A Detailed Explanation of Chemical Mulching Technology and Application Methods of Soil Structure Amendments
With the development of the economy and society, the problem of water scarcity has become a constraining factor for China's agriculture and economic and social development. Water-saving and moisture-preserving technologies for dryland agriculture are particularly important.
Chemical mulching technology is one of many water-saving technologies. It uses soil-surface moisture-preserving and humidifying agents such as asphalt emulsion, cyclohexane and higher alcohol formulations, and synthetic fatty acid residue formulations to make an emulsion, which is sprayed onto the soil surface to form a covering film. This film obstructs the evaporation of soil moisture but does not affect the infiltration of rainfall into the soil, thereby achieving the goals of water conservation, water saving, and effective water supply. At present, the main products used in dryland agriculture worldwide are two chemical formulations from the Belgian company La1ofima: one is the asphalt formulation Homofina, abbreviated HA. This formulation appears as a brown-black latex liquid, with asphalt as its basic component. It is a hydrophilic emulsion that can be diluted with water in any proportion without producing sediment, and can keep moisture in the soil. After its moisture evaporates, the dried asphalt can be re-dispersed upon contact with water, showing reversible changes, and it is suitable for arid regions. The other is a polyacrylamide formulation (Poyacryiamde), abbreviated PAM. This formulation appears as a milky white gelatinous liquid, with polyacrylamide as its basic component. It can also be diluted with water in any proportion without separating, carries many active groups, has strong biological stability, is not easily degraded by microorganisms in the soil, and is non-toxic. Although research on drought-resistant and water-saving chemical mulching technology has a history of several decades, it has not been promoted and applied on a large scale in production, and many problems still remain to be further solved.
The application of soil amendments in water-saving agriculture can play a role in improving soil, saving water, and preserving fertilizer. Soil structure amendments are based on the principle of aggregate structure formation and achieve the purpose of improving soil structure by improving the internal structure and material composition of the soil. Using plant residues, peat, lignite, and other materials as raw materials, substances such as humic acid, cellulose, lignin, and polysaccharide carboxylic acids are extracted from them as cementing agents for aggregating soil particles, or high-molecular polymers are synthesized by simulating the molecular structure and properties of natural aggregate cementing agents. The former type of formulation is a natural soil structure amendment, and the latter is called a synthetic soil structure amendment. Types of synthetic soil amendments include BIT emulsion, PAM, and other high-molecular polymer soil amendments.
The application methods of soil amendments are mainly spraying and mixing. Broadcast application is the direct spreading of powder into the surface soil. Because soil amendments are difficult to dissolve into the soil solution, the soil-improving effect of this application method is relatively small. Under the same conditions, dissolving the amendment in water and spraying it will noticeably improve the physical properties of the soil.
The amount of soil amendment used should follow the principle of an appropriate amount. If the amount is too large, not only will the cost be high and the investment large, but sometimes a concrete-like phenomenon may also occur; if the amount is too small, it will not be effective. Research shows that the application effects of the same soil amendment on soils of different types and properties differ significantly, and different application methods and different application amounts also lead to differences in the application effect of soil amendments. Even for the same soil amendment applied in different soil layers of the same soil, the application effect differs. Therefore, in specific application, a reasonable amount should also be determined based on the results of preliminary trials.