Effects of Ecological Ditch on Nitrogen and Phosphorus Reduction of Agricultural Wastewater in Different Periods

In order to explore the effects of ecological ditch on reducing agricultural non-point source nitrogen and phosphorus in different ob‐servation periods and identify the key reduction period in Guangxi,nitrogen and phosphorus concentration was monitored at Dongcun Village in Xing’an County from May 2019 to April 2021.Based on the monitored data,the variations of nitrogen and phosphorus concentration,ni‐trogen composition and reduction efficiency were analyzed in different observation periods of dry seasons,rainy seasons,spring,summer,autumn and winter.The results showed that the average concentrations of ammonium nitrogen（NH₄⁺-N）,nitrate nitrogen（NO₃^--N）,total ni‐trogen（TN）and total phosphorus（TP）during the whole monitoring period were 5.62～19.84,2.38～4.00,15.30～28.18 and 0.50～1.26 mg/L,respectively.The average ratios of NH₄⁺-N and NO₃^--N concentration to TN concentration at the monitoring points along the ecological ditch were 0.04～0.90 and 0.02～0.66,respectively,and the average ratios of NH₄⁺-N in autumn,winter and dry season was 0.41～0.90,which were significantly higher than those in other seasons.The reduction efficiency relative to the water inlet of each monitoring point along the ecological ditch was obvious,and the reduction efficiency of NH₄⁺-N,NO₃^--N,TN and TP were 0.31%～1.10%,0.07%～1.69%,0.31%～1.07%and 0.30%～0.91%,respectively.Autumn and winter were the key periods for the reduction of NH₄⁺-N,TN and TP,while the reduc‐tions of NO₃^--N were the highest in summer and autumn.