A soybean-corn combined planting belt on saline-alkaline land is seen at the Agricultural High-tech Industry Demonstration Area of the Yellow River Delta in Dongying, Shandong province. ZHAO YIMENG/CHINA DAILY

Most of the world's saline-alkaline soils are located in arid and semiarid regions that have low rainfall and high evaporation levels, which facilitates the formation of salty land, according to Li Baoguo, dean of the College of Land Science and Technology at China Agricultural University in Beijing.

China has the world's third-largest expanse of saline-alkaline soils, mainly across the northeastern, northwestern, northern and coastal areas, Li told Farmers' Daily last month.

However, local conditions, such as geography and climate, determine the degree and types of saline-alkaline land in different regions, increasing the difficulties of land management.

Among the most fertile black soils in Northeast China are 5 million hectares of saline-alkaline land on the Songnen and West Liaohe plains, including barren land, grassland, arable land and wetland.

Unlike such land in other places, the soda saline-alkaline soils on the Songnen Plain are affected by high salt content, low-lying terrain and a dry climate, which poses challenges for their management.

Moreover, the unequal degree of salinization across a large area exacerbates the problem and hinders agricultural production, Li said.

However, there will be great potential for the use and development of the region's relatively abundant water resources when construction of irrigation and drainage projects is completed.

Northwest China has the country's widest expanse of saline-alkaline land, covering parts of the Inner Mongolia autonomous region, the Xinjiang Uygur autonomous region, the Ningxia Hui autonomous region and Gansu province.

With scant rainfall, large-scale irrigation was used in Xinjiang to allow water to seep quickly through the soil to leach out the salt content. The method was highly successful, but it cost a lot of money and gradually drained local water resources.

In the past decade, different saline-alkaline areas have developed localized techniques to solve the problem, such as a method that leaches out salinity in seawater rice fields in the northeast, drip irrigation under mulch in the northwestern areas and a salt-control-and-fertilization technique that is employed along the coastal areas.

In recent years, soil management activities have focused on breeding saline-alkaline-tolerant crops.

In 2015, the Agricultural High-tech Industry Demonstration Area of the Yellow River Delta was established in Dongying, Shandong province, with the aim of cultivating crop strains suitable for saline-alkaline soils.

The area has collected more than 15,000 pieces of genetic material related to grains, forage crops, medicinal plants and fruit and vegetables. Quinoa, soybeans and several types of oats have been planted, with yields reaching record highs, according to documents released by the area's administration.

Meanwhile, saline-tolerant rapeseed strains have been planted in Aksu prefecture in Xinjiang and Baicheng city, Jilin province, contributing to the cultivation of forage crops and the production of rapeseed oil.

Scientists have conducted much research on salt-alkaline-tolerant varieties of rice. Evaluations of more than 80 such strains have been launched in the provinces of Jiangsu, Guangdong, Shandong and Liaoning, according to the Ministry of Agriculture and Rural Affairs.

Also, sunflowers, rapeseed and sweet potatoes, which all have strong resistance to salt and alkalis, are able to tolerate the saline-alkaline land in coastal areas and Northwest China. Peanuts, apples, grapes and other crops can also be grown in these types of soils.

In June, four types of wheat that can tolerate salt and alkalis were approved by agricultural authorities for the first time, the ministry said.