The novel nanosuperabsorbent copolymer (NSAP) was synthesized by grafting copolymerization of acrylamide (AM) and acrylic acid (AA) onto starch with montmorillonite (MMT) initiated using Co-60 gamma-ray irradiation. NSAP was characterized by IR spectroscopy and X-ray diffraction (XRD). Different synthesis parameters were studied, such as AM-to-AA ratio, radiation total dose, radiation dose rate, crosslinker content, and clay content. NSAP can effectively improve the water retention capacity of soil. The effects of NSAP on crops were also studied, showing that NSAP has an encouraging potential for agricultural application. (c) 2005 Wiley Periodicals, Inc.