Soil Salinity Characteristics Research Articles

Optimizing Biochar Application Rates to Improve Soil Properties and Crop Growth in Saline–Alkali Soil

There is great demand for the amelioration of saline–alkali soils, which requires efficient and economical amendments. Biochar addition could alleviate the adverse impacts of saline–alkali stress in crops. However, their efficiency and optimal amounts in saline–alkali soil restoration remain contradictory and inconclusive. The objective of this study was to investigate the effects of biochar application on the properties of saline–alkali soil and crop growth, as well as to determine the optimal application rate of biochar. We conducted pot experiments with biochar (B) application rates, including 0 (CK), 1% (B-1%), 2.5% (B-2.5%), 5% (B-5%), and 10% (B-10%), studying the impact of biochar on soil water content (SWC), soil salinity, soil electrical conductivity (EC), soil ion content, soil nutrients, soil enzyme activity, and crop growth. A four-parameter Gaussian function was established for the curves depicting the relationship between soil salinity characteristics and the biochar application rates to determine the most optimal application rate. The results indicated that: (1) Compared to the CK, all biochar treatments improved soil water-holding capacity and reduced soil Na+ content and sodium adsorption ratio (SAR). (2) B-1%, B-2.5%, and B-5% treatments reduced soil content, EC, Cl−, and SO42− content over CK, while the results were reversed for the B-10% treatment. (3) Compared to the CK, all biochar treatments significantly increased soil fertility, enhanced soil enzyme activity (alkaline phosphatase, catalase, and urease activity), and significantly promoted the growth of maize. (4) The results of the Gaussian model suggested that a biochar application rate of 3.16% is the optimal rate for alleviating soil salinity in saline–alkali soils. This research demonstrated the potential of biochar to improve soil properties and promote crop growth and provided useful information on biochar application rates for ameliorating saline–alkali soils.

Soil salinity and salt tolerance of plants

Global scarcity of water resources, ecological pollution and enlarged salinization of soil and water became a noticeable problem at the beginning of the 21st century. Soil pollution caused by industrial and agricultural activities is an environmental problem that poses serious threats to human health and ecosystems. This review provides, firstly soil salinity characteristics and salinity indicators. Secondly, we focused on saline areas in the world and causes of soil salinization. Thirdly, mapping and monitoring of soil salinity areas and improvement measures for saline soil tolerance. Fourthly, effect of salinity stress on plant and plant salinity response was discussed. This review is intended to provide a comprehensive overview on salinization of soil and presenting fundamental information for future research studies.

Characteristics of Soil Salinity in Representative Plastic Shed Vegetable Production Areas in Shandong Province, China

Characteristics of Soil Salinity in Representative Plastic Shed Vegetable Production Areas in Shandong Province, China

Spatio–Temporal Variability Characteristics of Coastal Soil Salinization and Its Driving Factors Detection

The utilization efficiency of land resources in the coastal area of the Yellow River Delta has been deeply affected by salinization hazards. Key to improvement of the utilization efficiency of resources in this area is to grasp the spatio–temporal variability law of soil salinity and identify the driving factors of salinization. Wudi County in the coastal area of the Yellow River Delta is taken as the study area. Based on the data obtained from field measurements and laboratory analysis, the characteristics of soil salinity in spring and summer were analyzed by classical statistical methods; the spatial differentiation characteristics of salinization were analyzed from two–dimensional and three–dimensional perspectives using the geographic information system (GIS) and groundwater modeling system (GMS); the time variation characteristics of salinization were quantitatively analyzed by introducing the salinization severity index (Si) and the dominant index of salinization degree change (Ci). The results show that: (1) In the study area, the soil salinity of the surface layer (0–15 cm) in summer is lower than that in spring, but the sub–surface layer (15–30 cm), the middle layer (30–45 cm) and the bottom layer (45–60 cm) are all larger than the corresponding layers in spring, and the correlation between the soil salinity of each layer in summer is generally lower than that in spring. (2) In two–dimensional space, the areas with a surface soil salinity greater than 0.4% in both seasons are mainly located in the northern part of the study area; in three–dimensional space, the soil is mainly moderately salinized in both seasons, and the complexity of the distribution of the salt profile is higher in summer than in spring; (3) Mashanzi Town was the area most seriously affected by salinization in both seasons (Si values were greater than three); In the process of seasonal alternation, the dominant change type of salinized soil is from mild aggravation to moderate, with Ci value of 38.43%, followed by severe alleviation to moderate, with Ci value of 35.49%; (4) The driving factors of soil salinization in spring are mainly the soil salinity of the subsurface and middle layer, and soil water content; and in summer, mainly the soil salinity of subsurface layer, vegetation coverage and vegetation cover type. The interaction between any two factors has greater influence on the spatial variation of salinization than the corresponding single factor.

Characteristics of soil salinity and its effects on poplar growth in a silting coastal area of Northern Jiangsu Province

Characteristics of soil salinity and its effects on poplar growth in a silting coastal area of Northern Jiangsu Province

The role of waterlogging stress on the distribution of salt marsh plants in the Liao River estuary wetland

The degradation of salt marsh plants due to human activities has accelerated in recent years, and this has decreased the ecological service functions of estuary wetlands and contributed to global climate change. In the threatened Red Beach area within the Liao River Estuary Wetland (LREW) of China, the factors that dominantly affect the distribution of salt marsh plants at large scale are unknown. Here, we used field observations and numerical simulation to identify factors influencing waterlogging stress and its role in the distribution of salt marsh plants (Suaeda heteroptera) in the LREW. Remote sensing image interpretation was then used to validate the results of the numerical simulation. Based on our field observations, the density of salt marsh plant communities may be highly sensitive to waterlogging. A hydrodynamic model was then used to reproduce the waterlogging distribution of the LREW. The distribution of the salt marsh plants was indirectly simulated by referencing the relationship between plant density responses to waterlogging. The simulation method proved consistent with remote sensing results. Our results show that the plant communities investigated here exhibited clear differences in density and inhabited environments based on waterlogging and soil salinity characteristics. S. heteroptera in the LREW can grow with 1.56–2.87 h/d of waterlogging. Our numerical model again confirmed this range and was consistent with field survey results. Based on these observations, drought tolerance and inundation tolerance determined the upper and lower boundaries of S. heteroptera distribution, respectively. Differences in waterlogging regimes that are suitable for growth resulted in a strip-shaped distribution of the salt marsh plants. Given the diverse threats posed by changing estuaries and coasts, our study provides a methodological framework for evaluating the distributions of salt marsh plants, in addition to baseline data to inform the protection and restoration of wetland plants.

Assessment of soil salinisation in the Ejina Oasis located in the lower reaches of Heihe River, Northwestern China

ABSTRACTRecognition of the spatial-temporal distribution characteristics of soil salinity has become an important basis for the formulation of strategies required in the utilisation and sustainable development of soil resources in arid and semi-arid area. In this paper, based on vegetation cover dataset during 1998–2015 in Ejina region combined with the collected soil salinity data, geostatistical methods were used to explore the temporal and spatial dynamic characteristics of soil salinity and its impact on vegetation in the study area. The results showed significant differences in soil salinisation characteristics with a large variability in the soil salinity among the different soil depths, with a variation coefficient ranging from about 0.97–1.47. Soils are represented by a continuous variation, both in space and time. Soil salinity showed an obvious spatial autocorrelation, with a plaque type distribution. The areas of the salinised soil found for the years 2003, 2011 and 2015 were approximately 18,565, 23,206 and 17,721 km2, respectively. From the relationships deduced between the normalised difference vegetation index (NDVI) and soil moisture and salt content in different soil depths, the present study ascertains that the soil moisture content is the most important limiting factor of vegetation growth in Ejina Oasis.

Characteristics of soil salinity in the typical area of Yellow River Delta and its control measures

The Yellow River Delta is one of important ecological areas in eastern China, however sustainable development of the Yellow River Delta is seriously restricted because of severe soil salinization. The main sources of soil salinity are chloride, sodium and sulfate ions. The distribution of soil salinity in soil profiles showed that surface accumulation of soil salt was significant in the Yellow River Delta. Some control measures including soil improvement and regulation, reasonable combination of salt-fresh water irrigation in farmland, land cover and effective drainage were put forward for soil salinity control.

Spatial Variability of Soil Salinity under Subsurface Drainage

In the coastal area of eastern China with monsoon climate and high water table, soil salinity exhibits strong spatial heterogeneity at the field scale. Using basic tools of geostatistics and geographic information systems (GIS), we explored the spatial characteristics of soil salinity under rain-fed conditions and subsurface drainage. The results showed that (1) spatial variability in soil salinity could be reduced significantly by leaching with rain water and subsurface drainage (LD) during the rainy season. The variability in soil salinity after LD decreased from strong to moderate. (2) After LD, soil salinity remained at more than 0.85 g/kg irrespective of values before the rainy season. In other words, it was almost impossible to remove all the salts in the plow layer. (3) Spatial heterogeneity of soil salinity showed a homogenizing tendency based on the critical point of 7 g/kg. Soil salinity less than 7 g/kg (79% of samples) homogenized to within 1.5–2 g/kg under LD and that more than 7 g/kg decreased to 1.5–4.5 g/kg. However, at this level, most salt-tolerant crops could grow. (4) The homogeneity was also reflected in the transformation of salinity grade in different areas. Before LD, the moderately and heavily saline (2–10 g/kg) soil area accounted for 88% of the pilot field in which the heavily saline area constituted 57.45% of the total salt load within the 0- to 30-cm layer; after LD, the mildly saline (1–2 g/kg) area was dominant with more than 75% ratio, contributing 65.24% of total salt load. (5) Intensive and frequent rainfall and long-term LD may reduce the spatial variability in salinity and allow for better reclamation and utilization of saline land. These results provide a scientific basis for integrated management of water and agricultural production.

Relationships and significance of contaminants in soils of the Transantarctic Mountains

The behaviour of Antarctic soils towards contaminant materials depends on the nature of the contaminant and the properties of the soil. Relevant properties are: depth to permafrost, whether the permafrost is ice-cemented or dry frozen; the active layer depth, active layer moisture content, and frequency of liquid water; soil salinity characteristics; and the geological composition of the soil materials.Soil contaminations in the McMurdo region have been investigated through several years in a number of studies, including site surveys, field investigations, and experiments. Results of these studies are summarized in this paper and the significance of the contaminations is discussed. The behaviour of contaminants at the sites investigated conforms to existing knowledge of the soil properties. In the presence of some summer water or occasional moisture influxes from snowmelt, soluble contaminants may be transported variable distances through soils, both downwards and laterally, depending on the amount of water available. Ice-cemented permafrost restricts the downward movement of most contaminants but may aid distribution via lateral flow, especially low-freezing-point contaminants such as hydrocarbons. In dry-frozen soils, low-freezing-point contaminants may penetrate deeply into the soil.With respect to the sites investigated, the heavy metal contaminations were typically above the values from undisturbed sites, but there may at times be appreciable natural variation. The presence of solid materials in soils — such as particles of plastics, wood, fibre, etc — represents a widespread and pernicious form of contamination, because they are foreign to the environment and are non-degradable.