The vice president of Chongqing Jiaotong University led the “sand to soil” research that caused doubts, and I responded exclusively

Wen | trainee reporter of China Science Daily Tian Ruiying reporter Zhang Nan

Editor| He Tao

Recently, a technology that the news media called “sand turning into soil” has sparked controversy.

The study was conducted by the team of Yi Zhijian, vice president and professor of mechanics at Chongqing Jiaotong University. In early 2022, Yi Zhijian published an article on “desert soilization” in the form of Editorial in The Innovation, an academic journal owned by Cell Press.

On April 20, Zheng Yongchun, a researcher at the National Astronomical Observatories of the Chinese Academy of Sciences, and Wu Bo, executive deputy director of the Institute of Desertification of the Chinese Academy of Forestry, issued a paper questioning the “sand-to-soil” technology, saying that the technology was misleading to desertification control.

They believe that the “sand to soil” technology is not suitable for promotion in arid desert areas, and the cost is high, the benefit is low, and it may also cause the groundwater level to drop and soil pollution, and damage the desert ecological environment. “There are only photos of the scene, no experimental data, and ‘sand turning into soil’ is not scientific.”

In response to these doubts, the two sides engaged in two rounds of fierce academic controversy. In its latest response, Yi Zhijian’s team said that the skeptics misled readers with deliberately “greening” satellite images and seriously inaccurate photos, and responded to the effect of desert soilization.

Around the controversy, China Science Daily interviewed Yi Zhijian. The reporter also contacted the questioners, but they collectively agreed that the current discussion was limited to the academic scope and it was not convenient to accept interviews for the time being.

Where is the technology used?

In January 2022, Yi Zhijian’s team published a short Article in English on desert soilization research in the form of Editorial at The Innovation, introducing the work of desert soilization technology in growing crops in Ulanbu and the desert in Inner Mongolia.

Sorghum grown in Ulanbu and the desert in Inner Mongolia

They pointed out in the corresponding Chinese WeChat tweet “Desert Soilization: Mechanics Code Point Green Desert” that for desert governance, mechanics proposed a new method of desert soilization, that is, to apply constraints between desert sand grains, and discrete sand bodies will obtain the ecological mechanical characteristics of soil and water retention and fertilizer retention.

The author said that the desert after soilization can become a plant carrier and has the function of consolidating the desert and ecological restoration. This technology has been successfully tested in many deserts, sandy lands, islands and reefs and gobi at home and abroad, turning 17,000 acres of barren land into an oasis.

According to reports, Yi Zhijian has long been engaged in scientific research in the fields of mechanics, roads, bridges and materials, and has achieved a series of innovative achievements in the research of elastoplastic fracture mechanical linear field analysis method and stress strength factor crack line method.

In 2008, Yi Zhijian discovered that there is a universal binding constraint between soil particles, and in 2013, he developed a plant cellulose bonding material; in 2016, the desert soilization technology began field trials. At present, the technology has obtained 22 invention patents authorized in China, the United States, Australia and other countries.

On April 20, zheng yongchun, Wu Bo and five other authors commented in English at The Innovation, saying that it was misleading to turn natural deserts into farmland. Subsequently, Zheng Yongchun and Wu Bo published Chinese WeChat tweet “‘Sand Changes Soil’ to Be Discussed”.

They believe that turning deserts into oases, or even wanting to destroy them, violates the laws of nature and is unscientific. “What really needs to be managed is the desertified land produced by irrational human exploitation activities, not the natural desert.”

Zheng Yongchun and Wu Bo said that the aeolian sand soil on the desert surface is itself a soil type, and as long as the moisture is guaranteed, plants can grow. “The use of traditional irrigation methods to grow crops in arid deserts not only fails to save water, but also causes the groundwater level to fall due to the heavy use of groundwater, resulting in waste of water resources and ecological degradation.”

Yi Zhijian said in an interview with China Science Daily, “We have never said that we want to eliminate all deserts, desert soil technology is not only to grow crops in the desert, but also an important function is ecological restoration, drought-tolerant plants such as Artemisia sand, Satawang and other drought-tolerant plants only after the appropriate amount of watering at the stage of sowing and germination, and then can grow naturally without watering.” ”

He told reporters that the current desert soilization technology experiments are all in desertified areas, “but the desert formation history of each region is different, and some of the places that are now called deserts were not deserts before.” For example, the location of the pilot base of Ulaanbu and desert soilification has been swallowed up by desertification for less than 100 years. Therefore, it cannot be simply distinguished between natural desert and desertification. ”

Yi Zhijian said that in addition to ordinary sand, desert soilization technology is also suitable for coral sand, broken stones, wood chips and other particulate matter scenarios, “where to use it, according to the actual situation of the government, before using it, it is also necessary to conduct water resources and ecological assessment.” ”

Is the technology innovative?

So, what exactly is this technology that makes “sand turn into soil”?

Yi Zhijian told reporters that initially he had been engaged in basic research on mechanics. In the process of participating in the construction of bridges and roads, he thought about the relationship between sand and mechanics.

“The essence of desert soilization is the ‘soilization’ of desert sand grains.” Yi Zhijian explained that it is through mechanical means to apply constraints between sand grains, so that the sand particles change the discrete state, and obtain two kinds of cyclic mechanical states unique to natural soil, that is, it is a rheological state when wet and a solid state when dry. At the same time, the “soil” transformed from sand also acquires the function of storing water, nutrients, air and breeding microorganisms.

The constraint between particles is achieved by adding a special modified cellulose material developed in-house to create an interaction force between sand particles.

However, Zheng Yongchun and Wu Bo believe that for desertification prevention and control, the “sand to soil” technology is not innovative in theory, nor is it a new technology.

They believe that the material used in this technology is a common soluble cellulose industrial raw material, which has not been promoted on a large scale due to the high cost and low cost performance for agriculture and sand fixation. This material is generally sodium salt, which will accumulate sodium ions in the soil and cause alkali pollution, which is an environmental risk.

Zheng Yongchun and Wu Bo also pointed out that although the use of cellulosic materials can bind the sand grains, the particle size of the sand grains has not changed, nor has it increased the moisture and fertility, and it is obviously wrong to call this practice “soilization”.

Yi Zhijian did not agree with this. He said that the constraint material developed was a modified CMC material, not an “ordinary industrial polymer” as the other party said, and he also showed reporters the sandy soil test report of a third-party agency.

For the effect of desert transformation, they said in “Desert Soilization: Force Science Code Point Green Desert” that sand grains can be planted immediately after soilization, and vegetation coverage can usually be achieved in 3 months. The desert after soilization is suitable for the growth of trees, shrubs, grasses and various crops, and the vast majority of plant yields or biomass exceed the local comparative agricultural land. For example, the average yield of radish in China does not exceed 5,000 kilograms per mu, but the yield of radish per mu in Ulan Bu and the desert pilot base reaches 13,699 kg.

Comparison of plant growth status in the Ulaanbu and Desert Soilization Plots (left, soilization team trial) versus unlocalized plots (right, another team’s experiment) (August 12, 2016) Image from the response article

An expert who had discussed with Yi Zhijian and visited the test site told China Science Daily, “I have been to their test base. The things grown in the modified sand are delicious, such as watermelons, grapes, small tomatoes, etc., and they taste very good. ”

He believes that sand improvement has a scientific nature, but also has key technologies, the principle is mainly by adding a small amount of substances, so that the sand grains have a certain interaction between the grains, so that the sand grain population has a certain water fixation effect.

However, he also pointed out that the name of “sand to soil” is easy to cause misunderstanding or simplification, saying that “sand changes soil” is not accurate, it should be said that sand land improvement.

The expert also said that when Yi Zhijian and others published a short article in Science in China in 2016, they discussed the research issues involved and the formulation of related statements.

Yi Zhijian believes that desert soilization is an interdisciplinary technology, the essence of which is to make sand have the function of soil, and it is not possible to frame new things with traditional soil formation theory, soil composition and other book knowledge.

He also told reporters that the team did not call it a “sand to soil” technology in the published article, which is often reported in new media reports. Yi Zhijian believes that there is not much point in tangling names, the most important thing is scientific principles and facts.

How to calculate the “water account”?

In the view of Zheng Yongchun and Wu Bo, the water resources in arid desert areas are very scarce, and to carry out desertification prevention or agricultural production in these areas, water conservation must be put in the first place.

For the water use in the test area, Yi Zhijian said in The Innovation’s article that in 2017, drought-tolerant plants such as Artemisia arvensis and Satawang planted in Ulaanbu and the desert (precipitation of about 100mm) were only watered appropriately at the stage of sowing and germination, and were no longer artificially watered in 5 years, and the plants grew in the natural environment. The average irrigation of vegetables, fruits and crops is less than 6 000 tonnes/ha, and the local water-saving irrigation quota is 8 250 tonnes/ha.

However, Zheng Yongchun and Wu Bo pointed out that 8250 tons/ha is the irrigation quota for rice cultivation in the “Industrial Water Quota” (DB15/T 385-2015) of the Inner Mongolia Autonomous Region that has been abolished in 2020, and 6000 tons/ha is lower than the rice irrigation quota, but it greatly exceeds other crops.

The reporter consulted the Inner Mongolia Autonomous Region’s “Industrial Water Quota” (DB15/T 385-2015), according to the corresponding three types of area regulations in Wuhai City, according to the average value of rice in several different irrigation methods to obtain data of 8250 tons / ha. However, including food crops, cash crops, etc., rice is the crop with the highest irrigation quota. The average irrigation quota for wheat in the three categories was 4 513 tons/ha, the highest crop except rice, such as tomatoes at 2,450 tons/ha and carrots at 1,350 tons/ha, both well below the experimental average irrigation of 6,000 tons/ha.

However, the above-mentioned DB15/T385-2015 standards have now been abolished, and the DB15/T385-2020 standards will be implemented from 2021. According to calculations, the average irrigation quota of rice in the three types of areas has been adjusted from 8250 tons/ha to 7257 tons/ha in the new standard, and the irrigation quota of other crops has almost been reduced.

In this regard, Yi Zhijian told reporters that when the pilot test was carried out in the Alashansha Ecological Industry Demonstration Zone in 2017, the management committee gave them a quota of 6,000 tons / ha for the test, and there was no specific planting requirement.

They conducted two experiments, desert ecological restoration and agricultural and pastoral planting. Taking 2019 as an example, only 2,000 mu of land used for agricultural and animal husbandry planting, the irrigation amount is less than 6,000 tons / ha, the remaining 4,000 mu are used for desert ecological restoration and conservation (5 consecutive years have not been watered, desert drought-tolerant plants develop and grow under natural conditions), 6,000 mu of test land, the average irrigation amount is less than 2,000 tons / ha.

Natural plants such as reeds grow near the test site provided by Zheng Yongchun and others

Zheng Yongchun and Wu Bo also pointed out that the groundwater level in the Ulan Bu and desert test areas was shallow — about 0.2 meters — and provided remote sensing images and photos of reeds growing around them.

Yi Zhijian did not agree with this. He said that the actual geological survey showed that the groundwater buried at the lowest location of the base was greater than 15 meters, and pointed out that the reed photos were actually taken near the 25-acre test site in 2016, a difference of more than 10 kilometers from the current pilot base. He said that groundwater was not used for cultivation and that “the existence of shallow groundwater is determined not through satellite imagery, but through geological exploration.” ”

In addition, he also said that the remote sensing images used in the other article were improperly processed and misleading readers. “Peer-reviewed images before publication were ‘processed’ all over the green, and I reminded the editorial board that the images that are now published have been made, but some soils with little vegetation have also been treated green.”

In this regard, Zheng Yongchun and Wu Bo said in their previous responses that the remote sensing images provided were true and effective, and the images were processed by remote sensing images, and the vegetation (displayed in light green) and water bodies (displayed in blue) were accurately extracted using the supervised classification method to distinguish them from the surrounding desert background.

Satellite imagery from Google Earth Pro provided by Zheng Yongchun et al. in the article

Gaofen-2 satellite imagery provided by Yi Zhijian et al

Zheng Yongchun and Wu Bo said that to prove the effectiveness and popularization of the “sand-to-soil” technology, the authors must carry out strict control tests and provide basic data on soil water content, irrigation water consumption, groundwater consumption, as well as the price, effective period, degree of degradation, and water holding capacity of the materials used.

The reporter found that in 2016, Yi Zhijian’s team published two papers related to the study of “desert soilization”, which were published in the form of Letter to Editor in “Science in China” (English version) and in the form of News & Focus in “Engineering” (English version). Two articles focus on the scientific findings, principles and first field applications of the technology.

Zheng Yongchun and Wu Bo believe that none of these three articles provide experimental designs and the above basic data.

Yi Zhijian explained that this time he posted at The Innovation at the invitation of the editorial department. Considering the long duration, type, scope, large amount of data and protection of technical details in recent years, the willingness to publish is not strong. In response, the editorial board proposed to publish about 1500 English word essays. “It’s not that the level of papers with less data is not high, like the first two papers in the two years after publication, they were ranked in the top three of the magazine Most Read, which had a greater impact.”

“We are still in the pilot stage, due to the confidentiality of technical details and the consideration of publishing higher-level papers in the appropriate period in the future, there is no intention to publish papers for some technical details and data for the time being.” This does not mean that we have no data, no results, and no high-level papers. Yi Zhijian said.

The scientific controversy surrounding the “sand-to-soil” technology has been held by both sides and has not been conclusive. China Science Daily will pay attention to the follow-up progress.

Related Introduction:

Yi Zhijian: Vice President of Chongqing Jiaotong University, candidate for the first and second levels of the national “100 Million Talents Project”, and a young and middle-aged expert with outstanding contributions in the country, enjoys the special government allowance of the State Council. He has been engaged in the research of mechanics and related fields for a long time, and has made a series of achievements in fracture mechanics, reinforced concrete structures, pavement materials and structures, ecological mechanics and desertification control, published more than 100 papers, and authorized more than 40 invention patents.

Wu Bo: Researcher, Executive Deputy Director of the Institute of Desertification, Chinese Academy of Forestry, Chief Expert of Desert Ecology, Director of the Key Laboratory of Desert Ecosystems and Global Change of the State Forestry and Grassland Administration, has been engaged in research on desert ecology and desertification prevention. He is a director of the Chinese Society for Sand Control and Sand Industry, a director of the Desert Branch of the Chinese Geographical Society, and an independent consulting expert of the Science and Technology Committee of the United Nations Convention to Combat Desertification (UNCCD).

Zheng Yongchun: Researcher, Interdisciplinary Scientific Research Group of the National Astronomical Observatories of the Chinese Academy of Sciences, mainly engaged in lunar and planetary scientific research. He graduated from Southwest Agricultural University in 2000 with a major in environmental protection and received a doctorate degree in geochemistry in 2005.








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