From the beginning of September, the corn in Northeast China has gradually entered the mature period, and corn farmers are preparing for harvest. In this harvest season, Zhang Xudong, head of the conservation tillage team at the Institute of Applied Ecology (IAE), Chinese Academy of Sciences, also harvested the fruit of his scientific research. From spring to autumn every year, Zhang Xudong and his team members travelled a distance of nearly 3,000 km to visit the 61 demonstration bases within the Northeast Corn Belt, and popularise corn straw mulching, no-tillage and conservation tillage technology.

Curbing black soil degradation, Zhang Xudong's team is in action

The black soil area in Northeast China is one of the most important commodity grain production bases of China. The Northeast Corn Belt in the black soil area starts from southern Heilongjiang, including Jilin Province and the eastern part of Inner Mongolia Autonomous Region, and extends to the northern part of Liaoning Province. With a corn growing area of nearly 190 million mu, the Northeast Corn Belt is also called the "Golden Corn Belt." However, the heavy price of years of high crop yield of the black soil is the decline of soil fertility. In 2002, Zhang Xudong led his team to investigate the status of the black soil in Northeast China, and found that the originally fertile soil layer was thinning due to long-term intensive use. In some locations, the thickness of the black soil layer was reduced from the original 70-100 cm to roughly 30-40 cm. On strong windy days, there are particles of sand and dust everywhere in the air. "In addition to the bare topsoil being blown away, another key factor that causes the degradation of black soil is water erosion. The flow of water during rainfall washes away the surface soil, causing soil erosion. The large arable land becomes fragmented, which not only reduces soil fertility, but also increases the difficulty of cultivation in the future," Zhang Xudong said in an interview with China Science Daily

The deteriorating environment in the black soil area has severely restricted the grain yield in Northeast China, which makes it urgent to curb soil degradation and protect the black soil. In view of the problems of poor nutrient cycling and low fertiliser utilisation efficiency in the black soil system, Zhang Xudong deeply studied the transitional characteristics and regulation process of the microbial nitrogen transformation in the black soil, and put forward the theory of "soil available nitrogen transition reservoir" according to the microbial process and mechanism of soil nitrogen retention. Prof. HE Hongbo, a member of Zhang Xudong’s team and a research scientist of IAE likened the "soil available nitrogen transition reservoir" to the "camel's hump," which has both functions of storing and releasing nutrients. Along with the microbial nitrogen transformation process, the nitrogen in crop straw and fertilisers is stored in this 'hump,' then released on demand, and then the 'hump' is replenished again and again.

Selecting Lishu as experimental site, aiming to create a model for demonstration

Conservation tillage technology is a modern farming technology system based on crop straw mulching and no-till sowing, which can effectively reduce soil erosion, increase soil fertility and drought resistance, save costs and improve farming efficiency. After analysing the no-tillage technology in the United States, Canada and other countries, Zhang Xudong hoped to find out whether conservation tillage technology will work on the black land in Northeast China. Thus, Zhang Xudong led his team members to the field of Lishu Town, hoping to create a model for demonstration and promotion. "Lishu County was selected as because it is located in Jilin and the middle of the black soil area. With Liaoning Province in the South and Heilongjiang Province in the North, it is relatively easy to promote this new technology from Lishu to other areas," Zhang Xudong told China Science Daily.

After more than ten years of research, Zhang Xudong's team has developed a set of mechanised conservation tillage model that is suitable for the black soil area in Northeat China. XIE Hongtu, a member of Zhang’s team and an associate professor of IAE, said:"After more than ten years of straw mulching and no-tillage sowing, the soil organic matter content of the experimental field increased from 1.8% in 2007 to 3.2% in 2018. If 30% of the farmland surface is covered with straw, the wind erosion can be reduced by 70%. In the farmland covered with straw, there are about 60-100 earthworms per square meter, but there are generally only 3 to 5 in the farmland soil without straw mulching. The three sets of data show that conservation tillage technology can significantly improve soil fertility, reduce soil erosion by wind and water, and improve soil biological properties.

Each year, Zhang Xudong's team traveled to agricultural counties in Heilongjiang, Jilin and Liaoning provinces to promote conservation tillage technology. At present, more and more agricultural machinery cooperatives have begun to adopt this technology because it not only saves fertiliser and labor, but also stabilises yields and increases income. The "Lishu model" is now well-known in the entire Northeast China.

"In order to enable conservation tillage technology to better benefit the vast number of farmers, together with related enterprises, we developed China's first no-tillage seeder and supporting machinery. At present, our technology is mature, but it will take time for some farmers to accept the new technology. In the future, what we have to do is to make greater efforts to promote it," said Xie Hongtu, who spends four months working in the fields every year, and has been awarded the title of "the most beautiful rural scientific and technological worker."

Storing grains with sufficient field and high-level technology

The R&D achievements of Prof. Zhang Xudong's team on conservation tillage have been highly praised, and his team's work directly contributed to the launch and implementation of the national black soil conservation strategy. The Action Plan for Conservative Farming of Black Soil in Northeast China (2020-2025), jointly issued by the Ministry of Agriculture and Rural Affairs and the Ministry of Finance, proposes that by 2025, the area of conservation tillage will reach 140 million mu, accounting for about 70% of the total area of cultivated land in Northeast China, and a relatively complete policy and technical support system will be built.

Science has no borders, but a scientist has his country. In Zhang Xudong's team, many members have experience of studying and working abroad. In 1999, Zhang Xudong, a full-time researcher at Bayreuth University in Germany, decided to return to China "hoping to combine his study and work experience at home and abroad to bring creative things to Chinese agriculture." After returning to China, he worked hard for years. Due to his outstanding achievements for scientific research and promotion, Zhang Xudong was awarded the title of "2020 Most Beautiful Scientific and Technological Worker in Liaoning". A technician of the Lishu County Agricultural Technology Extension Station once said:"Zhang Xudong and other agricultural experts are the 'volunteers' in the research and development of the Lishu model, the 'promoters' of the Lishu model, and guardians' of the black soil." At present, under the background of the intensive promotion of black soil conservation tillage in Northeast China, Prof. Zhang Xudong’s team will continue exerting its technical advantages, guide all parts of Northeast China to complete the national action plan, solve the problem of black soil degradation in Northeast China, and help implement the national policy of "storing grains with sufficient field and high-level technology" in the black soil area in order to ensure the National Grain Security (China Science Daily).