Because they are required in large quantities, primary and secondary macronutrients are actively managed through manufactured fertilisers, slurry and farmyard manure. Their balance, timing and method of application play a major role in determining nutrient use efficiency, crop yield and system resilience, and can also influence water use efficiency.
Historically, Irish farming relied on soil reserves, liming, organic manures and biological nitrogen fixation by legumes for these nutrients but the widespread adoption of manufactured fertilisers in the mid-20th century, particularly nitrogen, phosphorus and potassium, enabled by advances such as the Haber–Bosch process, led to major increases in agricultural output. Since then, research, advisory services and regulation have shifted the focus towards more efficient nutrient use. This includes routine soil testing, nutrient budgeting and targeted application strategies, alongside practices such as split nitrogen applications, improved slurry management, use of inhibitors and better timing to reduce losses to water and air.