Simulation of the influence of poor soil drainage on grass‐based dairy production systems in Ireland

Abstract

AbstractA dairy cow system simulator, Dairy_sim, designed for assessing the interaction of climate and management on dairy cow production, based on rotational grass grazing, was further developed by integrating a soil water model. The soil water model was based on the concept of soil water deficits, and influenced the growth of grass herbage in the simulator when there was an excess of water over field capacity and when water content in the soil was approaching wilting point. The soil water model was tested using baseline meteorological data (1961–1990) and then the system simulation was parameterized and tested for poorly drained soils using data from a research farm in the west of Ireland. After testing, the effects of regional differences in climate on system management on well‐ and poorly drained soils were compared. Down‐scaled Global Climate Model (GCM) data for the baseline years (1961–1990) were used for this purpose. These data resulted in slightly more favourable weather than that recorded. It was found that the simulator was capable of generating results in good agreement with published data for dairy production on poorly drained soils. The regional analysis showed dairy farms on well‐drained soils out‐performed their equivalents on poorly drained soils and, in general, were able to sustain higher stocking rates by 0·6–0·9 cows ha−1. Dry matter production was around 1·5–3 t ha−1 greater per annum on well‐drained soils compared to poorly drained soils. The simulator, Dairy_sim, also captured a large difference in the requirement for housing and forage between the well and poorly drained soils. The simulation model can now be used to evaluate interactions between soils, systems and weather, and is thus a more useful tool for developing practical advice and for evaluating the impacts of possible climate change.