A Meta‐Analysis on Nitrogen Retention by Buffer Zones. Issue 2 (1st March 2019)

• Record Type: Journal Article
• Authors: Valkama, Elena; Usva, Kirsi; Saarinen, Merja; Uusi‐Kämppä, Jaana
• Is Part Of: Journal of Environmental Quality. Volume 48:Issue 2(2019)
• Page Start: 270
• Page End: 279
• Publication Date: 2019-03-01
• Subjects: Agricultural ecology -- Periodicals; Environmental engineering -- Periodicals; Pollution -- Periodicals; 630
• DOI: 10.2134/jeq2018.03.0120
• Languages: English
• ISSNs: 0047-2425

Abstract

Abstract : Buffer zones, established between agricultural fields and water bodies, are widely used as a measure to reduce 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 NO3 –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 70% (−78 to −62%, n = 38) NO3 –N reduction in surface runoff and in groundwater, respectively, compared with 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‐regression, the N removal efficiency in surface runoff decreased in consort with increasing buffer zone age. Otherwise, the meta‐analysis revealed no effects of buffer zone characteristics such as the width or species number (for grass buffer zones) on the N retention in surface runoff and groundwater. Unlike groundwater quality, which responded equally well regardless of the source of pollution, buffer zone type, or buffer zone age, surface water quality is more sensitive, and it might not be satisfactorily improved by tree buffer zones or aged buffer zones, or when the source of pollution originates from grass production fields. Core Ideas: We performed a global weighed meta‐analysis by summarizing 46 studies (1980–2017). Buffer zones reduced NO3 –N by 33% in surface runoff and by 70% in groundwater. Surface water is more sensitive to buffer zone characteristics than groundwater. The higher the initial N concentrations, the larger the N retention by the buffer zones. Meta‐analysis revealed no effect of buffer zone width on N retention.