Good fertilization is necessary for perfect grass cover. People cannot live without nutrition, and neither can plants. A fertilization plan is based on a soil analysis and the specific needs of the turf grass. Remember  that various elements are washed away during the year or are consumed by the grass.
The kind and amount of fertilization depends on different aspects: grass species and cultivars (the mixture), purpose of the turf (golf, landscape, football, rugby, …), soil texture, organic matter content (%).

When overseeding, it is more benefi cial to the emerging new seedlings to apply fertiliser after germination rather than applying a pre-seed fertiliser. This may help to reduce the competition from the existing plants in the sod (especially undesirable grasses) and will assist establishment.
Guidelines for turf nutrition
The table below shows the % of the total N P K, to be applied to the different species during the year in the  specific climate zone for top quality of lawn (approximately -g/sqm-: N =15; P = 5; K = 15) The total  aplications is split in threefour applications due to the use of CRF (Control release fertilizers) or SRF (Slow  release fertilizers) or OF (organic fertilizers with high N content) If ready-soluble fertilizers are used, the  application of N has to be split in 5-6 applications.
  Sportmixtures with Lp and Pp
  N P K
April 30 50 20
June 30   30
August 20    
October 20 50 50
  100 100 100
(source: Landlab 2009)