Promotion of rice–duck integrated farming in the water source areas of Shanghai: its positive effects on reducing agricultural diffuse pollution

The paper aims to study the effects of replacing the conventional rice farming by the rice–duck integrated organic farming on the reduction of agricultural diffuse pollution around Dianshan Lake in the suburbs of Shanghai, Southeast China. Agricultural activities of 21 rice farms in Jinze Town nearby Dianshan Lake were tracked and investigated for the consecutive 5 years, with the questionnaires on the inputs of agro-chemicals within the rice-growing seasons under the conventional rice farming in detail. The nutrient amounts discharged from the conventional rice fields were calculated and these from the rice–duck integrated organic farming potentially implemented surrounding the lake were also estimated. The quantities of N and P₂O₅ applied to the conventional paddy fields of the six towns surrounding the lake were 2.01 × 10⁶ kg a^− 1 and 4.59 × 10⁵ kg a^− 1 on annual average, respectively; these discharged into the environment were estimated to 1.48 × 10⁵ kg a^− 1 and 1.34 × 10⁴ kg a^− 1 on annual average, respectively. The quantities of herbicides, fungicides, and pesticides discharged from the conventional rice fields of the six towns were 1.67 × 10⁴ kg a^− 1 on annual average. The potential replacement of the conventional rice farming by the rice–duck integrated organic farming around the lake will reduce the amounts of N and P₂O₅ discharges through runoff and leaching by 83.79% and 92.11%, respectively, and completely prevent the diffuse pollution of biocides. The implementation of the rice–duck integrated organic farming around Dianshan Lake will not only be beneficial to lake protection, but also to raising the incomes of local farmers, and, thus, should be highly encouraged.