A correct balance between macronutrients and micronutrients is essential to obtain the best results possible from grassland. A deficiency of any single nutrient is enough to limit growth and the availability of each nutrient needs to be related to requirements. A review of nutrient uptake and offtake reveals which nutrients are required however in the case of grassland it is essential to also account for the nutrients supplied or deposited as manures.
Macronutrient uptake by grassland
Nitrogen is the crucial nutrient for influencing grassland yield. Requirements for potassium, phosphate, sulphur, calcium, and magnesium are related to the amount of applied nitrogen. There is a large demand for these macronutrients during early spring growth and to avoid limiting yield it is critical that sufficient quantities of nutrients are available for uptake when required by the plant. The nutrient uptake and offtake from grassland depends on the intensity of production and whether it is mowed or grazed.
This table shows how the macronutrient offtake per tonne dry matter varies with yield and depending on whether it is grazed or mown.
Micronutrient uptake by grassland
A balanced crop nutrition strategy is essential and although much lower amounts are needed the correct balance of micronutrients should be available since these are essential elements for achieving high yields. The most important micronutrient on grassland yield are copper, manganese and zinc.
Other micronutrients which are not essential for grass but are required by grazing animals include sodium and selenium and also copper and zinc are required in higher levels in animals than are required for grass growth.
This table based on studies in the UK shows the wide variation in micronutrient uptake per ha depending on the management system.