Effective measures adopted to protect black soil
Northeast China promotes conservational tillage on fertile land
As China's most fertile land, the northeastern region, including the provinces of Heilongjiang, Jilin and Liaoning and the eastern part of Inner Mongolia autonomous region, accounts for about a quarter of the country's annual grain yields.
According to data from the National Plan for Soil and Water Conservation (2015-30), black soil covers an area of 1.09 million square kilometers in the region, including around 29 million hectares of farmland.
With a high density of organic matter, black soil is very suitable for growing crops. However, long-term cultivation and overuse of fertilizers have caused degeneration of the soil, threatening the local environment and grain production.
Over the past few decades, black soil, which has existed for thousands of years in Northeast China, has been eroded partly due to excessive reclamation, and this threatens biological diversity and sustainable food production, according to the Guideline on Protecting Black Soil in Northeast China (2017-30).
The document also said that the previously stable micro-ecological systems had been breached by long-term farming and the overuse of fertilizers and pesticides. Meanwhile, the expansion of rice-growing in the region has drained much of the underground water.
The thickness of the soil dropped from 60 to 70 centimeters in the 1950s to 20 to 30 cm at present.
"The soil is black because its surface is covered with a layer of soil rich in black humus," said Zhang Xingyi, a researcher on agriculture with the Northeast Institute of Geography and Agroecology of the Chinese Academy of Sciences, adding that "it takes 200 to 400 years to form a 1-cm-thick humus layer in black soil".
"Soil productivity decreased by an average of 12.7 percent for every 1 percentage point decrease in soil organic matter content," he said.
The practice of returning maize straw to the farmland for mulching purposes not only increased the amount of organic matter in the soil but also helped prevent wind and water-driven soil erosion and preserve soil moisture, Xi said, adding that the so-called Lishu model was worth promoting.
With a cultivated area of over 260,000 hectares, Lishu, a major grain-growing area in Jilin, had an annual grain output of more than 2.5 billion kilograms for many years, ranking steadily among the top five grain-producing counties in China.
However, around 1980, farmers in the county found that the nutrient-rich black soil was becoming increasingly eroded and using more fertilizer didn't result in greater yields from the farmland.
In 2009, Li Baoguo, dean of the College of Land Science and Technology at China Agricultural University, led his students to establish China's first academic black soil protection workstation in Lishu.
After years of joint research and cooperation with the Northeast Institute of Geography and Agroecology of the Chinese Academy of Sciences and the county's agricultural technology station, the model was created, revitalizing the thinner layers of black soil.
"The model is a revolution in traditional farming practices," said Wang Guiman, head of the station. "The key to conservational tillage is to plow less soil through the no-tillage and stalk-covering technology."
"In the past, farmers had to plow the land at least four times when they planted maize, which may destroy the structure of the black soil layers," he said. "Now with the technology of mechanized planting, the processes of cleaning straw, ditching, fertilizing, sowing and covering soil can be completed in a single operation."
"The reduction of rolling compaction in the field by agricultural machines can help improve the water percolating capacity of the soil and the maize straw can provide potassium and nitrogen to the farmland," he said.
"After five years of the no-tillage and stalk-covering operation in the experimental area, the soil organic matter increased by about 0.1 percent per year, six times that of conventional farming."
Since 2012, the Jilin provincial government has promoted the model across the entire province and 46 counties have carried it out on 1.23 million hectares of farmland.
After three years of research, drafting, review and modification, a regulation on black soil protection became effective in the province on July 1, 2018.
It became the first local regulation on black soil protection across the nation, specifying how to control soil loss, increase the density of organic matter, and preserve the moisture and fertility of the soil.
The regulation also sets June 25 as Jilin's black soil protection day.
Zhang Wendi, a farmer from Quanyangou, a village in Lishu, rented 420 hectares of farmland in 2020 and had a maize output of over 5 million kg.
"In the traditional planting model, it may cost around 2,200 yuan ($339) per hectare from planting to harvesting while the new model can save at least 800 yuan," he said. "Furthermore, the new model can help increase the output by over 500 kg per hectare."
He added that farmers who performed conservational tillage on their farmland could receive a government subsidy of 750 yuan per hectare.
The total area of conservational tillage is expected to increase to more than 2.6 million hectares by 2025, according to Jilin Department of Agriculture and Rural Affairs.
Soil thickness increased
The neighboring province of Heilongjiang also saw remarkable effects after years of effort in black soil protection.
Monitoring data showed that the average thickness of cultivated land increased from 19.8 cm in 2014 to 23.3 cm in 2019, according to the provincial department of agriculture and rural affairs.
The department also said that the farmland cultivated by farms and large agricultural machinery cooperatives saw a recovery in growth.
Faced with the eroded black soil, Heilongjiang has taken different measures according to local conditions, including returning straw to the farmland, as well as increasing the amount of organic fertilizer and crop rotation.
Since 2015, the province has established 20 pilot projects on the protection and utilization of black soil, covering an area of 348,400 hectares.
In 2018, Hailun, a major grain production area in the province, was identified as a pilot county to promote the integrated system of black soil protection and utilization by the Ministry of Agriculture and Rural Affairs.
Over 33,300 hectares of farmland in the county became experimental fields managed by local governments to carry out conservational tillage, including promoting rotation farming of corn and soybeans, returning straw to the farmland and increasing the amount of organic fertilizers.
"All of the 133 hectares of farmland of our cooperative has been classified as experimental fields," said Liu Chunsheng, head of Dongxing Cooperative. "Thanks to integrated planning and management by the government, the yields from the farmland have increased significantly."
"Over the past years, farmers in the cooperative have seen their incomes increase by 14,000 yuan," he said. "More importantly, their awareness of protecting the black soil is growing stronger as they benefit from the improved quality of the land."
According to the Guideline on Protecting Black Soil in Northeast China (2017-30), by 2030, Northeast China's 16.67 million hectares of black soil will be better protected and see improvements to its fertility, ecology and farming facilities which will yield higher crop yields.
"To realize the sustainable use of black soil, it is necessary to focus on scientific research of black soil conservation, nutrient balance and conservational tillage," Han Xiaozeng, a researcher with the Northeast Institute of Geography and Agroecology of the Chinese Academy of Sciences, said during a recent online seminar. "These research results can provide important support for maintaining the fertility of black soil and improving the overall grain yield."
Researcher Liu Xiaobing from the same institute suggested improving laws and regulations on arable land to urge land users to protect the black soil.
"Agriculture and soil and water conservation staff in the northeast region have explored some effective technical measures, but they didn't receive wide acceptance as some operators only seek to maximize economic benefits and lack an awareness of protection," he said.
"Therefore, special regulations on the protection of black soil should be introduced to solve these problems," Liu added.