A new nemesis emerges for soil cadmium pollution, with a cadmium reduction rate of up to 85%
Since the "cadmium rice" incident, Hunan has been continuously seeking and exploring effective technologies and methods for treating soil cadmium pollution, and many domestic research institutes and relevant enterprises have also used Hunan as a testing ground to verify the effectiveness of their products and technologies. Recently, a reporter witnessed on site in Youxian County, Hunan, where "cadmium rice" was first discovered, the effect of a soil conditioner using "double-salt chelation passivation technology" in treating cadmium pollution.
On October 15, at the demonstration plot of over 100 mu of soil improved and remediated with the "Hongling" brand soil conditioner at the Fengtai Rice Planting Cooperative in Youxian County, the reporter saw plump rice ears bending the rice plants over, presenting a delightful scene of a bumper harvest in the fields. The expert group took samples at multiple points on site for testing, and the results showed that the cadmium content of the sampled rice was all below 0.05mg/kg, far lower than the national standard of 0.2mg/kg. The expert group also sent the rice samples to a third-party testing agency, and the test report two weeks later showed a cadmium content of 0.013~0.028mg/kg, once again confirming the cadmium-reducing effect of this soil conditioner.
"The original background cadmium content of the unremediated soil was 0.75mg/kg. Judging from the current test results, the cadmium reduction rate can reach over 85%, and the effect is relatively ideal," said Lei Ming, a professor at the College of Resources and Environment of Hunan Agricultural University and a member of the expert group conducting the on-site evaluation.
Why can this soil conditioner effectively reduce cadmium content? Lei Zhigang, chief expert of Hunan Hongling Agricultural Technology Co., Ltd., told the reporter that currently, for acidic heavy metal-contaminated land in the south, there are methods such as "electrolysis," "leaching," and "soil replacement," but these have problems such as high cost and great operational difficulty. Our technology does not necessarily have to remove cadmium, but instead uses the original layered silicate and pyrophosphate "double-salt chelation passivation technology" to fix cadmium in the soil so that it cannot migrate and be transported into rice, thereby solving the problem of excessive cadmium in rice. And this technology is not only effective for reducing cadmium, but can also effectively treat other heavy metals except mercury.
Luo Zanxing, chairman of Hunan Hongling Agricultural Technology Co., Ltd., introduced that the company spent several years developing a series of comprehensive soil heavy metal treatment technologies with completely independent intellectual property rights and high-quality, high-yield, low-consumption rice planting technologies, forming a three-dimensional prevention and control system for comprehensive heavy metal treatment consisting of "double-salt chelation," "in-situ separation," "plant obstruction," and "comprehensive metabolism." It has successively conducted trials in 69 experimental demonstration areas in 15 provinces and cities, and the effects all reached or exceeded expected standards. In 2016, Hongling Company successively participated in the fifth-phase super rice 16-ton-per-hectare research project and the Ministry of Agriculture's soil conditioner off-site stability test. With soil background values between 0.6~10mg/kg, applying this technical product at 200~600 kg per mu can not only produce qualified agricultural products (cadmium content below 0.1mg/kg), but also increase yield by 10%~30%.
Luo Ximing, a senior agronomist at the Zhuzhou Municipal Agricultural Committee, told the reporter that current methods for treating soil cadmium pollution mainly include selecting low-cadmium-absorbing varieties, flooded irrigation, adjusting pH, deep plowing, using soil conditioners, using foliar inhibitors, and returning green manure to the field. However, farmers are already less willing to adopt some of these agronomic measures, so the government is also seeking technologies and products that are easy to promote and implement and affordable.
So is the cost of adopting this set of technologies high? In response, Luo Zanxing said that we are not simply a product, but a complete set of soil testing and improvement and remediation solutions. The state provides soil improvement subsidies for plots with excessive heavy metals. In Hunan, the government provides a remediation subsidy of 5,000 yuan per mu for problem plots, and in Shaoguan, Guangdong, it is 15,000 yuan per mu. Taking Youxian County, Hunan as an example, we remediated 104 mu of severely cadmium-exceeding plots with a total investment of about 500,000 yuan, and a single investment can remain effective for more than 10 years.
The reporter learned that for obstacle soils in different regions, Hongling Company will combine experts and intelligent systems to scientifically test the background values of the soil, implement "soil testing and formulated fertilization," and then apply soil conditioners and scientific management methods to effectively improve and remediate the soil. For healthy soil that meets standards, through the refined fertilizer production of straw, organic residues, livestock and poultry manure, etc., crop waste can be healthily returned to the field, thereby reducing the amount of chemical fertilizer applied and forming a virtuous cycle from soil improvement to crop residue treatment and safe crop production. Reporter Wang Tengfei