Nitrogen budgets for lowland temperate beef and sheep grazing systems: The North Wyke Farm Platform

Tom Misselbrook1, Alison Carswell1, Graham McAuliffe1, Taro Takahashi1,2, Laura Cardenas1, Michael Lee1,2

1 Rothamsted Resesarch, North Wyke, Okehampton, Devon EX20 2SB, UK, [email protected];

2 University of Bristol, School of Veterinary Sciences, Langford, Somerset BS40 5DU, UK

Abstract

The North Wyke Farm Platform comprises three 22 ha beef and sheep grazing ‘farmlets’ which are highly instrumented to monitor hydrology, weather, nutrient flows and productivity. Typical management for lowland UK grazing systems, based on permanent pasture, was applied to all three systems for an initial two-year baseline period. Following that, the platform has been progressively modified with the underlying principle being to improve the sustainability (economic, social and environmental) of two of the three farmlets, by reseeding of one with a grass-clover sward to drive production through nitrogen (N) fixation and one with a grass monoculture utilising the latest grass breeding advancements and higher yield potential. The third farmlet continued under permanent grassland. This paper presents the framework to be used in assessing the impacts of the reseeding period and to estimate system scale N budgets for the three systems. Data are being compiled with no results yet available, but will consist of a combination of measurements and modelled N pools and flows based on detailed management and production data. N use efficiency will be evaluated at the partial (forage production) and full (livestock product output) system level. A range of metrics expressing N flows on a product and land area basis will be derived. For a more complete understanding of the impacts of the system interventions and potential for future interventions to further improve NUE, further measurement data are required including N losses though denitrification, ammonia volatilisation and total N losses to water and N inputs through fixation.