Why is Northeast China's Plain becoming saltier and saltier?

The Songnen Plain in Northeast China is one of the world's three major saline-alkali land regions. Until now, evaluations of soil salinization have mostly relied on satellite images, leading to inconsistent results. Thanks to a Random Forest-based model, scientists have now mapped the distribution of salt and ions in the soil with high precision. The findings? About 16.93 million hectares of land are salinized or alkalinized, with pH and salinity levels rising alongside concentrations of chloride, sodium, magnesium, calcium, sulfur, and potassium. In the Songliao Plain, there's a clear geographical gradient: sulfates dominate in the northeast, while chlorides prevail in the southwest. Since the 1980s, strongly alkaline soils (pH > 9.5) have expanded by 80,300 hectares per year, with significant losses of organic matter and nitrogen. The culprits? A mix of geographical, hydrogeological, and climatic factors. But there's hope: stable farming practices can help slow down this process.

Soil salinization is a complex process involving various chemical and physical interactions. Ions like chloride and bicarbonate are the main culprits behind soil salinity in Northeast China's Plain. These ions accumulate in the soil due to natural processes like evaporation and limited runoff, as well as human activities such as excessive irrigation. Topography plays a crucial role: low-altitude areas (<200 m) are more prone to salinization due to poor drainage. Moreover, the region's continental climate, with cold winters and hot summers, exacerbates evaporation and salt accumulation. Scientists have also noted that salinization is more severe in areas with high-salinity groundwater. To combat this phenomenon, sustainable agricultural practices like crop rotation, using salt-tolerant species, and optimizing irrigation are essential.