A global perspective on integrated strategies to manage soil phosphorus status for eutrophication control without limiting land productivity

Authors: WITHERS, PAUL - LANCASTER UNIVERSITY; Vadas, Peter; UUSITALO, RISTO - NATURAL RESOURCES INSTITUTE FINLAND (LUKE); FORBER, KIRSTY - LANCASTER UNIVERSITY; HART, MURRAY - AGRICULTURE VICTORIA; FOY, ROBERT - AGRI-FOOD AND BIOSCIENCES INSTITUTE; DELGADO, ANTONIO - UNIVERSITY OF SEVILLE; RUBAEK, GITTE - AARHUS UNIVERSITY; DOUGHERTY, WARWICK - NSW DEPARTMENT OF PRIMARY INDUSTRIES; POTE, DANIEL; BURKITT, LUCY - MASSEY UNIVERSITY; BARLOW, KIRSTEN - AGRICULTURE VICTORIA; ROTHWELL, SHANE - LANCASTER UNIVERSITY

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/16/2019
Publication Date: N/A
Citation: N/A

Interpretive Summary: Phosphorus (P) use in agriculture continues to negatively impact water quality due to soil P accumulation. Despite years of research, the environmental benefits of erosion control and reductions in soil P, and the timescales over which these benefits occur, are not clear. We examined the impact of soil conservation measures and lowering of soil P in different regions (Europe, USA and Australia). Our analysis suggested that eutrophication control would be more achievable if soil P was kept at or below recommended agronomic optimum. APLE model simulations showed that P losses in three watersheds could be reduced by between 18 and 40% by drawing down soil P to the agronomic optimum, but it would take between 30 and 40+ years to achieve this reduction. Further reductions (up to 55%) could be obtained when soil P was reduced below the agronomic optimum. The APLE model was easy to parameterize and quickly prioritized important management strategies to limit eutrophication impacts. Its use is recommended to provide reliable information about the magnitude and timeframe of P loss reduction that can be realistically expected. Further innovation is needed on farms to improve P use efficiency and minimize soil P levels for long-term environmental gain.

Technical Abstract: Phosphorus (P) use in agriculture continues to negatively impact water quality and linked ecosystem services due to soil P accumulation. The management of soil and soil P fertility status is therefore an important option to mitigate potential eutrophication impacts, but despite the focus of much research, the relative environmental benefits of erosion control and reductions in soil P, and the timescales over which these benefits occur, are far from clear. To better guide policy strategies towards reduced P loadings from agricultural soils, we examined the impact of soil conservation measures and lowering of soil test P (STP) in different developed regions with intensive farming (Europe, USA and Australia). Summarizing relationships between STP and soluble reactive P (SRP) concentrations in land runoff suggested that eutrophication control targets would be more achievable if STP concentrations were kept at or below the recommended agronomic optimum. APLE model simulations showed that P losses in three contrasting catchments could be reduced by between 18 and 40% by drawing down STP in all catchment soils to the agronomic optimum but that it would take between 30 and 40+ years to achieve this reduction. In one catchment, STP drawdown was more effective in reducing catchment P loss than erosion control but combining these two strategies was always most effective. Further reductions (up to 55%) in catchment P loss were obtained when STP levels were reduced below the agronomic optimum. The APLE model was easy to parameterize and quickly prioritized important management strategies to limit eutrophication impacts. Its use is recommended to provide reliable information about the magnitude and timeframe of P loss reduction that can be realistically expected. Further innovation is needed on farms to improving P efficiency and minimize critical STP concentrations for long-term environmental gain.