Abstract: Mutual relations between calcium ( Ca) and other main elements and the effects of Ca on the growth and development of lettuce in NFT culture were studied. Results showed that Ca deficiency resulted in a reduct ion of
Chlorophyll, an increase in the incidence of tipbum and a decrease of both fresh and dry weigh, all these changes are the major reasons of low yield and bad quality. During the mid􀀁 and later growing period, Ca disturbance was easily appeared in inner leaves of plant. Assimilation of potassium ( K) and magnesium (Mg) was retarded by excessive Ca, while that of nitrogen ( N) and phosphor ( P) was little affected. Ca was less effect ive if the proportion of NH₄⁺ -N in nutrient solution was increased.

Key words: Natrient film technique, Calcium, Lettuce, Nutrive peculiarity, Growth and development