The Effects Of Amino Acids On The Availability Of Zinc And Their Application On The Research Of Water-Soluble Zinc Fertilizer

Zinc(Zn) is one of the essential trace elements for plant growth. As the component or activator of various enzymes, Zn involves in the respiration, photosynthesis, oxidation-reduction reaction, and other physiological processes of plants. In addition, it also plays an important role in the synthesis of nucleoprotein, auxin, and other primary chemical and vital substances of plants. Zn deficiency not only impedes the crop growth, but also debases the yields and quality of crops, and affects human and animal health ultimately. Zn fertilizer application is the main measure to correct the zinc deficiency of crops. The chelated Zn fertilizer has the more optimized character in the stability and efficiency of zinc than inorganic Zn fertilizer. However, the commonly used chemical chelating agents are expensive, and it is difficult to be absorbed by plants because of large molecular weight. Meanwhile, degradation-resistant of chemical chelating agents pose the threat to the safety of crops and the environment. In this study, we selected the amino acids, which have better ability in prompting crops growth and enhancing the Zn bioavailability, as chelating agents. The optimal process parameters of the chelate reaction between amino acids and zinc sulfate heptahydrate were investigated to develop highly efficient water soluble amino acid chelated zinc fertilizer. The Chinese cabbage potted experiments were conducted to verify the fertilizer efficiency. The results are shown as following.1.In the appropriate concentration range, the application of different amino acid alone or in combination with zinc sulfate could promote the growth and nutrient uptake of Chinese cabbage, and increase the utilization rate of zinc. The results of experiments showed that the optima concentration of foliar spraying for glycine, glutamic acid and threonine were as follows: 250-400 mg/L, 250-400 mg/L and 100-250 mg/L, and the same as application with zinc sulfate.2. The chelating reaction between different amino acids and zinc sulfate was effected by the molar ratio, pH value and temperature. The optimal process parameters of amino acid A, B and C alone chelated with zinc sulfate as following:(1) the molar ratio were 2.5:1, 2.0:1 and 3.0:1,(2) pH values were 7.1, 7.2 and 5.2,(3) Temperatures were 69℃, 69℃ and 69℃, respectively. With the above process parameters, the predicted chelate rates of zinc sulfate cooperated with glycine, glutamic acid or threonine could reach to 92.0%, 94.0% and 59.0%, respectively. Under optimal conditions, the zinc concentration, the water insoluble matter contents, and pH of the water-soluble amino acid chelated zinc fertilizer produced was 215 mg/L, 12.0g/L, pH 6.2, respectively.3. It was shown that the water soluble amino acid chelated zinc fertilizer was more effectively than other soluble zinc fertilizers in our research under both spraying and fertigation. The water soluble amino acid chelated zinc fertilizer obviously prompted the growth of the Chinese cabbage, enhanced the yields, and improved the quality. Compared with zinc sulfate, EDTA-Zn, two other common fertilizers, the application of the water soluble amino acid chelated zinc fertilizer by foliar spraying increased the biomass of Chinese cabbage by 14.06~52.35%, the Vc contents by 12.74~56.80%, and higher soluble sugar content by 10.87%~97.45%, respectively. Meanwhile, the application of the water soluble amino acid chelated zinc fertilizer by foliar spraying decreased nitrate content by 6.66%~12.95%. Compared with zinc sulfate, EDTA-Zn, two other common fertilizers, the application of the water soluble amino acid chelated zinc fertilizer by fertigation increased the biomass of Chinese cabbage by 36.30~65.84%, the Vc content by 10.26~58.32%, and higher soluble sugar content by 20.56%~97.45%. Meanwhile, the application of the water soluble amino acid chelated zinc fertilizer by fertigation decreased nitrate content by 7.51~16.63%. In addition, the application of water soluble amino acid chelated zinc fertilizer by foliar spraying and fertigation promoted the accumulation of Zn and the utilization efficiency of Zn. In conclusion, the water soluble amino acid chelated zinc fertilizer in this study is not only suitable for foliar spraying, but also available for fertigation of being applied to crop root directly.