease was occurred with increasing salinity levels. As for the contents of total soluble solids (TSS.), sodium and proline significantly increased with each increase in the saline level. In conclusion, celery cv. Balady can be irrigated with the limit of 1000 ppm saline water.

Assessing the environmental sustainability of irrigation with oil and gas produced water in drylands

Produced water (PW) is the largest by-product of the oil and gas industry. Its management is both economically and environmentally costly. PW reuse for irrigation offers an alternative to current disposal practices while providing water to irrigators in drylands. The aim of this investigation was to evaluate the environmental effects of irrigation with PW. The SALTIRSOIL_M model was used to simulate the irrigation of sugar beet with 15 PWs of a wide range of qualities in four climates of different aridity and on four contrasting soil types. The impacts on soil salinity, sodicity and pH as well as on crop yield and drainage water salinity were estimated. Well-drained soils with low water content at field capacity (Arenosol) are less sensitive to salinisation while a relatively high gypsum content (Gypsisol) makes the soil less vulnerable to both sodification and salinisation. On the contrary, clayey soils with higher water content at field capacity and lower gypsum content must be avoided as the soil structural stability as well as a tolerable soil electrical conductivity for the crop cannot be maintained on the long-term. Soil pH was not found to be sensitive to PW quality. Drainage water quality was found to be closely linked to PW quality although it is also influenced by the soil type. The impact of drainage water on the aquifer must be considered and reuse or disposal implemented accordingly for achieving sustainable irrigation. Finally, increasing aridity intensifies soil and drainage water salinity and sodicity. This investigation highlights the importance of adapting the existing irrigation water quality guidelines through the use of models to include relevant parameters related to soil type and aridity. Indeed, it will support the petroleum industry and irrigators, to estimate the risks due to watering crops with PW and will encourage its sustainable reuse in water-scarce areas.

Evaluating Drainmod‐s to Predict Drainage Water Salinity and Groundwater Table Depth During Winter Cropping in Heavy‐Textured Paddy Soils

AbstractSimulation models can quickly and cost‐effectively describe various aspects of management practices in newly reclaimed agricultural soils. In this research, the capability of the DRAINMOD‐S model was evaluated to predict the salinity of the subsurface drainage effluents in a newly subsurface drained paddy field during winter cropping. Measurements of groundwater table depths and drainage water salinity were taken in three conventional subsurface drainage systems at the Sari Agricultural Sciences and Natural Resources University, northern Iran, during three canola growing seasons (2011–2012, 2015–2016 and 2016–2017). The data were used to calibrate and validate the model. The model provided better predictions of groundwater table depths in shallower drainage systems. Measured and simulated drainage water salinities varied, respectively, from 620 to 1580 and 790–1430 mg l−1 in the calibration process and from 441 to 1640 and 656–1820 mg l−1 in the validation process. The differences between measured and simulated salt loads were in the range of 59–174 and 43–586 kg ha−1 in calibration and validation, respectively. The results indicated that DRAINMOD‐S can be used as a management tool to diminish environmental issues in heavy paddy soils from the viewpoint of salt load. © 2019 John Wiley & Sons, Ltd.

Irrigation water salinity effects on oregano (Origanum onites L.) water use, yield and quality parameters

Irrigation water salinity effects on oregano growth, water use, yield and quality parameters were investigated. For this aim, eight irrigation water salinity levels including 0.54 (control), 1.2, 1.8, 2.5, 3.5, 5.0, 7.0 and 10 dS/m were utilized. The plants in all of 7 and 10 dS/m and two out of five replications of 5 dS/m treatment could not survive until the end of the experiment. The mean soil salinity and seasonal averaged drainage water salinity values increased with increasing salinities of applied irrigation water. Compared to control 27, 33, 44 and 74% reductions in total dry yields, and 27, 38, 49, and 77% decreases in dry leaf yields were calculated for 1.8, 2.5, 3.5 and 5 dS/m treatments, respectively. In general, increased irrigation water salinity caused increases in total phenolic content, total flavonoid content, extract yield which shows the amount of water extractable matter from the plants and antioxidant activity whereas significant decreases in total oil content. Among the essential oil components, carvacrol, β-cymene and γ-terpinene contents decreased with increasing water salinities up to 2.5 dS/m and after this level sharply increased but linalool content showed a reversed pattern. A threshold value of 0.50 dS/m was calculated for total fresh yield of oregano but it was not possible to determine a threshold salinity value for total dry yield, dry leaf yield and total oil content. Based on these results, oregano is a very sensitive plant to salinity.