Two field experiments were conducted during the two successive winter
seasons of 2001 and 2002 to investigate the performance of lettuce plant (Lactuca
sativa L.) cv. 8alady in relation to different nitrogen sources, i.e. ammonium sulphate,
ammonium nitrate, urea and calcium nitrate as minerals as well as town refuse and
cattle as organic manures at rates of 20, 40 and 60 N unit/fed. on the growth, yield of
lettuce and its some physical and chemical properties. The important results could be summarized as follows :- 1· Increasing levels of nitrogen fertilizers up to 60 N unit/fed. increased vegetative
growth characters, i.e., plant length, stem length, number and area of leavesf plant
and its pigment content, fresh and dry weights of whole plant and its differents
organs as well as total yield (ton/fed.). 2- The vigor plant growth as expressed as length of plant, number and area of leaves
as well as head yield, all of them registrated their highest values with addinon of
ammonium nitrate as chemical nitrogen fertilizer. Moreover that plants received
cattle manure had a superior in its growth if compared with that plants applied by
town refuse manure. 3- Addition of ammonium nitrate as inorganic fertilizer at the highest rate of nitrogen
(60 N unit/fed.) gave the best growth characters and heads yield as ton per
feddan.       4-     Increasing nitrogen fertilizer rates up to 60 N unit/fed. significantly increased
chlorophyll content, nitrate, N, P and K contents of leaves tissues 5- Addition of ammonium nitrate as chemical fertilizer at 60 N unit/fed. increased
chlorophyll content, nitrate and N contents of leaves while ammonium sulphate at
60 N unit/fed. increased P and K cntents. Using cattle manure as organic fertilizer
at 20 N unit/fed. significantly decreased chlorophyll content, nitrate, N, P and K
contents of leaves.