Availability of nutrients is influenced by many factors including:
- nutrient concentration in soil solution
- nutrients held by soil particles
- soil particles, e.g. clay, organic matter
- interactions with other nutrients
- soil moisture
- microbial activity
- root growth
The PRG nutrient models and information on the relevant pages provide guidance on fertiliser requirements but cannot account for all these factors.
Tissue tests provide a measurement of the success of the applications.
The following links open presentations which give overviews of nutrient requirements.