AbstractA water culture experiment was conducted to interpret how three major nutrients (N, P, K) contribute to cabbage-head fonnation when they are supplied in a different amount and at different growth stages.The critical N, P, and K contents in the outer leaves which resulted in a 50% decrease in the cabbage-head yield due to each deficiency were 1.3, 0.1. and 0.3% on a dry basis, respectively. The longer the period of each nutrient supply, the higher was the cabbage-head yield. The contribution of nitrogen per unit weight to cabbage-head fonnation was the highest at the third growth stage (i.e. early cabbage-head development phase) and that of phosphorus and potassium at the first growth stage (i.e. outer-leaf expansion phase) among the four growth stages.The nitrogen supplied for 20 days at any growth stage of the four growth stages did not produce an ordinary cabbage-bead but the phosphorus at the second growth stage (i.e. outerleaf development phase) produced a big cabbage-head comparable to that of the plants receiving phosphorus during the whole growth stage. The potassium supplied at the first or the second growth stage produced a small cabbage-bead but failed to produce any cabbage-head at the later growth stages.