Design and synthesis of the agricultural and ecological superabsorbent materials with cost-efficient and fertilizer-release characteristics has recently attracted considerable interests. In this work, the novel poly(sodium-potassium acrylate-co-acrylamide)/plant ash (PNa-KA-co-AM/PA) superabsorbent composites with potassium-release characteristics were prepared using partially neutralized acrylic acid (Na-KA), acrylamide (AM), and plant ash (PA) as raw materials, ammonium persulfate (APS) as the initiator, and N,N'-methylenebisacrylamide (MBA) as the crosslinker. The structure, morphologies, and thermal stability of the composites were characterized by Fourier transform infrared spectrophotometer, scanning electron microscopy, and TGA techniques, respectively. The effects of MBA concentration and PA content on water absorbency were studied, and the swelling properties of the composites in saline solutions and various pHs solution as well as their potassium-release capabilities were also evaluated. Results indicate that the composites exhibit better thermal stability, salt-resistant performance, pH-stability, and potassium-release properties, and can act as a fertilizer and an effective water-saving material for agricultural and ecological application. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 115: 1814-1822, 2010