(25)In line with common practice, nitrogen, phosphorus and potassium should be referred to as ‘primary macronutrients’, and calcium, magnesium, sodium and sulphur should be referred to as ‘secondary macronutrients’. Also in line with common practice, fertilisers should be referred to as ‘straight’ when they contain either only one macronutrient – regardless whether it is primary or secondary – or only one primary macronutrient in combination with one or more secondary macronutrients. In line with the same practice, fertilisers should be referred to as ‘compound’ when they contain either more than one primary macronutrient – regardless whether they also contain one or more secondary macronutrients – or contain no primary macronutrient but more than one secondary macronutrient.