Zhang Bin, a farmland protection scientist at the Chinese Academy of Agricultural Sciences who has been visiting farms in Northeast China — a major grain production region — every year over the past two decades, has been getting more worried about erosion of its fertile black soil in recent years.

"Vast areas of land are planted with a single species, and you only see the same variety of corn while driving for more than 500 kilometers," he said. "This may cause land degradation. In the past, land use was much more diverse: trees, grass and wetlands coexisted with crops."

Intensive utilization of farmland in many areas of Northeast China — including planting the same species over a large area, use of heavy machinery and intensive input of chemicals such as fertilizers and pesticides — has resulted in increased erosion of the soil and reduced fertility, which has threatened crop production, Zhang said.

"In many areas land fertility has been greatly reduced, with input of 1 kilogram of synthetic fertilizers in the black soil only resulting in the production of 10 kilograms of grains, less than half of the production compared with two decades ago," he said. "If the trend continues, the yield may be even lower."

Food security has been a top priority in China, and protecting farmland, including the black soil in the northeast, has been included as a key task in a major blueprint for China's development over the next five years and longer that was adopted by the nation's top legislature earlier this month.

As a major measure to ensure food security and the supply of major agricultural products such as grains, cotton, edible oil, sugar, meat and milk, China will adhere to the strictest system for farmland protection, according to the blueprint, which outlined major tasks for the government during the 14th Five-Year Plan (2021-25) period and goals to the year 2035.

Strict standards will be adopted to protect the size and quality of farmland, and intensified efforts will be made to fight irregularities such as using farmland for nonagricultural purposes.

Meanwhile, China will carry out a program to protect black soil in the northeast and promote its restoration, the blueprint said.

Protection of farmland has been an essential national policy in China. About 103 million hectares of farmland across China has been designated as permanent farmland — accounting for more than 75 percent of the country's total. That puts it under strict, permanent protection and prohibits its use for other purposes such as industrial and property development, according to the Ministry of Natural Resources.

In addition to guarding against loss of farmland, authorities have also stepped up efforts to protect the quality of farmland in recent years by emphasizing the building of high-standard farmland that boasts good infrastructure, fertile soils and a good natural environment.

By the end of last year, 53 million hectares of such high-standard farmland had been established in China, and another 7 million hectares of high-standard farmland is expected to be established this year, according to the Ministry of Agriculture and Rural Affairs.

Although China has achieved a general balance between food supply and demand after decades of efforts and can feed a population of 1.4 billion, nearly 20 percent of the world's total, the cost to farmland is heavy, with decades of intensive use resulting in its degradation.

Most of the 135 million hectares of farmland in China is of medium or low quality, according to the Ministry of Agriculture and Rural Affairs.

Zhou Wei, a researcher in agricultural resources at the Chinese Academy of Agricultural Sciences, said large areas of farmland face problems such as acidification, salinization and soil loss due to improper practices such as the overuse of synthetic fertilizers, resulting in some farmland become unsuitable for farming.

In Northeast China, intensive farming since the 1950s has seen the organic matter content of black soil reduced to between 2.5 and 3.5 percent, down from as high as 10 percent, leading to a fall in grain yields, he said.

In addition to soil degradation, farmland in some places also faces risks from industrial pollution, and risks of being used for commercial purposes for more profit, which threatens food production.

Zhou said agricultural researchers across China have made major achievements in farmland protection over the past five years, including creating methods to improve the fertility of farmland soil in Northeast and South China, and technologies to repair acidified farmland and improve the efficiency of synthetic fertilizer use. More efforts will be made to achieve technological breakthroughs over the next five years, he said.

"A major problem facing protection of farmland in China is lack of research in the field, and related standards on farmland protection are absent," he said.

"Science and technology should play a more important role in solving problems facing farmland protection, such as farmland erosion and pollution, and providing solutions to find a balance between farmland protection and high-yielding crops."

Zhang said that in addition to more investment from the government, a farmland protection law is urgently needed.

"Farmland protection laws are available in some European countries and the United States, but we only have some related regulations," he said.

"We need to establish a law to protect farmland, including preventing it from shrinking in size and degrading in quality.