Brackish Water Irrigation Research Articles

Effects of irrigation methods and salinity on CO2 emissions from farmland soil during growth and fallow periods

Drip irrigation and brackish water irrigation are considered to be the two main ways to alleviate the current shortage of agricultural freshwater resources and have been widely used in countries around the world. Our purpose is to evaluate the effects of different irrigation methods (flood irrigation and drip irrigation) and irrigation water salinities (1.1 g·L−1, 2.0 g·L−1, 3.5 g·L−1, and 5.0 g·L−1) on the soil CO2 emissions during the growth and fallow periods of spring maize. Therefore, a two-year field experiment was conducted in Hetao Irrigation District in China from 2017 to 2019. The results showed that compared with flood irrigation, drip irrigation significantly decreased the soil CO2 emissions in the growth period. After irrigation with a salinity of 5.0 g·L−1, the soil moisture was the highest because the plant water absorption was inhabited by soil salt, and the soil CO2 emissions were also promoted during the growth period. Irrigation method and irrigation water salinity had no effect on the soil CO2 emissions in the fallow period. Soil temperature, moisture and inorganic nitrogen content were the main factors affecting the daily CO2 emission flux. The soil CO2 emissions during the growth period accounted for more than 83.93% of the annual soil emissions. Based on the goal of saving freshwater resources, ensuring soil safety, reducing soil CO2 emissions and increasing the size of the carbon pool, adoption of drip irrigation with 2.0 g·L−1 brackish water could be adopted to ensure the sustainable development of local agriculture.

Effects of fruit load intensity and irrigation level on fruit quality, water productivity and net profits of date palms

An integrated research coupling a field study with an agronomic-economic model (ANSWER-APP) was conducted to investigate the combined effects of irrigation levels and crop loads on fruit quality, water productivity and profitability of mature date palms. The study took place in Israel’s hyper-arid Arava Valley, where date palm trees are widely cultivated and rely exclusively on brackish water irrigation. Three fruit load intensities (low, FL1; commercial, FL2; high, FL3) and two irrigation levels (W1 and W2, equal to and higher than the local irrigation regime, respectively) were applied in a 22-year-old date palm orchard in 2018–2019. Irrigation amount, fruit quality and yield were measured. Profitability for each treatment was analyzed with the ANSWER-APP. Higher fruit load resulted in higher yield and water productivity, but on the other hand led to reduced fruit physical properties (size and mass), regardless of the irrigation treatment. The improved fruit physical properties and net profits in W2 compared to W1 treatment in each fruit load group resulted from excess salt leaching in the root zone. Notably, trees under W2FL2 treatment were found to have highest net profits. It is concluded that adequate irrigation amounts contribute to net profits in date palm trees treated with high fruit load intensity under saline irrigation conditions.

Treated Wastewater and Fertigation Applied for Greenhouse Tomato Cultivation Grown in Municipal Solid Waste Compost and Soil Mixtures

Low-fertility soil and the use of brackish water for irrigation act as obstacles and limit crop production. The utilization of municipal solid waste (MSW), compost (C), and treated wastewater (TWW) is receiving attention nowadays not only to overcome the above limitations but also as an efficient way for waste management and reuse of raw materials. In the present study, MSW compost in different ratios (5%, 10%, 20%, and 40%), fertigation and/or irrigation with TWW were studied in tomato plants (Solanum lycopersicum L.). The addition of compost increased organic content, pH, electrical conductivity (EC), and mineral content of the growing media, while fertigation and TWW supported the mineral status of the growing media, and this was reflected in the increase of N, K, and Na in tomato leaves. Plants grown in compost-based media with fertigation produced more leaves, compared to the control, while irrigation with TWW did not increase the number of leaves. Plant biomass increased with the application of ≥20% C, fertigation, and/or TWW applications. Plant yield increased in 40% C, while fertigation increased yield in case of lower (5%-10% C) compost ratios, but TWW application did not change the yield. The combination of high C ratios and fertigation and/or TWW decreased tomato fresh weight. Different levels of C did not affect leaf photosynthesis, stomatal conductance, internal CO2 concentration, and chlorophyll fluorescence, but, in general, the combination of compost with fertigation and/or TWW affected them negatively. Fruit total soluble solids, acidity, ascorbic acid, firmness, and total phenolics were increased with the high ratios of compost and/or fertigation and TWW applications, but marketability did not. Bacteria (total coliform and Escherichia coli) units increased in growing media subjected to TWW, but lower levels were counted on the fruit, mainly due to splashing or fruit contact with the soil. The results indicate that up to 40% C can be added into the substrate, as increased plant growth and maintained plant yield for greenhouse tomato cultivation is observed, while fertigation and TWW could be used in a controlled manner as alternative means for nutrient and irrigation in vegetables following safety aspects.

Production of Bambusa vulgaris seedlings from rhizomes under brackish water irrigation

ABSTRACT The objective of this study was to evaluate the influence of irrigation with brackish water on the production of bamboo seedlings (Bambusa vulgaris). The experiment was carried out at the Fazenda Experimental Piroás, in the municipality of Redenção, CE, Brazil (4° 14’ 53” S, 38° 45’ 10” W, and altitude of 230 m), in a completely randomized design with five treatments and six repetitions. The treatments consisted of five irrigation water electrical conductivity (ECw): 0.5 (control); 1.5; 2.5; 3.5 and 4.5 dS m-1. At 120 days after the beginning of the application of the treatments the leaf gas exchange, relative chlorophyll index (RCI), plant height (H), shoot dry matter (SDM), H/SDM ratio, and the concentrations of Na+ and K+ in stems and leaves were evaluated. Salt tolerance indexes were calculated based on SDM, H, photosynthesis rate and RCI. The increase in the ECw reduced leaf gas exchange, and the reduction in the photosynthesis rate was caused by stomatal and non-stomatal effects. The salinity affected negatively the growth and quality of bamboo seedlings, with the greatest effects being with ECw equal to or greater than 2.5 dS m-1. Bamboo seedlings present Na+ retention in the stems and low Na+/K+ ratio in the leaves. Bamboo seedlings are tolerant to salinity up to 1.5 dS m-1, indicating that waters with this salinity can be used for seedling production of this species, without loss of growth and quality.

EFFECT OF DRIP IRRIGATION WITH BRACKISH WATER ON THE SOIL CHEMICAL PROPERTIES FOR A TYPICAL DESERT PLANT (HALOXYLON AMMODENDRON) IN THE MANAS RIVER BASIN

AbstractDrip irrigation with brackish water is crucial for the efficient use of scarce water resources and ecological restoration. A 2‐year study was conducted to examine the effects of drip irrigation with brackish water on soil physicochemical properties and on the desert plant Haloxylon ammodendron which is essential in maintaining the ecological balance in desert areas. Field experiments were conducted to examine the effects of brackish water irrigation with different salinities (1, 3, 6, 9 and 12 g l−1) on the salt migration, ion contents and chemical characteristics of the soil solution. For irrigation salinities between 1 and 6 g l−1, the soil water content increased with elevated salinity, whereas, under treatments with salinities of 9 and 12 g l−1, the soil water content showed a decreasing trend with elevated salinity. Brackish water irrigation could accumulate salt and the soil salt content in the 60–80 cm soil layer was the highest; With elevated irrigation salinity, the changes in SO42−, Cl−, K+ and Na+ ion contents in the soil increased significantly. The cations in the soil aqueous solution gradually changed from Ca2+ to Na+, the anions changed from SO42− to Cl− and the hydrochemical facies changed from SO42− − Ca2+·Mg2+ to SO42−·Cl− – Na+. © 2020 John Wiley & Sons, Ltd.

Soil conditions affect cotton root distribution and cotton yield under mulched drip irrigation

Film-mulched drip irrigation with brackish water has been used widely for cotton (Gossypium hirsutum L.) production in arid regions. Full consideration of the promise of brackish water irrigation requires consideration of the dependence of cotton root characteristics on soil conditions. To date, these dependences are complex and poorly understood. The present study compared the impacts of soil temperature, water and salinity on root characteristics on cotton yield for brackish water irrigation treatment (BWT) and fresh water irrigation treatment (FWT). Spatial differences were observed for cotton root mass, root length, root surface-area and root volume distribution that corresponded with differences in the distributions of soil conditions. There existed a strikingly linear relationship between cotton root length and root mass. Soil temperature did not exert clear control on root system growth. Lower average root density and coarser roots were observed for BWT than for FWT as a result of the reduced soil temperature and the elevated soil salinity associated with BWT. Cotton shoot growth was more sensitive than root growth to salt stress for BWT. Higher root density and fine root proportion for FWT than BWT led to higher cotton yield. That is, more cotton roots were observed in the shallow mulched zone, which corresponded with high root water uptake rate and salt accumulation. Our study indicated that the easily-measured cotton root mass could be used as a practical surrogate for root length under mulched drip irrigation. Subsurface drip irrigation with drip tapes set in the shallow mulched zone may further promote cotton root system growth, allowing for sustainable cotton production with brackish water irrigation.

Soil Water-Salt Dynamics and Maize Growth as Affected by Cutting Length of Topsoil Incorporation Straw under Brackish Water Irrigation

Brackish water has been utilized extensively in agriculture around the world to cope with the global water deficit, but soil salt accumulation caused by brackish water irrigation cannot be ignored. Straw incorporation has been confirmed an effective sustainable means to inhibit soil salt accumulation. An experiment was conducted in growth tanks over two consecutive growing seasons to investigate the effects of wheat straw incorporation on soil moisture and salinity under brackish water irrigation (5g NaCl L−1). Furthermore, the trial investigated the effects of three wheat straw cutting lengths (CK = 0 cm; L1 = 5 cm, L2 = 10 cm, and L3 = 20 cm) on soil water-salt dynamics and summer maize growth. The results showed that soil properties and maize yields were favorably and significantly affected by the shorter straw segments incorporated into the cultivated field (p < 0.05), as indicated in the decrease in soil bulk density (7.47%–7.79%) and the rise of soil organic matter (SOM) content (2.4–4.5g kg−1) and soil total porosity (4.34%–4.72%) under treatment L1. Meanwhile, treatment L1 produced the greatest dry above-ground biomass (14447 ± 571 kg ha−1), 100-grain weight (34.52 ± 1.20 g) and grain yield (7251 ± 204 kg ha−1) of summer maize. Soil water content in the cultivated layer increased 4.79%–25.44%, and the soil salt accumulation rate decreased significantly due to the straw incorporation and the highest value of soil moisture content (19.10%–21.84%), as well as the lowest value of soil salt accumulation rates (2.12–9.06) obtained at treatment L1. Straw incorporation with cutting length in 5 cm is the optimal choice for alleviating the adverse effects due to brackish water irrigation and improving soil properties, which could be helpful for agricultural mechanization and straw field-returning practices.

Soil physicochemical properties and cotton (Gossypium hirsutum L.) yield under brackish water mulched drip irrigation

To alleviate surface water shortages during cotton (Gossypium hirsutum L.) cultivation in Xinjiang, the largest cotton producing area in China, we used brackish groundwater resources for mulched drip irrigation in a field. Soil moisture, salinity accumulation, pH, ion concentrations, water-use efficiency, and cotton yield were compared when irrigated using brackish water with five salinities (1g·L−1; 3g·L−1; 6g·L−1; 9g·L−1; and 12g·L−1). Salinity accumulation was significantly stronger in the top soil (0–20 cm depth) than in the deeper soil layer (20–100 cm depth). The soil pH increased and cotton yield decreased accompanied as the brackish water salinity increased. After brackish water mulched drip irrigation was implemented during the cotton growth period, salinity accumulation and cotton yield showed significant differences among the brackish water irrigation treatments. When the salinity was less than 6g·L−1, the accumulated salt in the soil did not seriously affect water absorption by cotton, and the cotton yield was higher than when the salinity was more than 6g·L−1. Therefore, less than 6g·L−1 was a suitable salinity for cotton irrigation with brackish water. As the irrigation salinity increased, the cations gradually changed from Ca2+ to Mg2+ and K+, the anions gradually changed from SO42- and HCO3- to Cl−, and hydro-chemical facies gradually changed from SO42-·HCO3–Ca2+·K+ to SO42-·Cl–Ca2+·K+. This study provides guidance for the scientific management of the soil environment and the used of saline water irrigation for agriculture in the Xinjiang area of Northern China and other regions with similar environments.

Response of ammonia-oxidizing Bacteria and Archaea to long-term saline water irrigation in alluvial grey desert soils

Soil nitrification via ammonia oxidation is a key ecosystem process in terrestrial environments, but little is known of how increasing irrigation of farmland soils with saline waters effects these processes. We investigated the effects of long-term irrigation with saline water on the abundances and community structures of ammonia-oxidizing bacteria (AOB) and archaea (AOA). Irrigation with brackish or saline water increased soil salinity (EC1:5) and NH4-N compared to irrigation with freshwater, while NO3-N, potential nitrification rates (PNR) and amoA gene copy numbers of AOA and AOB decreased markedly under irrigation regimes with saline waters. Moreover, irrigation with brackish water lowered AOA/AOB ratios. PNR was positively correlated with AOA and AOB amoA gene copy numbers across treatments. Saline and brackish water irrigation significantly increased the diversity of AOA, as noted by Shannon index values, while saline water irrigation markedly reduced AOB diversity. In addition, irrigation with brackish or fresh waters resulted in higher proportions of unclassified taxa in the AOB communities. However, irrigation with saline water led to higher proportions of unclassified taxa in the AOA communities along with the Candidatus Nitrosocaldus genus, as compared to soils irrigated with freshwater. AOA community structures were closely associated with soil salinity, NO3−N, and pH, while AOB communities were only significantly associated with NO3−N and pH. These results suggest that salinity was the dominant factor affecting the growth of ammonia-oxidizing microorganisms and community structure. These results can provide a scientific basis for further exploring the response mechanism of ammonia-oxidizing microorganisms and their roles in nitrogen transformation in alluvial grey desert soils of arid areas.

Impact of Irrigation with Saline Water on the Production of Tomato (Solanum lycopersicum) under Soilless and Traditional Techniques

A greenhouse experiment was carried out to evaluate the response of tomato (Solanum lycopersicum) to saline water irrigation under soilless and traditional techniques. A special fertigation technique with two different salinity levels (1 dS m-1 and 4 dS m-1) of water was used under different soilless media, namely, perlite, gravel, and pozzolana as inert media, in addition to traditional techniques. Results showed that among the three soilless substrates, perlite medium produced the highest total yields with larger fruit sizes. Furthermore, the perlite medium enabled significant savings in water, compared to gravel (-15%) and pozzolana (-20%). Moreover, the results corroborated the existing knowledge on the tolerance of tomato to brackish water irrigation, since there was no significant difference in yield of plants grown in the soil irrigated with water with salinity levels of 1.1 dSm-1 and 4-5 dS m-1. Plant biometric data revealed a better and quicker development of plants grown in the soilless media compared to those grown in the soil, even in the case of freshwater irrigation.

Modeling tomato evapotranspiration and yield responses to salinity using different macroscopic reduction functions

AbstractPlant responses to salinity can be used to manage irrigation with brackish water. This study evaluated effects of brackish water irrigation on tomato (Solanum lycopersicum L.) plants, proposed a new model to describe plant relative evapotranspiration (ET) and relative yield as a function of electrical conductivity of soil saturated paste extract (ECe), and compared the estimations of the new model with four other models (linear model of Mass and Hoffman, and three nonlinear models of van Genuchten, Dirksen, and Homaee). A greenhouse experiment was conducted with five salinity treatments: tap water of EC 0.6, brackish groundwater of EC 2 and 3, and reverse osmosis (RO) of EC 4 and 6 dS m−1. Results indicated no changes in leaf photosynthesis rate (Pn), transpiration rate (Tr), and stomatal conductance (Gs) up to 2 dS m−1 irrigation water salinity. Nonlinear models better described tomato yield and seasonal ET. The proposed new model performed best when compared with four previous models to predict tomato yield and ET responses to salinity. The calculated soil salinity threshold values (ECe*) from the new model were 1.73 dS m−1 for yield and 2.52 dS m−1 for ET. Data from published studies on effects of irrigation water salinity (ECw) on tomato yield and ET were analyzed to validate models. The results showed that the new model was simpler and superior in estimating plant responses to ECw. Tomato is a salt‐sensitive crop, and irrigation with brackish waters adversely influences growth and ET.

Application of time-lapse ERT to determine the impact of using brackish wastewater for maize irrigation

In agricultural practices the huge demand on fresh water for irrigation, together with water scarcity, encourages the reuse of wastewater as a water resource. Integrated management of water resources by considering the efficient use of wastewater could result in fresh water saving.A field experiment was conducted to compare the effects of two irrigation water sources, brackish secondary treated wastewater and surface canal fresh water, on maize crop. During the irrigation cycle, soil water content distribution was estimated by means of time-lapse mode electrical resistivity tomography (ERT), soil electrical resistivity being highly sensitive to soil moisture and water salinity. The effects of the two water sources on the spatial-temporal distribution of ERT-derived soil moisture values were assessed, and different roots’ behaviors observed. Results show a decreased root water uptake with brackish irrigation water with respect to fresh water.This result implies an increase in water savings due to reduced crop water requirement, which has significant implications for economic and environmental management.

Spatial Distribution of Salinity and Sodicity in Arid Climate Following Long Term Brackish Water Drip Irrigated Olive Orchard

The availability of brackish groundwater in the Negev Desert, Israel has motivated the cultivation of various salinity tolerant crops, such as olives trees. The long term suitability of surface drip irrigation (DI) or subsurface drip irrigation (SDI) in arid regions is questionable, due to salinity concerns, in particular, when brackish irrigation water is employed. Nevertheless, DI and SDI have been adopted as the main irrigation methods in olive orchards, located in the Negev Desert. Reports on continued reduction in olive yields and, essentially, olive orchard uprooting are the motivation for this study. Specifically, the main objective is to quantify the spatial distribution of salinity and sodicity in the active root-zone of olive orchards, irrigated with brackish water (electrical conductivity; EC = 4.4 dS m−1) for two decades using DI and subsequently SDI. Sum 246 soil samples, representing 2 m2 area and depths of 60 cm, in line and perpendicular to the drip line, were analyzed for salinity and sodicity quantities. A relatively small leaching-zone was observed below the emitters depth (20 cm), with EC values similar to the irrigation water. However, high to extreme EC values were observed between nearby emitters, above and below the dripline. Specifically, in line with the dripline, EC values ranged from 10 to 40 dS m−1 and perpendicular to it, from 40 to 120 dS m−1. The spatial distribution of sodicity quantities, namely, the sodium adsorption ratio (SAR, (meq L−1)0.5) and exchangeable sodium percentage (ESP) resembled the one obtained for the EC. In line with the dripline, from 15 to 30 (meq L−1)0.5 and up to 27%, in perpendicular to the drip line from 30 to 60 (meq L−l)0.5 and up to 33%. This study demonstrates the importance of long terms sustainable irrigation regime in arid regions in particular under DI or SDI. Reclamation of these soils with gypsum, for example, is essential. Any alternative practices, such as replacing olive trees and the further introduction of even high salinity tolerant plants (e.g., jojoba) in this region will intensify the salt buildup without leaving any option for soil reclamation in the future.

Transcriptional changes during tomato ripening and influence of brackish water irrigation on fruit transcriptome and sugar content

Efficient management and utilization of brackish water irrigation help to minimize yield losses and promote fruit quality and sugar content in tomato fruit. However, the functional genes involved in sugar metabolic pathways and potential molecular pathways responsive to brackish water irrigation remain unknown. To this end, physiological responses and comparative transcriptional profiling was used to analyze the tomato fruit during the white-ripe period (CK1) and mature period (CK2) in plants grown under four water management strategies (rotating irrigation with brackish and fresh water during fruit development, T1; fresh water irrigation, T2; mixed brackish and fresh water irrigation, T3; mixed water and fresh water irrigation in sequence, T4). Comparative analysis revealed that during fruit development (CK2 cv CK1) differentially expressed genes (DEGs) involved in photosynthetic pathways and sucrose-starch metabolism were downregulated. However, two DEGs encoding putative beta-fructofuranosidases were significantly upregulated at the mature stage, which promoted the accumulation of glucose and fructose in CK2. Comparing four types of management strategies, rotating irrigation with brackish water and fresh water (T1) led to reprograming of global gene expression. Moreover, the upregulated DEGs in T1 were significantly enriched for signaling, hormone metabolism, and stress tolerance, suggesting the coordination of both stresses signaling as well as the plant hormone. These results provide a valuable reference for rational use of brackish water in the production of high-quality tomato in arid and semi-arid regions.

Effects of Irrigating with Brackish Water on Soil Moisture, Soil Salinity, and the Agronomic Response of Winter Wheat in the Yellow River Delta

Water shortages due to low precipitation and seawater intrusion in the Lower China Yellow River Delta have occurred in recent years. Exploiting underground brackish water through well drilling is a potential alternative way to satisfy the demand for agricultural irrigation. However, how to successfully use brackish water for irrigation has become a new problem to solve. A two-year field experiment was conducted in this typical saline-alkaline region to investigate the effects of irrigating with brackish water on the soil water-salt dynamics, and the physiological response of winter wheat to drought-salt stress. The experiment was laid out in a randomized block design with three replications according to the quantity (160 mm and 240 mm) and quality (fresh water and brackish water with a salt concentration of 3 g L−1) of irrigation water: T1 was 240 mm of fresh water, T2 was 160 mm of fresh water, T3 was 80 mm of fresh water and 160 mm of brackish water, and T4 was 80 mm of fresh water and 80 mm of brackish water. The results showed that the soil moisture of T3 was almost the same as T1 after the harvest of winter wheat each year, therefore, irrigating with brackish water can maintain soil moisture while saving fresh water resources. After two years, the soil salinity of each treatment increased by 0.307, 0.406, 0.383, and 0.889 g kg−1, respectively. During the jointing-flowering stage, salt stress has a significant inhibitory effect on photosynthesis; T3 and T4 were lower than T1 and T2 in terms of plant height and dry weight. During the filling stage, because the effect of drought stress is more serious than that of salt stress, the photosynthesis of T3 was greater than that of T2 and T4. For both years, the yield of crops followed the rank order T1 > T3 > T2 > T4. Compared with irrigating with fresh water in T1, T3 changed the second and third irrigation into brackish water, however we did not find that soil salinity increased significantly, and this treatment was able to ensure crop growth during the filling stage. Therefore, the combination of fresh water (80 mm), then brackish water (80 mm), then brackish water (80 mm) is a feasible irrigation strategy in China’s Yellow River Delta for winter wheat.

Response of Water-Salt Migration to Brackish Water Irrigation with Different Irrigation Intervals and Sequences

Establishing methods for scientific and rational use of brackish water resources is the key to farmland irrigation in the Yellow River Delta region of China. In this study, we conducted laboratory simulation experiments with soil columns and monitored the changes in water infiltration and salt distribution under eight irrigation treatments, including four intervals (0, 30, 60, and 90 min between irrigations) and two sequences (brackish-brackish-fresh water and brackish-fresh-brackish water). The results showed that the duration of water infiltration into the soil was higher under intermittent irrigation than continuous irrigation, with the highest value recorded at the 90-min irrigation interval. There was no significant difference in the mean soil water content between the brackish-brackish-fresh water (28.01–29.71%) and brackish-fresh-brackish water (28.85–29.98%) irrigation treatments. However, the mean soil desalination rate of the brackish-brackish-fresh irrigation treatment (42.51–46.83%) was higher than that of the brackish-fresh-brackish irrigation treatment (39.48–46.47%), and a much higher soil desalination rate was observed at the 90-min irrigation interval, compared with the other intervals. In conclusion, brackish-brackish-fresh water irrigation at longer time intervals (e.g., 90 min between irrigations) is conducive to reduce soil salt content in the surface soil in the study region.

Effects of mixing Yellow River water with brackish water on the emitter’s clogging substance and solid particles in drip irrigation

The water shortage and soil salinization have become a great challenge for the Yellow River irrigation area. Mixing Yellow River water with brackish water for drip irrigation can be an effective solution because of the mixed water contents less sediment and salinity. However, the mixed water can still cause emitter’s clogging and significantly reduce drip irrigation system performance. In order to find out a proper method of relieving the emitter’s clogging in drip irrigation and increase the efficiency of irrigation water utilization, three different types of water including the Yellow River water, brackish water, and mixed water of Yellow River water and brackish water at the mixing ratio of 1:1 were used to cultivate the emitter’s clogging substance. The results showed that the clogging substance growth is a “S-curve.” The mixing of Yellow River water (YR) and brackish water (BW) can mitigate the formation of the clogging substance as the dry weight on mixed water was 6.07 mg/cm2, which was 47.38–65.71% less than YR and 26.53–47.40% less than BW. Moreover, the Si deposit had significant effect on the clogging substance in the condition of YR and the Ca/Mg deposit had significant effect on the clogging substance in the condition of BW. There was no deposit that had significant effect on the clogging substance in the mixed water. The contents of sediment and ions were reduced significantly after mixing Yellow River water and brackish water. The result can be helpful to facilitate utilization of brackish water in Yellow River irrigation area.

Effects of Irrigation Water Salinity on Soil Properties, N2O Emission and Yield of Spring Maize under Mulched Drip Irrigation

Brackish water has been widely used to irrigate crops to compensate for insufficient freshwater water supply for agricultural use. The goal of this research was to determine an efficient brackish water use method to increase irrigation efficiency and reduce N2O emission. To this end, we conducted a field experiment with four salinity levels of irrigation water (1.1, 2.0, 3.5, and 5.0 g·L−1 with drip irrigation) at Hetao Irrigation District (Inner Mongolia, China) in 2017 and 2018. The results show that irrigation with 3.5–5.0 g·L−1 water salinity increased the soil salinity compared with irrigation using 1.1–2.0 g·L−1 water salinity. The soil water content with 5.0 g·L−1 brackish water irrigation was significantly higher than with 1.1–3.5 g·L−1 water salinity due to the effect of salinity on crop water uptake. The overall soil pH increased with the increase in irrigation water salinity. Saturated soil hydraulic conductivity decreased with the increase in irrigation water salinity. These results indicate that brackish water irrigation aggravates the degree of soil salinization and alkalization. The soil N2O cumulative flux resulting from irrigation with 5.0 g·L−1 water salinity was 51.18–82.86% higher than that resulting from 1.1–3.5 g L−1 water salinity in 2017, and was 32.38–44.79% higher than that resulting from 1.1–2.0 g·L−1 in 2018. Irrigation with brackish water reduced maize yield, and the reduction in yield in 2018 was greater than that in 2017, but irrigation with 2.0 g·L−1 brackish water did not significantly reduce maize yield in 2017. These results suggest that reducing the salinity of irrigation water may effectively reduce soil N2O emission, alleviate the degree of soil salinization, and increase crop yield.

Biomass Production and Carbon Sequestration by Cultivation of Trees under Hyperarid Conditions using Desalinated Seawater (Sewage Water)

As growing economies – in particular in the Gulf region – use extreme and growing amounts of desalinated seawater for municipal purposes the use of produced waste waters is in the focus of science. The fixation of atmospheric carbon-dioxide by a safe cultivation of trees using this slightly salty water sources is of increased importance in times of ongoing climate change. Unfortunately, existing research relies on irrigation of trees in arid lands using ground water, any kind of precipitation, seasonal events like river flooding or a mix of them. To date no data support the biomass or tree production in total absence of natural precipitation and complete lack of ground water. In this study, seven timber and fuelwood tree species, namely, Eucalyptus occidentalis En., Eucalyptus tereticornis Smith, Eucalyptus camaldulensis Dehnh., Eucalyptus gomphocephala DC., Eucalyptus grandis Hybr. Hill ex Maid, Tamarix aphylla (L.) Karst., Tamarix nilotica (Ehrenb.) Bunge were tested for carbon sequestration and biomass-production. Above-soil and sub-soil parts were determined under two levels of drip-irrigation water supply: 25% and 50% of Evapotranspiration (ETo) over a period of two years and four months from planting to harvest. The trees were cultivated under hyper-arid climatic conditions using brackish irrigation water (3.5 dS m-1) on a research and development station in Arava, Israel. Purified waste water from a seawater desalination plant (reverse osmosis) was applied after municipal use. Eucalyptus gomphocephala DC. delivered the highest yields and had the highest water use efficiency, producing 70 t of Dry Matter (DM) /ha/a under the higher irrigation level. Compared with the other species, E. gomphocephala DC. showed a 32% to 65% superior performance . Whereas, lower amounts of saline irrigation water were favoured by E. camaldulensis and T. aphylla – both producing more than 50 t of DM/ha/a. Nevertheless, Tamarix, as a halophyte specialist plant, needed 30 % less water for this growth. Both Eucalyptus varieties mentioned before form a closed tree stand and reached a height of almost 10 m, two years after planting. Regardless of the particular use of the produced timber, about 15 – 25% of the trees’ total DM, approximately equal to the carbon-content, remains in the soil as long-term carbon-storage after harvesting the above ground biomass. Fast growing fuelwood tree species ensure a safe long-term biological fixation of carbon Irrigated with small amounts of saline waste water.

Effect of Surface Straw Incorporation Rate on Water–Salt Balance and Maize Yield in Soil Subject to Secondary Salinization with Brackish Water Irrigation

Secondary salinization induced by brackish water irrigation has forced agricultural development to increasingly rely on soil management. A two-year field experiment was conducted to explore the effects of different straw incorporation rates (SIRs) within 0 to 20 cm topsoil on the soil water–salt balance, maize yield production, and water use efficiency (WUE) under brackish water irrigation in a naturally non-saline area. Air-dried wheat straw was applied at the rates of 0, 4.5, 9.0, 13.5, and 18.0 t ha−1 (R0–R4) and two salinity levels of irrigation water with the salt content of 1.92 dS m−1 (SL) and 3.20 dS m−1 (SH) were applied for simulating the scenarios of secondary salinization. Results demonstrated that straw incorporation markedly increased the soil water content during two growing seasons, and SIR was directly correlated to the deep percolation, but inversely correlated to the soil water depletion, under both the SL and SH condition. Meanwhile, straw incorporation led to the increase in salt content within the straw incorporation zone, but the total mass of salt deposited in the 0–100 cm soil profile was comparatively reduced as SIR increased due to the increased deep percolation for salt leaching, and such relative alleviation was more pronounced under the SH condition. The significantly increased maize yield and its corresponding WUE were obtained in treatments with high SIR levels. Additionally, an exponential function was used to describe the trend of the yield-increasing rate as SIR increased, and the theoretical maximum of grain and biomass yield calculated from the fitting results were 6483 in 17,282 kg ha−1 under SL, and 5440 and 14,501 kg ha−1 under SH, respectively. Results in this study would be helpful in the adoption of straw incorporation and brackish water irrigation in ways that facilitate soil water availability and reduce the risk of soil salinization.