The Nutrients in the Fertile Water from Fish Pond Assimilated and Utilized by Paddy Field

Abstract：Wastewater from aquiculture sometimes is called fertile water for plants because it contains useful ingredients such as nitrogen and phosphorus.In order to realize zero-discharge of wastewater from aquiculture,a field experiment was done that aquiculture water（fertile water for plants） from fish pond was applied to irrigate paddy field.The results showed that： ①paddy field has an obvious effect on removal of some ingredients contained in irrigation water from fish pond,especially for NO-3-N and TP.When aquiculture water stranded in the paddy field for more than 8 hours,the nutrient in it may be assimilated by paddy field 65.23% for TN,71.97% for TP,87.28% for NO-3-N,66.84% for NH＋4-N and 51.06% for CODMn.②when aquiculture water entered to the field and contacted with soil surface and plants,the various forms of nitrogen adsorbed is more than that of the TP and CODMn,in which the NH＋4-N and NO-3-N adsorbed reach up to 49.92% and 41.78% respectively;when aquiculture water penetrates the soil,the absorption is 45.51% for TP,35.63% for CODMn and 37.36%for NO-3-N.③using fertile water from fish pond to irrigate paddy field,an output of rice may get to more than 9 000 kg/hm2 under 80% of the conventional fertilizer dosage which means fertilizer-saving 20% in contrast to the local conventional fertilizer use,and get to 7 950 kg/hm2 without fertilizer that undoubtedly is the most economical and friendly to environment.