Food security dependent on protecting fertile growing grounds
A revolutionary land management model is being applied across the fields of Northeast China to restore its precious and fertile black soil.
Black soil, characterized by its dark topsoil, is considered the "food basket" of the world because of its rich organic carbon and high degree of productivity. It contributes to 25 percent of China's grain production and one-third of its total grain output, serving as an important pillar of the country's food security.
However, China's black soil has been degraded over the years by poor land management practices and the heavy use of chemical fertilizers.
"The formation process of black soil is extremely slow, requiring hundreds of years to form a 1-centimeter-thick layer under natural conditions," said Jia Zhongjun, a researcher at the Chinese Academy of Sciences.
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Jia is among the experts who have introduced new land management models aimed at restoring China's black soil.
In January, these models won the 2024 Outstanding Scientific and Technological Achievement Award of the CAS.
"It represents the hard work of CAS researchers for decades in soil sciences and their great contributions to the holistic understandings of black soil protection under distinct utilization scenarios," Jia said.
For years, Jia has walked in the fields with colleagues, considering the issue of land degradation in black soil areas from the perspective of farmers and agricultural sustainability. The Northeast Institute of Geography and Agroecology of the CAS, where he works, launched a science and technological research campaign in 2021 to prevent land degradation in black soil areas and increase yields.
Northeast China is one of the world's four major black soil regions, with the others being in Ukraine, the United States and Argentina.
From the 1950s, the black soil in Northeast China attracted a large number of settlers, transforming the plain from the once unknown "northern wasteland" into an important commercial grain production base known as China's "northern granary".
However, in the 1990s, a growing number of farmers, including those in Lishu county, Jilin province, a major maize-producing county, found that the black soil was revealing yellow layers, and grain yields began to decline.
A 2020 survey revealed that the thickness of the black soil layer in Northeast China had decreased by 30 to 50 percent compared to half a century earlier, with some areas having less than 20 cm of black soil, and decreasing at a rate of 1 to 2 millimeters per year.
"Increasingly intensified activities of farming practices and natural factors leading to soil erosion have caused the black soil layer to thin and the organic matter content to decline. The problem of thinning, impoverishment and hardening of black soil in Northeast China has become prominent," said Jia, who is also the chief engineer of the Sci-Tech Innovation Campaign for the Black Soil Granary of the CAS.
Despite farmers applying a large amount of fertilizer, grain production has not continued to increase. Instead, crop resilience has decreased, posing great challenges to agricultural sustainability and food security.
"As a scientist for soil and agriculture, staying in the laboratory is far from enough to truly help farmers solve problems. We need to go into the fields, spend day and night with farmers," Jia said. "Farmers are most concerned about grain production, but it is often difficult for them to give up traditional agricultural management and adopt new methods to fertilize and increase yields, which is where our scientific research and methods come in.
"A seed entering the soil in spring grows into a 2-meter-high corn plant in autumn, with an increase in biomass of approximately 3,000 times. Almost all of this large biomass comes from the soil," Jia said.
"Yields come from organic matter in the soil, and such matter comes from organic fertilizers from plant residues and manure. After farmers harvest, the straw must be returned to the field to scientifically renew the organic matter and protect nutrient sustainability in the soil," said Jia.
Achieving straw return is not easy. Past excessive use of chemical fertilizers has led to soil acidification and compaction, meaning that the northeastern black soil region faces increased problems caused by low winter temperatures and freeze-thaw cycles, Jia said.
According to different conditions and areas, the team explored various organic matter return models tailored to Changchun, Jilin province, Liaohe, Liaoning province, and other cities.
"Clay soil, sandy soil, loamy soil and compacted soil require different methods for straw return. Regardless of the type of soil, we have managed to increase soil organic matter content by around 2 percent and achieve a yield increase of about 10 percent," he said.
Taking Heilongjiang as an example, the province has 15 types of soil, including black soil, black calcareous soil, sandy soil and saline-alkali soil, due to its diverse natural conditions.
"Targeted measures must be taken for different plots of land. Through continuous research and exploration, the team developed the Longjiang Model, which focuses on straw burial deep in the soil," Jia said.
For low-lying flatlands in the eastern part of the Songnen Plain, straw is crushed and buried deep to replenish soil organic matter.
For soils affected by wind and water erosion and thin black soil in medium- and low-yield fields, straw and organic fertilizers are mixed and buried underground. Additionally, corn and soybeans need to be rotated to build a fertile plow layer and nurture the soil, Jia added.
"In the western part of the Songnen Plain, where drought and salinization are severe, we advocate no-tillage management. This is largely attributed to high temperatures that could enhance the microbial activity of straw decomposition in this area to nourish the land," he said.
In the Lesser Hinggan Mountains area, where the farmland drainage flow varies greatly, the focus of land protection is on preventing soil erosion. Measures such as planting across contours, building dikes and planting biological hedges have been adopted, he said.
These four models are collectively referred to as the Longjiang Model, which has effectively addressed the issue of black soil degradation across the province.
"Through these methods, the thickness of the plow layer in the demonstration area has stabilized at around 30 cm, organic matter has increased by 2-3 grams per kilogram and crop yields have increased by over 10 percent," Jia said.
"Land management is a long and complex process that requires collective efforts to further pass these methods to the farmers. We must adhere to the combination of land use and land conservation," he said.
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Regarding the outstanding achievement award, Jia said: "This is a collective honor. The restoration of black soil involves multiple disciplines such as agricultural machinery, soil science, fertilizers and plants, reflecting the collaborative efforts of outstanding researchers in various fields. The cooperation is something that Chinese scientists can be proud of."
According to data from the CAS, the black soil restoration team has established dozens of demonstration areas in Northeast China and has promoted methods to increase soil organic matter content to millions of farmers, improving 173 million hectares of farmland.
Shi Yudie contributed to this story.
