Objective  Effects of application of aquatic green manure Azolla on fertilizer use reduction and productivity improvement for single-cropping rice farming were studied.

  Method  An experimentation using Azolla at a rate of 30 t·hm⁻² to replace 20%, 40%, and 60% N and K fertilizers was conducted. The resulting grain yield, plant biological characteristics, and soil fertility were monitored.

  Results  In comparison to the conventional fertilization, the application of Azolla to achieve 20% reduction on the use of N and K fertilizers rendered significant increases on plant height, effective tillers count, and panicles per plant with an 11.11% rise on the crop yield (P＜0.05). The pH, organic matters, alkali-hydrolyzed N, available P, and readily available K of the treated soil were improved to varying extents. In general, plowing Azolla into the field significantly increased organic matters in the soil (P＜0.05). The treatment to reduce 60% use of conventional chemical fertilizers with Azolla (T6) made a significantly difference on the readily available K in soil (P＜0.05).

  Conclusion  Application of Azolla at a rate of 30 t·hm⁻² to replace 20% of N and K for fertilization could significantly upgrade the soil fertility and increase the grain yield by 11.11%. It was considered an effective means not only to conserve fertilizer with green manure but also benefit the production of single-cropping rice farming.