Why salinization is a problem

Remote sensing of soil salinity: potentials and constraints. Remote Sensing of Environment 85, 1— Salinization from irrigation Photo: Ioannis Daliakopoulos. Artificially induced salinization , such as irrigation. Italy e. Campania and Sicily , Spain e. Also in North Europe countries e. Denmark, Poland, Latvia, and Estonia.

Poor condition or absence of vegetation, presence of salt-tolerant weeds, areas that take longer to dry or the presence of unnatural colour soil crusting white or dark. Leaching provided good drainage conditions. Use of compost or other organic soil amendments. Rainwater harvesting: A network of gutters channels rainwater to a metal tank, and is later used for irrigation. Biological soil amendments: Mycorrhiza supplement in the form of grey aggregates used during tomato transplantation.

Green manuring: Sorghum seeded in June and incorporated in the ground as in August using a tille. Salinity sensors are used for monitoring surface soil salinity in the field. Satellites retrieve data with SWIR and NIR bands for remote sensing analytics of water absorption and its possible correlation with salinity.

Soil salinization consequences are far from positive, covering multiple aspects of ecology and human life. It affects crop production and water supply industries, induces the risk of floods and soil erosion , and decreases biodiversity. Water saturation in plants depends on the level of salts in groundwater and the plant itself.

Water is absorbed in the process of osmosis and flows from less salt-concentrated areas to more concentrated ones. Plants suffer from osmotic stress when they fail to take up water, even when it is present in the soil. Basically, the process is similar to drought stress due to a lack of moisture in the ground. As a result, vegetation dies.

Salinization tampers with nitrogen uptake too, which slows plant development and causes a yield loss. Another soil salinity effect on agriculture is ionic stress due to harmful ions in soil salts, e. Apart from their toxic impact as such, these positively charged ions impede the acquisition of other positively charged ions vital for crop growth particularly potassium and calcium.

The result is the same as with osmotic stress due to salinization — vegetation dies. The problem with salinization is that salts not only accumulate in earths but penetrate to initially fresh water bodies as well, leading to their salinization.

It deteriorates drinking and irrigation water and adds to further salinization of drylands. The Colorado River basin is one of the most affected areas in the world.

The impact is multifold :. While non-saline soils do not affect crops, strongly saline ones are suitable only for salt-tolerant species and halophytes.

Thus, salinization reduces ecosystem varieties and threatens their normal conditions to exist. A reduction of flora diversity inevitably causes a reduction of fauna as well by shortening food chains and areas of habitats. Salinization reduces biodiversity in rivers or fresh-water lakes, shortening aquatic populations solely to salt-tolerant species. Soil salinization effects refer to crop diversity and, correspondingly, food variety as farmers are forced to produce plants that can survive in salty earths.

Soil salinization is a serious problem itself, but it rarely comes alone. Salinity causes continuous wetness of land surface and a lack of cover due to poor plant growing conditions. These make lands highly prone to erosion. With heavy rainfalls or river flooding, soils cannot cope with high amounts of water flows.

Thus, insufficient absorption results in runoffs and floods. Strong water currents ruin constructions, damage farmlands, increase sedimentation, and contaminate aquatic bodies. The best way to deal with soil salinization is not to let it happen. In case it did, it is important to eradicate the problem — the sooner, the better, before the consequences get too severe.

So, soil salinization solutions deal with prevention and management. Soil salinization prevention bases on avoiding excessive salt penetration. Even though plants require a certain amount of salts to develop, their needs are small compared to the content in salt-affected soils.

Here are some typical methods to prevent soil salinization :. When sodium salts accumulate in the soil, they usually impart undesirable physical characteristics to the soil, such as reduced permeability to water and reduced aeration. This increases the susceptibility of the soil to further salinization. Also many soil chemicals, including the nutrients nitrogen and phosphorus, are more mobile in the soil in the presence of high levels of sodium. This can increase the amount of water pollutants in run-off water and underground drainage.

Throughout the world, there are more than 10 million hectares of now saline land which was once fertile, and every year over , hectares of irrigated land fall victim to salinization. In it was estimated that up to 20 million hectares of irrigated land around the world may be affected by salinization.

Egypt is a case in point. Prior to the building of the Aswan Dam, the fields of the Nile delta and floodplain were annually flooded and the ebbing flood flushed away surplus salts. But the modern canal irrigation leaves the salt behind and is gradually poisoning on of the world's leading cotton-producing regions and turning it into desert. Each year, one ton of salt accumulates on each hectare of delta fields.

The country is spending tens of millions of dollars each year laying the largest drainage network in the world in an attempt to flush out the salt. In Pakistan, 15 million acres of the 37 million acres under irrigation are estimated to be salinized. Of the area earmarked to receive water via China's giant Yangtse Diversion scheme, 2.

An FAO study reported that , acres in Syria, half of the country's irrigated land, are waterlogged or salinized. In Iran, of In India, the amount of land devastated by water and salt has been estimated at between 6 million and 10 million hectares, almost a quarter of the 43 million hectares under irrigation. The Asia-Pacific region is responsible for around 75 per cent of all human-induced salinization in arid, semi-arid and dry sub-humid areas - the susceptible drylands - of the world.