Abstract Aquaculture effluent irrigation has been widely adopted to replace freshwater irrigation to save water and providing additional fertilizer to the crop. There is limited information on the performance of fertilizer supply levels under fishpond effluent irrigation. The objectives of this study were to investigate the effect of reducing a rate of fertilizer on the purification of wastewater from fishponds by paddy fields and the yield of rice under fishpond effluent irrigation in central China in 2015. The treatments included 100 %, 80 %, and 60 % of the normal fertilizer rate (NFR, 150 kg N ha−1, 120 kg P2O5 ha−1 and 75 kg K2O ha−1) with fishpond (freshwater-pond aquaculture) effluent as an irrigation source, designated NFR-E, 0.8NFR-E, and 0.6NFR-E, respectively; with an additional NFR with freshwater as an irrigation source (NFR-F). The results showed that 5700 m3 ha-1 freshwater was saved by the use of the NFR-E, 0.8NFR-E and 0.6NFR-E treatments. The concentrations of total nitrogen (TN), total phosphorus (TP), dissolved phosphorus (DP), ammonia-nitrogen (NH4+-N), nitrate-nitrogen (NO3--N) and particulate phosphorus (PP) in the surface water and seepage water of the paddy field and the residual soil N and P in the 0−60 cm soil depth after the rice harvest decreased with the decreasing NFR. The removal rates of the TN in the surface water across the tillering, booting, heading and filling stages were 25.1 %, 38.9 % and 50.5 % on average for the NFR-E, 0.8NFR-E and 0.6NFR-E treatments, respectively. The corresponding removal rates of the TP were 56.4 %, 71.2 % and 76.2 %, respectively. These increased removal efficiencies were related to the lower N and P concentrations in the surface water of the paddy field and the efficient use of nutrients by rice under the reduced fertilization treatments. Compared to the NFR-F treatment, the 0.8NFR-E treatment resulted in a comparable accumulation of N and P and grain yield of rice, while decreasing the contents of N and P in the water of paddy fields and the residual soil N and P in the 0−60 cm soil depth after the rice harvest. Thus, reducing the normal fertilizer rate by 20 % could improve the water quality of the paddy field without deleterious effects on the rice yield and save 5700 m3 ha-1 of fresh water under fishpond effluent irrigation. These results can also provide a basis for in-depth understanding of the mechanism of aquaculture effluent purification through paddy field ecosystem in response to fertilizer supply levels.

中文翻译：

---

鱼塘污水灌溉减施肥对水田水质及水稻产量的影响

摘要 水产养殖污水灌溉已被广泛采用以替代淡水灌溉，以节约水资源并为作物提供额外的肥料。关于鱼塘污水灌溉下肥料供应水平的表现的信息有限。本研究的目的是调查2015年华中地区降低施肥量对水田鱼塘污水净化效果和鱼塘污水灌溉水稻产量的影响。处理包括100%、80%、和正常施肥量的 60%（NFR，150 kg N ha-1、120 kg P2O5 ha-1 和 75 kg K2O ha-1），鱼塘（淡水池塘水产养殖）流出物作为灌溉源，指定为 NFR-E 、0.8NFR-E 和 0.6NFR-E；以淡水作为灌溉源的额外 NFR (NFR-F)。结果表明，使用 NFR-E、0.8NFR-E 和 0.6NFR-E 处理可节约 5700 m3 ha-1 淡水。地表水中总氮（TN）、总磷（TP）、溶解磷（DP）、氨氮（NH4+-N）、硝态氮（NO3--N）和颗粒磷（PP）的浓度和稻田渗水量和水稻收获后0~60 cm土层残留土壤N、P随NFR的降低而减少。NFR-E、0.8NFR-E和0.6NFR-E处理在分蘖、孕穗、抽穗和灌浆阶段对地表水中TN的去除率分别为25.1%、38.9%和50.5%。相应的TP去除率分别为56.4%、71.2%和76.2%。这些提高的去除效率与稻田地表水中较低的 N 和 P 浓度以及在减少施肥处理下水稻对养分的有效利用有关。与 NFR-F 处理相比，0.8NFR-E 处理导致水稻 N、P 的积累和籽粒产量相当，同时降低了稻田水分和残留土壤 N、P 中 N 和 P 的含量在水稻收获后的 0-60 cm 土层中。因此，将正常施肥量降低 20% 可以改善水田水质，而不会对水稻产量产生不利影响，鱼塘污水灌溉可节约淡水 5700 m3 ha-1。