Optimizing livestock manure applications to reduce nitrate and ammonia pollution: scenario analysis using the MANNER model

Measures to reduce ammonia (NH3) emissions by incorporating livestock manur es into the soil may increase the potential for nitrate (NO3-) leaching. Th e Manure Evaluation Routine (MANNER) model estimates the amount of N availa ble to crops following livestock manure applications after calculating loss es due to NH3 volatilization and NO3- leaching, The main objective of this study was to use the MANNER model to quantify the impact on NO3- leaching o f introducing measures to reduce NH3 emissions, following application of li vestock manures. The data produced were also used to make preliminary estim ates of the likely effect of selected NH3 abatement techniques on the poten tial for nitrous oxide (N2O) emissions. At typical UK rates of application, the potential for increased NO3- leaching following either injection of sl urry or rapid incorporation of solid manures was greatest for broiler/turke y manure (22-58 kg N ha(-1)) and least for straw-based cattle manure (6-10 kg N ha(-1)). The results suggest that in order to avoid substantially incr easing the potential for NO3- leaching as a consequence of NH3 abatement, l ivestock manures should not be applied by low NH3 emission techniques prior to autumn-sown crops in the UK. Instead, low-emission applications should be made from October onwards to grassland and where possible, late autumn-s own combinable crops or to arable land which will be planted in the spring. However, in several areas of England and Wales there is currently insuffic ient land planted to spring crops on which to incorporate the livestock man ures produced in those areas.