| PAA | Polyacrylic acid |
| HA | Humic acid |
| KHA | Potassium humate |
| PAA-KHA | Polyacrylic acid-potassium humate |
| ADP | Ammonium dihydrogen phosphate |
| ADP@PAA-KHA | Polyacrylic acid-potassium humate coated ammonium dihydrogen phosphate fertilizer |
| AA | Acrylic acid |
| APS | Ammonium persulfate |
| MBA | N, N′-methylene amide |
| w | coated rate (%) |
| m1 | the weight of fertilizer cores (g) |
| m2 | the weight of ADP@PAA-KHA (g) |
| H | water absorbency (g·g−1) |
| M1 | the mass of PAA-KHA (g) |
| M2 | the mass of PAA-KHA after fully swelling in deionized or salty water (g) |
| W | the cumulative release rate of each nutrient (%) |
| VE | the volume of sample solution (L) |
| V0 | the volume of solution in the container (L) |
| Ci | the concentration of nutrient in the sample solution (mg·L−1) |
| Cn | the concentration of the solution in the container (mg·L−1) |
| n and i | the number of samples |
| mx | the nutrient mass in the sample (mg) |
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