Soil Desalinization Research Articles

Recent Trends in Microbial Approaches for Soil Desalination

Soil salinization has become a major problem for agriculture worldwide, especially because this phenomenon is continuously expanding in different regions of the world. Salinity is a complex mechanism, and in the soil ecosystem, it affects both microorganisms and plants, some of which have developed efficient strategies to alleviate salt stress conditions. Currently, various methods can be used to reduce the negative effects of this problem. However, the use of biological methods, such as plant-growth-promoting bacteria (PGPB), phytoremediation, and amendment, seems to be very advantageous and promising as a remedy for sustainable and ecological agriculture. Other approaches aim to combine different techniques, as well as the utilization of genetic engineering methods. These techniques alone or combined can effectively contribute to the development of sustainable and eco-friendly agriculture.

Plant Growth Promoting Microorganisms Useful for Soil Desalinization

The salinization of cultivable soils is a major issue that humankind will soon have to face [...]

Desalination characteristics and efficiency of high saline soil leached by brackish water and Yellow River water

The rational development and utilization of saline soils and brackish water resources has aroused great concern in the world. In the present study, the soil column leaching indoor simulation method was conducted to explore the salt migration characteristics in highly saline soil. Both brackish water (2.84 g/L) and Yellow River Water (0.51 g/L) were used for leaching to analyze and compare their corresponding required leaching volume, soil desalination rate, chemical ion composition. The results showed that (1) the required leaching volume of Yellow River water and brackish water were 535–875 mm and 455–1125 mm (depth of soil column is 100 cm), respectively. The desalination time and required leaching volume of brackish water are less than Yellow River water for 0–20 cm layer, while for layers below 20 cm depth, the desalination time and required leaching volume of Yellow River water are less than brackish water. To satisfy the growth of general crops, the required leaching water volume of Yellow River water and brackish water were 472.7 mm and 754.20 mm, respectively (the planned desalination depth is 0–60 cm). (2) The desalination rate of the soil column leached with Yellow River water was 140% higher than brackish water. The soil salinity after leaching with Yellow River water and brackish water was only 21.01% and 31.96% of the initial salinity. Simultaneously, the pH and RSC (residual sodium carbonate) in each layer increased less under brackish water leaching than Yellow River water; while the SAR (sodium adsorption ratio) in the soil column leached with brackish water decreased more than Yellow River water. Therefore, the saline land reclamation with brackish water provides an alternative solution to alleviate freshwater scarcity and guarantee the general crops growth in the Yellow River Delta.

Saline-Sodic Soil EC Retrieval Based on Box-Cox Transformation and Machine Learning

Electrical conductivity (EC) is an important index of soil salinity level and an essential factor in judging whether improvement can be made and assessing the improvement, if any. However, saline soils of different types show different spectral characteristic bands, which affects the retrieval precision to a certain extent. To tackle this issue, we present a novel way of modeling. Specifically, we compare the correlation of sensitive bands, multiplication of sensitive bands, and spectral indexes with EC data to determine the optimal input parameters, and take the EC data after Box-Cox transformation as the output. We then try out several machine-learning algorithms to establish retrieval models for soil EC. Validation results show that the model precision increases by 3.23–85.71% after EC data transformation and machine learning models produce 29.41–86.67% higher precision than the linear regression model. Finally, using the optimal model, we retrieve pixel-level (10 m × 10 m) EC for the soil in our study areas. This provides necessary data support for working out soil desalinization initiatives and evaluating the effectiveness of such initiatives.

Identification of Saltol QTL in the breeding rice samples

One of the main problems in most of the world rice-growing regions is soil salinity. Rice is considered a saline sensitive crop, especially at the early stages of development and in the period of maturity. In the Rostov region, rice is grown in the south-eastern parts, where there are currently difficulties with the operation of the existing reclamation facilities. The problem of saline soils for this region is especially urgent, since a significant part of the arable lands has alkali complexes. In order to return the saline lands into exploitation, it is necessary to develop salt tolerant varieties, which, under crop rotation and maintenance, can contribute to soil desalinization. Due to the difficulty of determining salt tolerance only by estimating the phenotype, it is necessary to use molecular markers associated with this trait. Thus, the purpose of the current work was to identify one of the main Saltol QTL in breeding rice samples of the eighth generation (F8) obtained from hybridizing the donor variety NSYC Rc106 with Russian varieties. For that purpose, there have been used such marker-assisted selection methods as DNA isolation, polymerase chain reaction (PCR), electrophoresis on 2% agarose gels, gels’ coloring in ethidium bromide solution, photography in ultraviolet light and evaluation of the obtained electrophoregrams. As a result of the study of 398 breeding rice samples, there have been identified 67 samples with the functional allele of Saltol QTL (6865/3, 6874/2, Don 7343/4, Don 7343/5, Don 7343/6, Don 7343/7, Don 7343/8, Don 7343/9, Don 7343/10, Don 7337/1, Don 7337/3, Don 7337/4, Don 7337/5, Don 7337/6, Don 7337/7, Don 7337/8, etc.). There have been recommended to use these samples in the further breeding process in order to develop new salinity resistant rice varieties.

To the development of optimal methods for licorice seeds growing (Glycyrrhiza glabra L.) in irrigated lands of the Republic of Karakalpakstan

The research was carried out at the Nukus branch of the Tashkent State Agrarian University.The article presents the results of research on the development of optimal methods for growing licorice (Glycyrrhiza glabra L.) from seeds on salinity lands of the Republic of Karakalpakstan. In particular, the optimal rates of application of potassium geohumate for soaking licorice seeds, the rate of washing during soil desalination, the rates of mineral fertilizers and irrigation have been determined. The study of the effect of potassium geohumate on seed germination showed that soaking licorice seeds in a 0.05% solution of potassium geohumate for 3 days followed by drying the seeds in the open air provided the best germination on the 30th day after sowing and amounted to 72.6%, while the germination of licorice in the variant with the use of 0.03% potassium geohumate solution was 38.6%. The germination of the control variant was only 22.3%. It has also been established that the optimal rate of mineral fertilization for licorice is the application of 300 kg/ha of superphosphate, 150 kg/ha of potassium and 100 kg/ha of ammonium nitrate for 8 irrigations with a rate of 600 m3/ha.

Mechanism of Saline–Alkali land improvement using subsurface pipe and vertical well drainage measures and its response to agricultural soil ecosystem

Salinization is recognized as a threat to agricultural productivity and land resources in global arid desert regions. To date, field soil improvement schemes have met with minimal success to date. We aimed to improve saline–alkali soils by assessing the effects of combining subsurface pipe (Pa) and vertical well (Sa) drainage measures on agricultural soils ecosystem. In a five-year field experiment, soil was sampled 0.5 m, 5 m, 7.5 m horizontally away from the Pa, and 0.5 m, 30 m, 60 m horizontally away from the Sa. Findings indicate that the soil electrical conductivity (EC) decreased from 16 dS m−1 to 3 dS m−1 at a 0–80 cm depth, and the soil desalination efficiency was great at the 0–300 cm depths (≥ 32%) than at the 400–700 cm depths (−14%–74.7%). The combined Pa and Sa drainage measures significantly decreased the species richness and quantity of soil microbial communities, and their negative impact on observed species was irreversible within 1 year. The farther the horizontal sampling conducted from the Pa and Sa, the greater the structural similarity of the microbial community at the genus level, higher the catalase, acidic protease, and neutral phosphatase activities, and lower the alkaline phosphatase activity. The overall decrease in groundwater level from 2016 to 2020 was 5.7 m. The seed cotton yield increased by 3.2 t ha−1. The results suggest that the value of saline–alkali soil can be improved by combining Pa and Sa drainage measures. Our research provides guidance for further effective utilization of agricultural water and soil resources and the sustainable development of the soil ecosystem in arid desert areas.

Bioelectric field drives ion migration with the electricity generation and pollutant removal

A bioelectric field was developed by electricigens that metabolize organics and emit electrons in a soil microbial electrochemical system (MES). The bioelectric field intensity and accumulated charge of the soil MES increased with the addition of ions, which substantially promoted charge transfer in the soil. In MESs with added Zn 2 + , the bioelectric field intensity increased to 175 ± 3 mV ⋅ cm −1 from 26 ± 1 mV ⋅ cm −1 in the controls, while the accumulated charge was enhanced by 9-fold. Compared to open circuit MESs, the removal of total petroleum hydrocarbons increased by 108%–166% in closed circuit ones. In the presence of a bioelectric field, cations were transferred from the anode to the cathode and apparently amassed near the cathode, especially in the presence of Na + , K + , Mg 2 + , Ca 2＋ and Fe 2/3+ . For anions, the amount of NO 3 − decreased by half in treated soils, especially near the cathode. Unexpectedly, near the cathode, the contents of Cl − and SO 4 2 − increased to 176–807 mmol ⋅ kg −1 from 256 to 314 mmol ⋅ kg −1 in the original soil. This study verifies the effect of soluble ions on enhancing bioelectricity generation, reveals the quantitative profile of ion migration in the bioelectric field and proposes a potential method of soil desalinization by soil MESs with the advantages of electricity generation and pollutant removal. • A way of soil desalinization was put forward based on the soil MES. • Addition of K ＋ and Zn 2＋ obviously promoted the electron transfer in soils. • Migration of soil ions was quantificationally revealed in the bioelectric field. • Chlorion and SO 4 2− amassed while NO 3 − reduced near the cathode. • The role of cathode for the ion migration far exceeded the anode in soils.

Soil salinity variations and cotton growth under long-term mulched drip irrigation in saline-alkali land of arid oasis

The sustainable development and utilization of saline-alkali land are closely related to holding fast the minimum cultivated land area of China. The change of soil salt in cotton field under long-term mulched drip irrigation (MDI) is connected with the development of the national cotton industry. From 2015 to 2019, five cotton fields with different applying years of MDI, which were reclaimed in 2004, 2008, 2010, 2012 and 2015 respectively and were saline-alkali wasteland before, were monitored continuously in the Manas River irrigation area of Xinjiang. By means of continuous location monitoring and spatial–temporal variability (For example, the monitoring data of cotton fields under MDI in 2004, 2008, 2010, 2012 and 2015, and in the year of 2015 were counted as 12, 8, 6, 4 and 1 years, respectively), the spatial–temporal variations of soil salt and ions in cotton field with 1-16a MDI technology were presented. The cotton growth characteristics and its main influencing factors were also analyzed in the study. The results showed that saline-alkali cotton field experienced changed from intensive saline soil to moderate saline soil and finally to non-saline soil under long-term MDI. The change of soil salt and the response of cotton growth to soil salt were divided into three typical stages. Firstly, soil desalinated rapidly in 1-4a MDI cotton field, which the annual average desalination rate was 24.93% in 0–100 cm soil layer (root zone). Additionally, the survival rate of cotton rocketed from 1.48% to 42.04%, and yield increased sharply from 72.43 kg ha−1 to 3075.90 kg ha−1. Soil desalination was lower in 5-11a MDI cotton field, which the annual average desalination rate was 10.92% at the root zone. The annual survival rate and yield of cotton increased by 6.26% and 5.18%, respectively. After 12a MDI, the soil salt in cotton field tended to be generally constant, which the average salt content in root zone was less than 2.49 g kg−1. The survival rate of cotton was stable above 90.39%, and the yield per unit area exceeded 5401.32 kg ha−1. Ions, sodium absorption ratio and Cl− and SO42− equivalent ratio (CSER) in cotton soil also decreased with the extension of MDI. Salt composition changed year by year, but the type of intensive saline soil had always been chloride-sulphate solonchak (0.2 < CSER < 1). In practice, with a higher irrigation quota and ideal irrigation water quality, the soil salt environment of saline-alkali soil MDI cotton field had developed in favor of cotton growth in an oasis irrigation area. However, this management practice caused between 124.21–143.61 mm of water resources waste. Therefore, we should further enhanced the consciousness of water-saving and implemented quota management in practice.

Strategy of subsurface pipe drainage system to alleviate soil salinization based on the DRAINMOD model*

AbstractTo investigate the dynamics and influencing factors of water and salt in subsurface pipe drainage (SPD) systems, three field experiments (denoted as E0.8, E1.1, and E1.4) with different drainage pipe depths (80, 110, and 140 cm, respectively) were conducted in saline farmlands in the Xinjiang Autonomous Region, China. The cumulative water drainage and salt discharge were used to calibrate and validate the DRAINMOD model for simulating water and salt movements in SPD systems. Two indices, the effective leaching water amount (We) and the ratio of the salt discharge rate to the soil desalination rate (Rs/N), combined with the water drainage rate (Rw) and salt discharge rate (Rs), were used to evaluate the effects of salt discharge under different pipe layouts. The experimental results showed that water drainage only started when groundwater completely submerged the subsurface pipes. Furthermore, Rs and Rs/N increased with decreasing burial depth, while the total salt discharge decreased and Rw increased with We. The relationship among We, the burial depth of the subsurface pipe (B), the groundwater table (G), and the Rw or Rs/N of SPD was quantified under different soil textures. In addition, quantitative formulas for determining the water and salt discharge characteristics of SPD were also established.

EFFECTS OF SALINITY ON GROWTH AND PROLINE CONTENT ON BEAN AND ALFALFA

Soil salinity is a major agricultural constraint in many countries. Plants’ response to salinity depends on the species and the salt concentration in the soil. The objective of this study was to test the resistance of three leguminous plants - common bean (variety ‘El-Jadida’), broad bean (variety ‘Claro de Luna’), and alfalfa (variety ‘Diamon’) - to several salinity rates and to show which one was more resistant to salt stress. This study was carried out under controlled conditions, with six NaCl concentrations (0, 1, 3, 6, and 9 g/kg) added to a mixture of potting soil and sand. A completely randomised design was used, where the three legumes were cultivated with different salt concentrations to determine the effect of these doses on fresh biomass, dry mass, and physiological parameters (sodium and proline content). The results showed the negative effect of salinity on fresh biomass and dry mass of shoots and roots. Claro de Luna, the broad bean variety, was more adapted to salinity than alfalfa and common bean. The amount of sodium in the shoots and roots of the three species increased with increasing salinity. Alfalfa may play a role in soil desalination; at 53.33 mM NaCl, 100 mg alfalfa dry mass absorbed 4.5 mg Na per pot, which corresponded to the uptake of about 0.6 kg Na per hectare of soil. Proline content increased with increasing salt concentrations.

Quantitative assessment of the potential for soil improvement by planting Miscanthus on saline‐alkaline soil and the underlying microbial mechanism

AbstractPhytoremediation using Miscanthus is a valuable technique for the restoration of saline‐alkaline soil, but the potential is not quantified. To assess this potential, a 5 years field experiment was conducted on saline‐alkaline soils with three genotypes of Miscanthus and an unplanted control. The bulk soil (0–20‐cm depth) physicochemical properties were measured annually from 2015 to 2018, while the bacterial and fungal community structures of the rhizosphere soil were investigated by high‐throughput sequencing after 5 years under Miscanthus (2018). The results showed that Miscanthus cultivation on saline‐alkaline soil reduced soil salinization and improved soil fertility on this site. Specifically, compared with the blank control, the five‐years Miscanthus cultivation (mean of three different genotypes pooled) decreased the soil pH by 0.33 units (8.78–8.45) and electrical conductivity by 23.4 μS/cm (226.7–203.3 μS/cm), as well as increasing soil organic matter content from 18.9 to 34.9 g/kg and total potassium content from 15.2 to 18.0 g/kg. In addition, the soil improvement was more pronounced with a longer duration of growth. Miscanthus remediates saline‐alkaline soils by altering the microbial community compositional abundance rather than its diversity. The improvement is due to enrichment of beneficial bacteria leading to soil desalinization (e.g., by Gemmatimonadaceae), litter decomposition (e.g., by Chitinophagaceae), plant growth promotion (e.g., by Micrococcaceae), and the reduction of harmful fungi (e.g., Pleosporales and Chitinophagaceae). Soil pH, electrical conductivity, organic matter, and total potassium were the main physicochemical properties affecting bacterial and fungal communities. Our results quantify the soil improvement potential of Miscanthus and clarify the underlying microbial mechanisms, laying a solid foundation for further implementation of saline‐alkaline soil phytoremediation using Miscanthus. In the future, more extensive multi‐location trials are required to assess if these improvements are seen across a wide diversity of environments.

Tailoring Next Generation Plant Growth Promoting Microorganisms as Versatile Tools beyond Soil Desalinization: A Road Map towards Field Application

Plant growth promoting bacteria (PGPB) have been the target of intensive research studies toward their efficient use in the field as biofertilizers, biocontrol, and bioremediation agents among numerous other applications. Recent trends in the field of PGPB research led to the development of versatile multifaceted PGPB that can be used in different field conditions such as biocontrol of plant pathogens in metal contaminated soils. Unfortunately, all these research efforts lead to the development of PGPB that failed to perform in salty environments. Therefore, it is urgently needed to address this drawback of these PGPB toward their efficient performance in salinity context. In this paper we provide a review of state-of-the-art research in the field of PGPB and propose a road map for the development of next generation versatile and multifaceted PGPB that can perform in salinity. Beyond soil desalinization, our study paves the way towards the development of PGPB able to provide services in diverse salty environments such as heavy metal contaminated, or pathogen threatened. Smart development of salinity adapted next generation biofertilizers will inevitably allow for mitigation and alleviation of biotic and abiotic threats to plant productivity in salty environments.

ПРИКЛАДНАЯ МОДЕЛЬ СПОСОБОВ ОСВОЕНИЯ ЗАСОЛЕННЫХ ЗЕМЕЛЬ

Based on the available achievements in the field of methodology, natural sciences and research in the field of environmental management, a method is proposed for constructing an applied model for the development of saline lands as "activity-natural objects" of the «Soils", including cognitive activities, transforming activities, transformations natural materials and materials formed as a result of anthropogenic activities, within the framework of which an applied model of methods for the reclamation of saline lands has been developed. On the basis of an applied model transforming the activity of saline lands, a method for developing saline lands has been developed, including the preparation of temporary irrigation and drainage networks and checks, deep ameliorative loosening of the soil across the drains with alternating loosened strips with the same width with the subsequent supply of flushing water to the checks. The method differs in that the development of saline lands is carried out in two symmetrical and parallel-sequential actions in time in annual intervals, with desalinization of saline soils to a certain permissible level with the supply of a leaching rate, taking into account the environmental requirements of environmental management and classification of saline soils and salt tolerance of agricultural crops from very highly saline to highly saline, from highly saline to medium saline, from medium saline to slightly saline and from slightly saline to non-saline, with subsequent cultivation of the corresponding salt tolerant crops: very resistant – resistant – medium resistant – medium sensitive – sensitive.

Study on the Farmland Improvement Effect of Drainage Measures under Film Mulch with Drip Irrigation in Saline–Alkali Land in Arid Areas

Water scarcity and imbalances in irrigation and drainage are the main factors leading to soil salinization in arid areas. There is a recognized need for effective drainage measures to prevent and improve saline−alkali land. The principal objective of this project was to investigate the effects of drainage measures on soil desalination and farmland drainage in the process of improving saline–alkali soils; these measures included subsurface pipe drainage (SPD) and open ditch drainage (ODD). The results of the tests, conducted over two years, revealed that the soil desalination rate in the SPD test area was between 25.8% and 35.2%, the cotton emergence rate was 36.7%, and a 3.8 t hm−2 seed cotton yield could be obtained. The soil electrolytic conductivity (EC) decreased step by step over time, and the average annual decrease reached 10 dS m−1. The degree of soil salinization was reduced from a moderately saline soil level (8−15 dS m−1) to a weakly saline soil level (4–8 dS m−1). Thus, the phased goal of improving saline–alkali land was achieved. The soil desalination rate in the ODD test area was only 1/10 of the SPD area; high soil EC (9−12 dS m−1) and groundwater level (2–3 m) were the most limiting factors affecting cotton growth in the ODD test area. The current results show that the critical depth of groundwater level affecting farmland secondary salinization is 4 m. In order to improve the salt discharge standard, SPD technology should be used on the basis of ODD. For salt that has accumulated in the soil for a long time, the technical mode of drip irrigation and leaching, followed by SPD drainage, in combination with the current irrigation system can achieve the goal of sustainable agriculture development.

Artificial Macropores with Sandy Fillings Enhance Desalinization and Increase Plant Biomass in Two Contrasting Salt-Affected Soils

Salt accumulation in topsoil is a widespread restricting factor that limits agricultural production and threatens food security in arid and semi-arid regions. However, whether this upward enrichment was suppressed by macropores was less documented. Therefore, artificial macropores with sandy fillings (AMSF) method was proposed in this study. Soil column experiments showed a significant improvement of saturated hydraulic conductivity (Ks) by more than 260% under artificial macropore treatment. Freshwater irrigation was conducted to monitor the short-term water and salt movement. This research aimed at evaluating the potential benefit of AMSF method on soil desalinization in coastal farmland of northern China. The results demonstrated that downward movement of soil water was stimulated in AMSF method, accordingly, washing more salt ions out of top rooting zone. Particularly, 10 cm or more macropore depth treatments of AMSF method enhanced total desalinization by 52.1% to 176.6% in 0–30 cm soil layer, in comparison to the control group without macropore. Subsequent observations for alfalfa showed higher biomass by 20.8% under 15 cm macropore depth. The results here provided an exploration demonstration to pursue these studies with the ultimate goal of optimizing application strategies for amendment in coastal salt-affected lands of northern China.

Experimental study on macropore flow effects in unsaturated soil on subsurface drainage and soil desalination*

AbstractDischarging of moisture and salt from unsaturated soil has always been a difficult problem. Therefore, a laboratory experiment in unsaturated soil, under drip irrigation, on subsurface drainage and soil desalination through subsurface drainage pipes (SDP) was conducted for using soil flume, where artificial macropore flow tubes (MFT) were deployed and connected to SDP. We conducted seven different deployment treatments of the artificial MFT, including four deployment tube densities (0, 3, 4, and 5) and two deployment arrangements (curved and straight). The results showed that no flow was observed in the SDP under the base treatment without MFT, increasing flow rates to 9.71 L, 10.7 L, and 12.3 L under the three straight line treatments and 7.81 L, 9.81 L, and 11.2 L under the three curved line treatments. Water content in both the upper and lower soil layers was almost uniform in the treatments with MFT, and an overall desalination trend was observed; the average desalination rate of curved MFT treatments was lower than that of the straight MFT treatments under the same MFT density. The findings serve as the foundation for future studies on drainage and desalination in unsaturated soil and facilitate the design of tile drainage under drip irrigation.

ВЛИЯНИЕ ФЕРТИГАЦИИ НА ЗАСОЛЕНИЕ ПОЧВЫ

The salt state has a noticeable effect on the physical and water properties of the soil. That is why the distribution of its water-physical properties along the profile and in space in territories with different soil-climatic, hydrological and hydrochemical conditions should be individual. This is due, on the one hand, to the fact that water is directly involved in the processes of transfer and distribution of salts. On the other hand, the main parameters of the processes of moisture and salt transfer directly depend on the physical properties of the soil, which change under the influence of soluble salts. We have assessed the effect of fertigation on the physicochemical properties of the soil. Four fertigations with different salinity levels were tested. The influence of precipitation on soil desalinization through salt leaching was controlled by comparing changes in soil electrical conductivity during and after the growing season. To measure the studied characteristics, sensors of the 5TE type were used, which independently determine three indicators - the volumetric water content (VWC) by measuring the dielectric constant of the medium based on capacitive / frequency technology, temperature and EC. The stability of soil aggregates was also measured as an indicator of soil degradation. The electrical conductivity of the soil during pre-sowing (or after sowing) treatment was higher than at the end of the growing season. Experimental studies were carried out in the western part of the city of Prague on the campus of the Czech University of Life Sciences with geographic coordinates 50 ° 8'N and 14 ° 23'E. The altitude is 286 m, the average annual air temperature is 9.1 ° C, the amount of precipitation is 495 mm. The soil is loamy chernozem with a content of 22.0 ... 32.5% sand, 39.5 ... 54.0% silt and 22.0 ... 28.0% clay. The limiting field moisture capacity of the soil and the moisture content of stable wilting are 34 and 21%, respectively. It was found that fertigation in the short term is not harmful to the soil in the presence of sufficient precipitation

Different mulching materials influence the reclamation of saline soil and growth of the Lycium barbarum L. under drip-irrigation in saline wasteland in northwest China

The plastic mulch has been widely used for salinity controlling in arid-saline area for decades, but the residual plastic shows serious hazards to human and environmental health nowadays. To find an alternative from potential materials, a mulching experiment consisting of 4 treatments, the sown grass cover (GC), the black plastic film (BF), the straw curtain (SC), and the bare soil (CK), for the Lycium barbarum L. (LL) cultivation was conducted for 2 years. The soil physical and chemical parameters and LL responses were comprehensively evaluated. Results showed the average soil water content during a single irrigation interval was the highest in BF, followed by SC and CK that were comparable, and the lowest in GC in both years. The average soil temperatures within 0–20 cm depth in midsummer in BF was 4.1, 4.5 and 1.9 ℃ higher than those in SC, GC and CK, respectively. The soil desalination rates in GC, BF, SC and CK were 47.9%, 46.5%, 66.2% and 45.0% when compared with the initial salinity in the first year. And those became 43.6%, 82.5%, 73.5% and 76.4% when the second year terminated. The growing parameters of the LL in SC and CK were significantly larger than other treatments. The high soil temperature in BF and the water competition of sown grass in GC had adverse effects on the survival rate, growth, and photosynthetic efficiency of the LL, resulting in the yields and irrigation water productivities (IWP) in BF and GC being 45.8% and 46.3% lower than CK, respectively. While the yield and IWP in SC were 26.9% higher than CK. Considering the changes of soil parameter and LL response comprehensively, the straw curtain could be the best alternative of plastic film for the LL cultivation in saline soil in low-lying arid area.

Features of forming the salt balance in rice fields with various parameters and designs of the Danube rice irrigation systems

Ecological-reclamation state of rice irrigation systems harvest of cultivated crops determined by a number of factors, including natural (soil, topographical, hydrogeological, climatic factors) and technological (irrigation norm, designs and parameters of irrigation and drainage networks, etc.) factors. One of the main factors influencing the formation of rice yield which is traditionally grown by flooding technology is the efficiency of the rice irrigation system’s design. Construction features of irrigation fields and their parameters (distances between the drains, depth of the drainage network) affect the intensity of the processes of salinization of soils and groundwater. Analysis of the components of salt balances of rice fields with different parameters and designs on example of the Danube rice irrigation systems showed that fields with the distances between the drains from 200 to 250 m have significant advantages over Krasnodar-type fields with the same parameters and over fields with 500 m distance between the drains creating optimal salt regime for rice and, accordingly, obtaining higher yields of rice. As on the card-checks with drainage with the distances between the drains 500 m uniform desalinization of soils on all area cannot be reached and yield of rice on them is close to 20 c/ha such card-checks with drainage must be converted into card-checks with drainage with the distances between the drains 250 m.