An  optimum  plant  crop  nutrition status   during  critical stages  of growth  is  one of the most important   factors  shaping  their  ability   to yield.  It  has  been assumed  that  plant  nutrition  during  the  spring  wheat  stem  elongation  stage has  a significant influence  on the  growth and yield  of this  crop.  In  Poland, potassium  is a  critical nutrient for  plant  growth  and  yielding.  In order  to  verify  this  hypothesis,   three  series  of one factorial   experiment   were  conducted in 2003-2005 that  involved reduced rates  of potassium  applied  to cv. Zyta winter wheat.  The following rates  of potassium  were applied:  0, 25, 50 and 100  kg ha-1. The  assessment of wheat nutritional status  was  conducted at  the  beginning  of stem  elongation  (BBCH30/31) using  a German  model called  PIPPA. It  had been hypothesized  that  this  particular stage was decisive for  wheat  growth  and yielding.   Wheat  plants  showed deficiency  in Ca,  K, P  and  N irrespective  of the applied  potassium  rate.   Calcium and  potassium  deficiencies  were  crucial for the final  grain  yield.  However,  the relationships that  occurred between nitrogen and main nutrients, i.e.  pairs  of nutrients such  as  N:P,  N:K, N:Ca,  showed a much  better  prognostic value,  i.e.  the  relationship with  grain  yield,  than  the levels  of nutrients in  separation. The nitrogen  content  in  leaves  at  the beginning of shooting  showed  its  limiting effect  on grain yield,  provided  that  Ca  was deficient,  an  event  which  appeared  when  N:Ca  was  wider  that 34:1.  The same  correlation   was  noticed  for  potassium,   but  there  the  excess  of nitrogen revealed  its  harmful effect when  the  N:K   ratio  was  above 1.0.