Influence of Sediment, Plants, and Microorganisms on Nitrogen Removal in Farmland Drainage Ditches

Abstract

The removal of nitrogen from water is a consequence of the synergistic action of plant uptake, sediment sorption, and microbial decomposition. However, there is a lack of long-term experimental studies on the effects of each component in the process of nitrogen removal. In this study, we investigated the effect of sediment, plants, and microorganisms on nitrogen removal by setting up three systems: water–sterilized sediment, water–sediment, and water–sediment–plant. The nitrogen removal effect followed the following rank order of effectiveness: the “water–sediment–plant” system > the “water–sediment” system > the “water–sterilized sediment” system. The ditch sediment had a strong enrichment effect for nitrogen. In addition, the migration rate of nitrogen in the sediment with different depths was different. The ammonia-nitrogen migration rate in the sediment showed an increasing trend with time and depth. The nitrate-nitrogen migration process in the sediment showed a trend of enrichment toward the middle layer (15.0–25.0 cm). Aquatic plants and microorganisms can promote the removal of nitrogen in water, with the average purification rates of 13.92% and 19.92%, respectively.

Nitrogen Cycle in Farming Systems

“…At the same time, they are natural reservoirs of water, sediment, and N flowing from fields. Experimental studies simulating the interaction of water-sediment-plant systems made it possible to determine the roles of plants and microorganisms in purifying water from inorganic N [16]. The content of nitrate N during the experimental period, extending from April to October, followed the quadratic regression model, with the lowest value in the summer months (June-August).…”