Salinity is one of the important environmental risks affecting agricultural production in the world. Under this condition and with the conventional cultivation methods, glycophyte plants, like tomato, are subjected to many stresses, such as ion toxicity, osmotic stress, nutritional disturbance, oxidative damage and metabolic disorders, which cause growth inhibition and yield reduction. In this context, the main objective of our study was to compare the physiological, hormonal, metabolic and agronomic responses of tomato plants (Solanum lycopersicum L.) grown in monoculture (TM) or intercropping (TH) with the halophytic species Arthrocaulon macrostachyum in a salt affected soil. The results showed that the intercropping system (TH) reduced the soil electrical conductivity, and Na+ and Cl- contents, improving mineral nutrition in tomato plants compared to TM. In addition, TH decreased the osmotic stress, improved water potential and increased water use efficiency in tomato plants, whereas the integrity of gas exchange parameters were maintained; as a consequence, an increase in tomato yield was achieved. Moreover, the ratio of stress hormones (ABA, SA and JA) to growth regulating hormones (GA, auxins and cytokinins) decreased under TH. Metabolomic analysis showed clear defined patterns of differentially accumulated metabolites. Some of the metabolites with higher abundance in TH were linked to phenylpropanoid biosynthesis and phenylalanine metabolism, whereas alanine, aspartate and glutamate metabolism, monoterpenoid biosynthesis and butanoate metabolism pathways were downregulated. Our results support the importance of A. macrostachyum in the desalination of salt-affected soils and in the improvement of tomato yield in mixed culture. Indeed, this intercropping system offers farmers a low-cost biosolution that improves yields while respecting the environment.

In semi-arid Mediterranean regions, particularly in some wetland soils, salinity is thought to be an indicator of low-quality soils. In this study, a characterization is presented of the soils surrounding El Hito saline pond (Castilla La Mancha, Central Spain), an ecological halophyte niche within a natural semi-arid steppe land. The main aim is to classify the salt-affected soils and their morphology, genesis, and physico-chemical properties. Four soil profiles were opened with a backhoe machine for sampling and subsequent description on the basis of their pedogenetic morphology. Systematic surface sampling was also performed. Standard methods were followed to measure the soil properties of 27 samples. Overall electrical conductivity (EC) and pH levels of the wetland were mapped (using ArcGIS 3.1.3). Soil salinity at elevated levels was detected, inhibiting plant uptake of water and nutrients. Distinct sub-areas of extreme elevated surface salinity providing specialized plant habitats and poor soil structure were observed, as well as a mainly whitened-yellowish-greenish soil colour due to salt accumulation and poor drainage. The soils also showed alkaline pH values. In most samples, the pH was over 8.5, and EC was higher than 4 (dS m-1), and in several samples higher than 20 (dS m-1). A low sodium (Na) content was detected in the saturation extract where magnesium (Mg+) was the dominant soluble cation, followed by both calcium (Ca+) and sodium (Na+), and then potassium (K+), present in lower proportions. Sulphate (SO42-) and then chloride (Cl-) anions were dominant, although carbon trioxide, (CO3-) and carbonate (CO32-) anions were also present. The percentages of organic carbon (C) were very low, while total nitrogen (TN) and available phosphorus (P) were higher in the upper horizons, suggesting a degree of eutrophication. The present work will increase the existing knowledge about the role of El Hito saline pond, that play a vital ecological role in the broader biosphere, providing new suggestions to readers on how this knowledge can be used to improve these types of ecosystems. In particular, the agricultural pesticides and fertilizers continuously damage the soil fertility as evidenced by the high content of soluble phosphorus found in some points of the Hito saline pond.

Soil salinity is a serious problem facing many countries globally, especially those with semi-arid and arid climates. Soil salinity can have negative influences on soil microbial activity as well as many chemical and physical soil processes, all of which are crucial for soil health, fertility, and productivity. Soil salinity can negatively affect physiological, biochemical, and genetic attributes of cultivated plants as well. Plants have a wide variety of responses to salinity stress and are classified as sensitive (e.g., carrot and strawberry), moderately sensitive (grapevine), moderately tolerant (wheat) and tolerant (barley and date palm) to soil salinity depending on the salt content required to cause crop production problems. Salinity mitigation represents a critical global agricultural issue. This review highlights the properties and classification of salt-affected soils, plant damage from osmotic stress due to soil salinity, possible approaches for soil salinity mitigation (i.e., applied nutrients, microbial inoculations, organic amendments, physio-chemical approaches, biological approaches, and nano-management), and research gaps that are important for the future of food security. The strong relationship between soil salinity and different soil subdisciplines (mainly, soil biogeochemistry, soil microbiology, soil fertility and plant nutrition) are also discussed.