How does soil salinity affect plant growth?

BY soco

13 Apr 2022

Published in:

When it comes to "saline-alkali land", I believe most of you will think of a question like this reflexively:

    Is saline soil acidic?

    What grows saline soil?

    And after this two, how to improve it?

   "How do plants living in saline soil?"

    Are alkaline soils salty?

    Is saline soil acidic?

    What grows saline soil?

    And after this two, how to improve it?

    Are alkaline soils salty?



What is saline and alkaline land?

   To understand it easily we can put it in an easy way: Saline-alkali land is land with excessive saline-alkali content, which directly inhibits or harms plant growth.And how does this situation happen? For the reasons of it, I want to quote the word from Cheng Weixin who is an expert engaged in saline-alkali land treatment at the Institute of Geographical Sciences and Natural Resources Research of the Chinese Academy of Sciences. His description was concise and clear, it can be summed up in three words which are: ” High” , “ Large ” and “Accumulation ”. "High" means that with groundwater level getting higher, the salt in the groundwater rises with the water level and accumulates in the soil; "Large" means that the water in the soil evaporates greatly, which promotes the upward movement and accumulation of salt in the groundwater ; " Accumulation " refers to the accumulation of salt (alkali), which eventually reaches a certain concentration (such as unreasonable application of fertilizers, resulting in an increase in the amount of salt/ alkali in the soil), forming saline-alkali land.

Why need saline-alkali to be improved?

  First let me introduce a concept to you - Cultivated Land Reserves.Soil salinity effects on plant growth.It means that some of the non-cultivated land resources can be improved into cultivated land resources through specific technologies.As we all know, human is the foundation of a nation, and food is the foundation of human. So food sufficiency is the most vital factor for people’s life as well as economic and social development. So the cultivated land is the fundamental guarantee of food security. However, with the increase of the world population, as well as the abuse and destruction of cultivated land resources by human activities, the shortage of cultivated land resources has become one of the most serious resource problems that the world facing.Here, we take China as an example. China has large population and considerable arable land, yet less per capita arable land resources. Based on official statistics of 2021, China's total cultivated land was 1.3146 billion hectares, which ranks fourth globally. However, China's per capita cultivated land area is only 0.7 hectare which is far below the world average.

For the purpose of improving the situation and achieve a breakthrough, it is necessary to achieve "expenditure-reducing and new resource-detecting". Which means that while protecting existing cultivated land resources, strengthen the improvement, meanwhile it is also important to develop and rational use of "new cultivated land". The "new cultivated land" here is exactly the Cultivated Land Reserves.Cultivated Land Reserve is an important basis for the implementation of land reclamation, which is closely related to the strict protection of the redline of cultivated land, efficient use of land resources and ensuring food security, etc.As one of the main backup land resources which is suitable for developing into arable land, saline-alkali land has always been one of the main resources of Cultivated Land Reserve.According to the incomplete statistics of UNESCO and FAO, the area of saline-alkali land in the world is nearly 1 billion hectares, of which China has about 1 hundred million hectares, ranking third among the top ten countries. The effective improvement and rational utilization of the arable land resources will reverse the shortage of arable land resources in China as well as in the whole world. In the meantime it will contribute to increasing yield, ensuring food security and building effective agriculture.

Above all, you can see clearly the importance of improving saline-alkali land.

How to Remedy saline-alkali land?

  Understanding the definition and causes of saline-alkali land is the starting point for improving saline-alkali land. Now let’s see how to improve saline-alkali land:"Water" is the most critical factor. It is not only the medium of salt accumulation or alkalization of soil, but also the driving force of soil desalination or dealkalization. Therefore, reducing the evaporation loss of saline-alkali soil and increasing the moisture of saline-alkali soil are one of the effective ways to improve saline-alkali land.At the same time, improving the fertility retention of saline-alkali land is also a good way to effectively improve the condition of it. The ultimate goal of improving saline-alkali land is to turn saline-alkali land into good arable land, so as to achieve higher and stable yields. For this purpose, we must start from two aspects - one is desalination and dealkalization, the other is improving soil fertility. Without desalination and dealkalization, the soil cannot be fertilized and the potential fertility of the soil cannot be exerted. The result is that the yield cannot be guaranteed; without fertilizing the soil, the physical and chemical properties of the soil cannot be further improved, the desalination and dealkalization effect cannot be consolidated, the higher yield cannot be achieved. It can be seen that these two factors are closely related and they are the ways to build high and stable yield fields.

  It is a long-term task to develop the effective way to improve saline-alkali land. Today, a variety of effective methods have been explored, such as washing salt, land clearance, and increasing the application of organic fertilizers. Among them, soil water-retaining agents, as one kind of super absorbent polymer (SAP) with good water-absorbing and water-retaining capacity, are widely used in the field of agriculture. SAP can absorb a large amount of water, release water slowly, and repeatedly absorb when environmental factors change (the degree of drought of soil, etc). Many scientific researchers carry out soil improvement by adding water-retaining agents to soil to increase water content, increase water and fertilizer retention capacity of soil, and improve soil structure. Therefore, soil water-retaining agent allows people to see its potential in saline-alkali land improvement, and provides a possibility for the development and utilization of new land resources.

What plants grow best in alkaline soil?Do tomato plants like acid or alkaline soil?Plants for dry shade alkaline soil?Let's explore the answer together。

SOCO® Polymer-Solutions to saline and alkaline land

  Qingdao SOCO New Materials Co., Ltd. (hereinafter referred to as "SOCO") is a high-tech enterprise specializing in the research, development, production and sales of super absorbent polymer (SAP). SOCO has always been deeply focused on developing the technology of soil water-retaining hydrogel. So far it has developed a series of soil water-retaining crystals products called “SOCO® Polymer” which have solved many agricultural problems all over the world, such as increasing yield, saving irrigation water, improving soil condition, saving labor cost, etc. In addition to achieving better effect of water-saving and yield-increasing, it has also devoted to the field of improving saline-alkali land through developing new model of SOCO® Polymer.

In September 2020, SOCO’s R&D Laboratory officially launched the development project of Saline-alkali Resistant SOCO® Polymer. At the beginning of the project, SOCO's R&D team discussed and summarized the difficulties in the research and development of saline-alkali-resistant soil super absorbent polymer at this stage: the water absorption capacity of agricultural hydrogel prepared by the existing technology can be highly damaged in saline-alkali land (with high salt content), so it can easily cause the dilemma of "high input but low yield".Among them, Ca2+, Mg2+ and other ions in the saline-alkali soil have a great influence on the water absorption performance of superabsorbent polymers This is because the osmotic pressure inside and outside the network of the soil water retaining gel resin strictly holds the absorption efficiency of the it. As the ionic strength in the solution increases, the osmotic pressure inside and outside the network decreases, and the screening effect of Mg2+ and Ca2+ on anionic groups (carboxylate and sulfonate) is more obvious, which leads to the decrease of absorption efficiency.

  At the same time, in different cationic salt solutions with the same concentration, the absorption efficiency of super absorbent polymer sap decreased significantly with the increase of the number of charges carried by the cations. It was because the complexing ability of the carboxylic acid groups on the superabsorbent composite network could induce Divalent ions form intramolecular and intermolecular complexes, thereby affecting the water absorption properties of the super absorption polymer After finding the difficulties, next step is "precise strike". In order to improve the salt resistance of new model of SOCO® Polymer, the R&D team of SOCO has adopted the more advanced aqueous solution polymerization preparation method to prepare the Saline-alkali Resistant SOCO® Polymer through a lots of experiments.The aqueous solution polymerization method mainly polymerizes the monomers, crosslinking agents and initiators in the aqueous phase. Its advantages lie in the low viscosity of the entire polymerization system, uniform mass and heat transfer between components, easy temperature control during the reaction process, high initiator use efficiency, relatively uniform molecular weight of the product, safety and no pollution, and simple post-processing.

  Nowadays Saline-alkali Resistant SOCO® Polymer developed in this project has achieved a water absorption rate of 700 times in deionized water, and a water absorption rate of more than 100 times in 0.9% salt water. 

In addition, from the analysis of the preparation of raw materials, the cost of Saline-alkali Resistant SOCO® Polymer developed by SOCO is comparable to that of the existing products in the market. Considering product effect, Saline-alkali Resistant SOCO® Polymer of this project can be priced at about at least 2 times that of the common natural super absorbent polymer in current market.

  At present, the development project pf Saline-alkali Resistant SOCO® Polymer is still in progress, and is moving towards a higher goal. In that case, we are making further improvements in the production process to further improve the salinity and alkali resistance of the product. At the same time, the experimental was also carried out to test the product performance on the farmland.

It is foreseeable that, a new safe and eco-friendly agricultural technology with simple using instruction, will increases yield and saves water. Agriculture super absorbent polymer will become one of the key methods to solve the core problems of agriculture for a long time in the future. The development of saline-alkali-tolerant superabsorbent polymers  with better comprehensive performance, has great significance to solve the food crisis caused by insufficient arable land. It can also expand the application of superabsorbent polymers in the future and fill the market gap of saline-alkali- resistant superabsorbent polymers. As a leading brand in the global soil Potassium Polyacrylate industry, SOCO gathers scientific research strength, always sticks to the R & D of soil potassium polyacrylate technology, and actively explores more possibilities of it in the agricultural field. In the future, not only Saline-alkali Resistant SOCO® Polymer, SOCO will propose more solutions for problems and difficulties in modern agriculture, so as to promote the development of green agriculture, contribute our effort in protecting the global food security.



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