High Salinity Irrigation Research Articles

Modeling root zone water and salt transport using matric flux potential based root water uptake distribution

It is important to delineate the root water uptake (RWU) response to salt and water stress for assessing future water availability under extreme climatic conditions. The process of RWU in salt-affected soils is highly complex and not well understood. The present study proposed a matric flux potential based non-linear RWU model capable of calculating reduced RWU in water and salt stressed conditions. The study incorporates a sensitivity analysis of the model's parameters. For the inverse estimation of these parameters, an objective function has been formulated, utilizing data derived from the highly sensitive model's response. The proposed objective function provides unique estimates for these parameters. Using this objective function in an optimization process, the model is calibrated with observed data obtained from a soil column lysimeter experiment conducted on berseem crop (Trifolium alexandrium). The parameters are optimized through the coupling of the model with a genetic algorithm-based optimizer tool. Simulated data for soil moisture, electrical conductivity, and percolation are then compared to observed data. The simulated model's responses are found to be closely aligns with the experimentally observed values. The RWU under four irrigation of different salinity levels is simulated. The results highlight a reduction in RWU compensation under high-salinity irrigation treatment.

Nitrogen application rates influence on yield and water productivity of quinoa under saline irrigation water regimes and saline water table

There are areas with high saline water and saline irrigation water in Iran that may be used for quinoa cultivation. In these conditions, proper saline irrigation water regimes and nitrogen application should be determined and used. Therefore, the aim of this experiment is to investigate the effect of different saline irrigation water regimes (100, 75 and 50% of full irrigation, FI) and nitrogen application rates (0, 100, 200 and 300 kg ha−1) on growth and yield of quinoa with water table depth of 0.8 m, salinity of irrigation water and water table of 20 dS m−1. The irrigation of 75% FI and 50% FI decreased the applied water by 19 and 38%, respectively. Further, there was no reducing effect of irrigation water regimes in seed and shoot dry matter yield. Furthermore, groundwater contribution (GWC) increased significantly by 8 and 18% in 75%FI and 50%FI compared with that obtained in full irrigation, and resulted in no extreme water stress under high water table depth (0.8 m). Increasing application of nitrogen fertilizer significantly increased the yield components, ETc and GWC. In addition, reducing irrigation water did not show a significant decrease in water use efficiency (WUE) in high water table depth. However, water productivity increased significantly by decreasing irrigation water. It is concluded that under deficit irrigation, high water table depth could be a valuable source of water supply to meet quinoa water requirements. Moreover, application of nitrogen fertilizer at all levels significantly increased water use efficiency and water productivity.

Plant Growth Promoting Rhizobacteria and Silica Nanoparticles Stimulate Sugar Beet Resilience to Irrigation with Saline Water in Salt-Affected Soils.

Combined stressors (high soil salinity and saline water irrigation) severely reduce plant growth and sugar beet yield. Seed inoculation with plant growth-promoting rhizobacteria (PGPR) and/or foliar spraying with silica nanoparticles (Si-NP) is deemed one of the most promising new strategies that have the potential to inhibit abiotic stress. Herein, sugar beet (Beta vulgaris) plants were treated with two PGPR (Pseudomonas koreensis MG209738 and Bacillus coagulans NCAIM B.01123) and/or Si-NP, during two successive seasons 2019/2020 and 2020/2021 to examine the vital role of PGPR, Si-NP, and their combination in improving growth characteristics, and production in sugar beet plants exposed to two watering treatments (fresh water and saline water) in salt-affected soil. The results revealed that combined stressors (high soil salinity and saline water irrigation) increased ion imbalance (K+/Na+ ratio; from 1.54 ± 0.11 to 1.00 ± 0.15) and declined the relative water content (RWC; from 86.76 ± 4.70 to 74.30 ± 3.20%), relative membrane stability index (RMSI), stomatal conductance (gs), and chlorophyll content, which negatively affected on the crop productivity. Nevertheless, the application of combined PGPR and Si-NP decreased oxidative stress indicators (hydrogen peroxide and lipid peroxidation) and sodium ions while increasing activities of superoxide dismutase (SOD; up to 1.9-folds), catalase (CAT; up to 1.4-folds), and peroxidase (POX; up to 2.5-folds) enzymes, and potassium ions resulting in physiological processes, root yield, and sugar yield compared to non-treated controls under combined stressors (high soil salinity and saline water irrigation). It is worth mentioning that the singular application of PGPR improved root length, diameter, and yield greater than Si-NP alone and it was comparable to the combined treatment (PGPR+Si-NP). It was concluded that the combined application of PGPR and Si-NP has valuable impacts on the growth and yield of sugar beet growing under combined stressors of high soil salinity and saline water irrigation.

Ensemble HYDRUS-2D modeling to improve apparent electrical conductivity sensing of soil salinity under drip irrigation

Monitoring and mapping soil salinity are valuable for irrigation management and reclamation of salt-affected agricultural soils in arid and semi-arid regions. Proximal measurements of apparent soil electrical conductivity (ECa) can help characterize soil salinity spatial distributions. However, ECa is not solely a function of salinity. ECa is strongly influenced by soil salinity, water content, and edaphic properties such as texture and bulk density. Consequently, monitoring and mapping salinity based on geospatial ECa measurements is challenging in fields with dynamic and spatially complex patterns of salinity and water content, such as occurs under drip irrigation. We conducted a numerical modeling study to evaluate protocols for using proximal ECa sensing in drip irrigated systems, focusing specifically on the measurement distance from the drip-line that consistently identifies areas of high salinity in the rootzone. The measurement distance was evaluated as a function of six irrigation management parameters: soil hydraulic conductivity, irrigation discharge, irrigation interval, solute concentration, root-zone volume, and leaching fraction. HYDRUS-2D was used to run a 729 member ensemble of drip irrigation simulations of water and solute dynamics under different irrigation management scenarios. Two case studies were simulated for clay loam soil: (1) low salinity soil irrigated with high salinity irrigation water and (2) high salinity soil irrigated with low salinity water. Depth-averaged ECa measurements down to the 75 and 150 cm depths, such as can be obtained using an electromagnetic induction (EMI) sensor, were evaluated in the simulations. According to the ensemble results, a reliable EMI measurement distance from the drip-line was about 100 cm for the case of low salinity irrigation in saline soil and adjacent to the drip-line for the high salinity irrigation. The ensemble ECa and EC of saturated paste extract (ECe) distributions were twice as sensitive to the irrigation water salinity level as compared to the other irrigation management parameters. The probabilistic ensemble approach can be extended to a variety of case studies to aid soil scientists and agricultural consultants monitoring and mapping soil salinity with ECa-directed soil sampling for micro-irrigation systems.

The Mineral Composition of Date Palm Fruits (Phoenix dactylifera L.) under Low to High Salinity Irrigation.

Adaptability to salinity varies between different varieties of date palm trees. This research aims to explore the long-term impact of different salinity irrigation levels on the mineral content of 13 date palm varieties grown in the United Arab Emirates (UAE). Date varieties were grown using three irrigation water salinity levels of 5, 10 and 15 dS m−1. The mineral composition (B, Ca, Cu, Fe, K, Mg, Na, P and Zn) of date palm fruits was determined using Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES). High salinity levels showed no effect on the mineral content of Ajwat AlMadinah, Naghal, Barhi, Shagri, Abu Maan, Jabri, Sukkari and Rothan varieties. All date varieties remained good sources of dietary potassium, magnesium, manganese and boron even at high salinity levels. Increased salinity had no effect on the percent Daily Value (%DV) categories of most of the analyzed minerals. While no genotypes showed a general adaptation to different saline environments, Barhi, Ajwat Al Madinah, Khinizi, Maktoumi and Shagri varieties were more stable towards salinity variation. In the UAE, the genotype x saline-environment interaction was found to be high which makes it impossible to attribute the variation in mineral content to a single varietal or salinity effect.

Impact of Drought and Changing Water Sources on Water Use and Soil Salinity of Almond and Pistachio Orchards: 2. Modeling

California is increasingly experiencing drought conditions that restrict irrigation deliveries to perennial nut crops such as almonds and pistachios. During drought, poorer quality groundwater is often used to maintain these crops, but this use often results in secondary salinization that requires skilled management. Process-based models can help improve management guidelines under these challenging circumstances. The main objective of this work was to assess seasonal soil salinity and root water uptake as a function of irrigation water salinity and annual rain amounts. The manuscript presents a comparison of three-year experimental and numerically simulated root zone salinities in and below the root zone of almond and pistachio drip-irrigated orchards at multiple locations in the San Joaquin Valley (SJV), California, with different meteorological characteristics. The HYDRUS-1D numerical model was calibrated and validated using field measurements of soil water contents and soil solute bulk electrical conductivities at four root zone depths and measured soil hydraulic conductivities. The remaining soil hydraulic parameters were estimated inversely. Observations and simulations showed that the effects of rain on root zone salinity were higher in fields with initially low salinities than in fields with high salinities. The maximum reduction in simulated root water uptake (7%) occurred in response to initially high soil salinity conditions and saline irrigation water. The minimum reduction in simulated water uptake (2.5%) occurred in response to initially low soil salinity conditions and a wet rain year. Simulated water uptake reductions and leaching fractions varied at early and late times of the growing season, depending on irrigation water salinity. Root water uptake reduction was highly correlated with the cumulative effects of using saline waters in prior years, more than salt leaching during a particular season, even when rain was sufficient to leach salts during a wet year.

Synergistic and antagonistic interactions of soil water potential and osmotic potential linked to nitrogen fertilization on spinach traits and water use efficiency

Few studies have attempted to investigate the combined effects of soil matric potential (Ψm) and osmotic potential (Ψs) on plant production and water use efficiency (WUE). The purpose of this study is to evaluate the synergistic and antagonistic effects of Ψm and Ψs associated with nitrogen (N) fertilization on spinach (Spinacia oleracea L.) growth traits and WUE. Five levels of salinity (1, 4, 7, 9, 11 dS m−1), three levels of water use amounts including deficit-irrigation (W–), full-irrigation (W0) and over-irrigation (W+), and four levels of N application rates (0, 50, 75, and 100% of N requirement) were applied. A new parameter namely "WUEθ" is suggested based on soil water content (θ). Results showed that water deficit combined with high saline irrigation water caused the most reduction in the plant biomass, leaf area index (LAI) and evapotranspiration (ET). The acquired plant yield coefficient (Ky) of 1.003 indicates that the spinach is a moderately salt-sensitive vegetable. The highest WUE was observed under deficit-irrigation and intermediate salinity conditions, which was attributed to an adaptation mechanism in the plant. However, WUEθ (R2 > 0.98) was a better predictor of the plant yield than WUE (R2 > 0.48). Nitrogen use efficiency (NUE) decreased with increasing salinity and water deficiency. Also, Ψm and Ψs had a synergistic interaction on yield and ET, while their effect on WUE and WUEθ was antagonistic. Salinity greater than drought reduced yield, while both had equal reducing effects on ET. Furthermore, WUE and WUEθ were more influenced by Ψm than Ψs. Research Highlights The new parameter WUEθ is a better predictor of the spinach plant yield than WUE. WUE and WUEθ are more influenced by water potential (Ψm) than osmotic potential (Ψs). Synergistic interaction of Ψm and Ψs on yield and ET, but antagonistic effect on WUE and WUEθ. Salinity greater than drought reduces yield, while both have equal reducing effects on ET. Ψm shows negative effects on yield and ET, but positive effects on WUE and WUEθ.

The Effects of Biochar and Compost on Different Cultivars of Shallots (Allium ascalonicum L.) Growth and Nutrient Uptake in Sandy Soil Under Saline Water

High salinity irrigation will cause nutrient uptake and shallot growth to deplete due to its sensitivity to salinity. This research aimed to investigate the effect of biochar and compost on shallot growth and nutrient uptake in sandy soil like Entisol when irrigated using salty water. This research carried out some pot experiments and put on the field using a completely randomized design. The first factor was based on the amendment with control of 20 tons ha<sup>-1</sup> of Biochar, 10 tons ha<sup>-1</sup> of compost, and a mixture of 10 tons ha<sup>-1</sup> biochar and 5 tons ha<sup>-1</sup> of compost; the second factor was composed of 3 shallot cultivars (Brebes, Pemalang, and Purbalingga). Each pot was filled with 15 kg of soil; the pot 30 cm in diameter, incubated with saline water and irrigated by 2 dS m<sup>-1</sup>. The results show that irrigation with ground saline water causes Entisol to increase exchangable Na, Ece and SAR, decrease exchangeable Ca and Mg. The application of all treatments decreased SAR. The application of compost significantly increased N and K uptake but made soil pH, EC, and SAR to decrease while fresh weight and dry weight of bulb in Brebes cultivars increased. The combination of biochar with 5 tons ha<sup>-1</sup> of compost produced the highest yield on plant height and number of tuber in Pemalang cultivars and had the largest tuber diameter in Purbalingga cultivars. There is an interaction between amendment and cultivar on plant height, fresh weight of tuber (P<0.01), dry weight of tuber (P<0.01).

Effectiveness of Trichoderma harzianum in soil and yield conservation of tomato crops under saline irrigation

Protected horticultural crops in the Mediterranean region are typically under deficit irrigation and intensive cultivation practices and must cope with poor irrigation and soil quality due to salinization. The effects of variable irrigation water quality and use of the beneficial fungus Trichoderma harzianum on the evolution of soil salinization and yield during a single cropping season are examined at a small-scale Solanum lycopersicum L. cv Elpida greenhouse experiment. The experiment simulates typical coastal Mediterranean greenhouse cultivation conditions of the RECARE Project soil salinization Case Study in Greece (Timpaki basin in Crete). Local NaCl-free but highly calcareous planting soil as well as local cultivation practices were used to replicate prevailing conditions at the Case Study. Tomato plants were drip irrigated with NaCl solutions of low (L) (ECw = 1.1 dS m−1) and high (H) (ECw = 3.5 dS m−1) concentration to emulate a typical “good quality” and “marginal quality” irrigation water, respectively. T. harzianum (T) was selectively applied resulting in a total of 2 treatments colonized with the fungus (LT, HT) and two not (N) colonized (LN, HN). For high salinity irrigation treatments HN and HT, sodium adsorption ratio (SAR) values settled at 22.2 and 13.4, respectively, showing that T. harzianum reduced the effect salinity significantly. Monitoring of soil nutrients showed a significant decrease of P-Olsen in non-T. harzianum treatments versus no change in P-Olsen in T. harzianum treatments. Final total and marketable tomato yield for treatment HN were reduced compared to LN by 28% and 42%, respectively, with in T. harzianum treatments having no significant effect. Fruit quality characteristics were overall less sensitive to higher irrigation salinity than to timing of harvest. We conclude that, under high salinity irrigation, an early harvest and termination of the cultivation has no significant impact on tomato yield while obviating pressure on soil resources and conserving agricultural input.

Evaluation of bermuda and paspalum grass types for urban landscapes under saline water irrigation

ABSTRACTIn the arid regions, turfgrass cover is an integral part of landscape to protect the soil from erosion, enhance the aesthetic value, and improve the microclimate. The salinity and the scarcity of fresh water of the arid region are the major challenging factors in turfgrass production. Therefore, the need for salt tolerant turfgrass with functional quality is necessary to improve the turf performance. The detrimental effects of salinity include growth suppression, and lowered osmotic potential ultimately leading to firing of the leaf blades. In this context, the study was undertaken to determine the relative salt tolerance and growth response of turfgrass genotypes in order to recommend turfgrass cultivars that can tolerate high salinity irrigation and maintain excellent visual and functional qualities under United Arab Emirates (UAE) condition. The paspalum cultivars maintained the highest succulence percentage compared to the bermudagrass cultivars under enhanced salinity levels. The shoots count, fresh weight (FW), and dry weight (DW) were found highest in paspalum types. The chlorophyll a, chlorophyll b and the total chlorophyll content was found higher in bermuda grass types under high salinity levels. The bermudagrass cultivars showed significantly higher carotenoids, anthocyanins and proline compared to the paspalum types under salt stress condition. In the case of princess 77 and Yukon, an inherently high amount of proline was recorded which confirmed an increase up to 10,000 ppm and drastically declined beyond this concentration. Sea Dwarf paspalum and Sea Isle 2000 maintained uniformity in the proline level at all levels of salinity without significant variation. These findings point to the fact that both paspalum and bermuda types exhibited varied responses to different physiological and biochemical parameters under the saline conditions. Paspalum types have an edge over the bermudagrass in terms of shoot density, which is a potential factor in determining the high-quality turfs. Bermudagrass types can be applied in lower salinity conditions based on the responses as evidenced from the present results.

Erratum to: Mitigation of Salt Stress Negative Effects on Sweet Pepper Using Arbuscular Mycorrhizal Fungi (AMF), Bacillus megaterium and Brassinosteroids (BRs)

A study was conducted at the experimental farm of Faculty of Agriculture, Ain Shams University, Cairo, Egypt, during two successive summer seasons (2014 and 2015) to investigate the effects of arbuscular mycorrhizal fungi (Glomus irradicans 10% w/w), Bacillus megaterium (10 ml/pot) and brassinosteroids (24-EBL, C28H48O6; 2 µM) on growth, nutrient absorption, chlorophyll, proline content, antioxidant enzymes activity and fruit yield of sweet pepper plants (Capsicum annuum L.) cv. Marconi. Plants were grown under three levels of salinity (0, 25 and 50 mM). The obtained results showed that plants grown under non-saline water (0 mM NaCl), with or without treatments, significantly gave the most vigorous vegetative growth and had the highest fruit yield compared with those grown under salt stress conditions. All anti-salinity treatments (Mycorrhiza, Bacillus and Brassinosteroids) improved growth when compared with untreated plants (control). Plants inoculated with mycorrhiza or treated with brassinosteroids showed better vegetative growth and shoot biomass (total fresh and dry weight per plant), chlorophyll a and b concentrations, antioxidant content expressed as total soluble phenols and proline concentrations at all studied salinity levels followed by plants inoculated with Bacillus megaterium compared with control plants which showed severe growth retardant especially under higher salt concentration (50 mM). Carotenoids concentration increased proportionally with the increase of salinity concentration. The maximum leaf relative water content (LRWC) and lowest values of membrane permeability (MP) were significantly observed with mychorhiza inoculated plants and brassinosteroid application respectively, followed by Bacillus inoculated plants. Antioxidant enzyme activity were highest in plants irrigated with moderate saline water (25 mM) than plants under high salinity irrigation water (50 mM) except polyphenol oxidase (PPO) as compared with unstressed plants (0 mM). Mycorrhizal inoculated plants accumulated higher K and lower Na and Cl followed by plants treated with brassinosteroids and then plants inoculated with Bacillus megaterium. Anti-salinity treatments positively enhanced fruit yield of sweet pepper plants under all salinity stress levels and the highest fruit yield were significantly observed with brassinosteroid application followed by mychorhiza inoculated plants and then Bacillus inoculated plants.

USING SEAWATER IN AGRICULTURAL AND RESISTANT IT'S POSSIBLE HAZARDS ON SOIL AND PLANT

Water is certainly one of the most critical inputs in crop production in many parts of the world particularly in the arid and semi-arid regions, i.e. Egypt, in the near future the required development of irrigated agriculture is necessary to cope with the increasing food demands from increasing population and water scarcity in Egypt. It has thus become necessary to explore new water sources that can meet current or future demand for irrigation supply. The main objective of this study was to determine the maximum amount of seawater irrigation needed to produce a good yield and study the combined effect of diluted seawater (I1, I2, I3, I4, I5, and I6) and rates of compost addition (0.0, 4.0, 8.0 ton fad.-1) on plant growth, crop production and soil properties. Sandy soil Lysimeters were planted by salt-tolerant plants (barley) followed by sunflower crop under the same treatments. Results concluded that all diluted seawater prepared was suitable for irrigation crops according to the calculated criteria of water quality. The values of soil pH, Ec (ds/m) and ESP at the end of the two seasons were taken the same trend, which increased significantly with increasing the salinity of irrigation water or increasing the rate of compost addition as individual factors but in combination among them appeared insignificant variation in most studied properties. Also, available macronutrients residual in experimental soil were affected by the antagonism relationship between the studied factors, positively by addition of compost and negatively with salinity water supply. It was noticed that the interaction between treatments has positive role in reducing the hazards of the salinity irrigation water, which the biological yield of barley was decreased to maximum percentage (28.95%) at using the highest salinity irrigation water (I6). But, it was obtained the minimum reduction percentage (5.9%) if combined with the highest rates of compost addition compared with the control (I1). The residual effect of highest compost addition was more clearly on the parameters studied of sunflower cultivated in the second season which hadn't reduce the hazards of high salinity irrigation water (I6) alone but optimized with the values parameters studied particularly seed yield by 16.3% at the treatments (I6 × C3) compared with the control (I1).

Long-term field response of pistachio to irrigation water salinity

A three years field study was conducted to assess the effects of moderate and high saline irrigation water on the behavior of 5-year-old female trees of pistachio. Mateur cultivar was grafted on Pistacia vera L. and Pistacia atlantica Desf. rootstocks. Different water irrigation qualities were used: (i) tap water (ECw: 1.95dSm−1); (ii) moderately saline water (ECw: 5dSm−1); and (iii) highly saline water (ECw: 12dSm−1). Rootstock and scion growth were measured. Fruit yield was monitored during the three years of salt treatment and the following year after salt stress was relieved. Leaf mineral content and electrolyte leakage were determined monthly during growing seasons. Results showed that tree growth was not affected by moderate salinity after the first season of experiments but the response changed at higher salinity and when salt treatment duration increased. Salinity of irrigation water did not affect average fruit yield per tree but when saline water irrigation was stopped, yield of trees previously irrigated with highly saline water increased significantly on P. atlantica rootstock in comparison with control. Sodium and chlorides ions content in leaves accumulated proportionally to salinity level and duration. Nitrogen (N), phosphorus (P), potassium (K) and calcium (Ca) as well as K/Na and Ca/Na ratios decreased with increasing salt concentration in the irrigation water. This reduction was more significant in the second and third years of the study. Water management practice was proposed to take advantage from the stimulating effects of mild/short term salinity on growth and production of pistachio Mateur cultivar.

Medical therapy, refractory chronic rhinosinusitis, and productivity costs.

The purpose of this review is to address the most recent advances in the medical therapy for chronic rhinosinusitis (CRS), define recalcitrant and refractory CRS, and discuss the productivity costs associated with CRS. Recent studies evaluating anti-IL-4 receptor α antibodies and calcium channel blockers have demonstrated promising early results during management of CRS. Recent appropriateness criteria have been developed to assist clinicians with defining which patients have 'refractory' CRS and may be considered candidates for endoscopic sinus surgery. Productivity costs appear to be associated with disease severity and can be reduced with appropriate interventions. Topical corticosteroid therapy and high volume saline irrigation continue to be the cornerstone to medical therapy, whereas use of systemic corticosteroids and antibiotics depends on CRS phenotype and presence of acute exacerbation. More research is needed before routine use of novel immunomodulatory therapies such as anti-IL5, anti-IgE, anti-IL4, and calcium channel blockers. Clinicians should apply an appropriate definition for refractory CRS when discussing role of sinus surgery. Assessing the degree of work productivity impairment can assist in treatment decision-making and may help predict treatment outcomes.

Fruit-based agroforestry systems for saline water-irrigated semi-arid hyperthermic camborthids soils of north-west India

Large areas in arid and semi-arid regions remain barren due to lack of irrigation. The underground aquifers in these regions are either saline or sodic. Groundwater surveys indicate that poor-quality water is used to irrigate arable crops in 25–84 % of the total groundwater development areas in north-western states of India. The present long-term study assessed the performance of low-water-requiring, salt-tolerant fruit-based (Carissa carandas, Emblica officinalis, Aegle marmelos) agroforestry systems with saline irrigation under sem-iarid conditions. The companion crops such as Hordeum vulgare for malt, Brassica juncea, a seed oil (winter), and Cyamopsis tetragonoloba for gum and Pennisetum typhoides, a coarse grain/fodder (summer), were grown in inter-row spaces. The fruit trees were successfully established in the sill of furrows using low (EC 4–5 dS m−1) salinity water. Subsequently, all the systems were irrigated with water of low and high (8.5–10.0 dS m−1) salinity and their alternate use as per treatments. Fruit yields under alternate and high saline irrigation reduced by 18–27.5 % in Carissa, 41.6 % in Emblica and 31.7–54.8 % in Aegle, respectively. There was no significant reduction in grain yields of Pennisetum and Hordeum. However, in subsequent years, the seed yields of Cyamopsis and Brassica reduced with saline water and more so when intercropped with Aegle. Carissa with Pennisetum and Hordeum performed best with saline water. The study shows that saline water (ECiw up to 10 dS m−1) could be used sustainably for these fruit-based agroforestry systems without significant salinity build-up in sandy loam calcareous soils. Thus, such fruit-based agroforestry systems could be a viable option for the areas with only saline groundwater available for irrigation.

Effects of Zinc and Ascorbic Acid Application on the Growth and Photosynthetic Pigments of Millet Plants Grown under Different Salinity

Salinity stress impacts crop growth as well as production. The need for increased food production to feed the increasing population and the limited resources, i.e. optimal quality land and water, require developing strategies to mitigate marginal stresses, including salinity stress, for reasonable expectation of crop production. A pot experiment was conducted in a greenhouse at the National Research Centre, Dokki, Cairo, Egypt in the summer season of 2005 to evaluate the effects of foliar application of ascorbic acid alone or in combination with zinc sulfate on the growth and photosynthetic pigments of millet plants irrigated by tap water (250 ppm, 0.39 dS·m-1) or moderate to high salinity irrigation water [2500 ppm (3.9 dS·m-1) and 5000 ppm (7.8 dS·m-1)]. Increased salinity in the irrigation water decreased the plant growth, biomass, and carotenoid content. Foliar application of ascorbic acid alone increased number of leaves and leaf area, while in combination with zinc sulfate increased the plant height and total plant biomass. However, these treatments had no significant effects on the photosynthetic pigments. This study demonstrates that exogenous application of ascorbic acid can enhance foliar growth which may contribute to increased plant biomass and yield.

Effects of high salinity irrigation on growth, gas-exchange, and photoprotection in date palms (Phoenix dactylifera L., cv. Medjool)

Date palms are widely cultivated in arid Mediterranean regions and require large quantities of water to produce commercial fruit yields. In these regions the plantations are commonly irrigated with low-quality water, which results in reduced growth and yields. To study the effect of using saline water for irrigation, date palm seedlings (cv. Medjool) were subjected to long-term irrigation treatments with water containing between 2 and 105mM NaCl. The effect of saline irrigation was determined according to leaf gas exchange, chlorophyll a fluorescence, growth parameters and the distribution of key minerals in different plant organs. High salinity decreased plant growth and increased Na+ accumulation in the roots and lower stem. However, Na+ ions were mostly excluded from the sensitive photosynthetic tissues of the leaf. Thus, the reduction in the CO2 assimilation rate was primarily attributed to a reduced stomatal conductance. Consistent with this finding, the photosynthetic response to variable intercellular CO2 concentrations (A/Ci curves) revealed no permanent damage to the photosynthetic apparatus and implicated developed photoprotective mechanisms. Independent of salinity treatment, 80% of the energy absorbed by the leaf was directed to non-photochemical quenching, as presented in electron-equivalent units. Functioning at full capacity, the non-photochemical mechanism could not compensate for all the excess irradiance. Thus, of the remaining absorbed energy, a significant portion was directed to photochemical O2 related processes, rather than CO2 prevented photoinhibition. The exclusion of toxic ions and O2-dependent energy dissipation maintained photosynthetic efficiency and supported survival under salt stress.

Monitoring and assessing of changes in soil and groundwater salinity of Yemisli Irrigation District of Turkey using low quality irrigation water

Low irrigation efficiency, high saline irrigation water, heavy soil texture, lack of adequate field drainage systems may cause soil salinity and drainage problems in irrigated agriculture. The mentioned problems are major treats for the sustainability of irrigated agriculture. This study carried out in 2007 was undertaken in 7,110 ha of area under the directive of Yemisli Irrigation Association (YIA) in Lower Seyhan Plain, on Southern coastal plains in Turkey. Growers in the area use low quality irrigation return flows of up-stream areas for irrigation. Irrigation method commonly used in the region is flood irrigation with low field irrigation efficiency. This work examines if using low quality of irrigation water causes drainage and soil salinity problem. For this purpose, a year around survey of 55 groundwater observation wells was carried out. Groundwater depths in the observation wells in February, March, June, July and October were measured. Salinity of the water samples collected from the wells was measured as electrical conductivity (ECw at 25°C). Additionally, soil samples from 0 to 30, 30 to 60 and 60 to 90 cm depths at 34 randomly selected sites were analyzed for soil salinity (ECe at 25°C) and alkalinity (SAR). The mean groundwater depth was the minimum (0.97±0.29 m) in March, before starting of the irrigation season. In October, following completion of the irrigation season, the groundwater depth was the highest (1.59 ± 0.13 m). Groundwater EC, greater than 20 dS m-1, was noted commonly. In 93% of the study area, ECw was higher than 5 dS m-1. Mean soil salinity ECe was higher below 1 m depth compared with that of surface layers. Likely occurrence of soil alkalinity (that is, sodium effect) was greater in sub-soil below 30 cm depth compared with surface layers. The results of the study showed that the soils of the area may become salt or even sodium affected in the future unless the present practice of irrigation management is changed. Key words: Irrigation management, drainage, observation wells, water table, EM38, spatial and temporal variability.

Possible utilization of high-salinity waters and application of low amounts of water for production of the halophyte Kochia scoparia as alternative fodder in saline agroecosystems

Production of halophytes using saline waters and soils and feeding them to livestock is one of the most sustainable methods of conservation in desert ecosystems, in addition to accomplishing food production for the people living in these areas. Therefore, to study the possibility of irrigating Kochia ( Kochia scoparia L. Schrad) with minimum quantities of highly saline water for use as a fodder crop in arid environments stretching across saline waters, two experiments were carried out in the Research Farm of the Ferdowsi University of Mashhad, Iran. In the salinity experiments, two populations of Kochia, including the Sabzevar and Indian genotypes, were irrigated with ground water having electrical conductivity (EC) of 5, 15, and 20 dS m −1 . In the irrigation-treatment experiments, two local populations of Kochia, including Sabzevar and Borujerd, were subjected to four irrigation regimes as follows: complete irrigation (100%), 80%, 60%, and 40% of the water requirements using a saline ground water with EC = 5 dS m −1 . Because, the Indian genotype is preferred as an ornamental plant , it is not suitable for increased dry-matter production under high-salinity irrigation water compared to the local genotype (Sabzevar), which is suitable for forage. The Sabzevar genotype produced a large amount of dry matter (7530 kg ha −1 ), even when irrigated with 20 dS m −1 saline water. The best time for harvesting Kochia for fresh feeding is at the end of flowering (88 days after sowing or DAS), when the biomass is relatively high (6500 kg ha −1 ) and the leaf-to-shoot ratio, as a quality index, is approximately 50%. The highest green-area index was observed at 15 dS m −1 and decreased at high levels of salinity. Photosynthesis and transpiration rate did not decline significantly with increasing external salinity four weeks after salinization , but increased in both genotypes at 15 dS m −1 , indicating that the salinity-tolerance threshold of Kochia for both photosynthesis and transpiration reduction is above this salinity level. The Indian genotype also showed a very low seed yield (210 kg ha −1 ) at low levels of salinity, whereas Sabzevar produced 1120 kg ha −1 seed under the same conditions. Different irrigation regimes had a significant effect on the biomass and seed production of Kochia. The highest forage yield was obtained from complete irrigation, with 11.1 Mg ha −1 dry material. Sabzevar local population represented a better performance in terms of all characteristics, except accumulation of inflorescence dry matter, and no significant effects were recorded. In conclusion, Kochia's high foliage production capacity in the presence of salinity and limited irrigation make this plant suitable for use as an alternative forage crop in harsh environmental conditions. There is a wide range of intraspecific variation in K. scoparia, but more investigation is needed to introduce it as a cash crop.

CHLORIDE AND SODIUM UPTAKE POTENTIAL OVER AN ENTIRE ROTATION OF POPULUS IRRIGATED WITH LANDFILL LEACHATE

There is a need for information about the response of Populus genotypes to repeated application of high-salinity water and nutrient sources throughout an entire rotation. We have combined establishment biomass and uptake data with mid- and full-rotation growth data to project potential chloride (Cl−) and sodium (Na+) uptake for 2- to 11-year-old Populus in the north central United States. Our objectives were to identify potential levels of uptake as the trees developed and stages of plantation development that are conducive to variable application rates of high-salinity irrigation. The projected cumulative uptake of Cl− and Na+ during mid-rotation plantation development was stable 2 to 3 years after planting but increased steadily from year 3 to 6. Year six cumulative uptake ranged from 22 to 175 kg Cl− ha−1 and 8 to 74 kg Na+ ha−1, while annual uptake ranged from 8 to 54 kg Cl− ha−1 yr−1 and 3 to 23 kg Na+ ha−1 yr−1. Full-rotation uptake was greatest from 4 to 9 years (Cl−) and 4 to 8 years (Na+), with maximum levels of Cl− (32 kg ha−1 yr−1) and Na+ (13 kg ha−1 yr−1) occurring in year six. The relative uptake potential of Cl− and Na+ at peak accumulation (year six) was 2.7 times greater than at the end of the rotation.