Application of Polyaspartic Acid（PASP） in Water Soluble Fertilizers

Water-soluble fertilizer is a kind of multi-element compound and quick-acting fertilizer that can be completely dissolved in water. It has the characteristics of good water solubility, no residue, and can be directly absorbed and utilized by the roots and leaves of crops. As an important part of the integration of water and fertilizer, water-soluble fertilizer has obvious advantages. First, the utilization rate of fertilizer can be significantly improved. Secondly, water-soluble fertilizer has high nutrient content and comprehensive nutrition, which can significantly improve crop yield and quality. resource

There are still many problems to be solved in the production and use of water-soluble fertilizers. Poor water solubility, high insoluble content, easy to produce scale to block the pipeline, especially in areas with high calcium and magnesium ion concentration in irrigation water. The main component of water-soluble fertilizer is chemical fertilizer. Long-term use can easily cause soil compaction and imbalance of soil flora, which may eventually lead to the degradation of soil fertility. Based on the above reasons, with the development of water and fertilizer integration, major chemical companies at home and abroad have successively developed chemicals with scale and corrosion inhibition to solve the problems in the production and use of water-soluble fertilizers. Among them, polyaspartic acid and its Derivatives are the most widely studied substances.

Polyaspartic acid (PASP) is a synthetic water-soluble protein that naturally exists in the mucus of marine shell organisms such as oysters. It is an active substance for marine shell organisms to enrich nutrients and build shells. As a new type of fertilizer synergist, polyaspartic acid can strengthen the absorption of nitrogen, phosphorus, potassium and medium and trace elements by crops; in addition, polyaspartic acid is non-toxic, harmless and completely biodegradable, which is recognized by the world. Green chemicals. Research and application results at home and abroad show that polyaspartic acid, as a synergist for water-soluble fertilizers, has the following main functions. 

1 Dispersion of polyaspartic acid (PASP)

The main reasons for pipeline blockage during the use of water-soluble fertilizers include precipitation caused by chemical reactions between fertilizers, reduction in solubility caused by pH of water, and water-insoluble substances in fertilizers. Inside the road or at the water outlet, especially water-insoluble salts such as calcium and magnesium, thereby blocking the entire system.

As a new type of green dispersant, polyaspartic acid can prevent and alleviate the formation and aggregation of inorganic salt scales after being applied to drip (sprinkler) irrigation systems, and can disperse the formed scales to form fine particles suspended in the water system, thereby Reduce the clogging of the system during the use of water-soluble fertilizers. According to research, polyaspartic acid, as a chelating and dispersing agent in the water circulation system, has good chelating effect on iron oxide, calcium carbonate, titanium dioxide, zinc hydroxide, magnesium hydroxide, magnesium oxide, manganese dioxide, etc. dispersion. Koskan et al. believed that polyaspartic acid could prevent the deposition of scale on heat transfer surfaces and water system pipes.

At the same time, the research on the scale inhibition effect of polyaspartic acid molecular weight and system temperature confirmed that the scale inhibition effect of polyaspartic acid has a great relationship with the molecular weight of polyaspartic acid, but has little relationship with the system temperature. It is generally believed that the anti-scaling effect of polyaspartic acid synthesized by different methods has a great relationship with its corresponding scale. The polyaspartic acid and its derivatives as raw materials have better anti-scaling effect on BaSO4, SrSO4, CaSO4, etc. Ross et al. confirmed that the optimal weight average molecular weight range of polyaspartic acid for dispersing calcium carbonate, calcium sulfate, barium sulfate, etc. is 1000-4000. Quanzhenhua et al. found that when the water temperature of polyaspartic acid was lower than 60 ℃, the temperature change had little effect on the scale inhibition rate; when the Ca2+ was 800 mg/L, the amount of polyaspartic acid used was only 800 mg/L. At 3 mg/L, the scale inhibition rate can still reach more than 90%. At 20 °C, polyaspartic acid delayed the nucleation of calcium carbonate by at least 150 min. These studies all show the universality of the anti-scale properties of polyaspartic acid to temperature.

2 Corrosion inhibition of polyaspartic acid(PASP)

It is generally believed that the polar groups (containing N, O groups) in polyaspartic acid are adsorbed on the metal pipes, which greatly improves the activation energy of the metal ionization process, while the non-polar groups (alkyl R) It is arranged away from the metal orientation to form a hydrophobic film, thereby inhibiting the corrosion of the aqueous solution to the metal pipeline, effectively protecting the drip irrigation system in the integration of water and fertilizer, extending the service life of the equipment and reducing the production cost. Polyaspartic acid has corrosion inhibition effect on carbon steel, copper, brass, cupronickel and other metal materials of various systems; when the concentration of polyaspartic acid is 100 mg/L, the corrosion inhibition rate of carbon steel It can reach 93%, and at this concentration, polyaspartic acid can slow down the corrosion rate of carbon steel by 90%, thereby effectively prolonging the service life of the pipeline.

In related studies, the researchers found that polyaspartic acid has a good inhibitory effect on the corrosion of pipelines in water systems under different pH conditions. Benton's research believes that in a corrosive salt solution medium with a pH of 4.0 to 6.6, the use of polyaspartic acid and its salts with a molecular weight of 1000 to 5000 and a concentration of 25 mg/L can effectively inhibit the effect of carbon dioxide on carbon steel. corrosion. When Kalota et al. and Silverman et al. studied the corrosion inhibition performance of polyaspartic acid on iron under different pH, temperature and moisture conditions, they found that when the pH was greater than 10, polyaspartic acid had better corrosion inhibition performance. Mansfeld et al. found that a better effect can be achieved when the pH is between 8 and 9. Therefore, polyaspartic acid can solve the corrosion of pipelines during the use of water-soluble fertilizers with different formulas, and is helpful for the application of fixed or semi-fixed pipeline systems.

3 The synergistic effect of polyaspartic acid(PASP)

As a fertilizer synergist or nutrient fortifier, polyaspartic acid has been reported in the aspects of slow release and synergy, improving fertilizer utilization rate, improving crop quality, increasing production and income. Studies have shown that adding polyaspartic acid to water-soluble fertilizers can prolong the persistence of fertilizers and ensure that crops absorb nutrients evenly throughout the growth process, thereby ensuring the effective use of fertilizers. The experiments of Lei Quankui et al. showed that the utilization rate of N, P and K fertilizers in peanuts were improved to varying degrees after the application of polyaspartic acid, and the symptoms of nutrient deficiency were not easy to occur in the whole growing season of peanuts. Cao Dan et al. studied the lasting effect of polyaspartic acid, and proved that the use of polyaspartic acid once a year has the effect of increasing the yield of crops in both seasons.

According to reports, polyaspartic acid can effectively activate the medium and trace elements necessary for crop growth, and can improve the absorption efficiency of macroelements, thereby increasing the utilization rate of fertilizers. activity, increase yield and improve crop quality.

Li Jiangang and other studies found that after applying polyaspartic acid to vegetables such as vegetables, the content of vitamin C and soluble sugars increased to different extents, which could effectively improve the quality of vegetables and fruits. Jiao Yongkang et al. found through foliar spraying of different types of polyaspartic acid chelate salts that the use of polyaspartic acid can not only increase the yield of Huangguan pear, improve the quality of pear fruit, but also reduce the damage caused by chicken feet disease of Huangguan pear. loss. Tang Huihui et al. studied the application of polyaspartic acid nitrogen fertilizer to spring corn in Northeast China and found that PASP-N was used for corn cultivation under the condition that the total nitrogen content was reduced by 1/3, the corn yield was not reduced, and it could effectively regulate corn in different periods. The activity of enzymes in the body is conducive to weight loss and synergy. After applying urea containing polyaspartic acid to rice, it was found that the persistence of fertilizer was significantly improved, and there was no shortage of nutrients in the growing season.

4 Environmentally friendly properties of polyaspartic acid(PASP)

The main component of polyaspartic acid is a polymer of amino acids, which can be completely degraded by microorganisms into available low-molecular-weight amino acids, water and carbon dioxide in the environment. Some people use the method of OECD301A to study the biodegradability of polyaspartic acid and find that the carbon dioxide released by polyaspartic acid is close to the reference glucose. Polyaspartic acid is a green chemical with excellent biodegradability.

From Gansu Agricultural Science and Technology Subscription Issue 3, 2022