Soil Salt Leaching Research Articles

Application of Magnetized Ionized Water and Bacillus subtilis Improved Saline Soil Quality and Cotton Productivity.

Soil salinization, a significant global challenge, threatens sustainable development. This study explores the potential of magnetized ionized water irrigation and Bacillus subtilis application to mitigate this issue. The former method is hypothesized to enhance soil salt leaching, while the latter is expected to improve soil nutrient availability, thereby increasing microbial diversity. To address the unclear impact of these interventions on soil quality and cotton productivity, this study employs four different experimental methods: magnetized ionized water irrigation (M), application of 45 kg ha-1B. subtilis (B), a combination of 45 kg ha-1B. subtilis with magnetized ionized water irrigation (MB), and a control treatment with no intervention (CK). This study aims to clarify the effects of these treatments on soil bulk density (BD), field capacity (FC), salinity and alkalinity, nutrient content, microbial activity, and cotton crop yield and quality. Additionally, it aims to evaluate the efficacy of these methods in improving saline soil conditions by developing a soil quality index. The results showed that using magnetized ionized water for irrigation and applying B. subtilis, either alone or together, can effectively lower soil pH and salt levels, enhance microbial diversity and abundance, and improve the yield and quality of cotton. Notably, B. subtilis application significantly decreased BD and enhanced FC and nutrient content (p < 0.05). A correlation was found where soil nutrient content decreased as pH and salt content increased. Furthermore, a strong correlation was observed between the major soil bacteria and fungi with BD, FC, and salt content. Comparatively, M, B, and MB significantly boosted (p < 0.01) the soil quality index by 0.21, 0.52, and 0.69 units, respectively, and increased (p < 0.05) cotton yield by 5.7%, 14.8%, and 20.1% compared to CK. Therefore, this research offers eco-friendly and efficient methods to enhance cotton production capacity in saline soil.

Effects of Drip Irrigation Flow Rate and Layout Designs on Soil Salt Leaching and Cotton Growth under Limited Irrigation

Optimal drip irrigation management in shallow groundwater areas needs to clarify the effects of flow rate and layout designs on the soil moisture, salt distribution, cotton root length density, plant height, leaf area, and yield. In this study, a one-year field experiment was conducted from April to October 2018 in the fifth company of the 16th Regiment in Alar City, Xinjiang, to investigate the effects of various drip flow rates and layout designs of cotton growth. Two drip flow rates (2.8 and 5.6 L·h−1) and two layout designs (one film, two drip tapes, and six rows; one film, three drip tapes, and six rows) were applied to explore the optimal combination, resulting in a total of four treatments that were irrigated three times in the whole growth period. Soil moisture, salt distribution, cotton root length density, plant height, and leaf area were measured. The main results were as follows: (1) Under the same layout designs, the soil moisture content was higher and the soil salinity was lower when the drip flow rate was 5.6 L·h−1, and the cotton root length density, plant height, leaf area, and yield were significantly higher than that of 2.8 L·h−1. (2) Under the same drip flow rate, the soil desalination rate, cotton growth indexes, and yield under the three-tapes treatment were significantly higher than the values of the two-tapes treatment. The actual yield of treatment D was 21.56%, 19.23%, and 11.71% higher than that of treatments A, B, and C, respectively. (3) The crop evapotranspiration of cotton during the two irrigation cycles showed an increasing trend, and the groundwater contribution showed a smaller and then increasing trend. Overall, the combination of three tapes and a drip flow rate of 5.6 L·h−1 had the highest cotton yield and net income, which were 6211.36 kg·hm−2 and 4820.21 kg·hm−2 for the theoretical and actual yields. The results of this study can provide a reference for the management of limited irrigation leaching soil salinity and cotton cultivation in shallow groundwater areas.

Interactions between flue gas desulfurization gypsum and biochar on water infiltration characteristics and physicochemical properties of saline-alkaline soil

The application of flue gas desulfurization gypsum (FGDG) improves the soil structure, reduces soil pH, and accelerates soil salt leaching. Biochar amendment to soil can affect the soil infiltration rate, increase soil porosity, decrease soil bulk density, and enhance the water retention capacity. This study investigated the interactive effect of FGDG and biochar on water infiltration characteristics and physicochemical properties as well as determined the optimal amendment rate as a saline-alkaline soil conditioner. Seven experimental schemes were designed, and the newly reclaimed cultivated soil from Pingtan Comprehensive Experimental Zone in Fujian Province, China, was used in an indoor soil column experiment to simulate soil infiltration. Five models were employed to describe the infiltration process. The power function was used to represent the dynamic process of the wetting front. The conclusions of this study are as follows: (1) there was a reduction in the infiltration capacity of saline-alkaline soil (sandy soil) in each treatment, and the application of FGDG alone had the highest inhibition effect compared to the control (CK). The Kostiakov model provides the best fit for the experimental data of soil cumulative infiltration. (2) All treatments increased the total porosity and water content of saline-alkali soil, with the combined application of FGDG and biochar found to be more effective. (3) The application of FGDG alone or in combination with biochar decreased the pH and increased the electrical conductivity of the saline-alkali soil significantly, with the combined application having the most significant effect. In contrast, soil amended with biochar alone had minimal effect on the pH and EC of the soil. (4) The best improvement ratio was achieved with the F1B2 combination (75 g/kg FGDG + 30 g/kg biochar).

The successive infiltration of various saline waters accelerates the infiltration processes and enhances the salt leaching in a coastal saline soil

AbstractThe local saline water resource has been widely used for soil water and salt managements in saline‐alkali area. The soil desalinization is strongly affected by the infiltration mode, and the melting saline ice infiltration can obtain soil salt leaching effectively. In this work, four melting sections (S1, S2, S3, and S4) were divided artificially according to the changes in meltwater from 5 (W5), 10 (W10), and 15 g L−1 (W15) ice. Various saline water samples of the above four sections with different salinities and volumes were prepared and infiltrated successively into soil columns that were packed with the coastal saline soils. The infiltration parameters, distribution patterns of soil moisture, salt, and sodium adsorption ratio (SAR), and soil desalinization in different sections were investigated and analyzed. Results showed that the infiltration of higher salinity water in the initial section increased the infiltration rates of slightly saline and fresh water in the last section. A greater infiltration rate, cumulative infiltration, and infiltration depth were ranked as W5 &lt; W10 &lt; W15. Moreover, the faster infiltration process obtained higher soil water contents throughout the S1, S1 + S2, and S1 + S2 + S3 sections, and more water was ultimately distributed in the deeper soil layer (S1 + S2 + S3 + S4 section). Both the soil salt and SAR increased initially (Section S1) and then decreased in the following sections; &gt;80% of the total leached salt loads occurred in the S2 section for all treatments. Lower levels of soil salt contents and SAR developed within the later infiltration sections. Ultimately, the 30 cm desalinization layer was obtained among all treatments, and the treatments corresponding to the saline ice with higher salinity acquired lower salt contents and SAR values. These results indicate that the successive infiltration of water with various salinity levels, characterized by meltwater from saline ice, accelerated the infiltration process, and resulted in an obvious soil desalinization effect on the coastal saline soil.

Effects of soil salt-leaching terms on growth, development and yield of corn in Uzbekistan

The issue of growing field crops in saline soils and increasing their resistance to salt remains a topical issue in terms of land reclamation. In saline soils, it is important to increase the resistance of field crops to salinity on the basis of the use of advanced technologies, as well as to pay special attention to soil reclamation. The study shows that the salinity of the soils of the planned area, the lack of saline leaching and the presence of a seasonal salt accumulation process, the problem is solved from a scientific point of view, as well as its complexity. Proper timing of saline leaching is an important reclamation measure in eliminating the negative effects of salt accumulation in saline soils. When washing the soil brine in October-November, a complete leaching of the salt was achieved, resulting in a 17.6% higher biomass than the unsalted variant of the salt. The optimal irrigation rate for corn is determined by soil moisture. The number of irrigations for the biomass was set to 5 times during the growing season. At this irrigation rate, the soil moisture did not fall below 75-80% of the limited field moisture capacity (LFMC) until the oats sprouted. During the growing season, the first watering was started when the plant produced 5-6 leaves.

Water and salt replacement through soil salt leaching under brackish water conditions with subsurface pipe drainage

AbstractTo explore the improvement effect of subsurface drainage and brackish water on saline alkali soil, an orthogonal experimental design was used to conduct soil column experiments under nine parameter combinations of the depth of the buried subsurface pipe, irrigation amount and salinity of brackish water. A numerical model of soil water and salt movement was established, and the physical parameters of the soil were verified by using the software HYDRUS‐1D. The results indicated that the salinity of the brackish water only affected salt replacement. The salt replacement associated with subsurface drainage decreases with increasing water and salt replacement area at a constant irrigation volume. The salt replacement amount through subsurface pipe drainage increased with the irrigation amount in constant water and salt replacement areas. When the burial depths of the subsurface pipes were 140 and 160 cm and the irrigation amounts were &gt;3180 and 3990 m3 ha−1, respectively, the salt discharge through the subsurface pipes was greater than the salt content carried by the brackish water, and the salt content of the soil in the root zone reached the critical salt tolerance value of cotton, which can simultaneously show that the soil salt content would not affect cotton growth.

Modeling strategies to balance salt leaching and nitrogen loss for drip irrigation with saline water in arid regions

Soil salinization has severely constrained agricultural sustainability in arid and semi-arid regions. Generally, using additional irrigation water to leach excessive salts is a widely used strategy for alleviating soil salt accumulation in the root zone. Nevertheless, this practice simultaneously increases the risk of nitrogen loss. To address this contradiction, a new index, namely, the leaching balance index of soil salinity and nitrogen (LBI), which was defined by multiplying the nitrogen leaching fraction (NLF) by the absolute value of the discrepancy between the crop tolerance salinity threshold and soil salinity (|∆SSC|), was proposed. The lower the index value is, the better the soil salt and nitrogen leaching can reach an optimal equilibrium state. Soil salt leaching and nitrogen loss were simulated by the HYDRUS-2D model. The two-year field observation data of soil moisture, salinity, ammonium, and nitrate nitrogen contents were collected for calibration and validation. A model case was presented using the LBI to investigate the appropriate mulched drip irrigation and fertigation management practices with different levels of salty waters for cotton in Xinjiang in this study. In the testing process, the normalized root mean square error (nRMSE) provided by this model was 2–13 %, 5–14 %, 20–40 %, and 14–27 % for soil water content (SWC), soil salinity (EC1:5), NH4+–N, and NO3––N, respectively, and the index of agreement (d) was 0.63–0.94, 0.83–0.99, 0.69–0.97, and 0.86–0.96, respectively. Then, the simulation scenarios were established to minimize the NLF and the |∆SSC| and thus the LBI. The results showed that increasing the number of fertigation splits could reduce the LBI. Specifically, five fertigation splits during the growing season could result in a decrease in the LBI of 21–32 %. Furthermore, when applying an irrigation amount of 100% ETc, the alternate use of water salinities of 6.0 dS m−1 and 10.0 dS m−1 at the squaring stage and flower boll stage produced a lower LBI. The irrigation scheme of a higher water salinity and irrigation amount during the squaring stage, coupled with a lower water salinity and irrigation amount during the flower boll stage, was beneficial for decreasing the LBI. The lower the value of LBI is, the more sustainable the irrigation and soil management will be. The new index of the LBI proposed by our study represents one of the first efforts to solve the contradiction between salt accumulation and nitrogen loss, which will ultimately aid in the salt control and efficient utilization of water and nitrogen for arid and semi-arid regions.

Evaluating soil water and salt transport in response to varied rainfall events and hydrological years under brackish water irrigation in the North China Plain

• Responses of soil water and salt dynamics to varied rainfall events and hydrological years were evaluated. • Salt leaching and deep drainage occurred mainly due to summer-concentrated rainfall during wet year. • Salt decrease percentage in the CL was greater than that in the GL in all hydrological years. • One brackish water irrigation application is avail salt leaching both in cropland and grassland. Soil salination challenges sustainable agricultural production and management in the lowland area of the North China Plain (NCP). This study investigated the effect of varied rainfall events and hydrological years on deep drainage and salt leaching in Nanpi County in the NCP. Field experiments were conducted to measure soil matric potential (SMP) and soil water electrical conductivity (EC w ) in 300 cm profiles of an irrigated cropland (CL) and unirrigated grassland (GL). The HYDRUS-1D model was calibrated and validated to optimize soil water and salt transport parameters using the SMP and EC w data obtained in 2015 and 2016, respectively. The results showed that the HYDRUS-1D model was reliable to simulate soil water and salt migration in 300 cm profiles at both sites. The salt leaching depths and degrees were positively correlated with precipitation amount. The heavy rain (45 mm) and rainstorm (68 mm) favored salt leaching within 100 cm, and severe and extreme rainstorms resulted in salt leaching within 150–200 cm both in the CL and GL. The SDP in the CL was greater than that in the GL in all hydrological years owing to agricultural cultivation and irrigation. Salt leaching in the 300 cm profiles mainly occurred in the rainy seasons of wet year, with the salt decrease percentage (SDP) being 61% in the CL and 42% in the GL. Salt leaching due to precipitation was sufficient in the irrigated CL in all hydrological years, and precipitation in normal rainfall years could remove 70–80% of soil salts within 50–63 cm soil depth. Grass growth without irrigation led to water deficits and salt accumulation when the annual precipitation amount was less than that in wet years. The results demonstrated that precipitation, combined with irrigation using of brackish and freshwater, could be usefully for soil salt leaching. A recommended irrigation scheme for water saving and salt control in CL and GL is one brackish water irrigation application and three freshwater irrigation applications each year in the NCP.

Field irrigation using magnetized brackish water affects the growth and water consumption of Haloxylon ammodendron seedlings in an arid area.

Freshwater resources in arid areas are scarce, while there are abundant brackish water reserves that have great application potential for the irrigation of desert plants. However, brackish water irrigation will lead to soil salinization, which will inhibit plant growth. Magnetized water is a new technology that makes the use of brackish water feasible. The present study assessed the effects of irrigation using three water types (fresh, brackish, and magnetized brackish water) and five irrigation amounts (W1, 81 mm; W2, 108 mm; W3, 135 mm; W4, 162mm; and W5, 189 mm) on soil salinity and Haloxylon ammodendron seedling growth. Compared with fresh water, brackish water irrigation inhibited the growth of H. ammodendron and reduced water consumption. Irrigation with magnetized brackish water effectively improved the effect of soil salt leaching, promoted the growth and water absorption of H. ammodendron roots, and stimulated the growth of plant height, basal diameter, shoot length, and crown width. Based on the principal component analysis, the first three treatments of H. ammodendron comprehensive growth state were FW4, FW3, and MBW4, respectively. This showed that magnetized brackish water combined with an appropriate irrigation amount was helpful to optimize the growth of H. ammodendron seedlings on the basis of fresh water saving. Therefore, magnetized brackish water irrigation is an effective strategy for ensuring the establishment and growth of H. ammodendron seedlings in arid and water-deficient areas.

Interaction Between Brackish Water Intermittent Infiltration and Cultivated Soil Environment: A Case Study From Arid Piedmont Plain of Northwest China

Brackish groundwater was widely used in arid areas which may cause soil salinization and groundwater environmental declines. To ensure the sustainable development of agriculture in arid areas, brackish water intermittent infiltration experiments were conducted in Southern Xinjiang, Northwest China between June to September 2018, and Hydrus-2D numerical simulation was used to analyze the underground pipe drainage systems. The field experiments were carried out during cotton growth stages after the first freshwater flood infiltration and salt washing. Two control experiments were, respectively, designed as freshwater (0.68 g/L) and brackish water (1.66 g/L) with water amount of 1.0 Q = 572 mm. Other eight groups (1.05–1.40 Q) were compared to analyze the effect of soil salt leaching by increasing the brackish water amount. The results showed that the soil moisture content was almost less than the field capacity of 0.203 at depth of 0–60 cm before each infiltration due to roots water uptake, and the soil water holding capacity rate was lower than 0.2 after 5 days under 1.20–1.40 Q brackish water treatments. Variation of EC1:5 at depth of 0–30 cm was less than 0.5 dS/m. Salt mainly accumulated at the depth of 40–60 cm whether the water amount was excessive or insufficient even under the fresh water infiltration. The optimal brackish water amount was 1.15 Q = 657.8 mm, and the soil total salinity was less than 0.55 dS/m (EC1:5) and reached mild salinization degree. Numerical simulations were used based on the 2018 field experimental results and extended by another 10 years. The soil salt accumulated to 1.10–2.99 dS/m (EC1:5) at the depth of 40–60 cm during 0–30 days. The no salinization area expanded to depth of 40–45 cm after 120 days and reduced during non-infiltration period due to evaporation effect. The soil salt was gradually leached and less than 0.55 dS/m (EC1:5) after 10 years. The optimized leaching–drainage system could not only provide a low salinity soil condition for cotton growth and realize sustainable cultivation but also greatly protect the soil and groundwater environment.

Mechanism of snowmelt infiltration coupled with salt transport in soil amended with carbon-based materials in seasonally frozen areas

In midlatitude seasonally frozen areas, the freeze–thaw cycle affects the movement of soil water, which increases the uncertainty in salt transport and aggravates the risk of soil salinization. Based on this, a two-year field study was established on the Songnen Plain, a seasonally frozen area in northern China. Four treatments were set up: (i) control, (ii) corn stover, (iii) biochar, and (iv) combined (joint application of biochar and corn stover). The modified soil underwent seasonal freeze–thaw cycling, accompanied by the evaporation and infiltration of snowmelt water, and the soil salt migration and diffusion characteristics were determined. Both biochar and corn stover regulated the pore structure of the soil and enhanced the infiltration capacity of snowmelt water; notably, the maximum soil moisture contents in the corn stover, biochar and combined treatments increased by 9.33%, 22.12% and 16.37%, respectively, compared with that in the control group. However, biochar with abundant functional groups increased the cation exchange capacity and promoted the migration of salt ions (i.e., Na+, K+ and Cl−), and the surface soil salt content in the biochar treatment was 0.12–0.53 g/kg lower than that for the other three modes during the infiltration period. Additionally, soil water evaporation carried salts upwards, which greatly increased the salt content of the surface soil. Conversely, biochar presented a strong water-holding capacity, which reduced the ineffective evaporation of soil water, while stover acted as a barrier to hinder the return of salt. Among the treatments, the synergistic transport ability of soil salt and water was the lowest in the combined treatment. Overall, the combination of biochar and corn stover had advantages in terms of soil salt leaching and offered a healthy, effective strategy for soil salinization control in cold areas.

Field study on the influence of subsurface drainage pipes and envelopes on discharge and salt leaching in arid areas

AbstractThe selection of suitable drainage materials is crucial for the efficient operation of subsurface drainage systems. Previous studies on drainage material selection have focused on anti‐clogging characteristics, and less attention has been given to their effects on the process of soil salt leaching, which is an important consideration in arid and semi‐arid areas. To investigate the influence of subsurface drainage pipes and envelopes on salt leaching and discharge, field leaching experiments under flood irrigation and drip irrigation were conducted in Xinjiang region in China. Results show that the amount of drainage water in treatments that use gravel envelopes is higher than that in treatments that use synthetic envelopes. Meanwhile, the amount of drainage water in treatments that use gravel envelopes decreases the most after 1 year of operation. The synthetic envelope, the interaction between the perforation rate of the drainage pipe and the synthetic envelope significantly influence water and salt discharge. The optimal level of the synthetic envelope used in this study is spun‐bonded non‐woven geotextile, that of the layer number of envelopes is a single layer, and that of the perforation rate of the drainage pipe is 3.0%.

Hydrogeological and geochemical characterization of groundwater in the F'Kirina plain (eastern Algeria)

The F'Kirina plain in eastern Algeria is an endorheic basin suffering water scarcity due to a combination of natural and man-made causes. Its hydrogeological system is complex as made by interconnected aquifers represented by Mesozoic, Cenozoic, and Quaternary lithological units. The combination of drought indicators and water level data shows that a groundwater drought affected the plain during the last 15 years, which reflects on current water quality. The reported geochemical analyses, including major ions and trace elements, indicate that the groundwater resource is suffering from salinization, mainly due to evaporation and leaching of soil salts, a process that is coupled with simultaneous cation-exchange effects. In this framework, we observe a geochemical evolution from the fresh Ca–HCO3 facies, typical of springs bordering the plain, towards more saline groundwater characterized by chloride/sulphate-rich facies in the middle of the plain approaching the sebka. However, geochemical diagrams indicate that in few wells salinization is also influenced by upraising of deep groundwater. The water isotopic composition of the F'Kirina plain samples suggests that they diversely record both recharge and evaporation components. Moreover, the most 18O and D depleted compositions among the investigated ground-waters suggest recharge contributions by comparatively higher elevation or the involvement of old (fossil) water components.

Evaluating the saline water irrigation schemes using a distributed agro-hydrological model

Quantitatively assessing the practicality and sustainability of saline groundwater for irrigation at the regional level could provide a valuable reference for macro decision-making and management in terms of alleviating the severe contradiction between freshwater shortages and food production. In this study, the distributed agro-hydrological SWAP-WOFOST (Soil-Water-Atmosphere-Plant-WOrld FOod STudy) model was applied in the east-central North China Plain (NCP). The model was used to simulate the five saline water irrigation scenarios for a 20-year period, and the effects on the spatiotemporal variations in crop yield, water productivity (WP), and soil water and salt balances were analyzed. Furthermore, appropriate saline water irrigation schemes were solved considering crop yield reduction and soil salt accumulation. Finally, spatial matching between the appropriate irrigation schemes and saline groundwater resources from the perspectives of “water quality” and “water quantity” was evaluated. The main results were as follows. (1) The average yield and WP of winter wheat during the simulation period remained stable or increased slightly under saline water (2–6 g L−1) irrigation for winter wheat compared with that under freshwater irrigation, whereas the average yield and WP of the following summer maize decreased to varying degrees. (2) When the sum of seasonal precipitation and irrigation of summer maize was >450 mm, 401–450 mm, 351–400 mm, 200–350 mm and <200 mm, the average soil salt leaching depth was approximately 120 cm, 100 cm, 80 cm, 60 cm and 40 cm, respectively. (3) On the premise that the average salt content of the 2-m soil profile at summer maize harvest during the simulation period was less than 3 g kg−1, if the average crop yield reduction of the rotation system in the range of ≤500 kg hm−2, ≤1000 kg hm−2, ≤1500 kg hm−2 and ≤2000 kg hm−2 was permitted, the dominant maximum irrigation water salinity in the study area was 3 g L−1, 4 g L−1, 6 g L−1 and 6 g L−1, respectively. (4) The average saline water amount needed for winter wheat irrigation during the simulation period was approximately 22.78 × 108 m3, which was approximately 9% more than the exploitable amount of saline groundwater. The results could support decision-making related to developing and using shallow saline groundwater for irrigation.

Chemical Evolution and Formation Mechanism of Groundwater in Hetao Irrigation Area

Groundwater resources are important sources of water in the arid region of northwestern China, but their overexploitation and utilization has led to a series of ecological and environmental problems. Exploring the characteristics and mechanism of groundwater chemical evolution is important for the rational use of groundwater resources. The characteristics of groundwater chemical evolution were studied in the Yongji Irrigation Area of Hetao Irrigation District and the formation mechanism of the chemical compounds in groundwater were investigated using cluster analysis, factor analysis, and other statistical methods. The influence degree of different factors was calculated. The results showed that the major cations in groundwater in the study area were Na+ and K+, and the major anions were Cl- and HCO3-. Moreover, Na+, K+, and Cl- showed high spatial variability and were the main factors contributing to groundwater salinization. The major chemical compounds in the groundwater in the study area were Cl-Na, HCO3 ·Cl ·SO4-Na, and HCO3-Na. Based on the cluster analysis results, the groundwater was divided into four categories (A1, A2, B1, and B2), of which A1 was highly mineralized by Cl-Na type water, while A2, B1, and B2 were mainly HCO3 ·Cl ·SO4-Na and HCO3-Na type water. Principal component analysis results suggest that groundwater chemistry was mainly affected by salinization, carbonate karstification, and human activities with the influence degrees of 45.976%, 23.853% and 16.678%, respectively. Evaporation, salt rock dissolution, and cation exchange were important sources of Na+ and Cl- accumulation in the irrigation area. Agricultural irrigation (leaching of soil salts) and drought (intense transpiration) were the key drivers of groundwater salinization in the irrigation area.

Salt leaching process in coastal saline soil by infiltration of melting saline ice under field conditions

Freezing saline water irrigation (FSWI) in winter has been shown to be an effective way to reclaim heavy saline soils. In this four-year experiment, the salt leaching process during saline ice melting and infiltration after FSWI was investigated. Saline water was frozen in saline ice on top of soil after irrigation. Over 70 or 80 days of ice melting and infiltration, ice and soil samples were taken at 10-day intervals to quantify the soil salt leaching process. The results showed that salt leaching mainly occurred in the initial 30 days after irrigation (DAI); approximately 72% of the total salt reduction was the result of salt migrating out of the 0 to 20 cm soil layer. Furthermore, in this period, the amount of salt that leached out of the 0 to 20 cm soil layer with meltwater was greater than the total salt from the irrigation water. Approximately 15% of the total salt reduction in the 0 to 20 cm layer occurred from 60 to 80 DAI; in this period, the infiltrating meltwater accounted for more than 30% of the total irrigation water, and the electrical conductivity of the meltwater was below 4.5 dS m−1. After the meltwater had infiltrated the soil completely, the electrical conductivity of saturation paste (ECe) in the 0 to 20 cm layer for FSWI was below 4.3 dS m−1, significantly lower than the ECe of 16.7 dS m−1 of the nontreated soil. These results indicated the soil salt leaching was mainly determined by the melting process of saline ice under the FSWI treatment.

Effects of combined drip irrigation and sub-surface pipe drainage on water and salt transport of saline-alkali soil in Xinjiang, China

Developing effective irrigation and drainage strategies to improve the quality of saline-alkali soil is vital for enhancing agricultural production and increasing economic returns. In this study, we explored how irrigation and drainage modes (flood irrigation, drip irrigation, and sub-surface pipe drainage under drip irrigation) improve the saline-alkali soil in Xinjiang, China. We aimed to study the transport characteristics of soil water and salt under different irrigation and drainage modes, and analyze the effects of the combination of irrigation and drainage on soil salt leaching, as well as its impacts on the growth of oil sunflower. Our results show that sub-surface pipe drainage under drip irrigation significantly reduced the soil salt content and soil water content at the 0–200 cm soil depth. Under sub-surface pipe drainage combined with drip irrigation, the mean soil salt content was reduced to below 10 g/kg after the second irrigation, and the soil salt content decreased as sub-surface pipe distance decreased. The mean soil salt content of flood irrigation exceeded 25 g/kg, and the mean soil desalination efficiency was 3.28%, which was lower than that of drip irrigation. The mean soil desalination rate under drip irrigation and sub-surface pipe drainage under drip irrigation was 19.30% and 58.12%, respectively. After sub-surface drainage regulation under drip irrigation, the germination percentage of oil sunflower seedlings was increased to more than 50%, which further confirmed that combined drip irrigation and sub-surface pipe drainage is very effective in improving the quality of saline-alkali soil and increasing the productivity of agricultural crops.

Insights into groundwater salinization from hydrogeochemical and isotopic evidence in an arid inland basin

AbstractIn the Manas River basin (MRB), groundwater salinization has become a major concern, impeding groundwater use considerably. Isotopic and hydrogeochemical characteristics of 73 groundwater and 11 surface water samples from the basin were analysed to determine the salinization process and potential sources of salinity. Groundwater salinity ranged from 0.2 to 11.91 g/L, and high salinities were generally located in the discharge area, arable land irrigated by groundwater, and depression cone area. The quantitative contributions of the evaporation effect were calculated, and the various groundwater contributions of transpiration, mineral dissolution, and agricultural irrigation were identified using hydrogeochemical diagrams and δD and δ18O compositions of the groundwater and surface water samples. The average evaporation contribution ratios to salinity were 5.87% and 32.7% in groundwater and surface water, respectively. From the piedmont plain to the desert plain, the average groundwater loss by evaporation increased from 7% to 29%. However, the increases in salinity by evaporation were small according to the deuterium excess signals. Mineral dissolution, transpiration, and agricultural irrigation activities were the major causes of groundwater salinization. Isotopic information revealed that river leakage quickly infiltrated into aquifers in the piedmont area with weak evaporation effects. The recharge water interacted with the sediments and dissolved minerals and subsequently increased the salinity along the flow path. In the irrigation land, shallow groundwater salinity and Cl− concentrations increased but not δ18O, suggesting that both the leaching of soil salts due to irrigation and transpiration effect dominated in controlling the hydrogeochemistry. Depleted δ18O and high Cl− concentrations in the middle and deep groundwater revealed the combined effects of mixing with paleo‐water and mineral dissolution with a long residence time. These results could contribute to the management of groundwater sources and future utilization programs in the MRB and similar areas.

Soil salinity, sodicity and cotton yield parameters under different drip irrigation regimes during saline wasteland reclamation

A field trial consisting of cotton grown employing a combination of ridge planting, mulching with film, and drip irrigation was laid out on a plot with severely saline soil in a typical inland arid area of Xinjiang. The effect of five levels of soil matric potential set up 0.2 m below the drip emitter, namely −5 kPa, −10 kPa, −15 kPa, −20 kPa, and −25 kPa, were studied in terms of changes in soil salinity (ECe), sodicity (SAR), crop growth and yield components. Drip irrigation increased the leaching of soil salts and decreased the ECe and SAR of each soil layer. Although the levels of soil salt rose again, in spring and winter, after irrigation was discontinued, the root zone (0–40 cm) remained less saline: the ECe and SAR value under the soil matric potential of −5 kPa and −10 kPa were 63% and 49% of its values in 2009 respectively, before the land was brought under cultivation (p ≤ 0.05), showing maximum leaching. The yield of cotton peaked at the soil matric potential of −5 kPa. The germination rate, which was the main factor that influenced the cotton yield, was 67% of that in non-saline soil in the first two years, and increased to 84% in the third year. After three years, the rate of germination in all the treatments exceeded 67%, and the highest rate (78%) was at −5 kPa; in the same treatment, boll yield was 4.40 g per plant. Except for germination rate and the yield of lint and seed, all the yield components increased significantly (p ≤0.05) as ECe and SAR decreased in 2010 and 2011. The correlation between soil salt (salinity and sodicity) and other components such as the number of cotton bolls per plant, the average weight of a boll, and lint percentage varied, probably because water supply was being regulated and, as a result, the physicochemical properties of the soil kept changing constantly. Taking into account the extent of leaching, crop growth, and yield, the lower limit for the soil matric potential should be −5 kPa at 20 cm below the dripper for the first three years during reclamation to promote cotton cultivation on the saline-sodic soil of Xinjiang.

Improvements of soil salt characteristics and nutrient status in an impermeable saline–sodic soil reclaimed with an improved drip irrigation while ridge planting Lycium barbarum L.

Takyric solonetz is spread widely across the arid area of northwest China. The extremely poor soil structure and low hydraulic conductivity (Ks < 0.1 mm day−1) hinder its amelioration. The purpose of this study was to investigate the soil salt leaching characteristics, nutrient contents, and distributions in the impermeable saline–sodic soil reclaimed with an improved drip irrigation method, and to explore the impacting mechanisms of agronomic practices involved on the amelioration. A 3-year field experiment was conducted to investigate the success of planting Lycium barbarum L. in the highly saline–sodic wasteland of takyric solonetz using drip irrigation. The soil beneath the drip emitters near the plants was replaced with sand in niches that were 0.2 m in ground diameter and 0.2 m deep. Five treatments based on soil matric potential (SMP) were designed to find the optimal irrigation schedule: −5 kPa (S1), −10 kPa (S2), −15 kPa (S3), −20 kPa (S4), and −25 kPa (S5). A significant improvement was found in soil infiltration capability, which was demonstrated by the increasingly enlarged wetted area beneath the drip emitter. This improvement was resulting from the combined affects of all the agronomic practices involved, including drip irrigation, sand-filled niches, film mulching. After 3 years, soil salt leaching rates in S1–S5 root zones were 68.16 , 39.45 , 26.56 , 25.14 and 10.40%, respectively, indicating that the higher SMP improved soil salt leaching. The increased soil ECe/SAR ratio reflected the amelioration of soil physical properties. After planting, the soil nutrient status considerably improved. N fertilizer, which often was leached away, should be applied in the latter half of an irrigation event. Available P content in the soil was relatively low and it was necessary to apply adequate P fertilizer to meet crop growth needs, while the studied soil was rich in K and moderate supplement of K fertilizer was proposed. After 3 years, S2, S3, and S4 produced the significantly higher dry fruit yields (∼900 kg ha−1), which were close to those produced by local farmland. Our findings indicated that an improved drip irrigation made the reclamation of an impermeable saline–sodic soil possible. The key operations included drip irrigation, sand-filled niches beneath drip emitters, ridge tillage, film mulching, and the use of thresholds to control SMP.