Keeping agricultural soil out of rivers: Evidence of sediment and nutrient accumulation within field wetlands in the UK

Abstract

Intensification of agriculture has resulted in increased soil degradation and erosion, with associated pollution of surface waters. Small field wetlands, constructed along runoff pathways, offer one option for slowing down and storing runoff in order to allow more time for sedimentation and for nutrients to be taken up by plants or micro-organisms. This paper describes research to provide quantitative evidence for the effectiveness of small field wetlands in the UK landscape. Ten wetlands were built on four farms in Cumbria and Leicestershire, UK. Annual surveys of sediment and nutrient accumulation in 2010, 2011 and 2012 indicated that most sediment was trapped at a sandy site (70 tonnes over 3 years), compared to a silty site (40 tonnes over 3 years) and a clay site (2 tonnes over 3 years). The timing of rainfall was more important than total annual rainfall for sediment accumulation, with most sediment transported in a few intense rainfall events, especially when these coincided with bare soil or poor crop cover. Nutrient concentration within sediments was inversely related to median particle size, but the total mass of nutrients trapped was dependent on the total mass of sediment trapped. Ratios of nutrient elements in the wetland sediments were consistent between sites, despite different catchment characteristics across the individual wetlands. The nutrient value of sediment collected from the wetlands was similar to that of soil in the surrounding fields; dredged sediment was considered to have value as soil replacement but not as fertiliser. Overall, small field wetlands can make a valuable contribution to keeping soil out of rivers.

Sediment and nutrient storage in a beaver engineered wetland

“…Others have suggested smaller, strategically placed features could play a key role (Braskerud et al ., 2005; Ockenden et al ., 2014). However, such work commonly focuses on anthropogenic features with associated construction and maintenance costs (Ockenden et al ., 2012).…”

Public Perceptions and Willingness to Pay for Renewable Energy: A Case Study from Greece

“…On the contrary, undesirable inflows into the ecosystem, caused by anthropogenic activity, can shake this harmony and degrade living conditions [1]. Human influence on the environment is increasing due to mass production of technological goods [2], intensification of agriculture [3], the rapid rate of urbanization, and growing demand of fossil fuels for energy and transport [4]. According to data from the International Energy Agency, between 1971-2014, global primary energy consumption has increased by 2.5 times, as from 5.5 GTOE in 1971 to 13.7 GTOE for 2014 [5].…”

National Large-Scale Wetland Creation in Agricultural Areas—Potential versus Realized Effects on Nutrient Transports

“…Several studies have shown that in runoff from agricultural fields, phosphorus is transported largely as particulate phosphorus [15][16][17][19][20][21][22]. Therefore, sedimentation is likely to be the predominant phosphorus removal process in wetlands receiving high phosphorus loads [23][24][25][26][27]. In addition to estimations of nutrient removal in individual wetlands based on water monitoring data, measurements of particulate phosphorus accumulation on sediments [23] were therefore included here.…”