Improving slurry nutrient distribution on dairy farm holdings
This report modelled milking platform stocking rates where nutrients must be distributed to other parts of the farm outside the milking platform in order to optimise nutrient use efficiency and reduce potential loss to the environment, based on the platform stocking rates, chemical N application rate and cow banding.
By Teagasc
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Irish grass-based systems of milk and meat production rely on the conversion of human inedible forage into highly nutritious and digestible human-edible products. O′Brien et al. (2018) reported that the average diet of Irish dairy cows was 81.8% forage, with concentrates constituting just 18.2% of the annual feed budget on a dry matter basis. Of the 81.8% forage, 60.2% was grazed pasture, 19.8% was grass silage, and 1.8% was alternative forages. This is significantly different to farming systems being operated in most other EU countries.
Stocking rate is a key dairy farm-level efficiency factor in successful grazing systems which facilitates the achievement of high levels of grazed pasture utilisation and milk production per hectare (McCarthy et al., 2011, 2012). In defining the optimum stocking rate for resilient, pasture-based grazing systems, pasture production and utilisation is the principle consideration.
It is generally accepted that increasing stocking rate accompanied with increased fertilizer N and concentrate input will result increased nitrogen surplus resulting in increased N leaching, denitrification and nitrous oxide emissions (Murphy et al., 2024). However, on the basis of improved management practices, it is not correct to assume that N losses/ha through leaching increase as grass utilisation increases through increased stocking rate.