By Xu Enguang, Heilongjiang Academy of Forestry
Humic pesticides are a new type of green environment-friendly pesticides, differing greatly from conventional pesticides, which have a single-molecule structure. Many years of experiments prove that they have features of both humic acid and pesticides, and can stabilize and increase the pest-fighting effects, prevent the formation of drug-resistant genes in pests and reduce or eliminate the familiar residue of pesticides. They have major implications for the safety of crops, the diversification of organisms, the balance of ecology and the protection of the natural environment, and constitute an inevitable trend in the future development of pesticides.
Multiple effects display prominent advantages
Reduce the dosage of pesticides and minimize pollution of the natural environment.
Use of humic pesticides usually reduces the dosage of pesticides by 20-30%, greatly cutting down the amount of pesticide going into the environment. In the late 1980s, Heilongjiang Academy of Forestry used chlorimuron-ethyl alone and a mixture of chlorimuron-ethyl with sodium humate, respectively, in young poplar forests. In presence of the former, young poplars cannot survive, but the latter, young poplars can survive as usual and grow.
Inhibit the formation of drug-resistant genes in pests
Due to the development of drug-resistance in crops, the dosage of conventional pesticides has increased constantly, driving up the cost of pesticides for farmers. Take the fungicide carbendazim for instance. The required dosage was not big when it was first introduced but had increased several years later. If a mixture of humic acid and carbendazim is used, no drug-resistance is identified. Humic acid can also inhibit the formation of resistant genes in weeds. Pesticides mixed with humic acid can control the safety of crops through their entire life cycle.
Protect helpful organisms in soil
The residue of glyphosate in soil will increase the number of pathogens in soil and in turn endanger helpful microorganisms and crops. Lots of diseases happen in orchards and cash crops with frequent excessive use of glyphosate. If a mixture of humic acid with glyphosate is used on waxberries and grapes, despite several applications, diseases occur less frequently than with the earlier use of glyphosate alone.
Kill bacteria, insects and weeds
Humic acid can be used together with quite a few fungicides to produce remarkable bacteria-killing effect. For example, the mixture of chlorothalonil with humic acid can be used as a high-effect fungicide and has extensive applications in fruit preservation. Copper humate generated through the combination of humic acid and copper ions has excellent bacteria-killing effect and is extensively used in production. Mixtures of humic acid with insecticides are very effective and long-acting, and can reduce the required dosage and application frequency of pesticides. For example, a mixture of sodium humate with omethoate can effectively control injuries caused by parathrene tabaniformis rottenberg to poplar seedlings. A mixture of sodium humate with tefluthrin can effectively increase control of underground insecticide grubs. Humic acid itself has no weed-killing effect, but mixed with herbicides it can play the role of synergist and stabilizer, increase the effect, reduce the dosage (by 20% at least) and extend the active period of pesticides. Successful examples include nicosulfuron, 2,4-D butyl ester, glyphosate and chlorimuron-ethyl.
Helps regulate plant growth
The role of humic acid as a plant growth regulator is also very prominent. For example, humic rooting agent is produced by mixing sodium humate (or potassium humate) with chemical rooting agents indole butyric acid and naphthalene acetic acid. It costs little, dissolves easily in water and is extremely effective in promoting the rooting of plantlets and cuttings. It has gained extensive applications in tree nurseries, flower nurseries, city greening, transplanting grown trees and transplanting vegetable/rice seedlings in agriculture. The mixture of fulvic acid with gibberellin and cytokinin (6-BA) can boost the flowering and fruiting of fruit trees and increase vegetable output. Moreover, fulvic acid provides physiological drought resistance and increases wheat output.
The market-oriented road is long and tough
Despite various advantages of humic pesticides, their development outlook in China is unfavorable. They are, on the whole, still at the stage of local experimentation and most products have not yet entered the market. Major problems exist today, as follows. (1) The structure of humic acid is unique. Humic acid is a polymeric complex with no fixed molecular structure. Cut-in points for their research are not yet identified. (2) The molecular structure of humic acid has dramatic changes. Results of its reactions with other substances are therefore unforeseeable. Results of experiments have to be taken as the main references. Rules can be discovered only after many data sets are acquired. (3) Ideal methods for increasing the activity of humic acid are not yet found today. The active concentration of humic acid in mixing should be between 10-4 and 10-6. Conventional methods can hardly reach such concentration. (4) Raw materials for humic acid in different regions vary widely. Raw materials for biochemical fulvic acid vary even more. The behavior of fulvic acid extracted from different substances (such as beet pulp, sugarcane pulp and wastes of making traditional Chinese medicines) differ substantially. Active groups of humic acid extracted from peat, lignite and weathered coal are not the same either. The quality of humic pesticides is therefore hard to control, affecting their widespread use and large-volume sales. (5) As the structure of humic acid is uncertain and no relevant standards exist, the responsible administrative departments are hard put to approve and register them, and such products have no route to the market. Moreover, humic acid producers and pesticide producers have no coordination and management departments capable of organizing product formulation and dissemination. These factors have led to many difficulties in the production and application of humic pesticides.
Basic research and application development should be promoted simultaneously
First of all, the basic research of humic acid should be strengthened. It is necessary to design a national-level humic acid project, raise a great deal of capital and gather excellent research teams and grassroots units to undertake long-term R&D. Unique experimental conditions such as high magnetic field, laser stimulation, vacuum and outer space should be set up to observe and test structural changes of humic acid and identify optimal and practical methods for extracting highly active humic acid to meet the needs of production. Research methods of quantum mechanics should be introduced to grasp rules for molecular changes of humic acid. Activities and contents of humic acid in soil in different regions and rules for their changes should be assayed to seek the soil amelioration mechanisms of humic pesticides. Research on the physiological metabolism of crops should be strengthened to discover genes sensitive to the action of humic acid, identify how humic acid improves the adversity resistance (resistance to drought, cold, salinity and natural disasters) of crops and increase the quality and the output of grain crops.
Second, research on technologies for the application of humic pesticides should be strengthened. Humic pesticide producers should establish consortiums to conduct application tests on various crops, develop technologies for optimal product series and optimal formulas, procedures and applications, as well as formulate and promote methods and standards for the formulation, use and testing of humic pesticides. Guidance and promotion of tests should be strengthened to closely combine advanced artificial intelligence technology and drone pesticide spraying technology, in particular, with crop detection technology.
Third, humic pesticides with multiple functions should be developed. The development of chemical, biological, antibiotic and herbal humic pesticides should be accelerated, and fertilizers with humic pesticides added should be developed to simplify farmland management. Multi-function pesticides should be intensified to promote the full display of dual regulation functions (the function of achieving high quality or high output and the function of controlling pests) of humic pesticides.
Build a complete pesticide application system, set a green ecological precedent
The application of humic pesticides should be further promoted. Focus should be on highly effective products and convenient mixing and manufacturing such as humic rooting agents, sodium humate, potassium humate, fulvic acid and biological fulvic acid. Formulations of humic pesticides should be developed to build a complete humic pesticide application system.
First of all, a plant growth regulation system should be established. Efforts should be made to change endogenous hormones of plants and induce the growth of crops through the combination of humic acid and artificial growth regulators to meet physiological needs in the growth period of crops. Second, a pest control and safety system including herbicides, fungicides and insecticides should be established. Recipes of humic pesticides, application procedures and operating skills should be formulated according to rules for the incidence of weeds, diseases and pests. Third, a system of application technologies for comprehensive all-round promotion and protection of the growth of crops, with humic pesticides as the lead, should be developed. Humic pesticides should be combined with chemical fertilizers. Microbial fertilizers should be fully combined with other small-molecule active substances. The latest pesticide varieties should be employed to increase the multi-function effects of humic pesticides. Advanced modes for application and management of humic pesticides should be developed. R&D of drone pesticide spraying technology should be conducted. Precedents for using humic pesticides to launch green ecological projects should be established. Humic acid pesticides with high activity and trace elements should be used to change the global ecological environment and agricultural production.