Abstract
This paper describes an agricultural model (Roth-CNP) that estimates carbon (C), nitrogen (N) and phosphorus (P) pools, pool changes, their balance and the nutrient fluxes exported from arable and grassland systems in the UK during 1800–2010. The Roth-CNP model was developed as part of an Integrated Model (IM) to simulate C, N and P cycling for the whole of UK, by loosely coupling terrestrial, hydrological and hydro-chemical models. The model was calibrated and tested using long term experiment (LTE) data from Broadbalk (1843) and Park Grass (1856) at Rothamsted. We estimated C, N and P balance and their fluxes exported from arable and grassland systems on a 5km×5km grid across the whole of UK by using the area of arable of crops and livestock numbers in each grid and their management. The model estimated crop and grass yields, soil organic carbon (SOC) stocks and nutrient fluxes in the form of NH4-N, NO3-N and PO4-P. The simulated crop yields were compared to that reported by national agricultural statistics for the historical to the current period. Overall, arable land in the UK have lost SOC by −0.18, −0.25 and −0.08MgCha−1y−1 whereas land under improved grassland SOC stock has increased by 0.20, 0.47 and 0.24MgCha−1y−1 during 1800–1950, 1950–1970 and 1970–2010 simulated in this study. Simulated N loss (by leaching, runoff, soil erosion and denitrification) increased both under arable (−15, −18 and −53kgNha−1y−1) and grass (−18, −22 and −36kgNha−1y−1) during different time periods. Simulated P surplus increased from 2.6, 10.8 and 18.1kgPha−1y−1 under arable and 2.8, 11.3 and 3.6kgPha−1y−1 under grass lands 1800–1950, 1950–1970 and 1970–2010.
Highlights
Agriculture in the United Kingdom (UK) has a long history of human settlement and development which dates back to 6000 years ago when humans began domesticating plants and animals in Neolithic times (Edwards and Hirons, 1984; Woodbridge et al, 2014)
This paper describes an agricultural model (Roth-CNP) that was developed as part of an Integrated Model (LTLS-IM) to simulate the cycles of C, N and P for the whole of UK, comprising terrestrial, hydrological and hydro-chemical model over the long-term period from 1800 to the present
The Roth-CNP model summarises the CNP cycling in an agricultural ecosystem by aggregating soil and crop processes using a daily to monthly timestep
Summary
Agriculture in the United Kingdom (UK) has a long history of human settlement and development which dates back to 6000 years ago when humans began domesticating plants and animals in Neolithic times (Edwards and Hirons, 1984; Woodbridge et al, 2014). By 1300 CE, increasing demand for food brought the subsistence farming system under huge pressure because of increasing population as the land area available for agriculture was already in use. Agricultural land contributes 70% and 28% of the N and P load to the UK waters (Hunt et al, 2004; White and Hammond, 2007) Losses of these nutrients are associated with excessive or poorly timed applications of N or P or both (Dungait et al, 2012). Pretty et al (2000) calculated the annual external cost of agriculture for the UK in 1996 as £2343 M (£208/ha), with the major costs associated with contamination of drinking water by pesticides, nitrate and phosphate and increased greenhouse gas (GHG) emissions, soil erosion and organic carbon losses Losses of these nutrients are associated with excessive or poorly timed applications of N or P or both (Dungait et al, 2012). Pretty et al (2000) calculated the annual external cost of agriculture for the UK in 1996 as £2343 M (£208/ha), with the major costs associated with contamination of drinking water by pesticides, nitrate and phosphate and increased greenhouse gas (GHG) emissions, soil erosion and organic carbon losses
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