A meta-analysis on nitrogen retention by buffer zones

Buffer zones, established between agricultural fields and water bodies, are widely used as a measure to reduce nitrogen (N) in surface runoff and groundwater. However, the literature indicates inconsistent results on the N removal efficiency of buffer zones between studies. We performed a weighed meta-analysis on the buffer zone effects on nitrate-N and total N in surface runoff and groundwater by summarizing 46 studies published between 1980 and 2017. The overall effects of buffer zones were a 33% (–48% to –17%, n = 25) and a 70% (–78% to –62%, n=38) nitrate-N reduction in surface runoff and in groundwater, respectively, compared to controls with no buffer zone. In addition, buffer zones reduced the total N in surface runoff by 57% (–68% to –43%, n = 16). The effects of buffer zones on N retention were consistent across continents and in different climates. Nitrogen retention increased with increasing initial N concentrations discharged from the source of pollution. According to a meta...