Water-Preserving and Salt-Resistant Slow-Release Fertilizers of Polyacrylic Acid-Potassium Humate Coated Ammonium Dihydrogen Phosphate.

Hongping Li,Chenchen Nie,Guiming Xie,Wenxing Chen,Hao Liu,Lanwen Yang,Juan Tian,Jianxin Cao,Pinglan Geng

doi:10.3390/polym13172844

Abstract

Polyacrylic acid (PAA) has high water absorbency but poor salt resistance. Humic acid (HA) extracted from lignite was introduced into the cross-linked copolymer systems of AA to improve the water absorbency and salt-tolerance. A polyacrylic acid-potassium humate (PAA-KHA) coated ammonium dihydrogen phosphate (ADP) fertilizer with water-preserving, salt-resistant and slow-release properties was prepared. The main properties of HA extracted from lignite oxidized by H2O2 were studied. Furthermore, the synthesis process, water absorbency of PAA-KHA in deionized water and in NaCl solution, morphologies of PAA-KHA, and the slow-release performance of the fertilizer (ADP@PAA-KHA) were investigated. The results showed PAA-KHA had a layered interpenetrating network, which can provide sufficient storage space for water and nutrients. The salty water absorbency of PAA-KHA increased by about 3 times compared to PAA. Both the PO43− and NH4+ cumulative release of ADP@PAA-KHA with a coating rate of 10% in deionized water, were less than 20% within 24 h, and were 55.71% and 28.04% after the 15th day, respectively. The weight change of ADP@PAA-KHA before and after absorbing water was about 53 times in deionized water and about 4 times in 1 wt% of NaCl salty water. The results show that ADP@PAA-KHA has excellent properties of water retention, salt resistance and slow-release. This will efficiently improve the utilization of fertilizer and reduce the irrigation water consumption at the same time.

Highlights

Chemical Reagent Co., Ltd., Tianjin, China; hydrogen peroxide solution (H2 O2, 30 wt%), potassium hydroxide (KOH), calcium acetate, barium hydroxide (Ba(OH)2 ), sodium chloride (NaCl), sodium hydroxide (NaOH), ammonium dihydrogen phosphate (ADP) were purchased from Chengdu Jinshan Chemical Reagent Co., Ltd., Chengdu, China; N, N0 methylene amide (MBA) was purchased from Shanghai Yuanye Biotechnology Co., Ltd., Shanghai, China; phenolphthalein, sodium pyrophosphate and ammonium ferrous sulfate were purchased from Tianjin Zhiyuan Chemical Reagent Co., Ltd., Tianjin, China; potassium dichromate was from Beijing Balinwei Technology Co., Ltd., Beijing, China; 1,10-Phenanthroline monohydrate was purchased from Shanghai Ika Biotechnology
The chemical structure differences of lignite, oxygenated lignite and Humic acid (HA) are characterized by FTIR in Figure 1; the broadband at around 3400 cm−1 belongs to the stretching vibration of the -OH groups, and the broadband at around 3150 cm−1 belongs to the N-H or =C-H of the aromatic ring
−1 improved salt22.5 resistance of the coating material regardless of the concentration of Polyacrylic acid (PAA) wasthe only g·g. These results demonstrated that the addition of HA significantly salt solution.the salt resistance of the coating material regardless of the concentration of salt improved solution

Summary

Introduction

Chemical fertilizers became a useful method to increase grain production to meet the food needs of the rapidly growing global population. The direct application of chemical fertilizer causes the loss of fertilizer nutrients due to volatilization of nitrogen in the forms of NH3 and nitrous oxides, and leaching in the soil, leading to the rising cost of food production and environmental pollution [1]. The water-preserving and slowrelease fertilizer makes the release of nutrients match requirements of crops at every stage of growth and development, and can improve fertilizing, use efficiency to reduce irrigation water consumption and the risk of environmental pollution [3]

Methods

Results

Conclusion