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A 10‐year study of phosphorus balances and the impact of grazed grassland on total P redistribution within the soil profile
Author(s) -
Watson C. J.,
Matthews D. I.
Publication year - 2008
Publication title -
european journal of soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.244
H-Index - 111
eISSN - 1365-2389
pISSN - 1351-0754
DOI - 10.1111/j.1365-2389.2008.01083.x
Subject(s) - environmental science , eutrophication , surface runoff , fertilizer , drainage , zoology , grassland , phosphorus , hydrology (agriculture) , earthworm , water quality , agronomy , nutrient , soil water , nitrogen balance , nitrogen , chemistry , ecology , soil science , biology , geotechnical engineering , organic chemistry , engineering
Summary Phosphorus (P) inputs (wet deposition and fertilizer P) and outputs (animal product and drainflow) were studied on reseeded grazed grassland swards receiving different nitrogen (N) inputs (100–500 kg N ha −1 year −1 ) for 10 years (March 1989–February 1999), at an experimental site in Northern Ireland. All plots received the same maintenance application of P fertilizer (8.5 kg P ha −1 year −1 ) to meet grass requirements, to minimize the P surplus and to quantify the impact on P losses to land drainage water. The annual flow weighted mean total P concentrations in drainflow ranged from 187 to 273 μg P litre −1 and were well above the concentrations believed to trigger eutrophication. Annual total P lost to drainage water ranged from 0.28 to 1.73 kg P ha −1 , but was unaffected by N input. As the average annual P balance was zero, there was no significant change in total P in the top 15 cm of soil. However, there was a highly significant redistribution of P to the soil surface from the 10–15 cm depth, possibly as a result of root acquisition and earthworm activity. Total P in the top 5 cm of soil increased from 0.85 g kg −1 to 1.04 g kg −1 , over the 10 years of the study, despite there being no net P input. This P accumulation in the top few cm of soil is likely to exacerbate P losses in overland flow and make improvements in water quality difficult to achieve.