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Management Options to Reduce Phosphorus Leaching from Vegetated Buffer Strips
- Hille, Sandra, Graeber, Daniel, Kronvang, Brian, Rubæk, Gitte H., Onnen, Nils, Molina-Navarro, Eugenio, Baattrup-Pedersen, Annette, Heckrath, Goswin J., Stutter, Marc I.
- Journal of environmental quality 2019 v.48 no.2 pp. 322-329
- agricultural land, ammonium, conservation buffers, harvesting frequency, leaching, models, phosphorus, risk, soluble phosphorus, surface water, topsoil, vegetation
- Vegetated buffer strips (VBS) between agricultural areas and surface waters are important retention areas for eroded particulate P through which they may obtain critically high degrees of P saturation imposing high risk of soluble P leaching. We tested topsoil removal and three harvesting frequencies (once, twice, or four times per year) of natural buffer vegetation to reduce P leaching with the aim to offset erosional P accumulation and high degrees of P saturation. We used a simple numerical time-step model to estimate changes in VBS soil P levels with and without harvest. Harvesting offset erosional deposition as it resulted in an annual ammonium oxalate-extractable P reduction of 0.3 to 2.8% (25-cm topsoil content) in soils of the VBS and thus, with time, reduced potential P leaching below a baseline of 50 μg L⁻¹. Topsoil removal only marginally reduced potential leaching at two sites and not anywhere near this baseline. The harvest frequency only marginally affected the annual P removal, making single annual harvests the most economical. We estimate 50 to 300 yr to reach the P leaching baseline, due to substantial amounts of P accumulated in the soils. Even in high-erosion-risk situations in our study, harvesting reduced soil P content and the P leaching risk. We suggest harvesting as a practical and efficient management to combat P leaching from agricultural VBS, not just for short-term reductions of dissolved P, but also for reductions of the total soil P pool and for possible multiple benefits for VBS.