Farming is driving force in drying soil in Northern China

Purdue University News: An important agricultural region in China is drying out, and increased farming may be more to blame than rising temperatures and less rain, according to a study spanning 30 years of data. A research team led by Purdue University and China Agricultural University analyzed soil moisture during the growing season in Northern China and found that it has decreased by 6 percent since 1983.

The optimal soil-moisture level for farmland is typically 40 percent to 85 percent of the water holding capacity, and the region's soil is now less than 40 percent and getting drier. If this trend continues, the soil may not be able to support crops by as early as 2090, said study leader Qianlai Zhuang, Purdue's William F. and Patty J. Miller Professor of Earth, Atmospheric and Planetary Sciences and Agronomy.

"The soil moisture declined by 1.5 to 2.5 percent every decade of the study and, while climate change is still a factor, this water depletion appears to be largely driven by human activities," Zhuang said. "A 10 percent decline in soil moisture over the course of a century would have major implications for agriculture and the fresh water supply in this heavily populated area."

Forty percent of the nation's population resides in Northern China, according to the country's population census office. The region also accounts for 65 percent of the nation's cropland, Zhuang said.

"The drying of soil in Northern China has been well documented, but its causes and the impacts of agricultural intensification in general have been understudied," he said. "This information is critical to improvement of agricultural practices and water resource management. The demand for food and water is increasing, but current practices to meet this demand threaten the future security of water resources. Unfortunately, with the growing world population, more and more regions could face the same circumstances of agricultural intensification for food security."...

This is a map of soil moisture trends in Northern China during the growing seasons from 1983-2012. The shading shows the trend in satellite-observed surface soil moisture, and the circles represent monitoring stations within agricultural plots. A Purdue University-led research team found that farming was more of a driver in the drying of the soil than rising temperatures and declining rainfall. The change in volumetric water content is shown. (Purdue University image/Yaling Liu)