In this study, we aimed to develop a degradable nitrogen and phosphorus (NP) fertilizer with properties of slow release, water retention, and remediation of saline soil; the nitrogen and phosphorus was coated with starch/poly(acrylic acid-co-acrylamide) [poly(AA-co-AM)] superabsorbent (SAAmF) by reverse suspension radical copolymerization. The variable influences on the water absorbency were investigated and optimized. The results of the structure and morphology characterization of SAAmF show that poly(AA-co-AM) was grafted partly from the chain of starch, and the different contents of starch brought about a difference in the size of the three-dimensional net hole of the coating polymer. The property of water retention, the behaviors of slow release of nutrient, and the degradation of the SAAmF were evaluated, respectively, and the results revealed that the water transpiration ratio of soil with SAAmF was lower by approximately 8 percentage points than that of the blank test, about 60% nutrient was released from SAAmF by the 30th day, and 32 wt % of SAAmF with a content of starch of 20% was degraded after 55 days. Moreover, a considerable decrease in the conductivity was observed, which revealed a sharp reduction in the concentration of residual ions for the soil mixed with SAAmF. It may be inferred from these that the product seems to be a promising vehicle for the management of soils, including saline soils. (C) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 128: 407-415, 2013