What is it indeed?
Potassium polyacrylate is a white powder/granule that can absorb water and then turn into water gel form.
How does it work for plants?
After absorbing, the water gels would lock water in the soil. When it's drought, gels would release water to plans. (like a "mini- reservoir")
Tip: the water retention ability of potassium polyacrylate is 1.3-1.4 MPa and roots is about 1.6-1.7 MPa.
Like other super absorbent polymers, it's hard for potassium polyacrylate to absorb water that contained metal ions.
Actually, one gram can absorb hundreds of grams of purified water but can only absorb less than 100 grams of Saline.
So, the more metal ion fertilizer contains, the more potassium polyacrylate would be affected.
Absorbing water before put into the soil.
As fertilizer's metal ion would reduce the absorption of potassium polyacrylate, we can let potassium polyacrylate fully absorb water before use.
Avoid mixing potassium polyacrylate with fertilizer.
Potassium polyacrylate should be used in the soil at depth of 40cm below the surface. And make sure to make distance from fertilizer.
Tips: Use potassium polyacrylate in the right way, it'll be helpful in releasing the fertilizer efficiency slowly also.